Joint Node Scheduling and Radio Switching for Energy Efficiency in Multi-radio WLAN Mesh Networks

Multi-radio WLAN mesh networks (WMNs) are intended to provide a wireless access infrastructure with high throughput and reliable transmission. With the increasing demand for ubiquitous Internet access, access networks tend to be large-scale, complex and dense, and energy consumption has become a critical concern. Since the networks are designed to support peak traffic demand but does not serve peak traffic demand all the time, which leads to significant energy wastage in off-peak conditions. This means that energy consumption can be effectively reduced through scheduling nodes on/off according to the current traffic demand. In multi-radio WMNs, each node is equipped with multiple radios, and radios can also be switched on/off for further energy saving. Therefore, we investigate the problem of joint node scheduling and radio switching for energy efficiency in this paper, which is proven to be NP-hard. We first formulate the problem as an integer linear programming model, which aims to minimize the power consumption of the network while satisfying node-radio-link, traffic demand and routing constraints. Then, we propose an efficient heuristic algorithm, which iteratively finds routing paths for all mesh access points (MAPs) while satisfying their traffic demand. In each iteration, exact one MAP is selected, and the nodes on its routing path are scheduled on and the corresponding radios are switched on. Finally, extensive simulations are conducted to evaluate the performance of the proposed algorithm in terms of the number of active nodes and radios. The results not only show that the algorithm can achieve energy saving efficiently and effectively, but also demonstrate that the joint optimization of node scheduling and radio switching can obtain better performance on energy efficiency.