In recent years, considerable studies have been devoted to physical-layer network coding (PLNC) in a two-way relay channel (TWRC) network with the symmetric channel. However, it may not be appropriate for the asymmetric channel in which the source-to-relay channels are not equally strong and the two sources may utilise different modulation. In this study, the authors studied the heterogeneous PLNC design in the asymmetric TWRC network with high-order modulation and proposed a relay denoising mapping approach to reduce the decoding error probability. Firstly, they put forward a cluster maximisation algorithm to enlarge one cluster by sucking the neighbour points, which satisfy the exclusive law. Then, based on this algorithm, they designed the heuristic nearest-neighbour denoising mapping (HNDM) approach. The HNDM algorithm divides the nearest neighbour superimposed constellation points into the same cluster as far as possible. Points in the same cluster are coded into a new symbol by a specific mapping that achieves a many-to-one mapping. Performance results are provided in terms of symbol error rate. Under diversity channel conditions, the performances of 16-quadrature amplitude modulator (16-QAM)-8-phase-shift keying and 16-QAM-quadrature phase-shift keying are evaluated.

中文翻译：

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具有高阶调制的异构物理层网络编码的中继去噪映射方法设计和性能分析

近年来，大量研究致力于具有对称信道的双向中继信道（TWRC）网络中的物理层网络编码（PLNC）。但是，对于源到中继信道的强度不相等且两个源可能使用不同的调制的非对称信道可能不合适。在这项研究中，作者研究了具有高阶调制的非对称TWRC网络中的异构PLNC设计，并提出了一种中继去噪映射方法以减少解码错误的可能性。首先，他们提出了一种聚类最大化算法，通过吸取邻近点来扩大一个聚类，这满足排他律。然后，基于此算法，他们设计了启发式最近邻去噪映射（HNDM）方法。HNDM算法将最近的邻居叠加星座点尽可能地划分为同一群集。通过实现多对一映射的特定映射，将同一群集中的点编码为新符号。性能结果是根据符号错误率提供的。在分集信道条件下，评估了16正交幅度调制器（16-QAM）-8相移键控和16-QAM-正交相移键控的性能。