Abstract-Capacity analysis is used to determine the fundamental tradeoff between power and spectral efficiency for coded continuous-phase frequency shift keying (CPFSK). The modulation may use an arbitrary modulation index h and the number of tones M may be any power of two. Detection is noncoherent and the channel is either AWGN or fully-interleaved (ergodic) Reyleigh fading. Numerical results demonstrate the advantage of using nonorthogonal modulation and multiple tones when the bandwidth requirement is tight.
Abstract-The design of bit-interleaved coded continuous phase modulation (CPM) is characterized by the code rate, alphabet size, modulation index, and pulse shape. This paper outlines a methodology for determining the optimal values of these parameters under bandwidth and receiver complexity constraints. The cost function that is used to drive the optimization is the informationtheoretic minimum E b /N 0 , which is found by evaluating the constrained channel capacity. The capacity can be estimated using Monte Carlo integration. A search for optimal parameters is conducted over a range of coded CPM parameters, bandwidth efficiencies, and channels. To limit complexity and allow any modulation index to be considered, the receiver is constrained to use a soft-output differential phase detector. Bit error rate curves using a binary turbo code confirm that the constrained capacity is a very good indicator of the performance of the complete system. Index Terms-Bit-interleaved coded modulation (BICM), capacity, continuous phase modulation (CPM), differential phase detector.
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