Postdetection selection diversity effects in a digital fm land mobile radio with discriminator and differential detections

In the digital FM land mobile radio communication with fast fading whose maximum Doppler frequency reaches several ten Hz, the error occurs due to the signal amplitude variation and random FM noise caused by the phase variation. This paper discusses the performance improvement by the postdetection selection diversity for the digital FM radio communication with discriminator and differential detections under a fast Rayleigh fading environment. The conditional error ratio is derived for the instantaneous detector input amplitude at fast Rayleigh fading and the average error rate at the diversity reception is obtained as a general solution with the effect of random FM noise taken into account. Further, the improvement effect in the presence of co-channel interference is analyzed. The comparison is made with the postdetection synthesis diversity.