Cross-layer queuing control in mobile router for power saving

To extend the lifetime for mobile routers, it is necessary to introduce a power saving function. A mobile router has a wide area network (WAN) interface and a local area network (LAN) interface. Of the two interfaces, the LAN interface, which is operating as a wireless LAN (WLAN) access point (AP), does not have a power saving function in the IEEE 802.11 standard. In the conventional method, the AP enters the sleep state to save consumed power only when the Media Access Control (MAC) queue is empty. To reduce consumed power further, the AP has to actively enter the sleep state by creating an empty queue in the MAC layer. Therefore, this paper proposes a queuing control, PSAP/QC, between the Layer 3 and the MAC queue in a mobile router. The purpose is to create the opportunity of an empty MAC queue, assuming best-effort communication. By controlling dequeuing from the Layer 3 queue adequately, the MAC queue is emptied, and frames stored in the Layer 3 are aggregated. That is, the likelihood of the sleep state is increased by aggregating frames into the Layer 3 queue. The contribution of this paper is the cross-layer queuing control based on the frame arrival rate into the Layer 3 queue, in addition to the small amount of unnecessary delay caused by this control. Numerical analysis and simulation results revealed that the PSAP/QC reduces power consumption compared to the conventional method in a part of the offered traffic, and is low failure rate of dequeuing for frame aggregation.