tag:blogger.com,1999:blog-82406143915055894462024-03-28T11:44:34.949-05:00All about Wired and Wireless TechnologyUnknownnoreply@blogger.comBlogger40125tag:blogger.com,1999:blog-8240614391505589446.post-29982081256830233482023-01-01T18:49:00.004-06:002023-01-01T19:02:07.235-06:00Introduction to 6G <p> Wireless technology has come a long way in recent years, and the latest generation, known as 6G, is set to take things to the next level. In this blog post, we'll provide an introduction to 6G wireless technology and give you a sense of what this exciting new development means for the future of wireless communications.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEiYAXvigfwxu-KB1F_L4gTShJq2u1oewWV4oSOn9F-ovgliBb2pAZv5jMWbxvHpOGE5LZynvyeEZhKxt5f6lXK8z4K7b9mWYOAcOWIBN4Y0RCKuIZshRLeqv-74dh0pPY437dZZ2LuJPPWScm37MwMqq1rp4-Y0I69HFaAxRXDmT6rYB_5f0RN3QEOnJg" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="591" data-original-width="643" height="240" src="https://blogger.googleusercontent.com/img/a/AVvXsEiYAXvigfwxu-KB1F_L4gTShJq2u1oewWV4oSOn9F-ovgliBb2pAZv5jMWbxvHpOGE5LZynvyeEZhKxt5f6lXK8z4K7b9mWYOAcOWIBN4Y0RCKuIZshRLeqv-74dh0pPY437dZZ2LuJPPWScm37MwMqq1rp4-Y0I69HFaAxRXDmT6rYB_5f0RN3QEOnJg" width="261" /></a></div><br /><br /></div><br /><p>So, what exactly is 6G wireless technology? In short, it is the next generation of wireless technology that is expected to offer faster speeds, lower latency, and higher capacity than its predecessor, 5G. While 5G is still in the process of rolling out and being adopted by consumers and businesses around the world, researchers and industry experts are already looking ahead to the next generation of wireless technology.</p><p>One of the key benefits of 6G is that it is expected to offer significantly faster speeds than 5G. While 5G offers peak speeds of up to 10 Gbps, 6G is expected to offer speeds of up to 1 Tbps. This means that you'll be able to download and upload data much faster, with little to no lag.</p><p>In addition to faster speeds, 6G is also expected to offer lower latency, which refers to the time it takes for data to be transmitted from one device to another. This will be especially important for applications that require real-time communication, such as virtual reality and telemedicine.</p><p>Another key benefit of 6G is that it is expected to offer higher capacity, which means that it will be able to handle more devices and data traffic without experiencing congestion or interference. This will be particularly important as the number of connected devices continues to grow in the coming years.</p><p>While 6G is still in the early stages of development, it is clear that it has the potential to revolutionize the way we communicate and interact with each other. Whether you're a consumer, a business owner, or an industry professional, it's worth keeping an eye on this exciting new technology as it continues to evolve.</p>Unknownnoreply@blogger.com15tag:blogger.com,1999:blog-8240614391505589446.post-17263938548757752352023-01-01T18:41:00.008-06:002023-01-01T18:43:07.055-06:00Dynamic Spectrum Sharing (DSS)In the world of wireless communication, spectrum is a valuable resource. It is the range of frequencies that are used to transmit data over the airwaves, and the availability of spectrum determines the capacity and speed of a network. <div><br /></div><div>Traditionally, different types of communication have been allocated specific bands of spectrum. For example, cellular networks operate in the 700 MHz to 2700 MHz range, while Wi-Fi operates in the 2.4 GHz and 5 GHz bands. This approach has worked well for many years, but as the demand for data continues to grow, there is a need for more flexible and efficient use of spectrum. This is where Dynamic Spectrum Sharing (DSS) comes in. </div><div><br /></div><div>DSS is a technology that allows different types of communication to share the same band of spectrum. This brings a number of benefits to LTE networks, including: Increased capacity: By allowing different types of communication to share the same band of spectrum, DSS can increase the capacity of an LTE network. This is especially useful in areas where there is a high demand for data, such as city centers or busy airports. </div><div><br /></div><div>Improved coverage: DSS can also improve coverage in areas where there is a shortage of available spectrum. By sharing the spectrum with other types of communication, an LTE network can extend its reach and provide coverage to more people. More efficient use of spectrum: DSS allows for a more efficient use of spectrum, as it can be used by multiple types of communication rather than being dedicated to a single type. This can help to free up spectrum for other uses, such as 5G or Internet of Things (IoT) applications. </div><div><br /></div><div>DSS is an exciting technology that has the potential to bring greater flexibility and efficiency to LTE networks. As demand for data continues to grow, it will be an important tool in helping to meet the needs of users around the world.</div>Unknownnoreply@blogger.com4tag:blogger.com,1999:blog-8240614391505589446.post-433196268819638932023-01-01T18:39:00.001-06:002023-01-01T18:39:05.822-06:00PDCCH Blocking in LTE<p>In LTE, the Physical Downlink Control Channel (PDCCH) is used to carry control information for the downlink, such as scheduling assignments and hybrid automatic repeat request (HARQ) feedback. PDCCH blocking can occur when the network is overloaded and there are more scheduling assignments or control messages to be transmitted than there are available resources on the PDCCH. This can lead to delays in the transmission of control information, which can negatively impact the performance of the network. PDCCH blocking can also occur when there is interference on the channel or when there are problems with the channel quality.</p>Unknownnoreply@blogger.com4tag:blogger.com,1999:blog-8240614391505589446.post-71255668600774632582023-01-01T18:28:00.007-06:002023-01-01T18:32:50.551-06:00UE Categories in LTE<p> In LTE (Long-Term Evolution) networks, UE categories (or user equipment categories) are used to classify different types of mobile devices based on their capabilities and performance. UE categories till release 13 are shown in below Table </p><p></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEiiA3n_YEZoiSeLCoL_ekX_ItQJpE6kjqhQaUFpJymIoa7L8HsSxBoPaCAI8Pk0RKvrCPD-2FxPYgNuGaIHWqFPNyB0Twg5A3gs98SKH-uuJgJSzsTOVUDT_8rMerpNq8OZRbcGBG0Xz_57zN4PecNhSycwzf_qg6a1yYiRgrv-bzeynWLJW-nk0CCtGA" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="497" data-original-width="719" height="419" src="https://blogger.googleusercontent.com/img/a/AVvXsEiiA3n_YEZoiSeLCoL_ekX_ItQJpE6kjqhQaUFpJymIoa7L8HsSxBoPaCAI8Pk0RKvrCPD-2FxPYgNuGaIHWqFPNyB0Twg5A3gs98SKH-uuJgJSzsTOVUDT_8rMerpNq8OZRbcGBG0Xz_57zN4PecNhSycwzf_qg6a1yYiRgrv-bzeynWLJW-nk0CCtGA=w606-h419" width="606" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div>Each UE category is defined by a set of capabilities and performance parameters, including the maximum data rates that the device is able to support, the type of modulation and coding schemes it is able to use, and the maximum transmits power it is able to use. These capabilities and performance parameters are specified in 3GPP (3rd Generation Partnership Project) standards.<p></p><p>The UE categories are used to determine the maximum data rates that a mobile device is able to achieve in an LTE network, as well as the type of modulation and coding schemes that it is able to use. Higher UE categories correspond to higher maximum data rates and more advanced modulation and coding schemes, while lower UE categories correspond to lower maximum data rates and less advanced modulation and coding schemes.</p><div class="separator" style="clear: both; text-align: center;"><br /></div><br /><br /><br /><p></p>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-8240614391505589446.post-84376788167241499272017-04-26T17:56:00.001-05:002018-02-07T16:18:54.820-06:00Nokia 5GUnlike 2G, 3G and 4G, it is unlikely that 5G will be a single new Radio
Access Technology (RAT) nor will it replace macro cells. It will be a
combination of existing RATs in both licensed and unlicensed bands,
plus one or more novel RATs optimized for specific deployments,
scenarios and use cases. Check more details in below 5G white paper by Nokia<br />
<br />
<a href="http://www.5gamericas.org/files/3614/3898/6583/Nokia_White_Paper_-_Looking_ahead_to_5G.pdf" target="_blank">http://www.5gamericas.org/files/3614/3898/6583/Nokia_White_Paper_-_Looking_ahead_to_5G.pdf</a>Unknownnoreply@blogger.com424tag:blogger.com,1999:blog-8240614391505589446.post-49676148095889508212016-08-15T10:59:00.002-05:002016-09-07T10:14:02.869-05:00PDCCH Order in LTE<div dir="ltr" style="text-align: left;" trbidi="on">
PDCCH Order is a procedure to bring back uplink out-of-sync UE (user equipment) back to in-sync state incase there is downlink data available for it. This can happen in situation when the time alignment Timer gets expired because there is no uplink and dowlink data transmission for some time and also when there is no Time alignment command recieved from eNB. Time Alignment timer basically controls how long the UE is considered uplink time aligned.<br />
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For viewers to better understand PDCCH Order, here is an example :<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWN-OMBM9YFReedEnQ7KNQpKxcP1_JFWtKOViz_HvjHUKhe4s3JG8DTT_XAYrnnNq3Nfj7D8NRXqg553of1aLXhQOyiMsEwznebG3R3UabFngX-mWkZyvQVy18DTbGpUXbSbeB8KES6TE0/s1600/pdcchorder.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="550" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWN-OMBM9YFReedEnQ7KNQpKxcP1_JFWtKOViz_HvjHUKhe4s3JG8DTT_XAYrnnNq3Nfj7D8NRXqg553of1aLXhQOyiMsEwznebG3R3UabFngX-mWkZyvQVy18DTbGpUXbSbeB8KES6TE0/s640/pdcchorder.png" width="640" /></a></div>
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<ol>
<li>Lets assume we have a UE that is in RRC connected state</li>
<li>There is uplink / downlink user data being transmitted for some time (like facebook activity etc)</li>
<li>There is no more data to be transmitted. Time Alignment timer will start (expiry setting = 10 seconds). But remember the RRC Inactivity Timer will also start since there is no data activity but lets assume that our Inactivity Timer doesnt expire and we remain in RRC connected state for whole duration</li>
<li>Time Alignment timer expires and UE is considered uplink out-of-sync now. At this point UE releases all PUCCH (scheduling resources, CQI configuration) and SRS resources. UE also flushes its HARQ buffers</li>
<li>UE is still in RRC Connected state but it has no PUCCH/SRS resources as they were released previously. Now there is DL data in eNB buffer for UE (Like facebook notification or something) but first UE has to be brought back to in-sync state and also it needs to reconfigured again with PUCCH/SRS resources</li>
<li>eNB sends PDCCH order to UE using DCI 1A format. This is basically signal to UE to perform the contention less RACH with preamble index already included in DCI 1A </li>
<li>UE sends MSG1 using RACH preamble acquired from PDCCH order (To read more about RACH procedure in LTE, <a href="http://www.simpletechpost.com/2013/04/random-access-procedure-rach-in-lte.html" target="_blank">click here</a>)</li>
<li>eNB sends RACH response with new time advance value so that UE can be uplink in-sync</li>
<li>UE is in sync again ! </li>
<li>Next eNB sends RrcConnectionReconfiguration message which carries PUCCH/SRS as they were released when the time alignment timer was expired at step 4</li>
<li>UE confirms reception of RrcConnectionReconfiguration message and now can resume uplink/downlink transmission of data</li>
</ol>
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<div>
Why UE needs time alignment ? </div>
<div>
Due to different signal transmission paths and movement, UE can lose time synchronization to eNB subframe. eNB measures the time alignment of UE by measuring the difference between arrival time of PUCCH, PUSCH, SRS to its own uplink subframe</div>
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Unknownnoreply@blogger.com117tag:blogger.com,1999:blog-8240614391505589446.post-11025129732623752016-03-17T18:35:00.000-05:002016-04-07T10:17:05.466-05:00How to build your own LTE Quadcopter Having a quadcopter being controlled through LTE network without any limit in its flying range ( with an exception of battery backup and LTE coverage limit of course ) had always been a very appealing and interesting notion. There are few solutions available which are costly, So I wanted to come up with a cheaper alternative<br />
<br />
First, lets begin with the main parts that will be needed to build on your LTE controlled Quadcopter.<br />
See the required parts below<br />
<br />
- Raspberry Pi (<a href="http://www.amazon.com/Raspberry-Pi-Model-Project-Board/dp/B00T2U7R7I/ref=sr_1_4?s=pc&ie=UTF8&qid=1457382125&sr=1-4&keywords=raspberry+pi+2" target="_blank">Amazon Link</a>) price ~$40<br />
- F450 Quadcopter Kit (<a href="http://www.ebay.com/itm/F450-Quadcopter-Rack-Kit-Frame-w-B2212-920KV-Simonk-30A-ESC-1045-prop-DJI-3M-/191756297427?hash=item2ca590e4d3:g:sbcAAOSwxN5WZ~wH" target="_blank">Ebay Link</a>) price ~$80<br />
- LTE Dongle (<a href="http://www.amazon.com/100mbps-aircard-313u-network-original/dp/b00s69n1m6" target="_blank">Amazon Link</a>) price ~$50<br />
- Battery Pack (Lipo) (<a href="http://www.ebay.com/itm/Turnigy-2200mAh-3S-11-1v-20C-30C-Lipo-Battery-Pack-E-Flite-Blade-450-XT60-XT-60-/141226927130?hash=item20e1c7e41a:g:gSUAAOSwQM9UainA" target="_blank">Ebay Link</a>) price ~$18<br />
- Lipo Charger (<a href="http://www.ebay.com/itm/Imax-B6-LCD-Screen-RC-Li-po-Battery-Balance-Charger-AC-Adapter-EC3-XT60-DJI-/151899750520?hash=item235dee4078:g:BoYAAOSwcBhWW7f8" target="_blank">Ebay Link</a>) price ~$25<br />
- Flight Controller CC3D (<a href="http://www.ebay.com/itm/CC3D-Openpilot-Open-Source-Flight-Controller-32-Bits-Processor-With-Wires-/321767309753?hash=item4aead381b9:g:s0oAAOSwJkJWlLNB" target="_blank">Ebay Link</a>) price ~$13<br />
- PC Gaming Joystick (<a href="http://www.amazon.com/Extreme-3D-Pro-Joystick-Windows/dp/B00009OY9U/ref=sr_1_1?ie=UTF8&qid=1457387686&sr=8-1&keywords=logitech+joystick" target="_blank">Amazon Link</a>) price ~$29<br />
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<h4>
Some Background</h4>
A Quadcopter consists of four arms with a motor and propeller on the end of each arm. Two propellers are turning clockwise and the other two are turning counter-clockwise. There is a flight controller which keeps it leveled and converts your input commands into motion which it needs to fly. There are many cheap flight controllers available in the market. The one I used is called Open Flight CC3D. It costs only $13. Some other popular alternatives are<br />
<br />
- Hobbyking KK2.1.5 Flight controller<br />
- APM2.6 Ardupilot Flight Controller<br />
<div>
- Naze32<br />
<div>
<br />
