This paper investigates different precoding strategies for rate splitting multiple access (RSMA) in the downlink of multi-cell visible light communication (VLC) networks. Since classical Shannon capacity formula does not hold for VLC, we first provide a lower bound on the channel capacity for RSMA in such interfering networks. Then, we formulate a spectral efficiency maximization problem to jointly find the optimal rate-splitting and transmit precoding. Beside that, since cell-edge users suffer from additional inter-cell interference, we propose to design the precoders of different RSMA signals utilizing coordinated beamforming (CB). Subsequently, aiming to improve the performance of the CB design for RSMA, while maintain a reduced complexity, we introduce two enhanced precoding strategies for RSMA. To the best of the authors’ knowledge such a contribution has not been considered before in the open literature. It is shown in the paper that the formulated optimization problem is non-convex and a sub-optimal, yet, a low complexity solution can be obtained efficiently using semi-definite relaxation combined with successive convex approximation. Through analytical results, we illustrate the flexibility and superiority of the proposed precoding strategies for RSMA over conventional coordinated space division multiple access and non-orthogonal multiple access for different scenarios and network loads.

中文翻译：

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多用户多小区 MIMO VLC 系统的干扰管理策略

本文研究了多小区可见光通信 (VLC) 网络下行链路中速率拆分多址 (RSMA) 的不同预编码策略。由于经典的香农容量公式不适用于 VLC，我们首先为此类干扰网络中的 RSMA 提供信道容量的下限。然后，我们制定了一个频谱效率最大化问题，以共同找到最佳速率分割和传输预编码。除此之外，由于小区边缘用户受到额外的小区间干扰，我们建议利用协调波束成形 (CB) 设计不同 RSMA 信号的预编码器。随后，为了提高 RSMA CB 设计的性能，同时保持降低的复杂性，我们为 RSMA 引入了两种增强的预编码策略。据作者所知，以前在公开文献中没有考虑过这样的贡献。论文表明，公式化的优化问题是非凸的，是次优的，但是，使用半定松弛结合逐次凸逼近可以有效地获得低复杂度的解决方案。通过分析结果，我们说明了针对不同场景和网络负载的 RSMA 预编码策略相对于传统协调空分多址和非正交多址的灵活性和优越性。使用半定松弛结合逐次凸逼近可以有效地获得低复杂度的解决方案。通过分析结果，我们说明了针对不同场景和网络负载的 RSMA 预编码策略相对于传统协调空分多址和非正交多址的灵活性和优越性。使用半定松弛结合逐次凸逼近可以有效地获得低复杂度的解决方案。通过分析结果，我们说明了针对不同场景和网络负载的 RSMA 预编码策略相对于传统协调空分多址和非正交多址的灵活性和优越性。