Spatially Coupled LDPC Codes and the Multiple Access Channel
Spatially Coupled LDPC Codes and the Multiple Access Channel
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DOI：
10.1109/ciss.2019.8692899
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发表时间：
2019-01
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影响因子：
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通讯作者：
Sebastian Cammerer;Xiaojie Wang;Yingyan Ma;S. Brink
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作者：
Sebastian Cammerer;Xiaojie Wang;Yingyan Ma;S. Brink
为了避免将空间耦合低密度奇偶校验(SC-LDPC)码分量与迭代多用户检测器(MUD)进行繁琐的度轮廓匹配，我们考虑了非正交交织多址(IDMA)方案中的SC-LDPC码。除了优良的译码阈值之外，该方法还受益于使用相当简单和规则的基础块LDPC码的可能性，这是由于所得到的耦合码相对于信道前端的通用行为，即迭代MUD。此外，由于SC-LDPC本身可以在大范围的不同用户负载下保持恒定，因此额外的外部重复码使得该方案能够灵活地应对不同数量的用户和用户速率。译码门限通过密度进化(DE)得到，并通过误码率(BER)仿真进行验证。为了保持较小的译码复杂度和译码时延，我们引入了一种联合迭代加窗检测器/译码器，采用了仔细调整的子块交织器。最后，与加性高斯白噪声(AWGN)信道相比，所提出的编码方案同样适用于使用相同编码的Rayleigh信道，并且具有可容忍的性能损失。
We consider spatially coupled low-density parity-check (SC-LDPC) codes within a non-orthogonal interleave division multiple access (IDMA) scheme to avoid cumbersome degree profile matching of the LDPC code components to the iterative multi-user detector (MUD). Besides excellent decoding thresholds, the approach benefits from the possibility of using rather simple and regular underlying block LDPC codes owing to the universal behavior of the resulting coupled code with respect to the channel front-end, i.e., the iterative MUD. Furthermore, an additional outer repetition code makes the scheme flexible to cope with a varying number of users and user rates, as the SC-LDPC itself can be kept constant for a wide range of different user loads. The decoding thresholds are obtained via density evolution (DE) and verified by bit error rate (BER) simulations. To keep decoding complexity and latency small, we introduce a joint iterative windowed detector/decoder imposing carefully adjusted sub-block interleavers. Finally, we show that the proposed coding scheme also works for Rayleigh channels using the same code with tolerable performance loss compared to the additive white Gaussian noise (AWGN) channel.