A Block Processing Approach to CMA Equalization of SOQPSK for Aeronautical Telemetry

This paper presents the results of using the constant modulus algorithm (CMA) to recover a shaped offset quadrature-phase shift keying (SOQPSK)-TG modulated signal, which has been transmitted over an aeronautical telemetry channel using the iNET data packet structure. The iNET-packet structure contains known data bits (the preamble and asynchronous marker (ASM) bits) within each data packet, which can be used to determine the minimum mean square error (MMSE) and zero-forcing (ZF) equalizer. We present a block processing CMA equalizer which uses either the MMSE or the ZF equalizer for initialization, and compare its performance to the CMA equalizer with the usual method of center-tap initialization. These equalizers are shown to outperform the center-tap initialized CMA at higher SNRs, while providing a performance gain of about 1 dB to 3 dB over the fixed MMSE or ZF equalizer alone.