LDPC code optimization for diversity reception and turbo equalization

Abstract

Iterative “turbo” decoding of parallel or serial concatenated convolutional codes (CC) allows for a performance close to Shannon's channel capacity limit. Whereas “turbo” equalization (TE) for intersymbol interference (ISI) channels corresponds to serial concatenation, we show that the turbo decoding principle for parallel concatenation can be extended to a diversity receiver concept. “Turbo diversity” outperforms maximum-ratio combining (MRC) in forward error correction (FEC) encoded broadcast systems like “Digital Radio Mondiale” (DRM). In addition, we apply low-density parity-check (LDPC) codes instead of CC to turbo equalization and to turbo diversity, where an LDPC code design using fitted extrinsic information transfer (EXIT) functions is applied to optimize the system performance.