System Design for FEC in Aeronautical Telemetry

Abstract

This paper contains a description of two types of forward error correction (FEC) codes for shaped offset quadrature phase shift keying, telemetry group version (SOQPSK-TG). The FEC codes are a low-density parity check (LDPC) code and a serially concatenated convolutional code (SCCC). The contributions of this paper are on the system-design level. One major contribution is to design a SCCC code word format that is as compatible as possible with the LDPC code word, which simplifies other aspects of the system design. Another major contribution is to show exactly how demodulators and decoders can be decoupled from each other at the receiver. This simplifies the demodulation process because receiver synchronization is no longer intertwined with FEC decoding. Furthermore, this enables a mix-and-match design, where demods can be chosen based on their performance and complexity tradeoffs. In fact, for the first time, we show how symbol-by-symbol demods can be used with all FEC coding/decoding options, and we also show that these demods have very attractive BER performance given their simplicity.