This paper studies the coexistence between a downlink multiuser massive multi-input-multi-output (MIMO) communication system and MIMO radar. The performance of the massive MIMO system with maximum ratio ($\MR$), zero-forcing ($\ZF$), and protective $\ZF$ ($\PZF$) precoding designs is characterized in terms of spectral efficiency (SE) and by taking the channel estimation errors and power control into account. The idea of $\PZF$ precoding relies on the projection of the information-bearing signal onto the null space of the radar channel to protect the radar against communication signals. We further derive closed-form expressions for the detection probability of the radar system for the considered precoding designs. By leveraging the closed-form expressions for the SE and detection probability, we formulate a power control problem at the radar and base station (BS) to maximize the detection probability while satisfying the per-user SE requirements. This optimization problem can be efficiently tackled via the bisection method by solving a linear feasibility problem. Our analysis and simulations show that the $\PZF$ design has the highest detection probability performance among all designs, with intermediate SE performance compared to the other two designs. Moreover, by optimally selecting the power control coefficients at the BS and radar, the detection probability improves significantly.

翻译：本文研究了下行多用户大规模多输入多输出（MIMO）通信系统与MIMO雷达的共存问题。考虑信道估计误差和功率控制，从频谱效率（SE）角度刻画了采用最大比（$\MR$）、迫零（$\ZF$）和保护性$\ZF$（$\PZF$）预编码设计的大规模MIMO系统性能。$\PZF$预编码的核心思想是将信息承载信号投影到雷达信道的零空间，以保护雷达免受通信信号干扰。我们进一步推导了所考虑预编码设计下雷达系统检测概率的闭式表达式。利用SE和检测概率的闭式表达式，我们在雷达和基站（BS）处制定了一个功率控制问题，旨在满足每用户SE要求的同时最大化检测概率。该优化问题可通过求解线性可行性问题并利用二分法高效处理。分析与仿真表明，$\PZF$设计的检测概率性能在所有方案中最高，其SE性能介于另外两种方案之间。此外，通过最优选择基站和雷达的功率控制系数，检测概率得到显著提升。