TDD模式下无小区大规模MIMO系统的导频干扰抑制

Pilot interference mitigation for TDD cell-free massive MIMO systems

为了缓解无小区大规模MIMO系统的导频干扰、提高系统性能,提出了一种综合导频复用、AP选择和功率控制的导频干扰抑制策略。首先,提出了基于用户距离排序的导频分配,合理地避免了两个距离较近的用户复用导频,以减少导频干扰的影响。然后,通过分析系统吞吐量表达式中的影响因子确定AP选择的标准,只选择对用户的宏分集增益有主要影响的AP作为用户的服务AP。最后,提出了一种改进的最大最小功率控制算法,提高系统平均吞吐量。仿真结果显示,提出的导频干扰抑制策略有效地减轻了导频干扰带来的性能损失。

To alleviate the pilot interference for cell-free massive multi-input multi-output(MIMO) system and improve system’s performance, a comprehensive approach including the pilot reuse, access point(AP) selection and power allocation was proposed. Firstly, to alleviate the pilot contamination, the pilot assignment based on the order of user distance was proposed, in which the pilot sharing was only allowed when the distance between two users is large enough to reduce the impact of pilot reuse. Then, by AP selection, only the APs which have main impact on the macro diversity gain were selected as the user’s serving APs. Finally, a modified max-min power control algorithm was proposed to improve the system’s average throughput. Simulation results show that the pilot interference mitigation strategy proposed improves the performance of the system significantly.