On the Uplink Max-Min SINR of Cell-Free Massive MIMO Systems
On the Uplink Max-Min SINR of Cell-Free Massive MIMO Systems
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DOI：
10.1109/twc.2019.2892463
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发表时间：
2019-04-01
影响因子：
10.4
通讯作者：
Ngo, Hien Quoc
中科院分区：
文献类型：
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作者：
Bashar, Manijeh;Cumanan, Kanapathippillai;Ngo, Hien Quoc
考虑一种无蜂窝大规模多输入多输出系统，采用最大最小方法在每个用户功率受限的情况下最大化最小用户速率。首先，基于信道统计信息推导出近似的上行链路用户速率。然后，针对中央处理单元处的接收滤波器系数优化和用户功率分配，构建原始的最大最小信干噪比问题。为了解决这个最大最小非凸问题，我们将原始问题分解为两个子问题，即接收滤波器系数设计和功率分配。接收滤波器系数设计被表述为一个广义特征值问题，而几何规划（GP）用于解决用户功率分配问题。基于这两个子问题，提出一种迭代算法，在该算法中，当其中一个设计变量固定时，两个问题交替求解。这种迭代算法获得全局最优解，通过建立上下行对偶性证明了其最优性。此外，我们提出一种新的次优方案，该方案提供一种几何规划表述，以高效且全局地最大化最小上行链路用户速率。数值结果表明，所提出的方案在性能上大大优于文献中现有的方案。
A cell-free massive multiple-input multiple-output system is considered using a max-min approach to maximize the minimum user rate with per-user power constraints. First, an approximated uplink user rate is derived based on channel statistics. Then, the original max-min signal-to-interference-plus-noise ratio problem is formulated for the optimization of receiver filter coefficients at a central processing unit and user power allocation. To solve this max-min non-convex problem, we decouple the original problem into two sub-problems, namely, receiver filter coefficient design and power allocation. The receiver filter coefficient design is formulated as a generalized Eigenvalue problem, whereas the geometric programming (GP) is used to solve the user power allocation problem. Based on these two sub-problems, an iterative algorithm is proposed, in which both problems are alternately solved while one of the design variables is fixed. This iterative algorithm obtains a globally optimum solution, whose optimality is proved through establishing an uplink-downlink duality. Moreover, we present a novel sub-optimal scheme which provides a GP formulation to efficiently and globally maximize the minimum uplink user rate. The numerical results demonstrate that the proposed scheme substantially outperforms the existing schemes in the literature.