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Why separate channels are required for HARQ?

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Why separate channels are required for HARQ?Why PHICH is used for ACK/NACK why not PDCCH channel is used?

posted May 2, 2017 by Poonam

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1 Answer

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Hi,
A per my understanding,
PDCCH is common for all user, say example you send PHICH in PDCCH then all UE will decode those data and try to match but only those UE who transmits data have to receive PHICH. One more is PHICH data is o bit data so BPSK codes but PDCCH is QPSK coded. PHICH uses grouping technique to identify the user if you include this into PDCCH then decoding PDCCH will become complicated. so to avoid all these negative impact they introduced PHICH channel.

answer May 5, 2017 by Jaganathan
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