Asymptotics and error rate bounds for M-ary DPSK

The symbol error probability for M-ary differential phase shift keying with maximum a posteriori probability and differentially coherent detection of equiprobable, equal energy signals is given by an integral expression in which the bit energy-to-noise spectral density ratio figures. It is presently noted that an especially good asymptotic approximation to this expression is accurate to within a 3-percent error for most cases of usual interest.