Energy-Efficient Nonstationary Spectrum Sharing

We develop a novel design framework for energy-efficient spectrum sharing among autonomous users who aim to minimize their energy consumptions subject to minimum throughput requirements. Most existing works proposed stationary spectrum sharing policies, in which users transmit at fixed power levels. Since users transmit simultaneously under stationary policies, to fulfill minimum throughput requirements, they need to transmit at high power levels to overcome interference. To improve energy efficiency, we construct nonstationary spectrum sharing policies, in which the users transmit at time-varying power levels. Specifically, we focus on TDMA (time-division multiple access) policies in which one user transmits at each time (but not in a round-robin fashion). The proposed policy can be implemented by each user running a low-complexity algorithm in a decentralized manner. It achieves high energy efficiency even when the users have erroneous and binary feedback about their interference levels. Moreover, it can adapt to the dynamic entry and exit of users. The proposed policy is also deviation-proof, namely autonomous users will find it in their self-interests to follow it. Compared to existing policies, the proposed policy can achieve an energy saving of up to 90% when the number of users is high.

💡 Research Summary

The paper tackles the fundamental energy‑efficiency problem that arises when multiple autonomous wireless users share a common spectrum under conventional stationary policies. In stationary schemes each user transmits continuously at a fixed power level, which forces all users to operate at relatively high powers to overcome mutual interference and meet their minimum throughput requirements. This approach is especially wasteful for battery‑powered devices typical of IoT, mobile edge, and future 5G/6G networks.

To overcome this limitation the authors propose a non‑stationary spectrum‑sharing framework based on time‑division multiple access (TDMA). Unlike a simple round‑robin schedule, the proposed TDMA is dynamically optimized: at any time slot only one user transmits, and the identity of that user as well as its transmit power are chosen adaptively according to each user’s current queue length, channel condition, and a very limited feedback signal. The feedback is binary – it merely indicates whether the experienced interference exceeds a pre‑defined threshold – which reflects realistic constraints of many low‑complexity radios.

The system model consists of N autonomous users sharing a single channel. Each user i must guarantee an average throughput (R_i^{\min}). The design objective is to minimize the total average transmit power (\sum_i \mathbb{E}