Low-density parity-check (LDPC) coded OFDM systems - coding/decoding over time and frequency domains

摘要

Orthogonal Frequency Division Multiplexing (OFDM) is a very attractive technique for high-hit-rate data transmission. In a multipath fading channel, some subcarriers of OFDM may be completely lost because of the deep fades. Hence, the overall bit error rate (BER) will be largely dominated by a few subcarriers with the smallest amplitudes. To avoid this domination by the weakest subcarriers, forward-error correction coding is essential. There are many error-correcting codes applied to OFDM, convolutional codes, Reed-Solomon codes, Turbo codes, and so on. Recently, Low-Density Parity-Check (LDPC) codes have attracted much attention particularly in the field of coding theory. LDPC codes were proposed by Gallager in 1962 and the performance is very colse to the Shannon limit with practical decoding complexity like Turbo codes. In this report, we propose LDPC coded OFDM systems and show that LDPC codes are effective to improve the BER performance of OFDM in multipath fading channel.