Cooperative Positioning with the Aid of Reconfigurable Intelligent Surfaces and Device-to-Device Communications in mmWave

Reconfigurable intelligent Surfaces (RISs) have recently gained a lot of attention due to their capability in creating a smarter controllable radio environment. In this paper, we present a novel cooperative positioning (CP) technique to improve positioning accuracy in RIS-assisted systems with device-to-device (D2D) communications. We consider a scenario with one base station (BS), one RIS, and
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mobile stations (MSs). We assume that the line-of-sight (LoS) between the BS and all the MSs is blocked and the communication has to be established through the RIS. The proposed method uses beam sweeping in the downlink communication to determine the direction of each MS relative to the RIS location. In the uplink communication, the MSs communicate with each other and the power received from each MS is used to determine the distances between every pair of MSs. We then formulate an optimization problem to minimize the mismatch between the distance measurements subject to the relative direction information, and find the location estimates using a neural network. Finally, we test the performance of the proposed method through simulations.