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Energy-efficiency optimization and comparison for IRS-assisted bidirectional relay and direct transmissions
Caixia Cai1, Jiayao Zhang2, Fuli Zhong3
1Department of Electrical Engineering, Shanghai Maritime University, Shanghai, 201306, China. cxiacai@163.com.
Scientific Reports
|May 11, 2026
Summary
Intelligent Reflecting Surfaces (IRS) enhance energy efficiency in Beyond 5G/6G communications. IRS-assisted bidirectional relay transmission (BRT) outperforms bidirectional direct transmission (BDT) when total transmit power exceeds -5 dBm.
Area of Science:
- Wireless communication systems
- Signal processing
- Energy-efficient network design
Background:
- Future wireless networks (Beyond 5G/6G) demand high data rates and low power consumption.
- Intelligent Reflecting Surfaces (IRS) offer a promising solution for enhancing wireless transmission efficiency.
- Optimizing energy efficiency (EE) is crucial for sustainable communication systems.
Purpose of the Study:
- To optimize and compare the energy efficiency (EE) of IRS-assisted bidirectional relay transmission (BRT) and bidirectional direct transmission (BDT).
- To investigate the impact of joint phase shift (PS) and transmit power (TP) optimization on EE.
- To provide a comprehensive analysis of EE performance between BRT and BDT under various conditions.
Main Methods:
- Development of IRS-assisted BRT and BDT system models.
- Analysis of signal transmission and EE for both BRT and BDT configurations.
- Joint optimization of PS and TP using complex circle gradient descent and successive convex approximation.
- Derivation of optimal TP using Lagrange multipliers and Karush-Kuhn-Tucker conditions.
Main Results:
- IRS-assisted BRT demonstrates superior EE performance compared to BDT when total TP exceeds -5 dBm.
- Joint optimization of PS and TP leads to significant EE improvements: 61.36% for BRT and 65.51% for BDT, compared to individual optimization.
- The proposed optimization algorithms effectively solve the complex optimization problems.
Conclusions:
- IRS-assisted BRT is a more energy-efficient transmission strategy than BDT under higher transmit power conditions.
- Joint optimization of IRS phase shifts and transmit power is essential for maximizing energy efficiency in IRS-assisted wireless systems.
- The findings provide valuable insights for designing energy-efficient Beyond 5G and 6G communication networks.
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