Main parts of Quadcopter consists of a frame, a receiver, a flight controller, electronic speed controls, motors, and propellers. See below for complete picture<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPFAetpJrryIhqO1EKOQBgtKYOhxe5a9IupqHeX_kb2K5S3JxG-R5WUVrRDaaDpyLftPYk52xuUNiKkdJJAAfN7turPDe1yJZUBuzsIXuQA93Vz_sNqqc40iQt29yJFsf2N4gUwRgUtr1T/s1600/CC-overall-connections.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="190" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPFAetpJrryIhqO1EKOQBgtKYOhxe5a9IupqHeX_kb2K5S3JxG-R5WUVrRDaaDpyLftPYk52xuUNiKkdJJAAfN7turPDe1yJZUBuzsIXuQA93Vz_sNqqc40iQt29yJFsf2N4gUwRgUtr1T/s640/CC-overall-connections.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Quadcopter Operation</td></tr>
</tbody></table>
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<br />
<div class="separator" style="clear: both;">
</div>
Quadcopter motion (Throttle, Yaw, Pitch, Roll) commands are sent via RC Transmitter to RC Receiver and are converted to PWM signals which are then used by flight controller to control the speed of Motors via Electronic Speed Conrollers (ESC). Most modern transmitters use a 2.4 Ghz frequency. RC receivers come mostly with 6 channels receivers. Channels are the amount of things you can control. For example a four channel transmitter means you can only control four motors/servos/accessories. Mostly RC transmitter has 6 channels. These channels are controlling the Throttle, Yaw, Pitch, Roll, Aux 1, and Aux 2 (Aux can be used for different feature on your Quadcopter)<br />
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The output of the receiver is in the form PWM signals. PWM stands for Pulse Width Modulation. PWM is a technique used to transmit data in the form of a varying pulse width. In the case of R/C electronics this time is usually 1-2 milliseconds. For example, full throttle on your transmitter will send a 2 ms pulse to flight controller while zero throttle means puls of width 2 ms. Same rule applies to other controls on your transmitter. PWM pulse frequency is 20ms. The image below represents a typical PWM frame<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_o-QM2PDoO1PgrhrHm1e8gHAamAiA3zB_m3Jo_DhZoN3DI7pamNEIqZ60W2BtchDRO6aW4-Eej_nlsp1Y1g19DjP7LH1Sl1wNJx0Oo2B8Dx5P3ZYzeluyP_j23DeIF_NiBnIi7QnGJKG_/s1600/pwm.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="193" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_o-QM2PDoO1PgrhrHm1e8gHAamAiA3zB_m3Jo_DhZoN3DI7pamNEIqZ60W2BtchDRO6aW4-Eej_nlsp1Y1g19DjP7LH1Sl1wNJx0Oo2B8Dx5P3ZYzeluyP_j23DeIF_NiBnIi7QnGJKG_/s640/pwm.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">PWM Signal output from RC Receiver</td></tr>
</tbody></table>
<h4>
Replacing UHF Radio Link with IP Communication </h4>
Main objective here is to replace the UHF radio link (2.4 Ghz) with IP communication network. Instead of using RC Transmitter we will use a regular PC gaming joystick to send control commands to Quadcopter through IP network. The commands are received by LTE dongle connected to Raspberry pi computer which converts these commands to PWM signals. The PWM signals are then used by CC3D flight controller to control the motion of flight. See the below figure for end to end communication path<br />
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<div class="separator" style="clear: both; text-align: center;">
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhz7BrdSemixD047svWb99OJrJUtdAySjqnb6CxbTyCnWLONjU6JOq89hnRQLoOTSRu2Rhsl_4JpAmBzwanHp8KPb82u5_Sh_ljROwUFfyL5MuQFrsdAU9Hh6sakjKSThH3r-BXbvtgc30W/s1600/final.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="216" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhz7BrdSemixD047svWb99OJrJUtdAySjqnb6CxbTyCnWLONjU6JOq89hnRQLoOTSRu2Rhsl_4JpAmBzwanHp8KPb82u5_Sh_ljROwUFfyL5MuQFrsdAU9Hh6sakjKSThH3r-BXbvtgc30W/s640/final.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">LTE Quadcopter</td></tr>
</tbody></table>
<h4>
</h4>
Note: If you are not familiar with raspberry pi, please visit https://www.raspberrypi.org/ to get some understanding .To put it short, It is is wonderful cheap little computer that can be used to make home media center, VPN, make robot and many more interesting projects. You can use almost any language on RPi though I always prefer to use Python as being very easy , high level and dynamic programming language<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgy1raB1zg7mcftOYUDtU9mEV2Id9f1wgtWpDAf-bv8bJX8Ovk5scdigKsxzAnSovQsidKrWAoLmtLxJ4ljxDZ8GmTO4tJkzY_cY901-hucm_juygEflg6D6ceye_Lb1Bn9hFUmXASafr8R/s1600/raspberrypi2.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgy1raB1zg7mcftOYUDtU9mEV2Id9f1wgtWpDAf-bv8bJX8Ovk5scdigKsxzAnSovQsidKrWAoLmtLxJ4ljxDZ8GmTO4tJkzY_cY901-hucm_juygEflg6D6ceye_Lb1Bn9hFUmXASafr8R/s1600/raspberrypi2.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Raspberry Pi 2</td></tr>
</tbody></table>
<h4 style="clear: both;">
Installing LTE modem on Raspberry Pi</h4>
<div>
I used Sakis3g script to install the drivers and application to configure the LTE modem. You can find more information at http://www.sakis3g.com/<br />
<br /></div>
<h4 style="clear: both;">
How to communicate with LTE Dongle Private IP</h4>
One of the issue with LTE modem (dongle) is that it will be assigned private IP and will use Network Address Translation (NAT) to communicate to external world. NAT is the process where firewall assigns a public address to a network device inside private network. NAT save on the IP addresses as every network device (LTE dongle in our case) does not need a public address, and also it would hide these private devices from the outside world. For our quadcopter LTE dongle, it means that we wont be able to use the IP which is assigned to it in order to establish any IP communication to it. To overcome this problem we have to use our home Wifi router's port forwarding feature (application of NAT). Since our router's public IP is known to us ,therefore forwarding packet to our home PC coming from LTE quadcopter will not be an issue.<br />
<br />
Let's assume that LTE dongle is assigned private IP 10.10.10.50 by the LTE network, Let's also assume our home computer has private of 192.168.10.44 which was assigned by the Wifi router. Secondly our Wifi router has public IP of 173.75.180.60 which is known to us. We use TCP port 50050 for any communication from LTE quadcopter to Home PC. Now all we have to do is defining port forwarding table in our home wifi router. The basic rule that needs to be defined is to forward all incoming TCP packet with destination port of 50050 to our controller PC which has IP 192.168.10.44 and you are all set to have IP communication between Quadcopter and our home PC</div>
<div>
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Now here is how our end to end Communication will work <br />
<br />
- Using Python's socket module function, Raspberry Pi (with LTE modem connected) will open a TCP connection to a port 50050 and IP 173.75.180.60. <br />
<br />
- Python Socket Module on our home pc waits until a client connects to the port you specified<br />
<br />
- Our home router forwards all incoming TCP packet with destination port of 50050 to our controller PC which has IP 192.168.10.44<br />
<br />
- Once a socket is open, you can read from it like any IO object.<br />
<br />
Below is the very basic python code that I used to do the communication between Raspberry Pi and home Computer as explained above. The code is just to give you a starting point while you can optimize the code below to have much better stabilized flight :) <br />
<br />
<h4 style="clear: both; text-align: left;">
Python Code on PC side</h4>
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Python Code on Raspberry Pi side</h4>
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<h4>
Video Streaming from Quadcopter to Home Wifi Network </h4>
Currently I am having trouble transmitting video from Quadcopter to Home Computer. I used netcat utility to do the streaming but it makes RPi reset every time. I believe I need to provide separate power bank. I will give update on it once successful, hopefully soon.<br />
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Unknownnoreply@blogger.com102tag:blogger.com,1999:blog-8240614391505589446.post-22196512715982186392016-02-13T13:39:00.000-06:002016-02-16T10:41:02.678-06:00LTE Physical Uplink Control Channel (PUCCH)Physical Uplink Control Channel (PUCCH) carries Uplink Control Information (UCI) which is basically bits and pieces of information that eNB
requires from UE in order to understand what UE (user equipment) needs and
carries other information like channel quality that UE is seeing in downlink, etc<br />
<br />
UCI is divided into three main sub branches i.e. Channel State Information (CSI), Scheduling Requests (SR) and HARQ ACK/NACK shown with some details as below<br />
<br />
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<b>Note:</b> 3GPP Release 8 and Release 9 UEs cannot transmit PUCCH and PUSCH on same TTI. If UE has to transmit UCI and data simultaneously within
the same TTI, then PUSCH is used for UCI transmission but Release 10
allows simultaneous transmission of PUSCH and PUCCH <br />
<br />
3GPP has defined different PUCCH formats to transfer different combinations
of the information as can be seen in below table <br />
<br />
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<br />
A single PUCCH transmission always occupies 2 Resource Blocks <br />
Frequency diversity of those two RBs is ensured by slot based PUCCH frequency hopping (See figure below) Each pair of RBs allocated to PUCCH can be used simultaneously by multiple UEs by <br />
using different cyclic shifts and different orthogonal spreading codes<br />
<br />
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<br />
<br />
<h4>
PUCCH Capacity Calculations</h4>
Remember every RRC Connected UE needs to send CQI reports periodically!<br />
<br />
Basic formula to calculate how many UEs (RRC Connected) are supported by eNB is<br />
<br />
Number of UEs = Number Resource blocks used for CQI reporting x UEs Multiplexed per Resource Blocks x CQI reporting periodicity<br />
<br />
The CQI reporting periodicity (in subframes) are determined based on the parameter <br />
cqi-pmi-ConfigIndex given in Table 7.2.2-1A for FDD in 3GPP TS 36.213<br />
<br />
<b>Example</b> <br />
Lets assume we have reserved 5 resource blocks (eNB Parameter) for CQI reporting and 6 UEs can be multiplexed per resource blocks. Also lets assume that CQI periodicity is 40 ms then the total number of RRC Connected UEs that eNB can support is as below<br />
<br />
Number of UEs= 5 * 6 * 40 = 1200<br />
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<b>Note:</b> This is not the only limitation for how many RRC Connected users eNB can support. The above capacity calculation is just to explain the requirement atleast from UE CSI reporting perspective<br />
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<![endif]-->Unknownnoreply@blogger.com46tag:blogger.com,1999:blog-8240614391505589446.post-30089009640873190902015-10-24T14:13:00.000-05:002016-01-27T12:58:36.999-06:00Connected Mode DRX <br />
We know that 2G and 3G terminal uses discontinuous reception in idle mode. In LTE the tradition has continued and we have similar DRX in idle mode but in addition to that we also have DRX in RRC mode. In LTE, when there is no data to receive or transmit in RRC connected mode, UE would switch off its transceiver for a very short interval. It will start similar "wake up and sleep " cycle. During the wake up period, it will keep monitoring PDCCH channel for UL or DL grants whereas the sleep periods will improve the battery savings <br />
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<h3>
Without Connected Mode DRX </h3>
The main goal of Connected mode DRX is to minimize battery
consumption by discontinuous monitoring of PDCCH channel. Without DRX, UE has to monitor PDCCH channel every time. This results in high battery consumption as shown below<br />
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<h3>
With Connected Mode DRX </h3>
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With DRX enabled in connected mode, UE only monitors PDCCH channel when it is awake during the sleep/wakeup cycles as seen below. During the sleep time, UE doesn't monitor PDCCH channels which results in energy savings. All the DL grants are delayed to nearest wake up period<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbwB8DKAJCZ7KwkVFi3sW7Xjk-FHR-OxeiYDVCvf3aT9_WYwbLbOQN1l01KZNUEzso2exZXDZIzXvMD3swMNnz9v9YX4rpySbeUcdAFvz5OWiz1ACGRSulinT4U5XyAFfe7VP4pA_1vF86/s1600/WITH+DRX.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="388" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjbwB8DKAJCZ7KwkVFi3sW7Xjk-FHR-OxeiYDVCvf3aT9_WYwbLbOQN1l01KZNUEzso2exZXDZIzXvMD3swMNnz9v9YX4rpySbeUcdAFvz5OWiz1ACGRSulinT4U5XyAFfe7VP4pA_1vF86/s640/WITH+DRX.png" width="640" /></a></div>
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<h3>
Important DRX Parameters/Timers </h3>
Some of the important parameters used in configuring the DRX for UE are shown below. The parameters are transferred to UE through RRC reconfiguration message<br />
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<h3>
</h3>
<h3>
</h3>
<h3>
Basic Scenario</h3>
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To better understand these parameters, see the below picture which shows each parameter</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjCtyufn1-D1B63IUP6rjPJdbsSsKVX6FNJgAcq1J5fpcKB00j9gnkcfx_ofr3Iw3jAUQIfvUMEdkFtcv0hTnDlo0NQrV34bBiMuKKNctagAx2dcOozUB799NPXZ2GNtaXunvq60ftyR3y/s1600/Basic+DRX.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="384" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjCtyufn1-D1B63IUP6rjPJdbsSsKVX6FNJgAcq1J5fpcKB00j9gnkcfx_ofr3Iw3jAUQIfvUMEdkFtcv0hTnDlo0NQrV34bBiMuKKNctagAx2dcOozUB799NPXZ2GNtaXunvq60ftyR3y/s640/Basic+DRX.png" width="640" /></a></div>
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<ol>
<li> UE is in RRC Connected mode and is continuously monitoring PDCCH. At this point, there is DL Grant and downlink data. The DRX inactivity timer and the main RRC Inactivity timer are restarted</li>
<li>There is UL grant for UE. With DL Grant both DRX and RRC inactivity timers are restarted. 4 ms later UE sends data in uplink</li>
<li>The DRX Inactivity timer is expired since there were no further grants in uplink or downlink. Though UE was constantly monitoring PDCCH. UE now enters the short DRX cycle. The battery savings have just started</li>
<li> The DRX short cycle timer got expired therefore UE will end up its short DRX cycle and enter the long DRX cycle</li>
<li>The main RRC inactivity timer got expired since there was no activity in uplink or downlink for the duration for RRC Inactivity timer. The UE will go to RRC IDLE state. In idle state UE will use paging DRX cycle</li>
</ol>
<h3>
</h3>
<h3>
</h3>
<h3>
HARQ Retransmissions Scenario</h3>
In the above basic scenario it may seem complicated to include HARQ retransmission's scenarios, so here is another example below <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe4DTnWfFatmsJRHHgcdObWoD0wmGSJZITSuvRZ7lkX3A6nKn0Xk0zR3AGzCTl15TYf_zSG_0n34R84-xagxd6URMp-0J6xP8uuitDXAuWjsWp8DJdqLkRiqd2mKu_5TTGr6AI8noyhJ5z/s1600/retransmission.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="484" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhe4DTnWfFatmsJRHHgcdObWoD0wmGSJZITSuvRZ7lkX3A6nKn0Xk0zR3AGzCTl15TYf_zSG_0n34R84-xagxd6URMp-0J6xP8uuitDXAuWjsWp8DJdqLkRiqd2mKu_5TTGr6AI8noyhJ5z/s640/retransmission.png" width="640" /></a></div>
<ol>
<li> UE is in RRC Connected mode and is continuously monitoring PDCCH channel.
