Symbiotic Radio: Cognitive Backscattering Communications for Future Wireless Networks (2007.01506v1)

Abstract: The heterogenous wireless services and exponentially growing traffic call for novel spectrum- and energy-efficient wireless communication technologies. In this paper, a new technique, called symbiotic radio (SR), is proposed to exploit the benefits and address the drawbacks of cognitive radio (CR) and ambient backscattering communications(AmBC), leading to mutualism spectrum sharing and highly reliable backscattering communications. In particular, the secondary transmitter (STx) in SR transmits messages to the secondary receiver (SRx) over the RF signals originating from the primary transmitter (PTx) based on cognitive backscattering communications, thus the secondary system shares not only the radio spectrum, but also the power, and infrastructure with the primary system. In return, the secondary transmission provides beneficial multipath diversity to the primary system, therefore the two systems form mutualism spectrum sharing. More importantly, joint decoding is exploited at SRx to achieve highly reliable backscattering communications. To exploit the full potential of SR, in this paper, we address three fundamental tasks in SR: (1) enhancing the backscattering link via active load; (2) achieving highly reliable communications through joint decoding; and (3) capturing PTx's RF signals using reconfigurable intelligent surfaces. Emerging applications, design challenges and open research problems will also be discussed.

• The paper introduces the concept of Symbiotic Radio (SR), integrating cognitive radio (CR) and ambient backscattering (AmBC) for spectrum and energy efficiency in future wireless networks.
• It addresses challenges like improving backscattering signals via active loads/multiple antennas and enabling reliable communication through joint decoding techniques.
• Symbiotic Radio is applicable in e-health, smart homes, and environmental monitoring due to its low power consumption and enhanced efficiency.

An Overview of Symbiotic Radio in Cognitive Backscattering Communications

The paper "Symbiotic Radio: Cognitive Backscattering Communications for Future Wireless Networks" presents the innovative concept of Symbiotic Radio (SR) that combines cognitive radio (CR) and ambient backscattering communications (AmBC) to address the increasing demand for spectrum- and energy-efficient wireless communication technologies. By integrating these technologies, SR achieves mutualism spectrum sharing and highly reliable backscattering communications, making it a viable solution for future wireless networks.

Concept and System Model

Symbiotic Radio (SR) leverages the cognitive backscattering communication model where a secondary transmitter (STx) modulates data over the primary transmitter's (PTx) radio frequency (RF) signals to reach a secondary receiver (SRx). This system, unlike traditional cognitive radio that involves interference-laden spectrum sharing between primary and secondary users, fosters a mutualistic relationship. The secondary system utilizes the primary system's spectrum, power, and infrastructure, while simultaneously enhancing the primary system’s performance through multipath diversity. This cooperative approach facilitates reduced power consumption and enhanced spectrum efficiency.

Key Challenges and Solutions

The paper tackles three central challenges in SR: improving the backscattering link via active loads and multiple antennas, achieving reliable communication through joint decoding, and capturing desired RF signals using reconfigurable intelligent surfaces (RIS). Active loads amplify the backscattering signal, while RIS enables passive beamforming to capture specific RF signals, thus improving signal reliability and system efficiency.

Transceiver and Receiver Design

Advanced transceiver designs are proposed for SR, including maximum-likelihood (ML), linear detectors, and successive interference cancellation (SIC)-based methods. These designs collectively enhance the detection accuracy of primary and secondary signals by jointly exploiting the channel information for coherent detection or machine-learning assisted semi-blind techniques when partial channel knowledge is available.

Resource Allocation Strategies

The paper also explores resource allocation strategies under constraints such as peak and average transmit power and reflection efficiency. Strategies are formulated to optimize Beamforming and power allocation at PTx, especially in MISO setups, and potential full-duplex implementations, ensuring the desired performance metrics for both primary and secondary systems are met.

RIS-assisted and Full-Duplex Implementations

Reconfigurable Intelligent Surfaces (RIS)-assisted SR systems are addressed, which further leverages backscattering to capture and optimize the primary signals intentionally. Full-duplex configurations are examined, allowing the PTx to decode STx signals even as it simultaneously transmits its own signals, maximizing system throughputs.

Applications

SR has significant implications for various applications such as e-health monitoring, smart home environments, and environmental monitoring, all of which benefit from the passive, ultra-low power consumption of backscattering communications combined with the enhanced reliability and efficiency enabled through mutualist spectrum sharing.

Future Directions

Moving forward, deeper exploration into SR technology's theoretical limits and practical implementations is needed. Challenges such as precise channel modeling and estimation, hardware design specific to backscattering synchronization, and robust security measures are vital avenues for further research and development.

This paper provides a comprehensive overview of SR as an innovative approach to next-generation wireless communications, offering theoretically sound solutions that could drive practical advancements in smarter resource-efficient networks.