| Design of hybrid automatic repeat request （HARQ） for TDD-OFDM system |
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| 引用本文： | 温娜,Zhang,ping.Design of hybrid automatic repeat request （HARQ） for TDD-OFDM system[J].高技术通讯(英文版),2008,14(3):249-252. |
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| 作者姓名： | 温娜 Zhang ping |
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| 作者单位： | WTI Institute, Beijing University of Posts and Telecommunications, Beijing 100876, P.R. China |
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| 基金项目： | 国家高技术研究发展计划(863计划) |
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| 摘 要： | Reliability-based hybrid automatic repeat request （HARQ） （RB-HARQ） is a recently developed form of incremental-redundancy ARQ. It achieves good performance whereas large retransmission request packets should be fed back. In this paper, in order to reduce the number of the fed back bits, we propose a HARQ scheme applied in time duplex division orthogonal frequency division multiplexing （TDD- OFI）M） system over the slow fading channel which is named channel-based HARQ （CB-HARQ）. Because one bit which meets deep fading is always with small value of log likelihood ratio （LLR） during the process of decoding of LDPC code, the bits transmitted on the carrier with deep fading are retransmitted. At the receiver, the decoder will compute the locations of retransmission bits according to the channel fading values which are gotten by utilizing the feature of channel symmetry in TDD mode. So the indices of retransmission bits are avoided to be transmitted. Simulation results show that this method achieves better BER performance and requires much smaller request packets in feedback link.
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| 关 键 词： | 通信系统 正交频分复用技术 混合自动重复请求 低密度奇偶校验码 |
Design of hybrid automatic repeat request (HARQ)for TDD-OFDM system |
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| Wen Na,Zhang Ping.Design of hybrid automatic repeat request (HARQ)for TDD-OFDM system[J].High Technology Letters,2008,14(3):249-252. |
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| Authors: | Wen Na Zhang Ping |
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| Institution: | WTI Institute, Beijing University of Posts and Telecommunications, Beijing 100876, P.R.China |
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| Abstract: | Reliability-based hybrid automatic repeat request (HARQ) (RB-HARQ) is a recently developed form of incremental-redundancy ARQ.It achieves good performance whereas large retransmission request packets should be fed back.In this paper, in order to reduce the number of the fed back bits, we propose a HARQ scheme applied in time duplex division orthogonal frequency division multiplexing (TDDOFDM) system over the slow fading channel which is named channel-based HARQ (CB-HARQ).Because one bit which meets deep fading is always with small value of log likelihood ratio (LLR) during the process of decoding of LDPC code, the bits transmitted on the carrier with deep fading are retransmitted.At the receiver, the decoder will compute the locations of retransmission bits according to the channel fading values which are gotten by utilizing the feature of channel symmetry in TDD mode.So the indices of retransmission bits are avoided to be transmitted.Simulation results show that this method achieves better BER performance and requires much smaller request packets in feedback link. |
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| Keywords: | hybrid automatic repeat request (HARQ) orthogonal frequency division multiplexing (OFDM) low density parity check (LDPC) codes |
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