At this point, there is DL Grant and downlink data. The DRX and RRC inactivity timer is restarted ( RRC Inactivity not shown here)</li>
<li>There is UL grant for UE. With DL Grant both DRX and RRC inactivity timers are restarted 4ms later UE sends data in uplink. And after additional 4ms later ACK is sent by eNB</li>
<li>There is DL grant for UE with DL data. For some reason UE is not able to decode the data. 4ms later UE will send NACK towards eNB. Harq RTT timer is started which has fixed duration of 8ms. Now UE is expecting retransmission in downlink</li>
<li>HARQ RTT got expired which will trigger the DRX retransmission timer as the retransmission is expected</li>
<li>There is DL grant with retransmission data. This time UE is able to decode it. 4ms later UE sends ACK in uplink. Note DL grant for retransmission data does not restart DRX inactivity timer</li>
<li>DRX retransmission timer expires and UE enters the short DRX cycle</li>
</ol>
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<span style="font-size: large;"><b>Key points:</b></span><br />
<ul>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPfzFiwbadyHBLw48b8LB0696BxWY1T_4nOzca2n6xQFsuB9n77R-NCNsfeDEW3W1XsFqdEiEbc8EBABdEKsgq_ZYqEcAcv2d7kGFIZ0Bgdue3ljkJ1igQIeCN3LEz4ydkfYmJ5wEDwC9_/s1600/mac+ce.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="179" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPfzFiwbadyHBLw48b8LB0696BxWY1T_4nOzca2n6xQFsuB9n77R-NCNsfeDEW3W1XsFqdEiEbc8EBABdEKsgq_ZYqEcAcv2d7kGFIZ0Bgdue3ljkJ1igQIeCN3LEz4ydkfYmJ5wEDwC9_/s200/mac+ce.png" width="200" /></a>
<li><span style="font-size: small;"> DRX cycles are synchronized at UE and eNB side i.e. eNB knows when UE is in DRX sleep or awake period so that it can schedule UE accordingly</span></li>
<li><span style="font-size: small;">When UE is in DRX sleep state, it cannot read PDCCH channel therefore, the downlink grants must be delayed to nearest wake cycle as eNB is already aware of this UE DRX cycle. The introduces delay in dowlink transmission </span></li>
<li><span style="font-size: small;">Uplink transmission is not affected as UE can send SR in uplink whenever it wants i.e. UE is in DRX sleep period and it has uplink data so it will just wake up and send SR to receive UL grants from eNB. </span></li>
<li><span style="font-size: small;">Other than the timers/parameters mentioned above, eNB MAC can also control UE DRX by transmitting MAC CE DRX commands</span></li>
</ul>
<span style="font-size: small;"> </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGJJEXgIxOaUAH-G5z-_79QuzKdAUDOB6CDD5a8U1yYtNJXkUA6SFhP9hnXtABMRWhmkBgAayw0wumSJCvyQOs9S8YxFDRQDAX2J-QxbDJDTHiucU1PXJ4zJ6FV104x_B6LuHRbUVymeOL/s1600/DRX.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br /></a></div>
<br />Unknownnoreply@blogger.com131tag:blogger.com,1999:blog-8240614391505589446.post-26328506785450459152015-10-08T10:57:00.002-05:002015-10-08T14:53:09.171-05:00LTE in Unlicensed Spectrum (LTE-U)LTE in Unlicensed spectrum (LTE-U) is one of the hot topics in 2015
telecom industry. LTE-U extends the benefits of LTE and LTE Advanced to
unlicensed spectrum, enabling mobile operators to offload data traffic
onto unlicensed frequencies more efficiently.<br />
<br />
LTE-U also poses major challenges to WiFi as both will
operate in an unlicensed and un-controlled spectrum. However, various techniques have
been developed to share the unlicensed spectrum fairly between LTE and WiFi
technologies. Please check below white paper from Nokia for more details on LTE-U<br />
<br />
<iframe height="600" src="https://drive.google.com/file/d/0B-0WgooR2xXvTGJzOTBFRkxwMWc/preview" width="840"></iframe>
Unknownnoreply@blogger.com24tag:blogger.com,1999:blog-8240614391505589446.post-71973121722534433092015-05-22T10:38:00.001-05:002016-02-16T10:07:31.291-06:00RSRP, RSSI and RSRQ<div dir="ltr" style="text-align: left;" trbidi="on">
In LTE network, UEs need to measure signal strength of its own and neighbor cells constantly, during idle, connected mode or handovers in order to keep the signal quality constant. UE measures RSRP and RSRQ in LTE<br />
<br />
<h4>
Reference Symbol Received Power (RSRP):</h4>
<ul>
<li>RSRP is the linear average of the downlink reference signals across the channel bandwidth </li>
<li>RSRP provides information about signal strength and gives no indication of signal quality </li>
<li>RSRP measurements are used in handover, cell selection and cell re-selections </li>
<li>The reporting range of RSRP is defined from -140 dBm to -44 dBm with 1 dB resolution as shown in table below</li>
</ul>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPzJGwRskG4EN9xq1YNI7IJPP4scSbN-Evly4H9ILB7SQHhGNKeQEJfO_VnY6lOJ-nq5AfEchwijad7xdrziJ1uFGUwJGJRBxb9jfa782iAwLjQDJYEwMDhoU49ZdhQM2omsm41OuHsipm/s1600/RSRP+table.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPzJGwRskG4EN9xq1YNI7IJPP4scSbN-Evly4H9ILB7SQHhGNKeQEJfO_VnY6lOJ-nq5AfEchwijad7xdrziJ1uFGUwJGJRBxb9jfa782iAwLjQDJYEwMDhoU49ZdhQM2omsm41OuHsipm/s640/RSRP+table.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">RSRP measurement report mapping (3GPP Reference: TS 36.133)</td></tr>
</tbody></table>
<br />
<h4>
Received Signal Strength Indicator (RSSI):</h4>
<ul>
<li>RSSI represents the total received wide-band power by UE</li>
<li>RSSI is measured only in symbols containing Reference signals </li>
<li>RSSI includes power from serving cell as well as co-channel interference and noise</li>
<li>RSSI helps in determining interference and noise information </li>
<li>RSSI is never reported by UE</li>
</ul>
<blockquote style="border: none; margin: 0 0 0 40px; padding: 0px;">
</blockquote>
<br />
<h4>
Reference Signal Received Quality (RSRQ):</h4>
<ul>
<li>RSRQ indicates quality of received reference signal. RSRQ measurement and calculation is based on RSRP and RSSI since RSRP determines signal quality and RSSI determines co-channel interference and noise. RSRQ formula is shown below (N represents number of resource blocks)</li>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwwn3L-39KQoiIKgqafTKm6RK6YpyTu8SOpzciXcPhqj68bVZNRYQukNchlGM02nNHe1FcXOE6_jTAurt8HRv-VxWTFlP1r2R3uRuMoKs67o4pm6psw8hb6g3o62_t_8uKODbo9mEGbTF7/s1600/RSRQ+formula.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwwn3L-39KQoiIKgqafTKm6RK6YpyTu8SOpzciXcPhqj68bVZNRYQukNchlGM02nNHe1FcXOE6_jTAurt8HRv-VxWTFlP1r2R3uRuMoKs67o4pm6psw8hb6g3o62_t_8uKODbo9mEGbTF7/s1600/RSRQ+formula.png" /></a></div>
<li>The reporting range of RSRQ is defined from -19.5 dB to -3 with 0.5 dB resolution</li>
</ul>
<ul>
</ul>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWHkClVDtBgr8a4UdBGrVcV3kKATCw6214lXTQkwvaLSwhq-IOgaasEFw2eLl0Dmi4000jK9bm5P9aY7xsh6zfaOX66Uxbrcx3dx6Z3oC0z1fuIbVjJD9aFKM1je-gbG3eOtDat3ma1ZXQ/s1600/RSRQ+table.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="160" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWHkClVDtBgr8a4UdBGrVcV3kKATCw6214lXTQkwvaLSwhq-IOgaasEFw2eLl0Dmi4000jK9bm5P9aY7xsh6zfaOX66Uxbrcx3dx6Z3oC0z1fuIbVjJD9aFKM1je-gbG3eOtDat3ma1ZXQ/s640/RSRQ+table.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">RSRQ measurement report mapping (3GPP Reference: TS 36.133)</td></tr>
</tbody></table>
<br />
<h4>
Example</h4>
<div>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj9IvX97A6rs0hx_TOLRewX-pCPC3WJjsvkppgocAkfJi0oWCxcL6RsFlo0nHsFgwZqiNNfMzGgGUMjBBL58OyXrsODG9iQ9SGC1VFZEr1ZcV1h7vAffCCwAVstGIDkZnrKT-wbPn4PmmtQ/s1600/RB3.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj9IvX97A6rs0hx_TOLRewX-pCPC3WJjsvkppgocAkfJi0oWCxcL6RsFlo0nHsFgwZqiNNfMzGgGUMjBBL58OyXrsODG9iQ9SGC1VFZEr1ZcV1h7vAffCCwAVstGIDkZnrKT-wbPn4PmmtQ/s320/RB3.png" width="211" /></a>Lets try to calculate RSRP, RSSI and RSRQ for one very simple case of one resource block with 12 sub carriers and 0.5 ms in time domain. For sake of simplicity, lets assume the power of reference symbols (shown by red square) and power of other symbols carrying other data channels (shown by blue square) is same i.e. 0.021 watt<br />
<br />
<br />
Since RSRP is linear average of downlink reference signal for given channel bandwidth therefore<br />
<b>RSRP = 10*log (0.021*1000) = 13.2 dBm</b><br />
<br />
While RSSI is total received wide-band power. Therefore we have to add power of all 12 carriers in the given resource block<br />
<b>RSSI = 10*log(0.021*1000)+10*log(12) = 24 dBm</b><br />
<br />
RSRQ is now simple ratio of RSRP to RSSI with N=1<br />
<b>RSRQ = 10*log(0.021/(12*0.021)) = -10.79 dB</b><br />
<b><br /></b>
<b><br /></b></div>
<div>
<h4>
Why do we use dBm as a unit of Power</h4>
We use decibels-milliwatts to measures power levels in telecommunication and other fields instead of Watt. The reason to use logarithmic scale is that it helps in reducing massive values to smaller number<br />
<br />
<b>Example :</b> 0.00000000000080 watt which apparently looks very small value but<br />
can still be received by antenna. The logarithmic value is just -91 dbm by using below formula<br />
P (dBm) = 10 x Log (1000*P)<br />
<br />
<h4>
</h4>
<h4>
dBm vs dB</h4>
</div>
<div>
dB is ratio between two power values while dBm is used to express an absolute value of power. So when we mention RSRP and RSSI we shall always use dBm since we are talking about absolute power values but we need to use dB with RSRQ since it is the ratio of RSRP to RSSI<br />
<br /></div>
</div>
Unknownnoreply@blogger.com71tag:blogger.com,1999:blog-8240614391505589446.post-78971738231652551162015-03-16T21:02:00.000-05:002015-05-24T01:38:49.820-05:00Nokia Networks Technology Vision 2020<iframe width="568" height="340" src="https://www.youtube.com/embed/67by_UNcl4k" frameborder="0" allowfullscreen></iframe>Unknownnoreply@blogger.com9tag:blogger.com,1999:blog-8240614391505589446.post-68673725542877244352015-02-26T18:55:00.000-06:002015-03-02T09:58:29.865-06:00Overview of LTE 3GPP releases<!--[if gte mso 9]><xml>
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<br />
<h4>
<b><span style="font-family: 'Times New Roman';">Release 8 - LTE Introduced </span></b></h4>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><i><span style="font-family: 'Times New Roman';">Release frozen in Dec
2008 </span></i></b><span style="font-family: 'Times New Roman';"><o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">It was 3GPP release 8 when LTE was introduced
for the very first time. All the
releases following only enhanced the technology.<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">Based on release 8 standardization, following
were the main achievements<o:p></o:p></span></div>
<ul type="disc">
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">High peak data rates : Up to 300 Mbps in downlink and
75 Mbps in uplink when using 4x4 MIMO and 20 MHz bandwidth<o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">High spectral efficiency <o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">Flexible bandwidths: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15
MHz and 20 MHz<o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">Short round trip time: 5 ms latency for IP packets in
ideal radio conditions<o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">Simplified Architecture<o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">OFDMA in downlink and SC-FDMA in uplink<o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">All IP network <o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">MIMO multiple antenna scheme<o:p></o:p></span></li>
<li class="MsoNormal"><span style="font-family: 'Times New Roman';">Operation in paired (FDD) and unpaired spectrum (TDD)<o:p></o:p></span></li>
</ul>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<h4>
<b><span style="font-family: 'Times New Roman';">Release 9 - Enhancement to LTE</span></b></h4>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><i><span style="font-family: 'Times New Roman';">Release frozen in Dec
2009</span></i></b><span style="font-family: 'Times New Roman';"><o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">The initial enhancements were included to LTE in
release 9. These were in fact the improvements which were left behind from
release 8 or perhaps provided some minor improvements. These improvements are
listed below with brief description<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">PWS (Public Warning
System):</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">Public should
always receive timely and accurate alerts related to natural disasters or other
critical situations. Commercial Mobile Alert System (CMAS) was introduced in
release 9 in addition to ETWS introduced in release 8<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Femto Cell:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">Femto cell is basically a small cell used in
offices or homes and connected to providers’ networks through landline
broadband connection. 3G Femto cells are deployed around world and in order for
LTE users to take advantage of femto cell, new requirements were added to
release 9<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';"><br />
MIMO Beam forming:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">Beamforming is used to
increase cell edge throughput by directing beam towards specific UE by position
estimation at eNB.<b> </b>In release 8, LTE supported single layer beam
forming based on user-specific Reference Symbols. In release 9, single layer
beam forming has been extended to multilayer beam forming<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Self Organizing Networks
(SON):</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">SON means self
installation, optimization and healing of networks in order to reduce manual
work and cost associated with technical support. The idea of SON was
introduced in release 8 though the focus was more towards eNBs self
configuration where as in release 9, requirements for self optimization were
also added<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">eMBMS:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">With Multimedia broadcast Multicast
Services (MBMS), operators have capability to broadcast services over LTE
network. The idea is not novel to the LTE and has been used in legacy networks as well but
for LTE, the MBMS channel has evolved from data rate and capacity perspective.
