Chapter 17 587
W-CDMA Downlink Digital Modulation for Receiver Test
Transmit Diversity Overview
Figure 17-8 Generic STTD Encoder
In order to simulate two antennas for a transmit diversity application, both ESGs are configured the same
with the exception of one being designated as antenna one and the other as antenna two. The ESG selected
as antenna two will also modify the pilot bits for the dedicated primary common control channel (DPCCH).
TSTD is used only for the SCH and alternately transmits the SCH between the two antennas. Normally the
SCH is transmitted ten percent of the time for each slot of a radio frame. A radio frame is 10 ms long and is
comprised of 15 slots (0–14). During the TSTD transmission, the SCH is broadcasted on antenna one during
even numbered slots and on antenna two during odd numbered slots. This is demonstrated in Figure 17-9.
Figure 17-9 SCH TSTD Operation
The phase for the SCH is also inverted when the P-CCPCH is STTD encoded. When TSTD is turned off, the
SCH is broadcasted in every slot for the selected antenna. This is beneficial for synchronization purposes
when only a single ESG is used.
S
mbols
Antenna 1
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