RS codes: An attractive choice for low bit rate speech transmission in PCS

Differential coherent 8-DPSK, 16-DSPK and 8/8-DAPSK modulation schemes have been investigated for use in a frequency-hopping code division multiple access system. For this purpose, a Rayleigh and Ricean fading model for the frequency hopping system has been developed. A FH system which uses these modulation schemes and Reed-Solomon (RS) codes as forward error correction in the presence of Rayleigh and Rician fading channels has been simulated. A pilot symbol has been used at the beginning of each frequency hop slot in order to overcome the phase ambiguity caused by fading and as a result of hopping the carrier frequency. Block interleaving also been also used and simulated in the system. A performance comparison for the above system which uses each of the modulation schemes is presented for the cases with and without block interleaving.<
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