The MBMS was already defined at physical layer in release8 but with release 9,
higher layer and network layer aspects were completed<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">LTE Positioning:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">Three position methods are specified in LTE
release 9 i.e. Assisted GPS (A-GPS), Observed Time difference of arrival
(OTDOA) and Enhanced Cell ID (E-CID). The goal is to improve the accuracy of
user locations in case of emergency scenarios where the user itself is unable
to disclose his whereabouts<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<h4>
<b><span style="font-family: 'Times New Roman';">Release 10 - LTE Advanced</span></b></h4>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><i><span style="font-family: 'Times New Roman';">Release Frozen in March
2011</span></i></b><span style="font-family: 'Times New Roman';"><o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">THE LTE-Advanced specifications in release 10
includes significant features and improvements to fulfil ITU IMT-Advanced requirements
which sets higher speeds than what UE can achieve from 3GPP release 8
specifications. Some key requirements laid down by IMT-Advanced are as below<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- 1 Gbps DL / 500 Mbps UL throughput<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- High spectral efficiency<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- Worldwide roaming<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">Following are some significant improvements in release 10<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Enhanced Uplink multiple
access:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">Release 10 introduces
clustered SC-FDMA in uplink. Release 8 SC-FDMA only allowed carriers along
contiguous block of spectrum but LTE-Advanced in release 10 allows
frequency-selective scheduling in uplink<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">MIMO enhancements:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">LTE-Advanced allows upto 8x8 MIMO in downlink
and on the UE side it allows 4X4 in uplink direction<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Relay Nodes:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">In order to decrease coverage loop holes, Relay
nodes are one of the features proposed in release 10. The relay nodes or low
power enbs extending the coverage of main eNB in low coverage environment. The
relay nodes are connected to Donor eNB (DeNB) through Un interface. <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';"><br />
enhanced inter-cell interference coordination (eICIC): </span></b><span style="font-family: 'Times New Roman';">eICIC introduced in 3GPP release 10 to deal with
interference issues in Heterogeneous Networks (HetNet). eICIC mitigates
interference on traffic and control channels. eICIC uses power, frequency
and also time domain to mitigate intra-frequency interference in heterogeneous
networks<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Carrier Aggregatio</span></b><span style="font-family: 'Times New Roman';">n</span><span style="font-family: 'Times New Roman';"> </span><b><span style="font-family: 'Times New Roman';">(CA)</span></b><span style="font-family: 'Times New Roman';">: CA introduced in
release 10 is a cost effective way for operators to utilize their fragmented
spectrum spread across different or same bands in order to improve end user
throughput as required by IMT-Advanced. User throughput is increased by sending
data simultaneously over two or more carriers. LTE-Advanced supports bandwidths
up to 100 MHz formed by combining up to five 20MHz component carriers.
Contiguous and non-contiguous carriers may be aggregated<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Support for Heterogeneous
Networks:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">The combination of large
macro cells with small cells results in heterogeneous networks. Release 10
intended to layout the detail specification for heterogeneous networks<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">SON Improvements:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">Release 10 provides enhancements to SON features
introduced in release 10 which also considers self healing procedures</span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br />
<br />
<br /></div>
<h4>
<b><span style="font-family: 'Times New Roman';">Release 11 - Enhancement to LTE Advanced</span></b></h4>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><i><span style="font-family: 'Times New Roman';">Release Frozen in
september 2012</span></i></b><span style="font-family: 'Times New Roman';"><o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">Release 11 includes enhancements to LTE Advanced
features standardized in release 10. Some of the important enhancements are
listed below <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Carrier Aggregation
enhancements</span></b><span style="font-family: 'Times New Roman';">: Following are the
major enhancements to carrier aggregation in release 11<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- Multiple timing advances (TAs) for uplink
carrier aggregation<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- Non contiguous intra band carrier aggregation<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- physical layer changes for carrier aggregation
support in TDD LTE<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Coordinated multipoint
transmission and reception (CoMP):</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">With CoMP the transmitter can share data load even if they are not
collocated. Though they are connected by high speed fiber link<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">ePDCCH:</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">New enhanced PDCCH introduced in 3GPP release 11
to increase control channel capacity. ePDCCH uses PDSCH resources for
transmitting control information unlike release 8 PDCCH which can only use
control region of subframes<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Network based
Positioning:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">In release 11, support
for uplink positioning is added by utilizing Sounding reference signals for time
difference measurements taken by many eNBs. <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Minimization of drive
test (MDT):</span></b><b><span style="font-family: 'Times New Roman';"> </span></b><span style="font-family: 'Times New Roman';">Drive tests are always
expensive. To decrease dependency on drive tests, new solutions introduced
which are independent of SON though much related. MDT basically relies on
information provided by UE<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Ran overload control for
Machine type communication:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">For machine type devices
new mechanism has been specified in release 11 where network in case of mass
communication from devices can bar some devices to send connection
request to network<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">In Device Co Existence:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">Now a days, all mobile devices would usually
carry multi radio transceivers like for LTE, 3G, Bluetooth, WLAN etc. Now this
co existence results in interference. To mitigate this interference, release 11
has specified solutions as mentioned below<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- DRX based time domain solutions<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- Frequency domain solutions<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<span style="font-family: 'Times New Roman';">- UE autonomous denials <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Smartphone Battery
saving technique:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">Many applications on
smartphones generate background traffic which consumes battery power. Release
11 specifies a method where UE can inform network whether it needs to be
operated in battery saving mode or normal mode and based on UE request network can
modify DRX parameters<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<h4>
<b><span style="font-family: 'Times New Roman';">Release 12 - Further enhancement to LTE Advanced</span></b></h4>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><i><span style="font-family: 'Times New Roman';">Release Frozen in June
2014</span></i></b><span style="font-family: 'Times New Roman';"><o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Small cells
enhancements:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">Small cells were
supported since beginning with features like ICIC and eICIC in release 10.
Release 12 introduces optimization and enhancements for small cells including deployments
in dense areas. Dual connectivity i.e. inter-site carrier aggregation between
macro and small cells is also a focus area<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Carrier aggregation
enhancements:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">Release 12 now allows
carrier aggregation between co-located TDD and FDD carriers. In addition to
carrier aggregation between TDD and FDD, there is also now three carrier aggregations
possible for total of 60 Mhz spectrum aggregated<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Machine Type communication
(MTC):</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">Huge growth is expected
in machine type communication in coming years which can result in tremendous
network signaling, capacity issues. To cope with this, new UE category is
defined for optimized MTC operations<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Wifi integration with
LTE:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">With integration between
LTE and Wifi, operators will have more control on managing WiFi sessions. In
release 12, the intent is to specify mechanism for steering traffic and network
selection between LTE and WiFI <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">LTE in unlicensed spectrum:</span></b><span style="font-family: 'Times New Roman';"> An LTE operation in unlicensed spectrum is
one of the study items in release 12. Operations in Bandwidth rich unlicensed
spectrum brings many benefits to operators like increase in network capacity,
load and performance<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal">
<br /></div>
<h4>
<b><span style="font-family: 'Times New Roman';">Release 13 - Meeting the growing throughput demand</span></b></h4>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><i><span style="font-family: 'Times New Roman';">Ongoing - Release expected to be frozen in Dec 2015</span></i></b><span style="font-family: 'Times New Roman';"><o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Carrier Aggregation
enhancements:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">The goal in release 13
is to support carrier aggregation of upto 32 CC (component carriers) where as in release 10, the carrier
aggregation was introduced with support of only upto 5 CC.<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">enhancements for
Machine-Type communication (MTC):</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">Continuing from release 12, there are further enhancements in MTC,
a new low complexity UE category is being defined to provide support for
reduced bandwidth, power and support long battery life. <o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">LTE in unlicensed spectrum enhancements:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">The focus in release 13
is the aggregation of primary cell from licensed spectrum with secondary cell
from unlicensed spectrum to meet the growing traffic demand<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Indoor Positioning:</span></b><span style="font-family: 'Times New Roman';"> In release 13 there is w</span><span style="font-family: 'Times New Roman';">ork going on improving existing methods of indoor
positioning and also exploring new positioning methods to improve indoor
accuracy<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">Enhanced multi-user
transmission techniques:</span></b><span style="font-family: 'Times New Roman';"> Release 13 also covers p</span><span style="font-family: 'Times New Roman';">otential enhancements
for downink multiuser transmission using superposition coding<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<br /></div>
<div class="MsoNormal" style="margin-bottom: 0.0001pt;">
<b><span style="font-family: 'Times New Roman';">MIMO enhancements:</span></b><span style="font-family: 'Times New Roman';"> </span><span style="font-family: 'Times New Roman';">Upto 8 antenna MIMO systems are currently
supported, the new study in this release will look into high-order MIMO systems with up to 64
antenna ports<span style="font-size: 13.5pt;"><o:p></o:p></span></span></div>
<!--EndFragment-->Unknownnoreply@blogger.com10tag:blogger.com,1999:blog-8240614391505589446.post-34471466523163610442015-01-21T18:23:00.001-06:002015-01-23T13:40:34.258-06:00Carrier aggregation (CA) in LTE<div dir="ltr" style="text-align: left;" trbidi="on">
<h3>
<br />Background </h3>
The demand for higher peak and higher average throughput in mobile devices has always existed. Services like YouTube, video calls and live streaming require high data speeds. In order to meet the current throughput demands and increase LTE bandwidth, a very promising feature has been introduced in LTE Advanced (3GPP rel 10 onwards) known as carrier aggregation.<br />
<br />
<h3>
Introduction</h3>
<br />
<ul>
<li>CA is a cost effective way for operators to utilize their fragmented spectrum spreaded across different or same bands in order to improve end user experience</li>
<li>The basic idea of carrier aggregation is to increase user throughput by sending data simultaneously over two carriers</li>
<li>Regular cell known as primary cell (PCell) is combined/aggregated with logical cell (known as Secondary cell or SCell), serving the same cell site. Each aggregated carrier is known as component carrier, CC</li>
<ul>
<li><b>Example</b>: Operator A has a LTE network deployed using its 5MHz spectrum in band 3. Maximum throughput available in any cell with 2x2 MIMO is 36.2 Mbps. Operator A also has 5 MHz unused spectrum in band 5. Now the throughput can be doubled by combining both 5 MHz spectrums from two different bands using carrier aggregation </li>
</ul>
</ul>
<ul>
<li>The PCell is the main carrier with which UE will communicate i.e. RRC/NAS messages exchange, measurement, RACH etc. PCell always remains active in RRC Connected mode while SCell is activated/deactivated whenever required e.g. when high throughput is required</li>
<li>PCell has PDCCH in downlink and PUCCH in uplink but SCell has only PDCCH in downlink</li>
<li>'RRC Connection Reconfiguration' procedure is used to add/remove SCell</li>
<li>As per 3GPP standardization, maximum of five component carrier can be aggregated with each component carrier having bandwidth of 1.4, 3, 5, 10, 15 or 20 MHz. The maximum possible aggregated bandwidth can be 100 MHz (20 x 5)</li>
</ul>
<br />
<br />
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</div>
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</div>
<div class="separator" style="clear: both; text-align: center;">
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<br />
<br />
<ul>
<li>CA aggregation is available for both FDD and TDD and the feature is backward compatible which means that the users from rel8 and rel9 can connect to CA capable site by utilizing part of total bandwidth</li>
<li>The commercial deployment of carrier aggregation has already started since 2013</li>
</ul>
Three are three types of carrier aggregation<br />
<br />
<b>Intra-Band Contiguous CA</b><br />
<div>
When two or more component carriers belong to same frequency band and they are contiguous. There must be spacing of 300 khz x N between two contiguous component carriers (N is integer). This is the simplest form of CA aggregation from operators perspective</div>
<div>
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
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<br />
<b>Intra-Band Non-Contiguous CA</b><br />
<div>
When two or more component carriers belong to same frequency band but they are separated by one or more frequency gaps</div>
<div>
<br /></div>
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<br />
<b>Inter-Band Non-Contiguous CA</b><br />
<div>
When two or more component carriers belong to different frequency bands.<br />
This type of CA is implemented by operators who own fragmented spectrum</div>
<div>
<br /></div>
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<br />
<br />
<div>
<h3>
</h3>
</div>
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</div>
Unknownnoreply@blogger.com18tag:blogger.com,1999:blog-8240614391505589446.post-4402060947270095322015-01-08T15:08:00.002-06:002016-04-16T20:03:46.129-05:00RRC Connection Establishment in LTE<div dir="ltr" style="text-align: left;" trbidi="on">
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<h3>
Background</h3>
