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

Abstract

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 paper 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.