[论文解读] Integrated Sensing and Communication: Joint Pilot and Transmission Design

Hua Meng, Qingqing Wu+4 more|arXiv (Cornell University)|Nov 23, 2022

Distributed Sensor Networks and Detection Algorithms被引用 5

一句话总结

本文提出了一种通信中心型感知与通信（ISAC）系统中的联合导频与波束成形设计，其中多天线基站同时执行下行链路通信与目标检测。通过联合优化导频矩阵、训练时长与波束成形，以在满足速率约束的前提下最大化检测概率，作者提出了一种统一的导频结构，平衡了信道估计精度与感知性能，在与基准方案相比显著提升了速率-互信息（Rate-MI）区域。

ABSTRACT

This paper studies a communication-centric integrated sensing and communication (ISAC) system, where a multi-antenna base station (BS) simultaneously performs downlink communication and target detection. A novel target detection and information transmission protocol is proposed, where the BS executes the channel estimation and beamforming successively and meanwhile jointly exploits the pilot sequences in the channel estimation stage and user information in the transmission stage to assist target detection. We investigate the joint design of pilot matrix, training duration, and transmit beamforming to maximize the probability of target detection, subject to the minimum achievable rate required by the user. However, designing the optimal pilot matrix is rather challenging since there is no closed-form expression of the detection probability with respect to the pilot matrix. To tackle this difficulty, we resort to designing the pilot matrix based on the information-theoretic criterion to maximize the mutual information (MI) between the received observations and BS-target channel coefficients for target detection. We first derive the optimal pilot matrix for both channel estimation and target detection, and then propose an unified pilot matrix structure to balance minimizing the channel estimation error (MSE) and maximizing MI. Based on the proposed structure, a low-complexity successive refinement algorithm is proposed. Simulation results demonstrate that the proposed pilot matrix structure can well balance the MSE-MI and the Rate-MI tradeoffs, and show the significant region improvement of our proposed design as compared to other benchmark schemes. Furthermore, it is unveiled that as the communication channel is more correlated, the Rate-MI region can be further enlarged.

研究动机与目标

• 解决ISAC系统中准确信道估计与有效目标检测之间的基本权衡问题。
• 联合优化导频矩阵、训练时长与波束成形，以在满足用户最小速率约束的前提下最大化目标检测概率。
• 解决在无闭式检测概率表达式的情况下设计最优导频矩阵的挑战。
• 通过统一的导频结构平衡ISAC系统中的MSE-MI与Rate-MI权衡。
• 通过逐次精炼方法实现高效、低复杂度的设计，以支持实际部署。

提出的方法

• 提出一种新型协议，其中信道估计与波束成形依次进行，重用导频与数据信号以实现感知与通信的联合处理。
• 采用信息论准则，最大化接收信号与BS-目标信道系数之间的互信息（MI），以实现目标检测。
• 推导出一种最优导频矩阵，联合最小化信道估计误差（MSE）并最大化MI，从而形成统一的导频结构。
• 开发一种低复杂度的逐次精炼算法，联合优化导频矩阵、训练时长与波束成形。
• 通过严格的理论分析，研究导频长度与矩阵设计对MSE-MI与Rate-MI权衡的影响。
• 采用奇异值分解（SVD）与矩阵秩分析，刻画最优导频结构及其特性。

Figure 1: A communication-centric ISAC system.

实验结果

研究问题

• RQ1 如何联合设计导频矩阵，以同时提升ISAC系统中的信道估计精度与目标检测性能？
• RQ2 在感知方面，最小化信道估计误差（MSE）与最大化互信息（MI）之间的最优权衡是什么？
• RQ3 训练时长如何影响ISAC系统中通信速率与感知性能之间的平衡？
• RQ4 统一的导频结构能否有效平衡MSE-MI与Rate-MI权衡？
• RQ5 通信信道中的空间相关性如何影响可实现的Rate-MI区域？

主要发现

• 所提出的导频矩阵结构相较于基准方案在Rate-MI区域实现了显著提升，表明其在通信与感知性能之间具有更优的平衡。
• 导频矩阵、训练时长与波束成形的联合优化显著扩大了Rate-MI区域，尤其在空间相关信道中表现更优。
• 随着通信信道的空间相关性增强，可实现的Rate-MI区域进一步扩大，表明系统灵活性得到提升。
• 所提出的低复杂度逐次精炼算法能有效平衡MSE与MI，支持实际应用。
• 理论分析证实，所提出的导频结构在估计精度与感知增益之间实现了最优权衡。
• 仿真结果验证了所提设计在检测概率与频谱效率方面均优于传统方案。

Figure 2: Target detection and information transmission protocol.