Joint Tx/Rx Energy-Efficient Scheduling in Multi-Radio Wireless Networks: A Divide-and-Conquer Approach

Most of the existing works on energy-efficient wireless communications only consider the transmitter (Tx) or the receiver (Rx) side power consumption, but not both. Moreover, the circuit power consumption is often assumed to be constant regardless of the transmission rate or the bandwidth. In this paper, we investigate the system-level energy-efficient transmission in multi-radio access networks by considering joint Tx and Rx power consumption and adopting link-dependent dynamic circuit power model. A combinatorial-type optimization problem for user scheduling, radio-link activation, and power control is formulated with the objective of maximizing joint Tx and Rx energy efficiency (EE). We tackle this problem using a divide-and-conquer approach. Specifically, the concepts of link EE and user EE are first introduced, which have structures similar to the system EE. Then, we explore their hierarchical relationships and propose an optimal algorithm whose complexity is linear in the product of the total number of users and radio links. Furthermore, we investigate the EE maximization problem with minimum user data rate constraints. The divide-and-conquer approach is also applied to find a sub-optimal but efficient solution. Finally, comprehensive numerical results are provided to validate the theoretical findings and demonstrate the effectiveness of the proposed algorithms.