Optimum time diversity for channels subject to pulse-burstinterference
Ali, A.A.
Communications, IEE Proceedings-
Volume 143, Issue 1, Feb 1996 Page(s):43 - 46
Digital Object Identifier
Summary:Results of optimum time diversity for Gaussian and Rayleigh fading
channels subject to pulse-burst interference of large power and
duty-cycle λ are presented. For NC-BFSK and DPSK signals the
Chernoff upper bound is used to obtain expressions of the optimum
diversity and the average bit error rate. Both hard-decision and
soft-decision decoding are considered. It is particularly shown that the
optimum diversity obtained using exact analysis and the Chernoff upper
bound are nearly equal, and that the results are valid for conventional
as well as spread-spectrum systems. It is concluded that the optimum
time diversity known as the repetition code can be used as an effective
countermeasure against pulsed interference of high power. With optimum
diversity, the exponential relation between power and bandwidth is
recovered for both the Gaussian and Rayleigh channels. Using
soft-decision decoding, the combined effect of pulse-burst interference
and the noncoherent combining loss is a reduction in the effective
signal/noise ratio by factors of (I-λ0.25) and
(1-λ)2 for Gaussian and Rayleigh channels,
respectively. For Gaussian channels, exact analyses show that
hard-decision decoding results in an additional loss of 2 dB for
λ→0, increasing to 3 dB as λ→1. Using the
Chernoff upper bound, hard-decision decoding results in an additional
loss of 3 dB for all values of λ. For Rayleigh channels with
optimum diversity, hard-decision decoding is 3 dB inferior to
soft-decision decoding
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