If the HS-DSCH CRC decode is successful, then an ACK is inserted.
If the HS-DSCH CRC decode is unsuccessful, then a NACK is inserted. The CQI is a time-varying
indication of the channel the UE observes. The mapping of this quality to an indicator is accomplished
by sending the NodeB an index into a channel quality table indicating the best possible combinations
of modulation scheme, transport block size, and code rate the UE can receive at that particular time
instant. We will discuss this operation in more detail in the HSDPA section later in this chapter.
Five uplink physical channels were presented. The DPDCH and DPCCH are time slot aligned
along with the E-DPDCH and E-DPCCH channels. The HS-DPCCH channel is not necessarily time
aligned with these channels due to the uplink and downlink timing relationship required to support
HSDPA services.
Downlink Discussion. There are five types of downlink DPCHs: DPCH, F-DPCH, E-RGCH,
E-AGCH, and E-HICH. The downlink frame and time slot structure for the DPCH is given in
Fig. 7.38. The DPCH consists of DPDCH and DPCCH time multiplexed into the physical channel.
3G WIDEBAND CDMA 373
FIGURE 7.38 Downlink DPDCH and DPCCH time slot and frame structure.
DPCH
2560 Chips
Slot #i .
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