7.18 for a RAKE
having 1, 2, and 3 fingers in a fast fading environment with a Doppler spread 300 Hz, assuming a
convolutional Forward Error Correction (FEC) code.
356 CHAPTER SEVEN
RF
Section
RAKE
Output
ADC
Echo Profile
Manager
Finger #1
Finger #2
Finger #N
Combiner
P(t)
t1
t1
t2
tN
t t2 tN ??¦
.
.
.
FIGURE 7.17 RAKE high-level block diagram.
FIGURE 7.18 RAKE receiver BER performance results.
WCDMA Coded BER RAKE Performance
1.E??“04
1.E??“03
1.E??“02
1.E??“01
3 5 7 9 11 13 15
Eb/No (dB)
Coded BER
1 Finger
2 Fingers
3 Fingers
The results were obtained as follows: The one-finger RAKE performance curve assumed a flat
fading channel model. The two- and three-finger RAKE curves assume an FSF channel model with
two and three multipaths, respectively. All multipaths had equal average power. Here, one can see the
tremendous benefit in having an FSF channel with DS-CDMA. An important piece of information to
have is that the SF of the physical channel was set to 128, a relatively large number. This large PG is
used to suppress interference from other arriving multipaths in the RAKE finger.
7.4.1 General RAKE
In this section, we will present a more general RAKE architecture in detail.
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