This restriction is used in order to help the BS to
not incorrectly add multipaths from different users within the RAKE.
The uplink transmitted signals are given as
(7.19)
(7.20)
The BS receiver will see the summation of these two signals, respectively scaled and shifted in time
due to the propagation channel conditions.
S2(t) #2P # b2(t) # C1Qt
T
2 R# cos [2pfct]
S1(t) #2P # b1(t) # C1(t) # cos [2pfct]
I1(t) P # b1(t t1) # PG b2(t t1) # RC1C2
(0) noise terms
I1(t) P # b1(t t1) # 3Tb
0
C2
1 (t t1) dt P # b2(t t1) # 3Tb
0
C2(t t1) # C1(t t1) dt
I1(t) P # 3Tb
0
b1(t t1) # C2
1(t t1) dt P # 3Tb
0
b2(t t1) # C2(t t1) # C1(t t1) dt
t1 t^
1
V1(t) P # [b1(t t1) # C1(t t1) # C1(t t^
1) b2(t t1) # C2(t t1) # C1(t t^
1)]
Z1(t) P # [b1(t t1) # C1(t t1) b2(t t1) # C2(t t1)]
3G WIDEBAND CDMA 351
If we continue along the lines that we have a frequency flat fading channel, then the receiver architecture
in Fig. 7.13 exists for both users at the BS.
Considering User 1 only, we have the following equation where we have included a term to represent
the phase offset between the two received signals carrier frequencies:
(7.21)
This phase offset arises from the fact that ideal coherent detection was applied to User 1 in this example
and not to User 2.
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