Integrated Sensing and Communications for 3D Object Imaging via Bilinear Inference

TL;DR

This paper introduces two novel integrated sensing and communications schemes that simultaneously detect data and reconstruct 3D environmental images from channel information, outperforming existing methods in accuracy and robustness.

Contribution

The paper proposes two purpose-built message passing algorithms for joint data detection and 3D environment estimation in ISAC systems, with one leveraging bilinear inference and the other an alternating approach.

Findings

Bilinear inference method shows robustness to short pilots and channel blockages.

Alternating method offers lower complexity and better performance in ideal conditions.

Both methods outperform state-of-the-art in accuracy for data recovery and environment imaging.

Abstract

We consider an uplink integrated sensing and communications (ISAC) scenario where the detection of data symbols from multiple user equipment (UEs) occurs simultaneously with a three-dimensional (3D) estimation of the environment, extracted from the scattering features present in the channel state information (CSI) and utilizing the same physical layer communications air interface, as opposed to radar technologies. By exploiting a discrete (voxelated) representation of the environment, two novel ISAC schemes are derived with purpose-built message passing (MP) rules for the joint estimation of data symbols and status (filled/empty) of the discretized environment. The first relies on a modular feedback structure in which the data symbols and the environment are estimated alternately, whereas the second leverages a bilinear inference framework to estimate both variables concurrently. Both contributed methods are shown via simulations to outperform the state-of-the-art (SotA) in accurately recovering the transmitted data as well as the 3D image of the environment. An analysis of the computational complexities of the proposed methods reveals distinct advantages of each scheme, namely, that the bilinear solution exhibits a superior robustness to short pilots and channel blockages, while the alternating solution offers lower complexity with large number of UEs and superior performance in ideal conditions.