Downlink Pilot Based Integrated Sensing and Communication in Cell-Free Networks

In this paper, downlink (DL) pilot based integrated sensing and communication (ISAC) is explored in cell-free networks. To improve both accuracy of channel estimation and localization in the ISAC based cell free network, a group of pre-designed DL orthogonal pilot sequences are introduced in the proposed ISAC strategy for both channel estimation for communications and cooperative sensing with radars. A power allocation scheme is proposed with the objective of minimizing the maximum channel estimation error for each user, under the power constraints of APs and minimum mean square error of sensing based localization. The performance of the proposed ISAC strategy is evaluated under a realistic highway scenario, and compared to the conventional methods. The results show that the performances of both channel estimation and localization can be significantly improved at a relatively low cost of extra power needed for APs near users.