Due to the low SF used, the effects of IPI are more pronounced, and thus,
using the dedicated pilot bits to aid CE can suffer in quality due to this increased interference.
Now for the uplink, the situation is slightly different; here the modulation scheme is BPSK, and
the DCH and CCH are quadrature multiplexed. The 3GPP standard definition applies as follows
(assuming a voice service application):
(7.92)
If we consider the relative power offset (pilot to traffic channel) defined as , then we can
write down the Eb/No of the data channel as
(7.93)
Then the CCH Eb/No is given as
(7.94)
Hence, when evaluating the error rate performance on either the DCH or CCH channels, the above
equations will help determine the respective SNR per bit value. These equations take into account not
only the PG but also their respective powers.
Optimal Combining (OC). Let us, first, redraw the above RAKE finger receiver in the simplified
form as in Fig. 7.75.
aEb
NobCCH
aEP
NobdB
aEc
Nob 10 # loga1
1
b 10 # log(PG256)
aEb
NobDCH
aEd
NobdB
aEc
NobdB
10 # log(1 ) 10 # log(PGDCH)
CCH
DCH
Eb
No
Ec
No
# 3840 kcps
12.2 kbps
402 CHAPTER SEVEN
FIGURE 7.75 Generalization of a RAKE combiner.
Pages:
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663