Future wireless communication systems are expected to explore spectral bands typically used by radar systems, in order to overcome spectrum congestion of traditional communication bands. Since in many applications radar and communication share the same platform, spectrum sharing can be facilitated by joint design as a dual-function radar-communications system. In this paper, we propose a joint transmit beamforming model for a dual-function multiple-input-multiple-output (MIMO) radar and multiuser MIMO communication transmitter. The proposed dual-function system transmits the weighted sum of independent radar waveforms and communication symbols, forming multiple beams towards the radar targets and the communication receivers, respectively. The design of the weighting coefficients is formulated as an optimization problem whose objective is the performance of the MIMO radar transmit beamforming, while guaranteeing that the signal-to-interference-plus-noise ratio (SINR) at each communication user is higher than a given threshold. Despite the non-convexity of the proposed optimization problem, we prove that it can be relaxed into a convex one, where the relaxation is tight. We then propose a reduced complexity design based on zero-forcing the inter-user interference and radar interference. Unlike previous works, which focused on the transmission of communication symbols to synthesize a radar transmit beam pattern, our method provides more degrees of freedom for MIMO radar and is thus able to obtain improved radar performance, as demonstrated in our simulation study. Furthermore, the proposed dual-function scheme approaches the radar performance of the radar-only scheme, i.e., without spectrum sharing, under reasonable communication quality constraints.

中文翻译：

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多用户 MIMO 通信和 MIMO 雷达的联合发射波束成形

预计未来的无线通信系统将探索雷达系统通常使用的频段，以克服传统通信频段的频谱拥塞。由于在许多应用中雷达和通信共享同一平台，因此可以通过联合设计作为双功能雷达通信系统来促进频谱共享。在本文中，我们为双功能多输入多输出 (MIMO) 雷达和多用户 MIMO 通信发射机提出了一种联合发射波束成形模型。所提出的双功能系统发射独立雷达波形和通信符号的加权和，分别向雷达目标和通信接收器形成多个波束。加权系数的设计被表述为一个优化问题，其目标是 MIMO 雷达发射波束成形的性能，同时保证每个通信用户的信干噪比 (SINR) 高于给定临界点。尽管所提出的优化问题是非凸的，但我们证明它可以放松为凸问题，其中放松是紧的。然后，我们提出了一种基于用户间干扰和雷达干扰迫零的降低复杂度的设计。与之前的工作侧重于通信符号的传输以合成雷达发射波束模式不同，我们的方法为 MIMO 雷达提供了更多的自由度，因此能够获得改进的雷达性能，如我们的仿真研究所示。此外，