Owing to the promising ability of saving hardware cost and spectrum resources, integrated sensing and communication (ISAC) is regarded as a revolutionary technology for future sixth-generation (6G) networks. The mono-static ISAC systems considered in most of existing works can only achieve limited sensing performance due to the single observation angle and easily blocked transmission links, which motivates researchers to investigate cooperative ISAC networks. In order to further improve the degrees of freedom (DoFs) of cooperative ISAC networks, the transmitter-receiver selection, i.e., base station (BS) mode selection problem, is meaningful to be studied. However, to our best knowledge, this crucial problem has not been extensively studied in existing works. In this paper, we consider the joint BS mode selection, transmit beamforming, and receive filter designs for cooperative cell-free ISAC networks, where multi-BSs cooperatively serve communication users and detect targets. An efficient joint beamforming design algorithm and three different heuristic BS mode selection methods are proposed to solve the non-convex NP-hard problem. Simulation results demonstrates the advantages of cooperative ISAC networks, the importance of BS mode selection, and the effectiveness of proposed algorithms.

翻译：鉴于其在节省硬件成本和频谱资源方面的巨大潜力，集成感知与通信（ISAC）被视为未来第六代（6G）网络的革命性技术。现有研究大多考虑单站ISAC系统，但由于单一观测角度和易受遮挡的传输链路，其感知性能受限，这促使研究者探索协作ISAC网络。为了进一步提升协作ISAC网络的自由度（DoFs），发射-接收选择问题（即基站（BS）模式选择问题）具有重要研究价值。然而，据我们所知，该关键问题在现有工作中尚未得到充分研究。本文针对协作无蜂窝ISAC网络，研究联合基站模式选择、发射波束赋形与接收滤波器设计问题，其中多基站协作服务通信用户并探测目标。我们提出一种高效的联合波束赋形设计算法及三种启发式基站模式选择方法，以求解该非凸NP-hard问题。仿真结果验证了协作ISAC网络的优越性、基站模式选择的重要性以及所提算法的有效性。