Overview of LTE 3GPP releases

Release 8 - LTE Introduced  

Release frozen in Dec 2008 

It was 3GPP release 8 when LTE was introduced for the very first time.  All the releases following only enhanced the technology.

Based on release 8 standardization, following were the main achievements
  • High peak data rates : Up to 300 Mbps in downlink and 75 Mbps in uplink when using 4x4 MIMO and 20 MHz bandwidth
  • High spectral efficiency 
  • Flexible bandwidths: 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz
  • Short round trip time: 5 ms latency for IP packets in ideal radio conditions
  • Simplified Architecture
  • OFDMA in downlink and SC-FDMA in uplink
  • All IP network 
  • MIMO multiple antenna scheme
  • Operation in paired (FDD) and unpaired spectrum (TDD)

Release 9 - Enhancement to LTE

Release frozen in Dec 2009

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

PWS (Public Warning System): 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

Femto Cell: 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

MIMO Beam forming:
 Beamforming is used to increase cell edge throughput by directing beam towards specific UE by position estimation at eNB. 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

Self Organizing Networks (SON): 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

eMBMS: 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

LTE Positioning: 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

Release 10 - LTE  Advanced

Release Frozen in March 2011

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

- 1 Gbps DL / 500 Mbps UL throughput
- High spectral efficiency
- Worldwide roaming

Following are some significant improvements in release 10

Enhanced Uplink multiple access: 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

MIMO enhancements: LTE-Advanced allows upto 8x8 MIMO in downlink and on the UE side it allows 4X4 in uplink direction

Relay Nodes: 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. 

enhanced inter-cell interference coordination (eICIC): 
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

Carrier Aggregation (CA): 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

Support for Heterogeneous Networks: The combination of large macro cells with small cells results in heterogeneous networks. Release 10 intended to layout the detail specification for heterogeneous networks

SON Improvements: Release 10 provides enhancements to SON features introduced in release 10 which also considers self healing procedures

Release 11 - Enhancement to LTE Advanced

Release Frozen in september 2012

Release 11 includes enhancements to LTE Advanced features standardized in release 10. Some of the important enhancements are listed below 

Carrier Aggregation enhancements: Following are the major enhancements to carrier aggregation in release 11
- Multiple timing advances (TAs) for uplink carrier aggregation
- Non contiguous intra band carrier aggregation
- physical layer changes for carrier aggregation support in TDD LTE

Coordinated multipoint transmission and reception (CoMP): With CoMP the transmitter can share data load even if they are not collocated. Though they are connected by high speed fiber link

ePDCCH: 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

Network based Positioning: In release 11, support for uplink positioning is added by utilizing Sounding reference signals for time difference measurements taken by many eNBs. 

Minimization of drive test (MDT): 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

Ran overload control for Machine type communication: 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

In Device Co Existence: 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
- DRX based time domain solutions
- Frequency domain solutions
- UE autonomous denials 

Smartphone Battery saving technique: 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

Release 12 - Further enhancement to LTE Advanced

Release Frozen in June 2014

Small cells enhancements: 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

Carrier aggregation enhancements: 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

Machine Type communication (MTC): 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

Wifi integration with LTE: 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 

LTE in unlicensed spectrum: 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

Release 13 - Meeting the growing throughput demand

Ongoing - Release expected to be frozen in  Dec 2015

Carrier Aggregation enhancements: 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.

enhancements for Machine-Type communication (MTC): 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. 

LTE in unlicensed spectrum enhancements: 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

Indoor Positioning: In release 13 there is work going on improving existing methods of indoor positioning and also exploring new positioning methods to improve indoor accuracy

Enhanced multi-user transmission techniques: Release 13 also covers potential enhancements for downink multiuser transmission using superposition coding

MIMO enhancements: 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