Two-Time Scale Energy-Saving Scheme with Base Station Sleeping, Symbol Shutdown, and Power Allocation

Green communications (GC) is an urgent need for 5G and 6G. How to realize GC with guaranteed quality of service is still a challenging problem. This paper investigates the energy-saving problem in a multi-base stations (BSs) scenario, incorporating BS deep sleep on a large time scale and symbol shutdown and power allocation on a small time scale. To tackle this NP-hard problem, we decompose it into two subproblems: (1) collaborative BS sleep and (2) dynamic symbol shutdown and power allocation. For the first subproblem, we develop an efficient branch-and-bound (B&B) algorithm to determine the optimal BS on/off state and traffic distribution. For the second subproblem, we propose a Lyapunov method-based algorithm (LMBA) to address the joint optimization of symbol shutdown and power allocation while ensuring the long-term average rate demands of user equipments (UEs). By using Karush-Kuhn-Tucker (KKT) conditions, we derive the explicit expression of the optimal transmission power. Simulation results validate the effectiveness of the proposed algorithms, demonstrating significant energy-saving gains in comparison with the benchmark methods.