Abstract
This paper proposes a novel symbol-level combining hybrid automatic repeat request (HARQ) scheme based on analog chaotic code and named HARQ-Chaotic. The transmitter of HARQ-Chaotic adopts analog chaotic code to encode Quadrature Amplitude Modulation (QAM) symbols of retransmission packets to combat fading and noise. As the analog chaotic code can only handle sources with amplitudes in the range of [-0.5, 0.5], QAM symbols must be scaled into this range. We derived the optimal scaling factor through theoretical analysis. A joint algorithm combining with novel soft chaotic decoder and novel soft QAM demapper is proposed for the receiver to enhance the performance of the whole communication system. We implemented HARQ-Chaotic with LDPC codes and 16-QAM/64-QAM to carry out simulations in both AWGN channels and multipath fading channels. Massive simulation results demonstrate that the proposed HARQ-Chaotic has 1dB-4dB gain over traditional HARQ-Chase combining (HARQ-CC) scheme in block error rate (BLER) performance.
Highlights
As wireless channel is time varying and subject to fading, additive noise, and interference [1], hybrid automatic repeat request (HARQ) techniques that combine both forwarderror-correcting (FEC) codes and ARQ are often adopted to improve spectrum efficiency and transmission reliability
(1) We propose a novel symbol-level HARQ scheme based on analog chaotic code named HARQ-Chaotic, which can protect Quadrature Amplitude Modulation (QAM) symbols of retransmission packets to combat fading and noise directly
(2) We propose a soft joint algorithm combining with a novel soft chaotic decoder and a novel soft QAM demapper, which can improve the performance of the whole communication system greatly
Summary
As wireless channel is time varying and subject to fading, additive noise, and interference [1], hybrid automatic repeat request (HARQ) techniques that combine both forwarderror-correcting (FEC) codes and ARQ are often adopted to improve spectrum efficiency and transmission reliability. Traditional analog chaotic decoding algorithms work in the way of hard decision, which discard the probability information of the decoding value If these traditional decoding algorithms are applied to the proposed HARQ-Chaotic system directly, the lost probabilities will reduce the overall system performance. To solve this problem, we propose a soft joint algorithm combining with a novel soft chaotic decoder and a novel soft QAM demapper. (1) We propose a novel symbol-level HARQ scheme based on analog chaotic code named HARQ-Chaotic, which can protect QAM symbols of retransmission packets to combat fading and noise directly.
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