Low Complexity Joint User Association, Beamforming and RIS Reflection Optimization for Load Balancing in a Multi-RIS Assisted Network
Low Complexity Joint User Association, Beamforming and RIS Reflection Optimization for Load Balancing in a Multi-RIS Assisted Network
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DOI：
10.1109/wcnc55385.2023.10118734
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发表时间：
2023-03
期刊：
影响因子：
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通讯作者：
Byungju Lim;A. Alizadeh;Mai H. Vu
中科院分区：
文献类型：
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作者：
Byungju Lim;A. Alizadeh;Mai H. Vu
本文研究了在多个RIS辅助的多小区无线网络中，BS用户和RIS用户通信链路的波束形成、RIS相移和关联的联合优化问题。考虑具有许多RIS的网络设置，我们可以针对单个关联用户优化每个RIS的反射，即使RIS将反射所有用户的信号。我们首先设计最佳的BS发射波束形成与RIS的相移在一个封闭的形式，以最大限度地提高有效信道增益（ECG）。然后，我们设计了两种不同的BS-RIS-用户关联算法满足负载均衡约束。第一种算法在BS用户和RIS用户链路上使用最差连接交换，而第二种算法对RIS用户链路使用更简单的最大ECG规则，因为RIS处没有负载平衡。联合算法在BS-RIS-用户关联和波束成形/反射设计之间交替，直到收敛。该算法不仅具有比现有算法低得多的复杂度，而且优于传统的最大SINR关联，并有效地利用多个RI来提高网络的和速率。
We study the joint optimization of beamforming, RIS phase shift, and association for the links of BS-user and RIS-user communications in a multi-cell wireless network aided by multiple RISs. Consider a network setting with many RISs, we can optimize the reflection of each RIS for a single associated user, even though the RIS will reflect the signals of all users. We first design the optimal BS transmit beamforming together with the phase shift of RIS in a closed form to maximize the effective channel gain (ECG). Then, we design two different BS-RIS-user association algorithms satisfying the load balancing constraint. The first algorithm uses worst connection swapping on both the BS-user and RIS-user links, whereas the second algorithm uses a simpler max-ECG rule for the RIS-user link because of no load balancing at the RIS. A joint algorithm alternates between BS-RIS-user association and beamforming/reflection design until convergence. The proposed algorithms not only have substantially lower complexity than existing algorithms, but also outperforms the conventional max SINR association and effectively exploits multiple RISs to boost the network sum rate.