多用户大规模MIMO自适应安全传输策略

大规模MIMO系统采用空分多址可以提高系统吞吐量，同时利用多用户下行信号的相互协作可以对窃听者造成叠加干扰，带来了天然的安全增益。但目前该系统的物理层安全研究仍采用传统的人工噪声方案，忽略了多用户信号干扰带来的安全增益，造成严重的功率浪费。针对这一问题，该文分析了多用户信号干扰对系统可达平均安全速率和平均安全能效的影响，给出了系统的最佳接入用户区间。研究发现，在系统接入用户数较少和用户数较多时，系统安全能力较弱，针对此分别提出了N波束加扰和基于用户位置的用户调度的自适应安全传输策略。最后通过仿真验证了理论推导和所提策略的有效性，利用该文所提策略，能够保证系统天然安全能力不足时的安全通信。

Adaptive Secure Transmission Strategy for Multiuser Massive MIMO

Massive MIMO system using Space Division Multiple Access (SDMA) can improve system throughput, and the use of multi-user downlink signal collaboration can cause superimposed interference to the eavesdropper, bringing a natural security gain. However, the physical layer security research of the system still adopts the traditional artificial noise scheme to improve the system security, ignoring the safety gain caused by the multi-user signal interference, resulting in serious power waste. In response to this problem, the impact of multi-user signal interference on the system achievable average security rate and average safety energy efficiency is analyzed in this paper, and the optimal interval of access users is given. The research shows that the system security capability is weak when the number of access users is small or large. Therefore, an adaptive secure transmission strategy to transmit N scrambling beams and user scheduling based on user location is proposed respectively. Finally, the effectiveness of the theoretical derivation and the proposed strategy is verified through the simulation. By using the proposed strategy, the secure communication can be guaranteed when the system,s natural security capability is insufficient.