Question

How can we improve the performance of digital modulation under fading channels?

Answer 1

In this chapter, bit error rate (BER) performance of some of digital modulation
schemes and different wireless communication techniques is evaluated in additive
white Gaussian noise (AWGN) and fading channels. Further, the BER performance
of different diversity techniques such as selective diversity, EGC, and MRC is also
evaluated in Rayleigh fading channel.
2.1 BER Performance of Different Modulation Schemes
in AWGN, Rayleigh, and Rician Fading Channels
In this section, the effect of fading is evaluated on different modulation schemes.
The bit error probability Pb often referred to as BER is a better performance
measure to evaluate a modulation scheme. The BER performance of any digital
modulation scheme in a slow flat fading channel can be evaluated by the following
integral
Pb ¼
Z1
0
Pb; AWGNð Þc PdfðcÞdc ð2:1Þ
where Pb; AWGNð Þc is the probability of error of a particular modulation scheme in
AWGN channel at a specific signal-to-noise ratio c ¼ h2 Eb
N0
. Here, the random
variable h is the channel gain, Eb
N0 is the ratio of bit energy to noise power density in a
non-fading AWGN channel, the random variable h2 represents the instantaneous
power of the fading channel, and PdfðcÞ is the probability density function of c due
to the fading channel