The first thing UE does after switching on is to synchronize to each frequency and check whether this frequency is from the right operator to which it wants to connect to. UE does this by going through very initial <a href="http://4g-lte-world.blogspot.com/2012/06/primary-and-secondary-synchronization.html">synchronisation process</a>. Once synchronized, UE reads the <a href="http://4g-lte-world.blogspot.com/2012/06/master-information-block-mib-in-lte.html">master information block</a> and System information blocks to check if this is the right PLMN. Lets assume it finds that PLMN value to be correct and so UE will proceed with reading <a href="http://4g-lte-world.blogspot.com/2012/10/system-information-block-1.html">System information block 1</a> and <a href="http://4g-lte-world.blogspot.com/2013/02/system-information-block-2-sib2-in-lte.html">System information block 2</a>. The next step is known as <a href="http://4g-lte-world.blogspot.com/2013/04/random-access-procedure-rach-in-lte.html" target="_blank">Random Access Procedure</a> in which the network for the first time knows that some UE is trying to get access and the network provides temporary resources to the UE for initial communication.<br />
<br />
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<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<br />
<br />
Once the Random Access procedure is successfully completed, next is RRC connection establishment procedure which configures SRB1 for UE and let UE inform the network what exactly it wants i.e. Attach, Service Request, Tracking area update etc. RRC connection establishment is 3 way handshake procedure comprising of following messages.<br />
<br />
- RRC Connection Request<br />
- RRC Connection Setup<br />
- RRC Connection Setup complete<br />
<div>
<br />
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<br /></div>
<div>
<h3>
RRC Connection Request (RACH Msg3)</h3>
<div>
Actually the RACH Msg3 is the first message of RRC connection establishment procedure. Once the UE has obtained temporary resources via MSG2 in RACH process , its now ready to send 'RRC connection request' message using UL-SCH to eNodeB. UE is identified by temporary C-RNTI assigned in RACH Msg2</div>
<div>
<ul style="background-color: white; color: #444444; font-family: Arial, Tahoma, Helvetica, FreeSans, sans-serif; font-size: 14px; line-height: 19.6000003814697px; list-style-image: initial; list-style-position: initial; margin: 0.5em 0px; padding: 0px 2.5em;">
<li style="border: none; margin: 0px 0px 0.25em; padding: 0.25em 0px;">The message contains following information</li>
<ul style="line-height: 1.4; list-style: disc; margin: 0.5em 0px; padding: 0px 2.5em;">
<li style="border: none; margin: 0px 0px 0.25em; padding: 0.25em 0px;">UE identity (TMSI or Random Value )</li>
<ul style="line-height: 1.4; list-style: disc; margin: 0.5em 0px; padding: 0px 2.5em;">
<li style="border: none; margin: 0px 0px 0.25em; padding: 0.25em 0px;">TMSI is used if UE has previously connected to the same network. With TMSI value, UE is identified in the core network </li>
<li style="border: none; margin: 0px 0px 0.25em; padding: 0.25em 0px;">Random value is used if UE is connecting for the very first time to network. Why we need random value or TMSI? Because there is a possibility that Temp-CRNTI has been assigned to more than one UEs in previous step, due to multiple requests coming at same time (Collision scenario explained later)</li>
</ul>
<li style="border: none; margin: 0px 0px 0.25em; padding: 0.25em 0px;">Connection establishment cause: This shows the reason why UE needs to connect to network</li>
</ul>
</ul>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXGeJb9JI9A5zIXjqQY8zklwJ8eDXQjRJ9A2a74PCWZYYeXHC9QodRw3fxR4SioPXxugJ4YfLyVnDxgLUzs7B9TKoyb_qLWh0IsGx31Ig0uXzxoE2J3KmbZaDUmQG_PCNUackGPqByisSS/s1600/msg3.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXGeJb9JI9A5zIXjqQY8zklwJ8eDXQjRJ9A2a74PCWZYYeXHC9QodRw3fxR4SioPXxugJ4YfLyVnDxgLUzs7B9TKoyb_qLWh0IsGx31Ig0uXzxoE2J3KmbZaDUmQG_PCNUackGPqByisSS/s1600/msg3.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">RRC Connection Request message</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<h3 style="clear: both; text-align: left;">
RRC Connection Setup </h3>
<div>
The RRC connection setup message contain configuration details for SRB1 so that later messages can be transferred via SRB1. Remember the SRB2 is always configured after the security activation.<br />
<br />
RRC Connection setup message include default configuration for SRB1 but can also include configuration information for PUSCH, PUCCH, PDSCH physical channels, CQI Reports, Sounding reference signal, antenna configuration and scheduling requests.</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZ72Z7IUylPfwvAwijaeXAWtEvzKdpYZrlfP-1tQQU2wCVlJfIXelJEzhGlEdlSRKraJ0hHWo2gs9R25t7X8BYQ9FmZ8hCOz-74eh9NiIpRCmZrtkaINbQ1EaeveavfJQzhCC6vVQuY8cE/s1600/RRC+Connection+3+wayhandshake.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="290" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZ72Z7IUylPfwvAwijaeXAWtEvzKdpYZrlfP-1tQQU2wCVlJfIXelJEzhGlEdlSRKraJ0hHWo2gs9R25t7X8BYQ9FmZ8hCOz-74eh9NiIpRCmZrtkaINbQ1EaeveavfJQzhCC6vVQuY8cE/s1600/RRC+Connection+3+wayhandshake.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">RRC Connection Setup message IEs layout</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
It is not possible in this blog to explain all the information carried by this message but an example message taken from test network is shown below </div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgd2hg76nWYMP1KMNhBWnJlici1JJY067RKHZr9rbEdQxTCDAu2S4TmzTpkREEsJlVQFCxLYJjDUty4M46ocqfh6EtikoMQiLaTzHlCOF5DdymtctWpLiUQDcMsYb3_ZGnbKMcUqouNRZmy/s1600/connectionsetup.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgd2hg76nWYMP1KMNhBWnJlici1JJY067RKHZr9rbEdQxTCDAu2S4TmzTpkREEsJlVQFCxLYJjDUty4M46ocqfh6EtikoMQiLaTzHlCOF5DdymtctWpLiUQDcMsYb3_ZGnbKMcUqouNRZmy/s1600/connectionsetup.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">RRC Connection Setup message </td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<h3 style="clear: both; text-align: left;">
RRC Connection Setup Complete</h3>
<div class="separator" style="clear: both; text-align: left;">
After receiving the RRC Connection setup message, UE complete the three way handshake procedure by sending 'RRC Connection setup complete' message and moves to RRC Connected mode. </div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
The message contains following information</div>
<div class="separator" style="clear: both; text-align: left;">
</div>
<ul>
<li><i>selectedPLMN-Identity</i>: This is equal to 1 if UE selects the first PLMN from the <i>plmn-identityList</i> included in SIB1 or 2 if the second PLMN is selected in case UE belongs to more than one PLMN</li>
<li><i>dedicatedInfoNAS</i>: This IE is used to transfer UE specified NAS layer information between network and UE.</li>
</ul>
<br />
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
Example message is shown below</div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhua9y7s-H4Rjy0oBQeqRcDskRh_izX0VEk5oYcokgMByE7qz6GQl_7wZDqZ0EAFH5qP3qEEp5XsbKfwxX2-CsnABnnTIouTO8np0RxSFtGK53AkYdUd7VZktvq8xEtXA-2KlOI_J9BQjhL/s1600/msg3+2.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhua9y7s-H4Rjy0oBQeqRcDskRh_izX0VEk5oYcokgMByE7qz6GQl_7wZDqZ0EAFH5qP3qEEp5XsbKfwxX2-CsnABnnTIouTO8np0RxSFtGK53AkYdUd7VZktvq8xEtXA-2KlOI_J9BQjhL/s1600/msg3+2.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">RRC Connection Setup complete message</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
For more LTE call flows, please check out this <a href="http://4g-lte-world.blogspot.com/p/lte-call-flows.html" target="_blank">tool</a></div>
</div>
</div>
</div>
Unknownnoreply@blogger.com20tag:blogger.com,1999:blog-8240614391505589446.post-4471551710262146522014-05-19T13:35:00.000-05:002014-05-20T11:15:40.666-05:00Basics of scheduling in LTEScheduling is the process through which eNB decides which UEs should be given resources to send or receive data . In LTE, scheduling is done per subframe level (i.e. each 1 ms TTI) <br />
<br />
Before getting into basics of scheduling, it is important to understand following key terms:<br />
<br />
<h4>
CQI:</h4>
CQI (Channel quality indicator) is a four digit value sent to eNB by UE as a feedback for downlink channel.CQI informs eNB about the channel quality in downlink. This helps eNB to allocate proper MCS (Modulation and coding scheme) and RB (Resource block) for UE<br />
<br />
<h4>
BSR:</h4>
BSR (Buffer Status Report) is a UE way of informing network that it has certain data in its buffer and it requires grants to send this data<br />
<br />
<h4>
QoS:</h4>
<span style="font-family: inherit;">QoS (Quality of Service) defines how a particular user data should be treated in the network. QoS is implemented
between UE and PDN Gateway and is applied to a set of bearers. e.g. VoIP packets
are prioritized by network compared to web browser traffic.</span><br />
<br />
<br />
Now let's see how the scheduling works<br />
<ul>
<li>UE computes the CQI value from downlink channel and sends it to the eNB</li>
<li>UE sends BSR reports to eNodeB</li>
<li>Based on BSR, CQI and UE QoS, eNodeB computes MCS value and PRB mapping information and send it to the UE in downlink</li>
</ul>
<br />
<h4>
Factors that affects scheduling:<span style="font-weight: normal;"> </span></h4>
<ul>
<li><span style="font-weight: normal;">Traffic Volume</span>: Schedules those UEs with bearers waiting data in buffer</li>
<li>QoS Requirement: Schedules and allocates resources to UE to meet its QoS requirement</li>
<li>Radio Conditions: Schedules resources for UE that best suits its radio environment </li>
</ul>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiYKaX-c3gfYsvdP2GTrAbFLuLPwqH0S0fjGltVe5ffVHgfj5VvWs4k1TovqoS-mk_UWEgmMJvt_kRZsmDZngq3ISELvq6XOV7yzDja2TH7WdQyXYDE1vyVjvgDi-MX1ft2KPmBXrdsZzkU/s1600/Untitled.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiYKaX-c3gfYsvdP2GTrAbFLuLPwqH0S0fjGltVe5ffVHgfj5VvWs4k1TovqoS-mk_UWEgmMJvt_kRZsmDZngq3ISELvq6XOV7yzDja2TH7WdQyXYDE1vyVjvgDi-MX1ft2KPmBXrdsZzkU/s1600/Untitled.png" height="198" width="320" /></a></div>
<br />
<br />Unknownnoreply@blogger.com20tag:blogger.com,1999:blog-8240614391505589446.post-10956883703446582032013-09-14T21:19:00.000-05:002013-09-16T20:44:00.380-05:00Physical Control Format Indicator Channel (PCFICH) <div dir="ltr" style="text-align: left;" trbidi="on">
<h3>
Introduction</h3>
'Channels' are used to differentiate different kinds of traffic on radio path. For example, data channels carry users traffic (Youtube, Skype data etc) and control channels carry signaling traffic to manage radio resources, setting up connection etc<br />
<br />
The Physical Control Format Indicator Channel (PCFICH) is one of the control channels that works at physical layer. It is used to dynamically indicate the number of symbols to be used for PDCCH.<br />
<br />
<h3>
Why do we need PCFICH ? </h3>
With the help of PCFICH channel, following scenarios are possible:<br />
<br />
- Use less symbols for PDCCH if there are a few users with high data rates. Thus leaving more resource elements to be used for user plane data (PDSCH)<br />
<br />
- Use more symbols for PDCCH if there are many users with lower data rates e.g VoIP calls in the cell, thus allowing more users capacity.<br />
<br />
<h3>
Signalled value</h3>
<div>
PCFICH signalled value depends on channel bandwidth. For channel bandwidth of 3MHz up to 20 Mhz it can carry value of 1, 2 or 3. But for 1.4 Mhz channel bandwidth it can carry value of 2, 3 or 4. Because in case of 1.4 Mhz bandwidth, there are few subcarriers in frequency domain.Therefore, more space is required in time domain to carry PDCCH symbols<br />
<br />
<h3>
Location of PCFICH symbols on Resource Grid</h3>
</div>
PCFICH occupies 16 resource elements in frequency domain. These resource elements are divided into groups of four quadruplets distributed within first OFDMA symbol of each 1 ms subframe. The exact position of PCFICH can be measured from Cell ID and bandwidth using formula given in 3GPP spec 36.211 as below<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJO4Hx7M4kqjjvE019QRXRmyLe4FwAV0yi69k-9C5TpRvnLxHbuAeZkHDD8AQ1Pf5sLkzG_zAMO6YUNWEi2HD4AHGY8Yq42cK9czU8A-0nil5qUj3JM7fDSsMS3mCYbXwQ192tj2PM07je/s1600/PCFICH+Formula.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="188" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJO4Hx7M4kqjjvE019QRXRmyLe4FwAV0yi69k-9C5TpRvnLxHbuAeZkHDD8AQ1Pf5sLkzG_zAMO6YUNWEi2HD4AHGY8Yq42cK9czU8A-0nil5qUj3JM7fDSsMS3mCYbXwQ192tj2PM07je/s640/PCFICH+Formula.png" width="640" /></a></div>
Where<br />
<div class="MsoNormal">
N<sup><span style="font-size: xx-small;">RB</span></sup><sub><span style="font-size: xx-small;">SC</span> </sub>= Number of frequency carriers per Resource block</div>
<div class="MsoNormal">
<o:p></o:p></div>
<div class="MsoNormal">
N<sup><span style="font-size: xx-small;">DL</span></sup><sub><span style="font-size: xx-small;">RB</span> </sub>= Number of resource blocks per bandwidth<o:p></o:p></div>
<div class="MsoNormal">
N<sup><span style="font-size: xx-small;">cell</span></sup><sub><span style="font-size: xx-small;">ID</span> </sub>= Physical Cell id<br />
<o:p></o:p></div>
<div class="MsoNormal">
<br />
It may look complicated but lets try to understand it with simple example<br />
<br />
Lets suppose<br />
Physical Cell id = 20<br />
Bandwidth = 10Mhz (N<sup><span style="font-size: xx-small;">DL</span></sup><sub><span style="font-size: xx-small;">RB</span> </sub>= 50)<br />
<br />
Then according to 3GPP Formula<br />
<br /></div>
<div class="MsoNormal">
k_Bar =
(12/2).(20 mod 2*50) = 6*20 = 120<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Then the four
PCFICH mapping values are below <o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
120</div>
<div class="MsoNormal">
120 + (50/2)*(12/2) = 270<o:p></o:p></div>
<div class="MsoNormal">
120 + 2*(50/2)*(12/2) = 420<o:p></o:p></div>
<div class="MsoNormal">
120 + 3*(50/2)*(12/2) = 570<o:p></o:p></div>
<div class="MsoNormal">
<br /></div>
<div class="MsoNormal">
Visit LTE Resource Grid generator to validate above mapping values (Enter Cell id = 20 and Bandwidth = 10Mhz)<br />
<a href="http://paul.wad.homepage.dk/LTE/lte_resource_grid.html">http://paul.wad.homepage.dk/LTE/lte_resource_grid.html</a> </div>
<div class="MsoNormal">
<br /></div>
</div>
Unknownnoreply@blogger.com26tag:blogger.com,1999:blog-8240614391505589446.post-90573846816212715872013-04-29T06:40:00.001-05:002016-04-16T20:04:27.438-05:00Random Access Procedure in LTE<div dir="ltr" style="text-align: left;" trbidi="on">
<h3>
Background</h3>
When you switch on smartphone for the very first time, it will start searching for the network. There is a possibility that there are many networks or to put in other words , there are many frequencies from different operators available in the air to which UE (user equipment) can connect. Therefore, UE needs to synchronize to each frequency and check whether this is frequency from the right operator to which it wants to connect to. UE does this by going through very initial <a href="http://4g-lte-world.blogspot.com/2012/06/primary-and-secondary-synchronization.html" target="_blank">synchronisation process</a>. Once synchronized UE reads the <a href="http://4g-lte-world.blogspot.com/2012/06/master-information-block-mib-in-lte.html" target="_blank">master information block</a> and System information blocks to check whether this is the right PLMN. Lets assume that it finds that PLMN value to be correct and so UE will proceed with reading <a href="http://4g-lte-world.blogspot.com/2012/10/system-information-block-1.html" target="_blank">System information block 1</a> and <a href="http://4g-lte-world.blogspot.com/2013/02/system-information-block-2-sib2-in-lte.html" target="_blank">System information block 2</a>. The next step is known as Random Access Procedure in which the network for the first time knows that some UE is trying to get access.<br />
<br />
At this stage, UE does not have any resource or channel available to inform network about its desire to connect to it so it will send its request over the shared medium. Now there are two possibilities at this stage, either there are many other UEs in the same area (same cell) sending same request in which there is also a possibility of collision among the requests coming from various other UEs. Such random access procedure is called contention based Random access procedure. In second scenario, network can inform UE to use some unique identity to prevent its request from colliding with requests coming from other UEs. The second scenario is called contention free or non contention based random access procedure.<br />
<br />
<h4>
RACH preambles</h4>
The concept of RACH preamble though a little confusing is important in understanding the random access procedure.<br />
<br />
When UE sends the very first message of random access procedure to some network, it basically sends specific pattern or signature which is called RACH preambles. The preamble value differentiate requests coming from different UEs. But if two UEs uses same RACH preambles at same time then there can be collision. There are totally 64 such patterns or signature available to the UE for the very first message of random access procedure and UE will decide any one of them randomly for contention-based random access procedure but for non-contention based procedure, actually network will inform UE about which one to use<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBuOg0giGKR-xyeHLE8KpjAtcIGn9iXUqipCL8xsNB2YWCnMJ1z_gv5HZ8p7d-xk1uY5lKdVwVTQe2RELV4W473ARbXasUldmd0bdDBohpiS9QdQzpq5sLmZDSOPE4YtBOxcWoTJlByiVo/s1600/RACH+Type.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="293" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBuOg0giGKR-xyeHLE8KpjAtcIGn9iXUqipCL8xsNB2YWCnMJ1z_gv5HZ8p7d-xk1uY5lKdVwVTQe2RELV4W473ARbXasUldmd0bdDBohpiS9QdQzpq5sLmZDSOPE4YtBOxcWoTJlByiVo/s640/RACH+Type.png" width="640" /></a></div>
<br />
