On Space-Time Block-Encoded 16-APSK in Aeronautical Mobile Telemetry

The two-antenna problem in aeronautical mobile telemetry is created by the reception of two copies of the same RF waveform with different phases and time delays. Alamouti and Alamouti-like space-time block codes can solve the two-antenna problem, but the decoder/detector needs to account for the different time delays between the signals received from the two transmit antennas. This article compares the performance of Alamouti space-time block codes and time-reversed space-time block codes with 16-APSK to solve the two-antenna problem. The maximum likelihood decoder/detector for Alamouti-encoded 16-APSK is a sequence detector operating on a trellis with a large number of states. A practical state-reduction technique is presented that produces a trellis with 256 states and a small loss in bit error rate performance. The decoder/detector for the time-reversed space-time block requires only waveform manipulations and pulse shape-matched filtering in the case where the two channels are simple delays. The bit error rate performance of the simplified decoder/detector produces no detectable loss in the bit error rate performance.