Resource Allocation for Mutualistic Symbiotic Radio with Hybrid Active-Passive Communications

2025-09-17

AI Summary

This work addresses the rate limitation of secondary users (SUs) in mutualistic symbiotic radio (MSR). We propose a hybrid active-passive communication (HAPC) resource allocation framework that jointly optimizes reflection coefficients, transmit power, and time-slot allocation to maximize the aggregate SU rate, subject to primary transmitter (PT) rate-gain constraints and energy causality constraints. To the best of our knowledge, this is the first study to introduce HAPC into MSR. We formulate the problem as a non-convex mixed-integer program under both fixed and dynamic successive interference cancellation (SIC) ordering scenarios. An iterative algorithm integrating successive convex approximation (SCA) and block coordinate descent (BCD) is designed for efficient solution. Simulation results demonstrate that the proposed scheme significantly improves the aggregate SU rate. Moreover, dynamic SIC achieves superior performance under stringent PT rate-gain requirements, while attaining comparable performance to fixed SIC under relaxed constraints—validating its adaptability and effectiveness.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Constraint Satisfaction and Optimization: Mixed Discrete/Continuous Optimization
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Assisted, interactive, and conversational search
• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments

Abstract

Mutualistic SR is a communication paradigm that offers high spectrum efficiency and low power consumption, where the SU transmits information by modulating and backscattering the PT's signal, enabling shared use of spectrum and power with PT. In return, the PT's performance can be enhanced by SU's backscattered signal, forming a mutualistic relationship. However, the low modulation rate causes extremely inferior transmission rates for SUs. To improve the SU transmission rate, this paper proposes a new mutualistic SR with HAPC to explore the tradeoff between BC and AC in terms of power consumption and transmission rate, enabling each SU to transmit signal via passive BC and AC alternatively. We propose two problems to maximize the total rate of all SUs under the fixed and dynamic SIC ordering, respectively. The fixed SIC ordering-based problem is to jointly optimize the SUs' reflection coefficients, the transmit power of each SU during AC, and the time allocation for each SU during BC and AC, subject to the energy causality constraint and the PT's transmission rate gain constraint. In addition to pondering the constraints involved in the fixed SIC ordering-based problem, the dynamic SIC ordering-based problem, which is a mixed integer programming one, further considers the SIC ordering constraint. The above two problems are solved by our proposed SCA-based and BCD-based iterative algorithms, respectively. Simulation results demonstrate that: 1) the proposed mutualistic SR system outperforms traditional designs in terms of the rates achieved by SUs under the same constraints; 2) the total rate of all SUs under the dynamic SIC ordering is larger than that of the fixed one when the PT's minimum rate gain is high, and becomes nearly identical when the PT's minimum rate gain is low.

Problem

• Optimizing resource allocation for mutualistic symbiotic radio systems
• Maximizing secondary users' total rate under energy and primary user constraints
• Exploring hybrid active-passive communication tradeoffs for improved spectrum efficiency

Innovation

• Hybrid Active-Passive Communication for mutualistic SR
• Joint optimization of reflection coefficients and power allocation
• SCA and BCD algorithms for dynamic SIC ordering