The very first step for UE to gain initial access to the network after completing initial cell synchronization is to read the Master information block (MIB) on BCCH (Logical
channel), BCH (Transport channel) and PBCH (Physical channel). Resource elements used by MIB are the
first 4 OFDMA symbols of second slot of first subframe of a radio frame. On
frequency domain it occupies 72 subcarriers. MIB carries very little but most important information
for UE initial access. The content of MIB includes
·
Downlink channel bandwidth in term of resource
blocks (RBs)
·
PHICH configuration (PHICH duration and PHICH
resource)
·
System Frame Number
New MIB is broadcasted every radio frame for which
SFN mod 4 = 0 (40ms repetition) while its copies are broadcasted in the middle 10ms
radio frames as shown in the figure below
Why PHICH is carried by MIB?
After decoding MIB, UE has to decode
PDCCH to read other system information blocks (SIBs). PDCCH, PHICH and PCFICH
share the resources in the control region of a subframe. So to find the available resources for PDCCH, UE has to know the PHICH configuration only, as PCFICH resources are fixed and known
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ReplyDeleteNo not the copies are broadcasting in the middle 10ms.. extracting all the data in 40ms at this position i.e SFN mod 4 = 0,1,2 and 3 forms complete 1920 bits MIB block..
ReplyDelete
ReplyDeleteEach of the repeated transmission is self decodable to make one complete MIB provided the radio conditions are very good. Otherwise in bad SIR, soft combination over four radio frames is used to improve decoding performance
See page 191,192 "LTE - The UMTS Long Term Evolution: From Theory to Practice"
Please share your source of information
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DeleteCan a UE read the MIB information in the camped but non-attached state?
ReplyDeleteIf you mean ECM idle (EMM Registered) then yes it can ..
DeleteSFN field in the MIB records only the most significant 8 bits of the actual SFN; the remaining 2 bits are determined by which of the 4 repetitions the UE is looking at (00 for the first copy, 01 for the second, and so on can any one explain me wt it means..
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Suppose an eNB receives some how the MIB from a neighbor cell working on different freq. and the eNB wants to transfer this information to a specific connected UE. How can the eNB do that?
ReplyDelete1- in a dedicated RRC control message?
2- on what logical channel ?
3- will that specific UE interrupts its data during the reception of that information?
Any answers?
What is the use of sending the PHICH configuraton in MIB.
ReplyDeletePlease see the updated post above for answer to your question..
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