Reduced Complexity Detection of Shaped Offset QPSK

Shaped offset QPSK (SOQPSK) is a constant envelope, bandwidth efficient modulation that has been adopted into the standard for aeronautical telemetry channels. Due to the memory inherent in this modulation, the optimum detector for it requires a trellis and consequently has fairly high complexity. In this paper we explore the bit error rate performance of reduced complexity detectors for SOQPSK. We show that for SOQPSK a factor of 128 reduction in the number of trellis states of the detector can be achieved with a loss of only 0.2 dB in bit error rate performance.