In case, when UE goes from idle state to RRC connected state, there is no way for network to inform UE about which preamble out of 64 values should be used. Therefor UE has no choice but to use one of the preambles randomly which also result in possibility of collision if the same preamble is being used by another UE, provided the requests comes at same time (same frame)<br />
<br />
In another scenario if UE has to take handover to another eNB, in this case actually the UE can be informed about which preamble it can use, since UE is already in connected state<br />
<div>
<br /></div>
<h4>
Steps of Random access procedure</h4>
<div>
Random access procedure consist of four steps explained below (Only contention based procedure is shown below)<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6XEm828qwL0Yka9quOj0IY7PSS7ijDL9K94pexy3-9sxuMCCWUiklnJS7vQ6LcCpPdld9oGT0-1oDFvv0AEBIRvM8rIhip2jYLU2T0_jbfMsN6KraumVztDkPhThYtc4G-iNb4Tq1VMUB/s1600/Rach+steps.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="352" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6XEm828qwL0Yka9quOj0IY7PSS7ijDL9K94pexy3-9sxuMCCWUiklnJS7vQ6LcCpPdld9oGT0-1oDFvv0AEBIRvM8rIhip2jYLU2T0_jbfMsN6KraumVztDkPhThYtc4G-iNb4Tq1VMUB/s400/Rach+steps.png" width="400" /></a></div>
<br />
<br /></div>
<h3>
Step 1: Msg1</h3>
<ul>
<li>UE selects one of the 64 available RACH preambles</li>
<li>Now UE also needs to give its own identity to the network so that network can address it in next step. The identity which UE will use is called RA-RNTI (Random access radio network temporary identity). Basically its not some value sent by UE but interestingly RA RNTI is determined from the time slot number in which the preamble is sent</li>
<li>If UE does not receive any response from the network, it increases its power in fixed step and sends RACH preamble again</li>
</ul>
<div>
<br /></div>
<div>
<h3>
Step 2: Msg2</h3>
</div>
<div>
<ul>
<li>eNodeB sends "Random Access Response" to UE on DL-SCH (Downlink shared channel) addressed to RA-RNTI calculated from the timeslot in which preamable was sent, as explained in step 1 (about RA-RNTI calculation)</li>
<li>The message carries following information </li>
<ul>
<li>Temporary C-RNTI: Now eNB gives another identity to UE which is called temporary C-RNTI (cell radio network temporary identity) for further communication</li>
<li>Timing Advance Value: eNodeB also informs UE to change its timing so it can compensate for the round trip delay caused by UE distance from the eNodeB</li>
<li>Uplink Grant Resource: Network (eNodeB) will assign initial resource to UE so that it can use UL-SCH (Uplink shared channel)</li>
</ul>
</ul>
<div>
<br /></div>
<div>
<h3>
Step 3: Msg3 </h3>
</div>
</div>
<div>
<ul>
<li>Using UL-SCH, UE sends "RRC connection request message" to eNodeB</li>
<li>UE is identified by temporary C-RNTI (assigned in the previous step by eNodeB)</li>
<li>The message contains following</li>
<ul>
<li>UE identity (TMSI or Random Value )</li>
<ul>
<li>TMSI is used if UE has previously connected to the same network. With TMSI value, UE is identified in the core network </li>
<li>Random value is used if UE is connecting for the very first time to network. Why we need random value or TMSI? Because there is possibility that Temp-CRNTI has been assigned to more than one UEs in previous step, due to multiple requests coming at same time (Collision scenario explained later)</li>
</ul>
<li>Connection establishment cause: The shows the reason why UE needs to connect to network</li>
</ul>
</ul>
<div>
<br /></div>
</div>
<div>
<h3>
Step 4: Msg4</h3>
</div>
<ul>
<li>eNodeB responds with contention resolution message to UE whose message was successfully received in step 3. This message is address towards TMSI value or Random number (from previous steps) but contains the new C RNTI which will be used for the further communication</li>
<ul>
</ul>
</ul>
<div>
<br /></div>
<div>
<h4>
Collision Scenario</h4>
The above example didn't consider any collision. Collision can occur because of following example scenario<br />
<ul>
<li>Lets assume two UEs send same RACH preamble at same time in step 1</li>
<li>Same Temp C-RNTI and up-link grant will be received by two UEs in step 2</li>
<li>In step 3 eNodeB may be able to receive Msg3 from only one UE or none of them due to interference. </li>
<li>In step 4 the UE which does not receive Msg4 from eNodeB will back-off after expiration of RACH specific timers. Possibility is also that none of them receive Msg4 </li>
<li>UE which receive msg4 will move to next step and decode RRC connection setup message</li>
</ul>
<div>
<br /></div>
</div>
<div>
<br /></div>
<div>
For more LTE call flows, please check out this <a href="http://4g-lte-world.blogspot.com/p/lte-call-flows.html" target="_blank">tool</a></div>
</div>
Unknownnoreply@blogger.com126tag:blogger.com,1999:blog-8240614391505589446.post-35916161588101246752013-03-17T08:34:00.001-05:002013-03-17T23:47:52.163-05:00GPRS Tunneling Protocol (GTP) in LTE<div dir="ltr" style="text-align: left;" trbidi="on">
<h3>
Introduction</h3>
GPRS Tunneling protocol is an important IP/UDP based protocol used in GSM, UMTS and LTE core networks. It is used to encapsulate user data when passing through core network and also carries bearer specific signalling traffic between various core network entities. This protocol has several advantages which will be discussed later.<br />
<br />
<br />
<h3>
GPRS Tunneling Protocol Types</h3>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlnl5XeqjWK6nf2Wy8bCrvJonqM8dmJ6pbgY0LCtIgDhIpLIkuV-Fv4JN8F9AXTprRI-BcuOm-o5tPe-bQ9-2yqOK7Sk2omGnWtxYQAoI0KFmYMwP6E4xxIkhCbJ1CM6V7T7z7GUIqhm1P/s1600/GTP.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="468" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlnl5XeqjWK6nf2Wy8bCrvJonqM8dmJ6pbgY0LCtIgDhIpLIkuV-Fv4JN8F9AXTprRI-BcuOm-o5tPe-bQ9-2yqOK7Sk2omGnWtxYQAoI0KFmYMwP6E4xxIkhCbJ1CM6V7T7z7GUIqhm1P/s640/GTP.png" width="640" /></a></div>
<br />
<br />
<h3>
</h3>
<h3>
Why is GTP used in LTE?</h3>
<ul style="font-size: medium; font-weight: normal;">
<li>It provides mobility. When UE is mobile, the IP address remains same and packets are still forwarded since tunneling is provided between PGW and eNB via SGW </li>
<li>Multiple tunnels (bearers) can be used by same UE to obtain different network QoS</li>
<li>Main IP remains hidden so it provides security as well</li>
<li>Creation, deletion and modification of tunnels in case of GTP-C</li>
</ul>
<div>
<br /></div>
<div>
<h3>
GTP Interfaces in LTE</h3>
<div style="font-size: medium; font-weight: normal;">
In LTE, version 2 is used for GTP-C and version 1 is used for GTP-U</div>
<div style="font-size: medium; font-weight: normal;">
In simple LTE network implementation, GTP-v2 is used on S5 and S11 interfaces and GTPv1 is used on S1-U, S5, X2-U interfaces (as shown below). In inter-RAT and inter PLMN connectivity, S3, S4, S8, S10, S12 and S16 interfaces also utilize GTP protocols<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii9yuTaOWemPbTd-rwCrXd_nC7KnkYQ5-nvPXDCW86aGYnNt_z2cM1vfAZQ2K0cr4u_GANTc2IuREL-NrMdUywzB9YfANdwCS7HWaXLL93IYP45LA8yrcrWF7GT6whYwu4X3enYaiH-fTS/s1600/GTP+Interfaces.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em; text-align: center;"><img border="0" height="393" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii9yuTaOWemPbTd-rwCrXd_nC7KnkYQ5-nvPXDCW86aGYnNt_z2cM1vfAZQ2K0cr4u_GANTc2IuREL-NrMdUywzB9YfANdwCS7HWaXLL93IYP45LA8yrcrWF7GT6whYwu4X3enYaiH-fTS/s640/GTP+Interfaces.png" width="640" /></a></div>
</div>
<h3>
How GTP-U Works ?</h3>
GTP-U encapsulation of UE user plane traffic can be easily understood by taking any simple example. Lets see what happens when IP packet generated by UE reaches to eNodeB and is then forwarded to SGW.<br />
<br />
Consider any application on UE creates an IP/TCP packet. This packet consist of actual data by application, TCP or UDP header and then IP field information which has source address of UE and destination address of application server (e.g. Facebook)<br />
<br />
When the eNodeB receives this packet over air interface, it will put the IP packet inside GTP header which has information related to tunnel IDs. Then further, it is encapsulated inside UDP and IP header and forwarded as ethernet frame towards SGW. Here the IP header contains eNodeB IP as a source address and SGW IP as a destination address<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4wgWrvsTo9nEVHgCSJSDbtNASEEIL49OT2RPSGhPBJjytTtyktCgPuB71VEcwL7xN67OQrT7OVj9dwHmt-Rsc6zk3cYXN43ByJ3_X756GyxcYzwxHitDVEqMYCRHn_P3oNhLEeA6wNzyP/s1600/GTP+encap.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="286" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4wgWrvsTo9nEVHgCSJSDbtNASEEIL49OT2RPSGhPBJjytTtyktCgPuB71VEcwL7xN67OQrT7OVj9dwHmt-Rsc6zk3cYXN43ByJ3_X756GyxcYzwxHitDVEqMYCRHn_P3oNhLEeA6wNzyP/s640/GTP+encap.png" width="640" /></a></div>
<h3>
</h3>
<h3>
GTP-C signalling messages</h3>
<div>
As GTP-Cv2 in LTE is used for tunnel management, some of the signalling messages are listed below which use GTP-Cv2 protocol </div>
<div>
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
</div>
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</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglDNPq72gi6HVx2I4X-3kN7784uxUntjHQOUxKlDDXAr98fem8F1SZJVUYeTseCK8uO20OgItazs1zEZKHYx1IV9MhpLJ3iS5UyBJslK0aaZLwu-C-olQ9LWyQIS6jaSc82dh6BxLgqggx/s1600/gtpc.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglDNPq72gi6HVx2I4X-3kN7784uxUntjHQOUxKlDDXAr98fem8F1SZJVUYeTseCK8uO20OgItazs1zEZKHYx1IV9MhpLJ3iS5UyBJslK0aaZLwu-C-olQ9LWyQIS6jaSc82dh6BxLgqggx/s640/gtpc.png" width="458" /></a></div>
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</div>
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<br /></div>
<div class="separator" style="clear: both; text-align: left;">
Please check Table 6.1-1(3GPP TS 29.274) for more detailed list of GTP-C based messages.</div>
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<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
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<h3>
</h3>
</div>
Unknownnoreply@blogger.com85tag:blogger.com,1999:blog-8240614391505589446.post-31861759592263109582013-02-25T20:03:00.004-06:002013-02-25T20:09:07.340-06:00System information block 2 (SIB2) in LTE After <a href="http://4g-lte-world.blogspot.kr/2012/06/primary-and-secondary-synchronization.html">initial cell synchronization process</a> is completed, UE will read <a href="http://4g-lte-world.blogspot.kr/2012/06/primary-and-secondary-synchronization.html">master information block</a> which contains important information regarding downlink cell bandwidth, PHICH configuration and System frame number. Then UE can read <a href="http://4g-lte-world.blogspot.kr/2012/10/system-information-block-1.html">System information block 1</a> and System information block 2 to obtain useful information related to cell access, SIB scheduling and radio resource configuration<br />
<br />
System information block 2 carries radio resource configuration information which is common for all UEs.<br />
<br />
SIB2 information can be divided in following sub categories<br />
<ul>
<li>Random access channel (RACH) related parameters </li>
<li>Idle mode paging configurations </li>
<li>Uplink physical control channel (PUCCH) and shared channel (PUSCH) configurations </li>
<li>Uplink power control and Sounding reference signal configurations </li>
<li>Uplink carrier frequency / Bandwidth </li>
<li>Cell barring information </li>
</ul>
<div>
<br /></div>
<div>
<h3>
SIB2 Example</h3>
</div>
<div>
Example SIB2 info is shown below (Taken from UE logs). This SIB2 does not represent any real network</div>
<div>
<br /></div>
<div>
<div>
<span style="font-family: Courier New, Courier, monospace;">value BCCH-DL-SCH-Message ::= </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> message c1 : systemInformation : </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> criticalExtensions systemInformation-r8 : </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> sib-TypeAndInfo </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> sib2 : </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> radioResourceConfigCommon </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> rach-ConfigCommon </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> preambleInfo </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> numberOfRA-Preambles n40,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> preamblesGroupAConfig </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> sizeOfRA-PreamblesGroupA n32,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> messageSizeGroupA b144,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> messagePowerOffsetGroupB dB10</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> powerRampingParameters </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> powerRampingStep dB2,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> preambleInitialReceivedTargetPower dBm-104</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ra-SupervisionInfo </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> preambleTransMax n10,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ra-ResponseWindowSize sf5,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> mac-ContentionResolutionTimer sf32</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> maxHARQ-Msg3Tx 3</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> bcch-Config </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> modificationPeriodCoeff n8</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> pcch-Config </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> defaultPagingCycle rf64,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> nB oneT</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> prach-Config </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> rootSequenceIndex 30,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> prach-ConfigInfo </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> prach-ConfigIndex 4,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> highSpeedFlag FALSE,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> zeroCorrelationZoneConfig 8,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> prach-FreqOffset 3</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> pdsch-ConfigCommon </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> referenceSignalPower 11,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> p-b 1</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> pusch-ConfigCommon </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> pusch-ConfigBasic </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> n-SB 1,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> hoppingMode interSubFrame,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> pusch-HoppingOffset 6,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> enable64QAM FALSE</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ul-ReferenceSignalsPUSCH </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> groupHoppingEnabled FALSE,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> groupAssignmentPUSCH 0,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> sequenceHoppingEnabled FALSE,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> cyclicShift 0</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> pucch-ConfigCommon </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaPUCCH-Shift ds2,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> nRB-CQI 1,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> nCS-AN 0,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> n1PUCCH-AN 36</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> soundingRS-UL-ConfigCommon release : NULL,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> uplinkPowerControlCommon </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> p0-NominalPUSCH -100,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> alpha al1,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> p0-NominalPUCCH -100,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaFList-PUCCH </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaF-PUCCH-Format1 deltaF0,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaF-PUCCH-Format1b deltaF1,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaF-PUCCH-Format2 deltaF0,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaF-PUCCH-Format2a deltaF0,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaF-PUCCH-Format2b deltaF0</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> deltaPreambleMsg3 1</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ul-CyclicPrefixLength len1</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ue-TimersAndConstants </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> t300 ms200,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> t301 ms200,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> t310 ms500,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> n310 n10,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> t311 ms3000,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> n311 n1</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> freqInfo </span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ul-CarrierFreq 20600,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ul-Bandwidth n50,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> additionalSpectrumEmission 12</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> ,</span></div>
<div>
<span style="font-family: Courier New, Courier, monospace;"> timeAlignmentTimerCommon sf10240</span></div>
<br />
<br />
<br />
<h3>
Definition of important Parameters</h3>
<div>
<br /></div>
<h4>
<b>Rach Configurations</b></h4>
<div>
<b>numberOfRA-Preambles:</b> Total number of random access preambles available for contention based random access. Since there are maximum 64 preambles sequences available, others could be reserved by eNB for Non-Contention based random access. Range of this parameter is 4 to 64</div>
