Saturday, May 18, 2013

LTE BCH TRANSPORT BLOCK SIZE


BCH Transport Channel is used to carry BCCH. In LTE, BCH carries only Master Information Block (MIB) whereas all the SIB are transmitted using BCCH mapped on DL-SCH.

BCCH mapped to BCH as well as DL-SCH.

Transport Block size of BCH is set to 24 bits.

On this 24 bits , 16 bits CRC is added and makes 40 bits.

On 40 bits,  1/3 convolution coding is applied and converted in 120 bits.

On 120 bits, rate matching is applied and converted into 1920 bits.

This 1920 bits are spread across 40ms ( 4 frames). It means 4 frames carrying the original 24 bits.

X : MIB on PBCH on slot 1 on subframe 0  
Y: MIB' on PBCH on slot 1 on Subframe 0

 <---(X)---> <---(X) ---> <---(X)---> <---(X)--->  <---(Y)---> <---(Y)---> <---(Y)---> <---(Y)--->
<-10ms->      <-10ms->      <-10ms->  <-10ms->    <-10ms->  <-10ms->   <-10ms->     <-10ms->

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