Adaptive sleep mode algorithm in IEEE 802.16e

Much research has been performed to minimize energy consumption of mobile nodes with high speed mobility. Among them, the IEEE 802.16e has adopted sleep mode to reduce energy consumption. If the base station (BS) has no data to be sent to a mobile node at the instant of ending its current sleep window interval, the mobile node with the sleep mode increases the sleep window interval by double until the window interval reaches to the maximum sleep window interval. After the sleep window interval of the mobile node hits the maximum sleep window interval, the node keeps its sleep window interval as the maximum interval. However, if the node keeps the maximum sleep window interval for a long time, the frame delay is increased and energy is wasted. To shorten the frame delay and deal with the energy of the node effectively, this paper comes up with an algorithm that reduces the next sleep window interval to the medium between the minimum and the maximum sleep window interval after the current sleep window reaches to the maximum sleep window interval. The proposed algorithm decreases the delay by a maximum of 20% and energy consumption by about 5%, compared with the basic algorithm adopted by IEEE 802.16e.