PERFORMANCE OF FH MFSK SYSTEMS FOR SPEECH WITH ACTIVITY DETECTOR OVERRAYLEIGH FADING CHANNELS/

This paper presents the performance of FH/MFSK systems, which exploit silent gaps in speech to accommodate more users, over Rayleigh fading channels. Two kinds of receivers are considered: one uses a threshold on the received signal strength to declare whether the signals were pr esent or not, and the other is assumed to have perfect transmitter-sta te information obtained from using additional bandwidth. Results show that, if the codeword dropping and codeword error are assumed to be eq ually costly, the former can achieve slightly better performance than the latter in the decoding error probability. This finding suggests th at, for the system to exploit silent gaps in speech, it is advantageou s for the receiver to use a threshold to declare whether signals were present or not instead of relying on the transmitter-state information .