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Cooperative Cell-Free ISAC Networks: Joint BS Mode Selection and Beamforming Design

Sifan Liu, Rang Liu, Ming Li, Qian Liu

TL;DR

The paper addresses enhancing ISAC performance by leveraging cooperative cell-free networks with flexible BS mode selection. It casts a non-convex joint optimization of BS mode, transmit beamforming, and receive filtering as a two-subproblem problem and solves the beamforming/filter design with a FP-MM approach while proposing three simple BS mode-selection heuristics. The main contributions are a FP-MM-based joint beamforming/filter design algorithm, and three low-complexity heuristics (C-C, S-C, Joint) for BS mode selection, validated via simulations that show notable gains from multi-BS cooperation and mode selection. The work demonstrates a practical path to improving sensing SINR in 6G ISAC deployments through cooperative, mode-adaptive cell-free architectures.

Abstract

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.

Cooperative Cell-Free ISAC Networks: Joint BS Mode Selection and Beamforming Design

TL;DR

The paper addresses enhancing ISAC performance by leveraging cooperative cell-free networks with flexible BS mode selection. It casts a non-convex joint optimization of BS mode, transmit beamforming, and receive filtering as a two-subproblem problem and solves the beamforming/filter design with a FP-MM approach while proposing three simple BS mode-selection heuristics. The main contributions are a FP-MM-based joint beamforming/filter design algorithm, and three low-complexity heuristics (C-C, S-C, Joint) for BS mode selection, validated via simulations that show notable gains from multi-BS cooperation and mode selection. The work demonstrates a practical path to improving sensing SINR in 6G ISAC deployments through cooperative, mode-adaptive cell-free architectures.

Abstract

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.
Paper Structure (14 sections, 21 equations, 4 figures, 4 algorithms)

This paper contains 14 sections, 21 equations, 4 figures, 4 algorithms.

Table of Contents

  1. Introduction
  2. System Model and Problem Formulation
  3. System Model
  4. Problem Formulation
  5. Joint Transmit Beamforming and Receive Filter Design
  6. Receive Filter Optimization
  7. Transmit Beamforming Optimization
  8. Summary
  9. BS Mode Selection
  10. Communication-Centric
  11. Sensing-Centric
  12. Joint Communication and Sensing
  13. Simulation Results
  14. Conclusion

Figures (4)

  • Figure 1: Cooperative cell-free ISAC network.
  • Figure 2: Sum of sensing SINR versus the number of BSs ($K = 8$, $\gamma = 8\text{dB}$, $P_\text{max}=30\text{dBm}$).
  • Figure 3: Sum of sensing SINR versus communication SINR requirement ($J = 16$, $K = 8$, $P_\text{max}=30\text{dBm}$).
  • Figure 4: Sum of sensing SINR versus the number of users ($J = 16$, $\gamma = 8\text{dB}$, $P_\text{max}=30\text{dBm}$).