<div>
<b>sizeOfRA-PreamblesGroupA:</b> Total number of random access preambles sequences available within Group A. Preambles are divided into Group A and Group B. Group A preambles are intended for sending small packets and Group B preambles are intended for sending large packets. Range of this parameter is 4 to 60</div>
<div>
<b>messageSizeGroupA:</b> Message size threshold for selecting preamble Group A in term of bits (56, 144, 208 or 256 bits)</div>
<div>
<b>messagePowerOffsetGroupB: </b>Power offset for selecting preamble Group B (0, 5, 8, 10, 12, 15 or 18 dB)</div>
<div>
<b>powerRampingStep: </b>power ramping step size with possible values of 0, 2, 4 or 6 dB</div>
<div>
<b>preambleInitialReceivedTargetPower: </b>Preamble initial received target power with values from -120 dBm to -90 dBm with step size of 2 dBm </div>
<div>
<b>preambleTransMax:</b> Maximum number of preambles transmissions. Possible values are 3, 4, 5, 6, 7, 8, 10 ,20, 50, 100, 200.</div>
<div>
<b>ra-ResponseWindowSize:</b> Duration of RA response window. RA response window size is in unit of subframes (2, 3, 4, 5, 6, 7, 8, or 10 subframes)</div>
<div>
<b>mac-ContentionResolutionTimer:</b> Mac contention resolution timer in unit of subframes (8, 16, 24, 32, 40, 58, 56 or 64 subframes)</div>
<div>
<b>maxHARQ-Msg3Tx: </b>Maximum number of HARQ retransmissions for message 3 of RACH process (contention-based Random access) with possible values from 1 to 8 in step of 1</div>
<div>
<br /></div>
<h4>
BCCH Configurations</h4>
<b>modificationPeriodCoeff: </b>The value (2,4,6,8) of this parameter is multiplied with default DRX cycle (e.g. 320ms, 640ms) to generate the BCCH modification period. It is the period in which the change in SI is repeated to UEs so that the change in SI is acquired by UE. <br />
BCCH modification period = modificationPeriodCoeff x idle mode DRX cycle<br />
</div>
<div>
<br />
<h4>
PCCH Configurations</h4>
<div>
<b>defaultPagingCycle:</b> The default DRX cycle in idle mode in unit of radio frames (rf64 means 640ms )</div>
<div>
<b>nB: </b>This parameter value is used in finding the actual paging frames and paging occasions in RRC idle mode with the following formula</div>
<div>
SFN modT = (T/N) x (UE_ID mod N)</div>
<div>
<br /></div>
<div>
Where </div>
<div>
T = Drx cycle </div>
<div>
N = Min (T, nB) (nB is broadcasted in SIB2) </div>
<div>
UE_ID = IMSI mod 1024</div>
<br />
<h4>
PRACH Configurations</h4>
<div>
<b>rootSequenceIndex:</b> RA preambles are generated from Zadoff Chu sequence which consists of series of root sequences. Each root sequence can be cyclic shifted to obtain preamble sequence. Range of rootSequenceIndex is 0 to 837. </div>
<div>
<b>prach-ConfigIndex: </b>This parameter defines exactly when UE should send RACH in frequency/time grids (Details TS36.211 Table 5.7.1-2)</div>
<div>
<b>highSpeedFlag: </b>For high speed UEs , as this can impact the correlation between cycles</div>
<div>
<b>zeroCorrelationZoneConfig: </b>The zero correlation zone is used to guarantee orthogonality of generated sequences. The value depends on particular condition in the cell</div>
<div>
<b>prach-FreqOffset: </b>With this information cell informs UE and other neighbor cells know about which PRB is available for RACH access</div>
<div>
<br /></div>
<h4>
PDSCH Configurations</h4>
<div>
<b>referenceSignalPower:</b> This defines the energy per resource element for the reference signal using a range from -60 to 50 dBm. </div>
<div>
<b>p-b:</b> It is used to calculate the power difference between PDSCH and Reference Signal. Value is from 0 to 3</div>
<br />
<h4>
PUSCH Configurations</h4>
<b>n-SB: </b>Number of subbands (range 1 to 4)<br />
<b>hoppingMode:</b> Hopping mode can be inter-subframe, intra or inter-subframe<br />
<b>pusch-HoppingOffset: </b>Offset values range from 1 to 98<br />
<b>enable64QAM:</b> if 64QAM capable UE should use it (True or False)<br />
<br />
<b>groupHoppingEnabled:</b> True or False<br />
<b>groupAssignmentPUSCH: </b>Gives sequence shift pattern for group hopping (0 to 29)<br />
<b>sequenceHoppingEnabled:</b> True or False<br />
<b>cyclicShift:</b> Frequency shift for demodulation (0 to 7)<br />
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<h4>
PUCCH Config</h4>
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<b>deltaPUCCH-Shift:</b> 1,2 or 3</div>
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<b>nRB-CQI:</b> Number of PRBs per slot for PUCCH2 (0 to 98)</div>
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<b>nCS-AN:</b> Cyclic shift used for PUCCH1 (0 to 7)</div>
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<b>n1PUCCH-AN:</b> PUCCH to be used for HARQ (0 TO 2047)</div>
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<h4>
Sounding Reference Signaling Configurations:</h4>
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The uplink Sounding Reference Signal (SRS) is configured in terms of bandwidth and subframes</div>
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Uplink Power Control</h4>
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<b>p0-NominalPUSCH: </b>It impacts the calculation of PUSCH transmit power and applicable to non-persistent scheduling only (-126 to 24 dBm)</div>
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<b>alpha: </b>It also impacts the calculation of PUSCH transmit power and also scales the contribution of path loss. Possible values are 0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1</div>
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<b>p0-NominalPUCCH:</b> This parameter impacts the calculation of PUCCH transmit power (-127 to -96 dBm)</div>
<b>deltaFList-PUCCH:</b> These parameters impacts the calculation of PUCCH transmit power<br />
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<b>deltaPreambleMsg3:</b> It impacts the transmit power of PUSCH when responding to random access response grant (-1 to 6dB)<br />
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<b>ul-CyclicPrefixLength:</b> To differentitate between normal (len1) OR extended (len2) cyclic prefix for uplink transmission<br />
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<h4>
UE Timers and Constants</h4>
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<b>T300:</b> Time during which UE waits for RRC connection request message response (100, 200, 300, 400, 600, 1000, 1500, 2000 ms)</div>
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<b>T301:</b> Started after RRC Connection Reestablishment request message. On expiration UE will go to RRC idle (100, 200, 300, 400, 600, 1000, 1500, 2000 ms)</div>
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<b>T310:</b> Started after receiving N310 out of sync indications (0, 50, 100, 200, 500, 1000, 2000 ms)<br />
<b>T311:</b> Started after initiating connection re-establishment procedure. On expiration UE goes to RRC idle mode if it is unable to locate suitable cell (1, 3, 5, 10, 15, 20, 30 seconds)</div>
<div>
<b>N310:</b> Consecutive out of sync indications (1, 2, 3, 4, 6, 8, 10, 20)<br />
<b>N311:</b> Consecutive in-sync indications (1, 2, 3, 4, 6, 8, 10, 20)</div>
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<h4>
Frequency Information</h4>
<div>
<b>ul-CarrierFreq: </b>Defined in terms of EARFCN</div>
<div>
<b>ul-Bandwidth: </b>Defined in terms of resource blocks</div>
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<b>additionalSpectrumEmission: </b>This allows spectrum emission limits to be configured according to local requirements (1 to 32)</div>
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<b>timeAlignmentTimerCommon: </b>it tells UE how long it should consider itself to be time aligned in uplink in unit of subframes. (500, 750, 1280, 1920, 2560, 5120, 10240 or infinity subframes)</div>
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Unknownnoreply@blogger.com46tag:blogger.com,1999:blog-8240614391505589446.post-50059885463144506872013-01-31T06:43:00.000-06:002013-02-12T04:46:26.832-06:00Quality of Service (QoS) in LTE<div dir="ltr" style="text-align: left;" trbidi="on">
<h3>
Background: Why we need QoS ? </h3>
<span style="font-family: inherit;">There are premium subscribers who always want to have better user experience on their 4G LTE device. These users are willing to pay more for high bandwidth and better network access on their devices. Not only the subscribers but some services itself need better priority handling in the network (e.g. VoIP call). To be able to full fill this, QOS plays the key role. QOS defines priorities for certain customers / services during the time of high congestion in the network</span><br />
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<h3>
3GPP definition for QoS</h3>
<div>
<span style="font-family: inherit;">In LTE Network QoS is implemented between UE and PDN Gateway and is applied to a set of bearers. 'Bearer' is basically a virtual concept and is a set of network configuration to provide special treatment to set of traffic e.g. VoIP packets are prioritized by network compared to web browser traffic.</span><br />
<span style="font-family: inherit;">In LTE, QoS is applied on Radio bearer, S1 bearer and S5/S8 bearer, collectively called as EPS bearer as shown in figure below.</span><br />
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In order to comprehend the concept of QoS , we must understand the bearer types and properties associated with each bearer through hierarchical chart as shown below. First there are two types of Bearer, i.e. Dedicated bearer and Default bearer. There is at-least one default bearer established when UE is attached to LTE network while dedicated bearer is always established when there is need to provide QoS to specific service (like VoIP, video etc). Please go through the article <a href="http://4g-lte-world.blogspot.com/2012/05/default-bearer-dedicated-bearer-what.html" target="_blank">Default and Dedicated Bearer</a> which hopefully will help to explain the concept in more detail.</div>
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<span style="font-family: inherit;">Dedicated bearer can be subdivided into Non-GBR and GBR types. </span></div>
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<span style="font-family: inherit;">GBR provides guaranteed bit rate and is associated with parameters like GBR and MBR</span></div>
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<span style="font-family: inherit;"><b>- GBR:</b> The minimum guaranteed bit rate per EPS bearer. Specified independently for uplink and downlink</span></div>
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<span style="font-family: inherit;"><b>- MBR:</b> The maximum guaranteed bit rate per EPS bearer. Specified independently for uplink and downlink</span></div>
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<span style="font-family: inherit;">On the other hand, Non-GBR bearer does not provide guaranteed bit rate and has parameter like A- AMBR and UE- AMBR</span></div>
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<span style="font-family: inherit;"><b>- A-AMBR: </b>APN Aggregate maximum bit rate is the maximum allowed total non-GBR throughput to specific APN. It is specified interdependently for uplink an downlink </span></div>
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<span style="font-family: inherit;"><b>- UE -AMBR: </b>UE Aggregate maximum bit rate is the maximum allowed total non-GBR throughput among all APN to a specific UE</span></div>
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<span style="font-family: inherit;">As you can see, the default bearer can only be non-GBR type. Some other important terms associated with each bearer type are discussed below:</span></div>
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<span style="font-family: inherit;"><br /></span></div>
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<span style="font-family: inherit;"><b>- ARP: </b>Allocation and retention priority is basically used for deciding whether new bearer modification or establishment request should be accepted considering the current resource situation.</span></div>
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<span style="font-family: inherit;"><b>- TFT: </b>Traffic flow template is always associated with dedicated bearer and while default bearer may or may not have TFT. As mentioned earlier, dedicated bearer provides QoS to special service or application and TFT defines rules so that UE and Network knows which IP packet should be sent on particular dedicated bearer. It usually has rules on the basis of IP packet destination/source or protocol used.</span></div>
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<span style="font-family: inherit;"><br /></span></div>
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<span style="font-family: inherit;"><b>L-EBI:</b> It stands for Linked EPS bearer ID. As I discussed in previous article about dedicated and default bearer, we know that each dedicated bearer is always linked to one of default bearers. L-EBI tells Dedicated bearer which default bearer it is attached to. </span></div>
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<span style="font-family: inherit;"><b>IP Address/ PDN:</b> Each default bearer is attached to some PDN network and has its own IP address while dedicated bearer does not need this since it is linked to default bearer.</span></div>
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<span style="font-family: inherit;"><br /></span></div>
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<span style="font-family: inherit;">You can also see one other parameter associated with all bearers i.e. QoS class of identifier (QCI).This parameter basically defines IP level packets characteristics as shown below</span></div>
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<b><span style="font-family: inherit;">EXAMPLE</span></b></div>
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<span style="font-family: inherit;">Let me try to explain here again with the same example I gave in <a href="http://4g-lte-world.blogspot.com/2012/05/default-bearer-dedicated-bearer-what.html" target="_blank">Default and Dedicated Bearer</a> section</span></div>
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<span style="background-color: white; color: #444444; font-family: inherit; line-height: 18px;">Usually LTE networks with VoLTE implementations have two default and one dedicated bearer</span></div>
<span style="font-family: inherit;"><br style="background-color: white; color: #444444; line-height: 18px;" /><span style="background-color: white; color: #444444; line-height: 18px;">Default bearer 1: Used for signaling messages (sip signaling) related to IMS network. It uses qci 5</span><br /><span style="background-color: white; color: #444444; line-height: 18px;">Dedicated bearer: Used for VoLTE VoIP traffic. It uses qci 1 and is linked to default bearer 1</span><br /><span style="background-color: white; color: #444444; line-height: 18px;">Default bearer 2: Used for all other smartphone traffic (video, chat, email, browser etc), assuming qci 9 is used here</span></span><br />
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<span style="font-family: inherit;">This means that Default bearer 1 is associated with IMS PDN and has specific IP address. It has throughput limitations defined in terms of A-AMBR and UE-AMBR. Since it has qci 5 which means that its IP packets has the highest priority over other IP packets and maximum delay as 100ms between UE and PGW with packet loss percentage up to 10<sup>-6</sup></span></div>
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<span style="font-family: inherit;">Default bearer 2 is associated with internet PDN and has specific IP. It has throughput limitations defined in terms of A-AMBR and UE-AMBR as well. Since it has qci 9 which means that its IP packets has the lowest priority over other IP packets and maximum delay possible as 300ms between UE and PGW with packet loss percentage up to 10<sup>-6</sup></span></div>
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<span style="font-family: inherit;">Dedicated bearer will be linked to Default bearer 1 with L-EBI and it also has TFT which basically defines which IP packets should be allowed to travel on this bearer. It has throughput limitations defined in terms of MBR and GBR. Since it is using QCI 1, the IP packets traveling on this bearer have the second highest priority. The maximum delay possible to IP packets on this bearer is 100 ms and the percentage of packet loss will be under </span>10<sup>-2</sup></div>
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Unknownnoreply@blogger.com364tag:blogger.com,1999:blog-8240614391505589446.post-71179569463473522212012-12-23T07:45:00.003-06:002015-11-03T16:51:19.638-06:00Transport Block Size, Throughput and Code rate<div dir="ltr" style="text-align: left;" trbidi="on">
Since the size of transport block is not fixed, often a question comes to mind as to how transport block size is calculated in LTE.<br />
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<b>Back Ground</b><br />
If we only consider "Uplink direction" and we assume that the UE is already attached to the network, then data is first received by PDCP (Packet data compression protocol) layer. This layer performs compression and ciphering / integrity if applicable. This layer will pass on the data to the next layer i.e. RLC Layer which will concatenate it to one RLC PDU.<br />
