Space-Time Coding for Aeronautical Telemetry: Part II—Decoder and System Performance

This paper describes the use of Alamouti-encoded-shaped offset QPSK version TG (SOQPSK-TG) to solve the two-antenna problem in aeronautical telemetry. The Alamouti space-time block code is used to encode the phase states in the complex exponential representation of SOQPSK-TG. Because SOQPSK-TG possesses memory, the Alamouti decoder is a sequence estimator. Maximum likelihood and least squares sequence decoders are derived. To reduce the number of states, the eight-waveform cross-correlated trellis-coded quadrature modulation (XTCQM) approximate representation of SOQPSK-TG is used. A prototype decoder based on the least squares decoder and the estimators described in Part I and operating at a data rate of 10 Mb/s was tested in the laboratory in test flights at the Air Force Test Center, Edwards AFB. The test flights demonstrate that Alamouti-encoded SOQPSK-TG, as described in this paper, using the least squares decoder based on the estimators described in Part I solves the two antenna problem in aeronautical telemetry.