Energy Efficiency and Spectral Efficiency Tradeoff in Multi-BD Symbiotic Radio Systems

Symbiotic radio (SR) systems with multiple backscatter devices (BDs) have attracted significant attention due to their mutually beneficial spectrum sharing and high spectral efficiency (SE). However, the use of passive BDs results in the need for additional energy for signal modulation and reflection, consequently leading to a decrease in energy efficiency (EE). Thus, it is crucial to investigate the tradeoff between SE and EE in SR systems. In this study, we propose a joint bandwidth and power allocation strategy to maximize the weighted sum of SE and EE in a multi-BD SR system. The problem is formulated as a non-convex problem and then solved using the Dinkelbach method. Subsequently, the Lagrange multiplier method is used to obtain the optimal bandwidth and power allocation. Simulation results show the superiority of the proposed resource management strategy over the existing methods that solely consider SE or EE.