Multi-Antenna Broadband Backscatter Communications

TL;DR

This paper introduces a multi-antenna broadband backscatter communication system that enhances reliability, range, and data rate for IoT devices by employing cyclic delay diversity and advanced receiver design, achieving significant performance improvements.

Contribution

It proposes a novel BBBC system with multi-antenna BDs and CDD, providing improved diversity and reliability without requiring channel state information, validated through analysis and simulations.

Findings

Achieves spatial and frequency diversity gains under Rayleigh and LoS channels.

Reduces outage probability and bit error rate with increased BD antennas.

Outperforms conventional backscatter schemes in reliability and data rate.

Abstract

Backscatter communication offers a promising solution to connect massive Internet-of-Things (IoT) devices with low cost and high energy efficiency. Nevertheless, its inherently passive nature limits transmission reliability, thereby hindering improvements in communication range and data rate. To overcome these challenges, we introduce a bistatic broadband backscatter communication (BBBC) system, which equips the backscatter device (BD) with multiple antennas. In the proposed BBBC system, a radio frequency (RF) source directs a sinusoidal signal to the BD, facilitating single-carrier block transmission at the BD. Meanwhile, without requiring channel state information (CSI), cyclic delay diversity (CDD) is employed at the multi-antenna BD to enhance transmission reliability through additional cyclically delayed backscattered signals. We also propose a receiver design that includes preprocessing of the time-domain received signal, pilot-based parameter estimation, and frequency-domain equalization, enabling low-complexity detection of the backscattered signal. Leveraging the matched filter bound (MFB), we analyze the achievable diversity gains in terms of outage probability. Our analysis reveals that spatial diversity is achievable under general Rayleigh fading conditions, and both frequency and spatial diversity are attainable in scenarios where the forward link experiences a line-of-sight (LoS) channel. Simulation results validate the effectiveness of the proposed BBBC system. As the number of BD antennas increases, our results show that the proposed scheme not only enhances array gain but also improves diversity order, significantly reducing both outage probability and bit error rate (BER). Consequently, it outperforms conventional schemes that yield only minor gains.