# Multistatic Scatter Radio Sensor Networks for Extended Coverage

## TL;DR

This paper compares monostatic and multistatic scatter radio sensor networks, demonstrating that multistatic architectures offer superior performance, coverage, and energy efficiency, supported by theoretical analysis and a practical proof-of-concept demonstration.

## Contribution

It provides a comprehensive comparison between monostatic and multistatic scatter radio architectures, including theoretical performance bounds and the first experimental multistatic WSN demonstration.

## Key findings

- Multistatic architecture outperforms monostatic in diversity, BER, and coverage.
- Energy outage due to RF harvesting is less frequent in multistatic systems.
- A practical multistatic scatter radio WSN covering 3500 m² is experimentally demonstrated.

## Abstract

Scatter radio, i.e., communication by means of reflection, has been recently proposed as a viable ultra-low power solution for wireless sensor networks (WSNs). This work offers a detailed comparison between monostatic and multistatic scatter radio architectures. In monostatic architecture, the reader consists of both the illuminating transmitter and the receiver of signals scattered back from the sensors. The multistatic architecture includes several ultra-low cost illuminating carrier emitters and a single reader. Maximum-likelihood coherent and noncoherent bit error rate (BER), diversity order, average information and energy outage probability comparison is performed, under dyadic Nakagami fading, filling a gap in the literature. It is found that: (i) diversity order, BER, and tag location-independent performance bounds of multistatic architecture outperform monostatic, (ii) energy outage due to radio frequency (RF) harvesting for passive tags, is less frequent in multistatic than monostatic architecture, and (iii) multistatic coverage is higher than monostatic. Furthermore, a proof-of-concept {digital} multistatic, scatter radio WSN with a single receiver, four low-cost emitters and multiple ambiently-powered, low-bitrate tags, perhaps the first of its kind, is experimentally demonstrated (at $13$ dBm transmission power), covering an area of $3500$ m$^2$. Research findings are applicable in the industries of WSNs, radio frequency identification (RFID), and emerging Internet-of-Things.