5.71.
r ST # h n
r cr1(t)
r2(t) d cd1(t) d*2
(t)
d2(t) d*1
(t)d # ch1(t)
h2(t) d cn1(t)
n2(t) d
r2(t) d2(t) # h1(t) d*1
(t) # h2(t) n2(t)
r1(t) d1(t) # h1(t) d*2
(t) # h2(t) n1(t)
h1(t)>h1(t TS)
282 CHAPTER FIVE
Channel Estimation
Linear
Combiner
Ts
Ts
Pilot Signal
r d1
h1
d2
r1
r2
h2
?† ?†
FIGURE 5.71 STTD decoder receiver.
For the sake of this discussion, we will assume the channel has been estimated using any reliable
technique. The particular implementation of WCDMA utilizes pilot symbols that are orthogonal
across both transmit antennas. We will have the specifics of this in a later chapter where we discuss
the WCDMA application.
The linear combiner makes use of the consecutive received symbols to jointly estimate the transmitted
symbols. The equations used are as follows:
(5.146)
(5.147)
This can be rewritten in matrix form as follows:
(5.148)
After applying the matrix operations, we arrive with the following estimates:
(5.149)
(5.150)
Here we see we have extracted the diversity combining aspect of the channel to improve the receiver??™s
performance.
d ^
2 d2 # CZh1 Z2 Zh2 Z2D h*1
# n2 h2 # n*1
d ^
1 d1 # CZh1 Z2 Zh2 Z2D h*1
# n1 h2 # n*2
cd1
d2 d cr1 r*2
r2 r*1
d # ch*1
h2 d
d2 h*1
# r2 h2 # r*1
d1 h*1
# r1 h2 # r*2
5.
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