Fading in mobile GMSK-II

Receiver structures, even though insensitive to high levels of intersymbol-interference, may perform poorly in a fading channel. A year ago, a receiver algorithm was proposed for decoding a GMSK signal in a channel with randomly varying gain. The algorithm was derived on the basis of the reference probability method for hidden Markov models. This paper continues the earlier work and shows that a simply implemented recursion can be derived which has diminished sensitivity to random attenuation and delay in the transmission channel. A nonlinear decoder is presented which has improved detection probability with reduced spectral bandwidth. On-line estimates of relevant channel parameters are also given.