Hi Pix
After 2 long years,I’m back and found my questions still unanswered.
Anyways,here are the answers.
1.SF-512 is not used in UL because each Ue has its own code tree and we have no channelization code shortage,there is no point in having so many SF’s.
2. If an error is detected in HS-SCCH, the Ue sends back over the uplink channel HS-DPCCH a NACK indicating an error. If no error is detected, the Ue checks whether the user data on the allocated HS-PDSCH(s) are erroneous. If they are not, an ACK is transmitted over the HS-DPCCH, else a NACK is transmitted.