Iterative Detection of Unity-Rate Precoded FFH-MFSK and Irregular Variable-Length Coding

摘要

Iterative decoding of an irregular variable-length coding (IrVLC) scheme concatenated with precoded fast frequency-hopping (FFH) $M$-ary frequency-shift keying (MFSK) is considered. We employ EXtrinsic Information Transfer (EXIT) charts to investigate the three-stage concatenation of the FFH-MFSK demodulator, the rate-1 decoder, and the outer IrVLC decoder. The proposed joint source and channel coding scheme is capable of operating at low signal-to-noise ratios (SNRs) in Rayleigh fading channels contaminated by partial-band noise jamming (PBNJ). The IrVLC scheme is composed of a number of component variable-length coding (VLC) codebooks employing different coding rates that encode particular fractions of the input source symbol stream. These fractions may be chosen with the aid of EXIT charts to shape the inverted EXIT curve of the IrVLC codec so that it can be matched with the EXIT curve of the inner decoder. We demonstrate that using the proposed scheme, an infinitesimally low bit error ratio (BER) may be achieved at low SNR values.