270 CHAPTER FIVE
DPSK Performance for MRC in Rayleigh Fading Channel
1.E??“01
1.E??“02
1.E??“03
1.E??“04
1.E??“05
1.E??“06
0 10 20 30 40 50
Eb/No (dB)
BER
DPSK (M = 1)
DPSK (M = 2)
DPSK (M = 3)
DPSK (M = 4)
FIGURE 5.58 DPSK BER performance for MRC combining.
Next we wish to show the BER performance gain when comparing MRC and SC diversity combining
techniques for BPSK modulation. Earlier in this chapter, we have shown the combiner output
mean SNR gain for both of these techniques. It was also shown that as the number of receiver antennas
increases the performance difference between EGC and MRC remains relatively the same, while
it increases when comparing MRC to SC. First we wish to provide the equations used to plot the
curves that follow. The BER performance for MRC is given by [57].
(5.106)
The BER performance for selection combining (SC) is given by
(5.107)
Given these two equations we can compare the performance of MRC and SC for M 2 and 4 antennas
in Fig. 5.59.
Pb
1
2 c1 aM
k1 QM
k R(1)k1a g
g kb1>2 d
Pb
1
2 c1 a g
g 1b1>2 aM1
k0 Q2k
k R# 1
[4(1 g)]k d
Above we can see for the M 2 antenna diversity receiver, the performance difference between
the MRC and SC is approximately 1.
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