Adaptive-rate nonbinary LDPC coding for frequency-hop communications

We evaluate the performance of irregular low-density parity-check (LDPC) codes in slow frequency-hop spread-spectrum systems with nonbinary orthogonal modulation. We also evaluate the performance of two adaptive coding protocols for the LDPC codes. The protocols use information derived by the iterative decoder during the decoding of each packet to select the code rate for the next packet. Performance results are presented for static partial-band noise channels and for partial-band noise channels with time-varying interference bandwidth or power. The adaptive coding protocol is shown to have good performance, even on channels that cause some of the individual codes to exhibit nonmonotonic throughput.