# Sum Throughput Maximization in Multi-Tag Backscattering to Multiantenna Reader

## TL;DR

This paper develops joint transceiver and backscattering coefficient designs for multi-antenna reader systems to maximize sum throughput in backscatter communication, providing asymptotic solutions and practical algorithms that outperform existing benchmarks.

## Contribution

It introduces a novel joint optimization framework for transceiver and backscatter coefficients, including asymptotic solutions and a low-complexity iterative algorithm for multi-antenna backscatter systems.

## Key findings

- Proposed designs significantly improve sum-backscattered throughput.
- Asymptotic solutions are effective in low and high SNR regimes.
- Numerical results validate the performance gains over benchmarks.

## Abstract

Backscatter communication (BSC) is being realized as the core technology for pervasive sustainable Internet-of-Things applications. However, owing to the resource-limitations of passive tags, the efficient usage of multiple antennas at the reader is essential for both downlink excitation and uplink detection. This work targets at maximizing the achievable sum-backscattered-throughput by jointly optimizing the transceiver (TRX) design at the reader and backscattering coefficients (BC) at the tags. Since, this joint problem is nonconvex, we first present individually-optimal designs for the TRX and BC. We show that with precoder and {combiner} designs at the reader respectively targeting downlink energy beamforming and uplink Wiener filtering operations, the BC optimization at tags can be reduced to a binary power control problem. Next, the asymptotically-optimal joint-TRX-BC designs are proposed for both low and high signal-to-noise-ratio regimes. Based on these developments, an iterative low-complexity algorithm is proposed to yield an efficient jointly-suboptimal design. Thereafter, we discuss the practical utility of the proposed designs to other application settings like wireless powered communication networks and BSC with imperfect channel state information. Lastly, selected numerical results, validating the analysis and shedding novel insights, demonstrate that the proposed designs can yield significant enhancement in the sum-backscattered throughput over existing benchmarks.