Turbo coding with differentially coherent and non-coherent modulation on non-fading and fading channels

This paper determines the performance of the turbo coding technique using M-ary (M=2, 4, 8) differentially coherent and non-coherent modulation schemes in both a non-fading and a Rayleigh fading environment. The constituent codes are convolutional and the specific modulation techniques include differential phase shift keying (DPSK), double differential phase shift keying (DDPSK), and non-coherent detection of frequency shift keying (FSK). Note that these modulations are all constant envelope, which is a desirable characteristic for hard limited channels such as transmission over satellite transponders. The emphasis is on constructing modulation/turbo coding schemes that perform at a lower required Eb/No and greater bandwidth efficiency than current coding approaches that use these modulation techniques. The turbo coding approaches developed in this paper require a small interleaver delay (to allow use in packet transmission systems with packet sizes ranging up to about 2048 bits) and a low number of decoding iterations for processing the constituent codes. They are robust in AWGN and Rayleigh fading channels, relatively easy to implement, and power and bandwidth efficient.