The base station (BS) transmitter looks like that in Fig. 7.10, where different PN sequences, C1(t) and
C2(t), have been used for each user.
The transmitted signal is represented as
(`7.10)
We will assume we have a frequency flat channel with AWGN, so the received signal becomes
(7.11)
where h(t) fading channel variations, propagation time delay, and N(t) Gaussian noise with
zero mean.
X(t) h(t) # S(t t) N(t)
S(t) 22P # ca2
i1
bi(t) # Ci(t) d # COS[2pfct]
Rx(t)
NAgrees NDisagrees
T
Rx(t)
1
Rxx(0)
# 1
T 3
T
2
T
2
x(t) # x(t t) dt
3G WIDEBAND CDMA 349
The mobile station received signal is represented as
(7.12)
which can be rewritten as (for j 1, 2)
(7.13)
Here we have used the index j to denote the user of interest number and the index i for the number
of users transmitted. Since the receiving MS will be located in physically different locations
within the cell, the fading and propagation time delays are assumed to be different. In Fig. 7.11, we
present the receivers for each user.
Xj(t) hj(t) ea2
i1
Ci(t tj) # bi(t tj) f# cos [2pfct fj] Nj(t)
Xj(t) hj(t) ea2
i1
Ci(t tj) # bi(t tj) f# cos [2pfc(t tj)] Nj(t)
350 CHAPTER SEVEN
FIGURE 7.
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