无小区大规模MIMO系统中基于图着色的导频分配与功率控制算法

Pilot Assignment with Graph Coloring and Power Control Algorithms in Cell-Free Massive MIMO Systems

无小区大规模MIMO(Cell-Free Massive MIMO,CF-mMIMO)系统中大量的无线接入点在同一时间频率资源中服务所有的用户,具有较高的网络覆盖率和频谱效率,是下一代无线通信的前沿技术之一。然而,正交导频数量的限制以及用户信道质量的差异造成了较严重的用户间干扰。为了优化这一干扰问题,本文提出了无小区大规模MIMO系统中基于图着色的导频分配与功率控制算法。利用基于图着色的导频分配算法降低导频污染,提高了信道估计精度。在此基础上,通过最大-最小功率控制算法降低多用户同频干扰,满足了系统中用户的混合服务质量需求。数值仿真结果表明:所提出的基于图着色的导频分配与功率控制算法可以显著提高系统的95%用户频谱效率以及最小用户速率,较好抑制了CF-mMIMO系统中的用户间干扰。

A large number of wireless access points(AP)in cell-free massive multiple input multiple output(CFmMIMO)system is an advanced technology in next-generation wireless communications,which serves all users in the same time-frequency resource with high network coverage probability and spectrum efficiency.However,the limitation in the number of orthogonal pilot and the difference in the channel quality of the users lead to more severe inter-user interfer⁃ence.To optimize the interference problems,the pilot assignment with graph coloring and power control algorithms are pro⁃posed in cell free massive MIMO systems.In the scheme,the pilot assignment algorithm with graph coloring is proposed to reduce the pilot contamination and improve the accuracy of channel estimation.Furthermore,the max-min fairness power control algorithm is presented to inhibit the multi-users co-frequency interference and thus satisfying the various quality-ofservice requirements of users.Numerical simulation results show the proposed algorithms can significantly improve 95%user spectrum efficiency and the minimum user rate of the system,the inter-user interference is also well suppressed.