The eNodeB needs to allocate PUCCH code channel resources to UEs for sending HARQ-ACKs.
Anyone knows how eNB send PUCCH code channel resources to UE?
In SIB2. The two parameters mainly decide the PUCCH resources for ACK/NACK… n1PUCCH_AN and deltaPUCCHShift.
This pucch in sib2 is common, multiplexing by some UE to transmit ack/nack.
So, eNB should send each UE a code to multiplex them.
That depends on deltaPUCCHShift. If it is ds3, I can multiplex 36 UEs per PRB for PUCCH format 1/1a/1b.
Each of 36 UE should have different code?
No… 12 cyclic shifts and 3 orthogonal codes.
Number of orhogonal code is equal to number of DMRS symbol per slot which is 3 for 1/1a/1b.
Is it possible if somes UE using same codes & cyclic shift?
No. Otherwise eNB will not be able the differentiate the UEs when they will send ACK/NACK.
The ACK/NACK in PUCCH is related to the downlink CCE index using which the PDSCH is received.