Simple Tight Upper Bounds for Average SEP and BEP of Coherent Diversity $M$-ary Biorthogonal Signals Over Fading Channels

This paper presents simple tight upper bound expressions for the average symbol error probability and bit error probability of coherent M-ary biorthogonal signals over fading channels with diversity reception. The upper bounds, which do not involve numerical integration and are expressed with only elementary functions, can be efficiently evaluated. In addition, they are valid for different diversity-combining techniques, as well as for arbitrarily correlated and/or nonidentically distributed channels. The tightness of the derived upper bounds is clarified under various channel conditions. Numerical results are also provided to demonstrate the impact of nonidentical channels on the system average error performance.