Collaborative Precoding Design for Adjacent Integrated Sensing and Communication Base Stations

Integrated sensing and communication (ISAC) base stations can provide communication and wide range sensing for vehicles via downlink (DL) transmission, thus enhancing the driving safety. One major challenge for achieving the high performance of communication and sensing is how to deal with the DL mutual interference among adjacent ISAC base stations, which includes not only communication-related interference but also sensing-related interference. In this article, we establish a DL mutual interference model of adjacent ISAC base stations, and analyze the relationship between the communication and sensing mutual interference channels. To mitigate the mutual interference, we propose a collaborative precoding design for adjacent base stations under the transmit power constraint and constant modulus constraint. To solve the nonconvex collaborative precoding design problem, we first relax the problem into a convex programming by omitting the rank constraint, and propose a joint optimization algorithm to solve the problem. To reduce computational complexity, We further propose a sequential optimization algorithm, which divides the collaborative precoding design problem into four subproblems and finds the optimum via a gradient descent algorithm. Finally, we evaluate the collaborative precoding design algorithms by considering sensing and communication performance via numerical results.

I. Introduction

As shown in the Tri-Level study of the causes of traffic accidents, 90%–93% of vehicle incidents are caused by human errors [2], which brings an impending need for ensuring the driving safety. Most of the current intelligent vehicles are equipped with high-precision onboard sensors. However, onboard sensors have shortcomings in terms of sensing range and blind spot. Recognizing this fact, Zhang et al. [3] proposed the perceptive mobile network (PMN) using the integrated sensing and communication (ISAC) technology. ISAC base stations in PMN are installed at high points on the roadside, which can provide wide range sensing for vehicles. Moreover, IMT-2030 (6G) working group put forward a technical scheme to realize high performance sensing of adjacent ISAC base stations [4].