Backscatter Multiplicative Multiple-Access Systems: Fundamental Limits and Practical Design

TL;DR

This paper introduces a new multiplicative multiple-access channel model for ambient backscatter systems, analyzing its capacity and practical detection error rates, showing it outperforms traditional schemes in many scenarios.

Contribution

It proposes the M-MAC model for ambient backscatter systems, analyzes its capacity region, and provides practical detection error rate insights for system design.

Findings

M-MAC has a larger achievable rate region than TDM in many cases.

Multiplicative backscatter improves throughput in high SNR regimes.

Detection error rates are characterized for various modulation and synchronization scenarios.

Abstract

In this paper, we consider a novel ambient backscatter multiple-access system, where a receiver (Rx) simultaneously detects the signals transmitted from an active transmitter (Tx) and a backscatter Tag. Specifically, the information-carrying signal sent by the Tx arrives at the Rx through two wireless channels: the direct channel from the Tx to the Rx, and the backscatter channel from the Tx to the Tag and then to the Rx. The received signal from the backscatter channel also carries the Tag's information because of the multiplicative backscatter operation at the Tag. This multiple-access system introduces a new channel model, referred to as multiplicative multiple-access channel (M-MAC). We analyze the achievable rate region of the M-MAC, and prove that its region is strictly larger than that of the conventional time-division multiple-access scheme in many cases, including, e.g., the high SNR regime and the case when the direct channel is much stronger than the backscatter channel. Hence, the multiplicative multiple-access scheme is an attractive technique to improve the throughput for ambient backscatter communication systems. Moreover, we analyze the detection error rates for coherent and noncoherent modulation schemes adopted by the Tx and the Tag, respectively, in both synchronous and asynchronous scenarios, which further bring interesting insights for practical system design.