FM Backscatter: Enabling Connected Cities and Smart Fabrics

Abstract: This paper enables connectivity on everyday objects by transforming them into FM radio stations. To do this, we show for the first time that ambient FM radio signals can be used as a signal source for backscatter communication. Our design creates backscatter transmissions that can be decoded on any FM receiver including those in cars and smartphones. This enables us to achieve a previously infeasible capability: backscattering information to cars and smartphones in outdoor environments. Our key innovation is a modulation technique that transforms backscatter, which is a multiplication operation on RF signals, into an addition operation on the audio signals output by FM receivers. This enables us to embed both digital data as well as arbitrary audio into ambient analog FM radio signals. We build prototype hardware of our design and successfully embed audio transmissions over ambient FM signals. Further, we achieve data rates of up to 3.2 kbps and ranges of 5-60 feet, while consuming as little as 11.07{\mu}W of power. To demonstrate the potential of our design, we also fabricate our prototype on a cotton t-shirt by machine sewing patterns of a conductive thread to create a smart fabric that can transmit data to a smartphone. We also embed FM antennas into posters and billboards and show that they can communicate with FM receivers in cars and smartphones.

• The paper introduces FM backscatter as a low-power, passive communication method that leverages FM radio infrastructure for data transmission.
• It details a novel system architecture where passive tags modulate incoming FM signals to reliably deliver data across several meters.
• Empirical results demonstrate improved data rates and energy efficiency, underscoring its potential in IoT applications and smart fabrics.

FM Backscatter: An Overview

The paper "FM Backscatter" by Anran Wang presents a thorough exploration of Frequency Modulation (FM) backscatter technology, a communication method potentially transformative for low-power and passive communication devices. This paper articulates the development and experimental validation of an FM backscatter system, which leverages the existing FM radio infrastructure to enable communication with devices that do not require active transmission capabilities.

Technical Summary and Methodology

FM backscatter represents an advancement over traditional methods by enabling communication with extremely low power consumption. Unlike active transmitters that require significant energy, FM backscatter communicates through modulating and reflecting incoming radio frequency signals. This process allows passive devices, such as sensors and implanted medical devices, to interact with receivers without needing an internal power source for signal transmission.

The paper details the system architecture, which includes both the passive tags and the receiver framework. The passive tags are equipped with circuitry that modulates incoming FM signals based on the data to be sent, reflecting these modified signals back towards the receiver. The receiver, in turn, is responsible for demodulating these signals to retrieve the transmitted data. Importantly, the system is designed to be integrated into existing FM radio networks, leveraging widespread infrastructure and frequency allocation.

Performance Evaluation

The performance metrics presented in the paper indicate promising results for FM backscatter systems. The authors report successful data rates and ranges that outperform previous benchmark techniques for passive communication. Notably, the system achieves considerable data throughput across several meters of distance despite the inherently low-power nature of the backscattering method. The paper provides detailed empirical data showcasing the impact of various environmental variables, such as obstacles and interference, on system performance.

Implications and Future Prospects

This work on FM backscatter has significant implications for both practical applications and further research in low-power communication technologies. Practically, it provides a viable communication option for Internet of Things (IoT) devices, particularly in scenarios where power saving is paramount, or where battery replacement is impractical. Theoretically, the paper opens new avenues for research into integrating passive communication techniques with smart environments and ubiquitous computing paradigms.

Looking forward, the research may lead to further development in the modulation schemes used within the backscatter communications domain. Potential future enhancements could involve optimizing the energy efficiency of the system or expanding its capabilities to support multichannel or multiplexed communication strategies. Additionally, efforts might be concentrated on improving the robustness of the system against environmental factors, possibly through advanced adaptive algorithms or machine learning techniques.

In conclusion, the FM backscatter paper by Anran Wang provides a meticulous study and introduces an innovative approach to passive communication, providing the groundwork for both applied and theoretical advancements in the field. This research represents a significant stride towards sustainable and energy-efficient communication technologies.