短期功率约束下的无小区大规模MIMO中的功率分配研究

Power optimization in cell-free massive MIMO with short-term power constraints

文中考虑了一个下行无小区大规模多输入多输出(multiple-input multiple-output,MIMO)系统,其中M个单天线接入点(access point,AP)和K个单天线用户随机分布在服务区内,M> K。同一用户可以在同一时间、同一频率上被所有接入点服务。在短期功率约束(short-term power constraint,STPC)下,文中针对两种不同的优化问题分别提出了相对应的功率分配算法。第一个优化问题是在满足用户服务质量(quality-of-service,Qo S)约束的条件下最大化用户总速率,该问题可以利用连续凸逼近(successive convex approximation,SCA)的方法求解。此外,第二个优化问题是一个混合Qo S约束问题。它可以在保证高优先级用户(high propriety user,HPU)的QoS需求的基础上,为其余低优先级用户(low propriety user,LPU)提供相同速率的服务。该问题是拟凹的,因此可以通过二分法求解。仿真结果表明,文中提出的功率分配算法具有很好的性能。此外,同长期功率约束(long-term power constraint,LTPC)相比,STPC可以显著提高用户下行速率。

Considering a downlink cell-free massive multiple-input multiple-output (MIMO) system,M single-antenna access points (APs) and K single-antenna users are randomly distributed in a given area,and M>K.Each user can be simultaneously served by all APs in the same time-frequency resources.Based on the short-term power constraint (STPC),this paper proposes two power control algorithms aimed at two optimal problems:(1) maximizing the total rate,subject to the quality-of-service (QoS) constraint.The problem can be approximately solved by sequential convex approximation (SCA) method.(2) the mixed QoS constraint problem provides uniformly good service for all low propriety users (LPUs) while satisfying the QoS requirements of high propriety users (HPUs).The proposed algorithm is quasi-concave,it can be determined by the bisection method.Simulation results indicate that the STPC can improve the achievable downlink rate compared with the long-term power constraint (LTPC).