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Downlink Resource Allocation in Multiuser Cell-free MIMO Networks with User-centric Clustering
arXiv - CS - Performance Pub Date : 2021-08-13 , DOI: arxiv-2108.06316
Hussein A. Ammar, Raviraj Adve, Shahram Shahbazpanahi, Gary Boudreau, Kothapalli Venkata Srinivas

In this paper, we optimize user scheduling, power allocation and beamforming in distributed multiple-input multiple-output (MIMO) networks implementing user-centric clustering. We study both the coherent and non-coherent transmission modes, formulating a weighted sum rate maximization problem for each; finding the optimal solution to these problems is known to be NP-hard. We use tools from fractional programming, block coordinate descent, and compressive sensing to construct an algorithm that optimizes the beamforming weights and user scheduling and converges in a smooth non-decreasing pattern. Channel state information (CSI) being crucial for optimization, we highlight the importance of employing a low-overhead pilot assignment policy for scheduling problems. In this regard, we use a variant of hierarchical agglomerative clustering, which provides a suboptimal, but feasible, pilot assignment scheme; for our cell-free case, we formulate an area-based pilot reuse factor. Our results show that our scheme provides large gains in the long-term network sum spectral efficiency compared to benchmark schemes such as zero-forcing and conjugate beamforming (with round-robin scheduling) respectively. Furthermore, the results show the superiority of coherent transmission compared to the non-coherent mode under ideal and imperfect CSI for the area-based pilot-reuse factors we consider.

中文翻译:

具有以用户为中心的集群的多用户无小区 MIMO 网络中的下行链路资源分配

在本文中,我们优化了实现以用户为中心的集群的分布式多输入多输出 (MIMO) 网络中的用户调度、功率分配和波束成形。我们研究了相干和非相干传输模式,为每种模式制定了加权和速率最大化问题;众所周知,找到这些问题的最佳解决方案是 NP 难的。我们使用分数规划、块坐标下降和压缩感知中的工具来构建一种算法,该算法优化波束成形权重和用户调度,并以平滑的非递减模式收敛。信道状态信息 (CSI) 对于优化至关重要,我们强调了对调度问题采用低开销导频分配策略的重要性。在这方面,我们使用层次凝聚聚类的变体,它提供了一个次优但可行的导频分配方案;对于我们的无小区情况,我们制定了一个基于区域的导频重用因子。我们的结果表明,与基准方案(例如迫零和共轭波束成形(具有循环调度))相比,我们的方案在长期网络总和频谱效率方面提供了巨大的收益。此外,对于我们考虑的基于区域的导频复用因素,结果显示了在理想和不完美 CSI 下相干传输与非相干模式相比的优越性。我们的结果表明,与基准方案(例如迫零和共轭波束成形(具有循环调度))相比,我们的方案在长期网络总和频谱效率方面提供了巨大的收益。此外,对于我们考虑的基于区域的导频复用因素,结果显示了在理想和不完美 CSI 下相干传输与非相干模式相比的优越性。我们的结果表明,与基准方案(例如迫零和共轭波束成形(具有循环调度))相比,我们的方案在长期网络总和频谱效率方面提供了巨大的收益。此外,对于我们考虑的基于区域的导频复用因素,结果显示了在理想和不完美 CSI 下相干传输与非相干模式相比的优越性。
更新日期:2021-08-16
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