HARQ - HSDPA

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 HARQ process in HSADPA goes as illustrated below. In reality with high throughput condition, multiple HARQ processes (Usually 5 HARQ processes) are running in parallel in interleaved manner to achieve high data rate.

i) HS-SCCH is transmitted 2 slots before HS-DSCH (Refer to 7.8 HS-SCCH/HS-PDSCH timing of 25.211).
ii) HS-DSCH carrying user data is transmitted.
iii) UE decode it and send ACK/NACK via HS-DPCCH.



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