Optimization of Rate-Splitting Multiple Access with Integrated Sensing and Backscatter Communication

TL;DR

This paper proposes an optimized rate-splitting multiple access scheme for integrated sensing and backscatter communication systems, significantly improving communication rates while maintaining low power increases.

Contribution

It introduces a novel RSMA-based optimization framework for ISABC systems, jointly optimizing beamforming, reflection, and rate allocation for enhanced efficiency.

Findings

Achieves 350% increase in communication rate over NOMA-based ISABC.

Maintains only 24% increase in transmit power with ten antennas.

Provides concrete solutions for beamforming and reflection coefficient optimization.

Abstract

An integrated sensing and backscatter communication (ISABC) system is introduced herein. This system features a full-duplex (FD) base station (BS) that seamlessly merges sensing with backscatter communication and supports multiple users. Multiple access (MA) for the user is provided by employing rate-splitting multiple access (RSMA). RSMA, unlike other classical orthogonal and non-orthogonal MA schemes, splits messages into common and private streams. With RSMA, the set of common rate forms can be optimized to reduce interference. Optimized formulas are thus derived for communication rates for users, tags, and the BS's sensing rate, with the primary goal of enhancing the transmission efficiency of the BS. The optimization task involves minimizing the BS's overall transmission power by jointly optimizing the BS's beamforming vectors, the tag reflection coefficients, and user common rates. The alternating optimization method is employed to address this challenge. Concrete solutions are provided for the received beamformers, and semi-definite relaxation and slack-optimization techniques are adopted for transmit beamformers and reflection coefficients, respectively. For example, the proposed RSMA-assisted ISABC system achieves a 350% communication rate boost over a nonorthogonal multiple access-assisted ISABC, with only a 24% increase in transmit power, leveraging ten transmit/reception antennas at the BS.