Reduced-complexity detectors for Multi-h CPM in aeronautical telemetry

A two-index, partial response continuous-phase modulation (CPM) known as ARTM CPM was adopted for use in aeronautical telemetry in the IRIG 106 standard in 2004. This waveform was selected because it achieves approximately three times the spectral efficiency of PCM/FM, the legacy modulation in IRIG-106. However, the optimum receiver requires 128 real-valued matched filters and keeps track of the waveform state with a trellis of 512 states and 2048 branches. Various complexity-reducing techniques are applied and the resulting loss in detection efficiency is quantified. It is shown that the full 512-state trellis is not required to achieve desirable detection efficiency: two different 32-state configurations were found to perform within 0.05 dB of optimal; two different 16-state configurations were found to perform within 0.80 dB of optimal; and an 8-state configuration was found to perform within 1.05 dB of optimal. The analysis and simulation results show that to achieve a given state complexity, proper combination of two or more complexity-reducing techniques generally outperforms the use of a single complexity-reducing technique