The symbol error probability of Gaussian MSK using differential detect
ion in a Rician fast fading channel is investigated. In the analysis,
the effect of the infinite sequence of intersymbol interference inhere
nt in this modulation is included exactly, and the performance can be
evaluated at narrow shaping bandwidths where the intersymbol interfere
nce is extensive. Numerical results are presented for parameters typic
ally encountered in the satellite-to-mobile channel.