Generalized concatenated CPFSK modulation

Using the principles of generalized concatenation we introduce a new design for encoded M-ary CPFSK systems with modulation index h=1/M. This technique is based on a set partitioning method of inner CPFSK into nested subsystems with increasing free Euclidean distance. The subsystems are combined with several outer convolutional codes having different error-correcting capabilities. We describe a multistep decoding algorithm of generalized concatenated encoded CPFSK and give simulation results. The comparison of the generalized concatenated codes with the best known trellis-coded CPFSK schemes is also presented.