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RLC layer will concatenate or segment the data coming from PDCP layer into correct block size and forward it to the MAC layer with its own header. Now MAC layer selects the modulation and coding scheme configures the physical layer. The data is now in the shape of transport block size and needed to be transmitted in 1ms subframe.<br />
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<h4>
Transport Block size</h4>
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Now how much bits are transferred in this 1ms transport block size? </div>
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It depends on the MCS (modulation and coding scheme) and the number of resource blocks assigned to the UE. We have to refer to the Table 7.1.7.1-1 and Table 7.1.7.2.1-1 from 3GPP 36.213</div>
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Lets assume that eNB assigns MCS index 20 and 2 resource blocks (RBs) on the basis of CQI and other information for downlink transmission on PDSCH. Now the value of TBS index is 18 as seen in Table 7.1.7.1-1</div>
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After knowing the value of TBS index we need to refer to the Table 7.1.7.2.1-1 to find the accurate size of transport block (Only portion of the table is shown here while for the complete range of values refer to 3gpp document 36.213 <a href="http://www.quintillion.co.jp/3GPP/Specs/36213-920.pdf">http://www.quintillion.co.jp/3GPP/Specs/36213-920.pdf</a>)</div>
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Now from the Table 7.1.7.2.1-1 the value of Transport block size is 776 bits for I<span style="font-size: xx-small;">TBS</span> = 18 and N<span style="font-size: xx-small;">PRB</span>=2<br />
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<h4>
Throughput</h4>
Throughput is simply = Transport block size*(1000) = 776 *1000 = 776000 bits / seconds = 0.77 mbps (Assuming MIMO not used)<br />
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Please check this <a href="http://4g-lte-world.blogspot.com/p/throughput-calculator.html" target="_blank">Throughput Calculator</a> which takes MCS values and number of resource blocks as input to calculate the downlink throughput<br />
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<h4>
Code Rate</h4>
In simple words, code rate can be defined as how effectively data can be transmitted in 1ms transport block or in other words, it is the ratio of actual amount of bits transmitted to the maximum amount of bits that could be transmitted in one transport block<br />
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code rate = (TBS + CRC) / (RE x Bits per RE)<br />
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where<br />
TBS = Transport block size as we calculated from Table 7.1.7.2.1-1<br />
CRC = Cyclic redundancy check i.e. Number of bits appended for error detection<br />
RE = Resource elements assigned to PDSCH or PUSCH<br />
Bits per RE = Modulation scheme used<br />
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While we know the values of TBS, CRC and bits per RE (modulation order), it is not easy to calculate the exact amount of RE used for PDSCH or PUSCH since some of the REs are also used by control channels like PDCCH, PHICH etc<br />
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In our case, lets assume that 10% of RE's are assigned for control channels then<br />
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TBS = 776<br />
CRC = 24<br />
RE = 2 (RB) x 12 (subcarriers) x 7 (assuming 7 ofdm symbols) x 2 (slots per subframe) x 0.9 (10% assumption as above) = 302 REs<br />
Bits per RE = 6 (Modulation order from table 7.1.7.1-1)<br />
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So<br />
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code rate = (776 + 24) / (302 * 6 ) = 0.4<br />
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Unknownnoreply@blogger.com368tag:blogger.com,1999:blog-8240614391505589446.post-27953601289439903632012-11-17T08:25:00.001-06:002012-11-22T20:23:02.352-06:00AKA Digest authentication scheme for VoLTE (IMS)<div dir="ltr" style="text-align: left;" trbidi="on">
<span style="font-family: Arial, Helvetica, sans-serif;">When a VoLTE client needs to connect to IMS network, it has to authenticate the network while network also needs to make sure that only the correct user is registered to its network. AKA Digest is one of the scheme to authenticate VoLTE client to the IMS server</span><br />
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<br />
<h4>
<span style="font-family: Arial, Helvetica, sans-serif;">AKA</span></h4>
<div>
<span style="font-family: Arial, Helvetica, sans-serif;">AKA stands for "Authentication and key agreement". This scheme comes from the legacy 3gpp networks and has been widely used in LTE, 3G, CDMA and WiMAX technologies. In this mechanism, a secret key is already known to both user device (USIM, iSIM) and authentication servers (HSS, HLR). </span><br />
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<span style="font-family: Arial, Helvetica, sans-serif;">The server will challenge the end user using AKA algorithms and shared key and sends RAND, AUTN values towards UE. UE will authenticate network and prepares result (RES for network to authenticate UE) with the help of shared key in UICC and parameters sent by Server.</span><br />
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<br />
<h4>
<span style="font-family: Arial, Helvetica, sans-serif;">HTTP Digest</span></h4>
</div>
<div>
<span style="font-family: Arial, Helvetica, sans-serif;">Http Digest is the popular authentication scheme used for authenticating users to access web servers and other applications which requires security and data integrity. This scheme is much secure than the basic authentication as it applies hash function to the password before sending it [RFC2617]. </span><br />
<br />
<span style="font-family: Arial, Helvetica, sans-serif;">HTTP Digest is username / password based authentication procedure. The authentication server provides one time created " nonce " value to the client. The client uses the nonce value and creates a secure response that contains the password, username and other parameters to the server. The password which is known both to server and client, is always fixed</span><br />
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<h4>
<span style="font-family: Arial, Helvetica, sans-serif;">Now For IMS</span></h4>
</div>
<div>
<span style="font-family: Arial, Helvetica, sans-serif;">Now since IMS is a part of 3GPP and on the contrary SIP signaling defines http digest for authentication [RFC3261]. Therefore in order to use 3GPP AKA with IMS, the parameters from AKA are mapped onto http digest [RFC3310]. In simple words the parameters / headers used to transport http digest information, will transport AKA information in identical format</span><br />
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<span style="font-family: Arial, Helvetica, sans-serif;">With 3GPP AKA digest, the "nonce" now contains RAND, AUTN. The password now contains the one time RESPONSE generated by client with help of UICC (USIM, ISIM). Thus the method is even more secure. </span><br />
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<br />
<h4>
<span style="font-family: Arial, Helvetica, sans-serif;">Authentication in IMS networks</span></h4>
</div>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">VoLTE Client sends SIP register request to IMS Server. The user is not authenticated at this </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">point. The SIP register request contains IMS related identities (private identity, public identity, URI, etc)</span></li>
</ul>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">The IMS server (S-CSCF) obtains</span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;"> authentication vector and SQN from HSS that contains a random challenge RAND, </span><span style="font-family: Arial, Helvetica, sans-serif;">authentication token AUTN, expected authentication result XRES, a
session key for integrity check IK, and a session key for
encryption CK</span></li>
</ul>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">The server creates an authentication request, which contains the </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">random challenge RAND, and the network authenticator token AUTN</span></li>
</ul>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">The authentication request is delivered to the client with "401 UNAUTHORIZED" message</span></li>
</ul>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">The client </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">verifies the AUTN with the ISIM. If the verification is </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">successful, the network has been authenticated. The client then</span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;"> produces an authentication response RES, using the shared secret</span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;"> K and the random challenge RAND</span></li>
</ul>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjd6cZtNyJ5-ZXNu3twH6gF9rf2ojpTYaWftH7FTOCH_zCP6eHoC0v2PBzlwdSjNjAz5I5uXFIAypT0o5P6AkjhJXQn_OxnGs0SUx2FLm7hUlTx1COiCpXrD23ZYxBFsljYYCd2N735bCsS/s1600/IMS+authentication.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><span style="font-family: Arial, Helvetica, sans-serif;"><img border="0" height="390" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjd6cZtNyJ5-ZXNu3twH6gF9rf2ojpTYaWftH7FTOCH_zCP6eHoC0v2PBzlwdSjNjAz5I5uXFIAypT0o5P6AkjhJXQn_OxnGs0SUx2FLm7hUlTx1COiCpXrD23ZYxBFsljYYCd2N735bCsS/s640/IMS+authentication.jpg" width="640" /></span></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: small;">3GPP AKA Operation in IMS</span></td></tr>
</tbody></table>
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<br />
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">The authentication response RES is delivered to the server using new regiser sip message</span></li>
</ul>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">The server compares the authentication response RES with the </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">expected response. If the two match, the user has been </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">successfully authenticated</span></li>
</ul>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">Session keys IK and CK can be </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">used for protecting further communications between the client and </span><span style="font-family: Arial, Helvetica, sans-serif; font-size: 1em;">the server</span></li>
</ul>
<ul>
<li style="text-align: justify;"><span style="font-family: Arial, Helvetica, sans-serif;"><span style="font-size: 1em;">Server sends "200 OK" message to inform the VoLTE client about </span>successful<span style="font-size: 1em;"> registration</span></span></li>
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Unknownnoreply@blogger.com34tag:blogger.com,1999:blog-8240614391505589446.post-37013686884173128452012-10-08T00:08:00.003-05:002012-11-17T17:52:12.130-06:00 Android Operating System and Radio Interface Layer<div dir="ltr" style="text-align: left;" trbidi="on">
<span style="font-family: Arial, Helvetica, sans-serif;">When the mobile phone is switched on, in the first step Linux Kernel is loaded along with the drivers for modem and the first process called "init" is started. 'Init' will start initial dummy process named 'zygote' which helps in starting other services like audio manager, surface flinger, power manager, RIL Daemon (to be explained later), service manager, Telephony service etc </span><br />
<div class="MsoNormal">
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span></div>
<div class="MsoNormal">
<span style="font-family: Arial, Helvetica, sans-serif;">All the smartphone applications communicate to external
ports or environment via Application programming interface (API). For
communication towards radio modem, Telephony framework (mentioned above) performs the
role of APIs. It helps to access network related services by applications i.e. PDP connection establishment, SMS, MMS etc. Whenever these applications make
any query, it is forwarded to Radio interface Layer (RIL) by telephony
framework APIs. RIL is interface between telephony framework and radio hardware
(modem)</span><br />
<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<span style="font-family: Arial, Helvetica, sans-serif;">RIL has two sub layers </span><br />
<br />
<ul>
<li><span style="font-family: Arial, Helvetica, sans-serif;"><b>RIL Daemon:</b> It communicates with Vendor RIL for call processing and other functions</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;"><b>Vendor RIL:</b> It contains Library of functions and drivers to particular modem. It communicates with the radio hardware </span></li>
</ul>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiE_yJ_FPWJL_ScqSngC8Oi7dxPlfXCNf1TXa0np0k_zBFi0NEeABMLI859wBmJqICnKo5ykNK08ttoV8aVw2moaPMfyqKtI0RaTOcxlsk7aVChsaVPYqEvxTLlbX1GfpJq2deHWq7xHfRQ/s1600/RIL.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiE_yJ_FPWJL_ScqSngC8Oi7dxPlfXCNf1TXa0np0k_zBFi0NEeABMLI859wBmJqICnKo5ykNK08ttoV8aVw2moaPMfyqKtI0RaTOcxlsk7aVChsaVPYqEvxTLlbX1GfpJq2deHWq7xHfRQ/s400/RIL.png" width="223" /></a></div>
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<span style="font-family: Arial, Helvetica, sans-serif;"><br /></span>
<span style="font-family: Arial, Helvetica, sans-serif;">RIL Daemon is
responsible for initializing Vendor RIL and forwards all requests from telephony
framework to Vendor RIL. Vendor RIL communicates to modem protocol stacks via
Hayes AT commands and forwards requests from modem to RIL Daemon or vice versa.
Please see the figure above.</span><br />
<br />
<span style="font-family: Arial, Helvetica, sans-serif;">So here it is what happens:</span><br />
<br />
<ol>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Android Mobile is switched on</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Linux Kernel is loaded</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Initial temporary process named zygote is started on initialization by Linux Kernel</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Zygote helps in quick start of other services including Android Telephony network and RIL Daemon (RILD)</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">RILD initializes the vendor RIL for communication</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Vendor RIL initiates the radio modem</span></li>
<li><span style="font-family: Arial, Helvetica, sans-serif;">Network attach procedure is started</span></li>
</ol>
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Unknownnoreply@blogger.com49tag:blogger.com,1999:blog-8240614391505589446.post-35496121832756456912012-10-04T02:55:00.000-05:002013-02-23T01:49:29.454-06:00System Information Block 1<div dir="ltr" style="text-align: left;" trbidi="on">
After <a href="http://4g-lte-world.blogspot.kr/2012/06/primary-and-secondary-synchronization.html" target="_blank">initial cell synchronisation</a> and reading <a href="http://4g-lte-world.blogspot.kr/2012/06/master-information-block-mib-in-lte.html" target="_blank">Master information block</a>, UE will proceed to read system information blocks to obtain important cell access related parameters.<br />
<br />
SIB1 broadcasts common information to all UEs in the cell related to cell access parameters and information related to scheduling of other SIBs. SIB1 is broadcasted in subframe # 5 in the SFN for which SFN mod 8 = 0. While the repeated copies are sent in subframe # 5 for which SFN mod 2 = 0 . Thus the new copy of SIB1 is transmitted every 80ms as shown below<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzCa6R1yG5N1mN7MTY0TRozSqIlVxzj9VcJYGQkTiyV4ASuOtId6z_pWxTmVekwYv5TP1WYuEMN948AYHNp8TvirwxpPTZW5fQvgw7A05OrWQLXtkADtR6tFaXz3ieLxUI_5su5QkYw_ie/s1600/SIB1.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="144" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzCa6R1yG5N1mN7MTY0TRozSqIlVxzj9VcJYGQkTiyV4ASuOtId6z_pWxTmVekwYv5TP1WYuEMN948AYHNp8TvirwxpPTZW5fQvgw7A05OrWQLXtkADtR6tFaXz3ieLxUI_5su5QkYw_ie/s640/SIB1.png" width="640" /></a></div>
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<br />
The cell access related parameters are listed below<br />
<br />
<ul>
<li><b>PLMN identity : </b>Upto 6 PLMN identies can be specified</li>
<li><b>Tracking area code:</b> Range from 0 to 65546</li>
<li><b>Cell Id:</b> It contains eNB identity and has length of 28 bits</li>
<li><b>Cell barred: </b>whether cell is barred or not</li>
<li><b>Intra Frequency cell reselection info:</b> To select other cells when the target cell is barred</li>
<li><b>CSG indication:</b> To indicate whether this cell is CSG cell or not. If it is CSG cell, then CSG identity stored in the UE should match with CSG id of the cell</li>
</ul>
<div>
Other information broadcasted by SIB 1 are </div>
<div>
<ul>
<li><b>q-RxLevMin: </b>Minimum required level in the cell </li>
<li><b>Band indicator:</b> Cell frequency band indicator</li>
<li><b>scheduling information of other system information blocks</b></li>
</ul>
<div>
Complete SIB1 info is shown below (taken from UE logs). This SIB1 does not represent any real network</div>
</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGrrDPszmYShEt0XiD6anep_bLEqgT_LRwUYMZID4GnwCG5iXirWDZUcATFqVDG99SEOunO1caRJnARF4h4B2YhdCQ5zaZCs_J7HBCXJfoqVEKL50qZbnkOHq0zMcdzSkR4Jj_1tlJuSzV/s1600/sib1+info.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGrrDPszmYShEt0XiD6anep_bLEqgT_LRwUYMZID4GnwCG5iXirWDZUcATFqVDG99SEOunO1caRJnARF4h4B2YhdCQ5zaZCs_J7HBCXJfoqVEKL50qZbnkOHq0zMcdzSkR4Jj_1tlJuSzV/s1600/sib1+info.png" /></a></div>
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Unknownnoreply@blogger.com214