Information-theoretic analysis and practical coding schemes for spectrally efficient FDM-CPM systems

We consider a frequency division multiplexed system where each user employs a continuous phase modulation (CPM). In such a system, the spectral efficiency (SE) can be increased by reducing the spacing between adjacent channels, at the expense of increasing the relevant interference. We investigate this aspect from an information-theoretic point of view, and describe a framework for computing the information rate (IR) and the SE of such systems when multiuser detection algorithms are employed at the receiver side. Furthermore, we consider practical schemes, where CPMs are serially concatenated with an outer code through an interleaver, and iterative detection/decoding is employed at the receiver, showing that the theoretical limits predicted by the IR analysis can be approached.