Performance Comparison of Selected Bandwidth-Efficient Coded Modulations

Bandwidth-efficient modulations may be used to reduce the possibility of future congestion in the deep-space frequency bands due to a growing demand for higher data rates and to an increasing number of simultaneous missions. High-rate error-correcting codes such as punctured turbo codes and low-density parity-check (LDPC) codes can improve bandwidth usage while still providing large coding gains essential for deep-space communications. This article examines the throughput and bit-error rate performance of various coding and modulation combinations. As the number of such combinations is unlimited, the study concentrates upon bandwidthefficient quadrature modulations compatible with the DSN Block V Receiver and selected turbo and LDPC codes. Capacity limits are derived for modulations under bandwidth constraints, and a comparison of selected uncoded and coded modulation schemes on the basis of bandwidth-normalized throughput and bit-error rate performance, obtained via theory and/or simulation, is presented. The effect of nonlinear amplifier operation is also analyzed. Finally, candidates for high-data-rate Mars missions are identified.