Joint source/channel coding using trellis-coded CPFSK

A combined source/channel coding and modulation technique is developed for the transmission of memoryless sources over an AWGN channel. Combined source/channel coding is implemented using the concepts of trellis coded quantization (TCQ) in conjunction with an Ungerboeck code defined for a continuous phase frequency shift keying (CPFSK) signaling scheme. The Viterbi algorithm is employed by the source encoder to find a minimum mean-square-error (MSE) path through the source code trellis. The resultant minimum distortion sequence is mapped to an appropriate set of CPFSK symbols for transmission. A mapping is pragmatically developed to simultaneously preserve the original branch labelings of both the source and channel code trellises. Source symbol recovery is performed by maximum likelihood sequence estimation. The total distortion is experimentally determined over a range of channel signal-to-noise ratios. Furthermore, it is demonstrated that the use of a CPFSK signaling scheme avoids the production of spectral line components in the transmitted waveform spectrum that are usually associated with joint source/channel coding schemes.