A pseudo automatic repeat request scheme for a LDPC decoder is presented which dramatically improves the probability of an error in an information binary digit over the signal-to-noise ratio (SNR) range 0 dB to 2 dB, by sacrificing the information throughput, with the added advantage of not being adversely affected by a fluctuation in the channel SNR. A frame, which consists of the concatenation of several code words, is retransmitted only if the channel signal- to-noise ratio estimate is found to be lower than a set threshold. Overall, the throughput is only briefly reduced as required to ensure excellent performance over low and high SNRs. Simulation results are presented for rate ½ (288, 576) WiMAX 802.16e LDPC code over an AWGN channel with binary phase shift keying (BPSK) modulation.
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