Spectrally Efficient Concatenated Convolutional Codes with Continuous Phase Modulations

Abstract

We develop bandwidth-efficient serially concatenated coded (SCC) continuous phasemodulation (CPM) techniques for aeronautical telemetry. The concatenated code consists of an inner and an outer code, separated by an interleaver, and is decoded using relatively simple near-optimum iterative decoding algorithms. CPM waveforms such as shaped-offset quadrature phase shift keying (SOQPSK) and pulse code modulation/ frequency modulation (PCM/FM), which are currently used in military satellite and aeronautical telemetry standards, can be viewed as inner codes due to their recursive nature. For the outer codes, we apply serially concatenated convolutional codes (SCCC) because of their large coding gains, high coding rates, and because their decoding algorithms are readily implemented. High-rate codes are of special interest in aeronautical telemetry applications due to recent reductions in available spectrum and ever-increasing demands on data rates. We evaluate the proposed coding schemes with a large set of numerical simulation results and make a number of recommendations based on these results.