Low-density parity-check (LDPC) coded ultra high-data-rate OFDM system in frequency-selective fading

摘要

In this paper, we investigate the performance when low-density parity-check (LDPC) coding is deployed in DPC-OF/TDMA (dynamic parameter controlled orthogonal frequency and time division multiple access) system, which is actually an orthogonal frequency division multiplexing (OFDM) system aiming at providing ultra high-data-rate transmission capability beyond 100 Mbps. The new DPC-OF/TDMA system is most likely to encounter the severe frequency-selective fading due to the fact that the bandwidth is large even in each subchannel (subband), and the error probability performance could be jeopardized by the subcarriers in deep fading. LDPC coding has excellent error correction capability, and this feature motivates us to deploy LDPC in DPC-OFATOMA system. The log-domain sum-product algorithm is considered as the decoding method of LDPC codes due to its computational complexity is lower than its probability-domain counterpart. In order to support the decoding algorithm., we introduce how to generate the log-likelihood ratio (LLR) for the codeword bits which are transmitted through the spectral-efficient multi-level modulation modes such as 16QAM. The frequency-selective fading encountered by DPC-OF/TDMA system is modeled by using the statistical channel model instead of any tap-delayed model, because our intention is to investigate the performance from the statistical point of view.