Capacity -based parameter optimization of bandwidth constrained CPM

Continuous phase modulation (CPM) is an attractive modulation choice for bandwidth limited systems due to its small side lobes, fast spectral decay and the ability to be noncoherently detected. Furthermore, the constant envelope property of CPM permits highly power efficient amplification. The design of bit-interleaved coded continuous phase modulation is characterized by the code rate, modulation order, modulation index, and pulse shape. This dissertation outlines a methodology for determining the optimal values of these parameters under bandwidth and receiver complexity constraints. The cost function used to drive the optimization is the information-theoretic minimum ratio of energy-per-bit to noise-spectral density found by evaluating the constrained channel capacity. The capacity can be reliably estimated using Monte Carlo integration. A search for optimal parameters is conducted over a range of coded CPM parameters, bandwidth efficiencies, and channels. Results are presented for a system employing a trellis-based coherent detector. To constrain complexity and allow any modulation index to be considered, a soft output differential phase detector has also been developed.;Building upon the capacity results, extrinsic information transfer (EXIT) charts are used to analyze a system that iterates between demodulation and decoding. Convergence thresholds are determined for the iterative system for different outer convolutional codes, alphabet sizes, modulation indices and constellation mappings. These are used to identify the code and modulation parameters with the best energy efficiency at different spectral efficiencies for the AWGN channel. Finally, bit error rate curves are presented to corroborate the capacity and EXIT chart designs

The capacity of noncoherent continuous-phase frequency shift keying

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. I

A Capacity-Based Search for Energy and Bandwidth Efficient

Abstract — This paper addresses the general problem of finding the combination of code rates and continuous phase modulation (CPM) parameters that have the best energy efficiency for a given spectral efficiency and de-modulator complexity. More specifically, bit-interleaved coded modulation (BICM) with noncoherently detected M-ary Gaussian frequency shift keying (GFSK) is con-sidered for the fading channel. First, a sequential, soft-out (SO), soft-decision differential phase detector (SD-DPD) is presented for noncoherent detection of GFSK signals. Next, the capacity for the proposed system under modulation, channel and receiver design constraints is calculated. For a wide range of spectral efficiencies, the optimal (in terms of energy and bandwidth efficiency) combination of GFSK parameters and code rates is found using information theoretic bounds on reliable signaling. Bit error rate simulations using a capacity-approaching binary turbo code reveal that performance within 1 dB of the constrained capacity can be obtained