Power consumption improvement of IEEE 802.16e system based on class harmonization and remaining energy awareness

Abstract

In wireless networks, a power saving mechanism has attracted considerable attention as a key technique for increasing the life time of mobile station (MS). Hence, in the IEEE 802.16e standard, three types of Power Saving Class (PSC) are defined to satisfy the quality of service (QoS) for different traffic. Each type of PSC has its own characteristic and parameter for power saving. When multiple PSCs are used, the most important factor of power saving mechanism is to harmonize the sleep window of all the PSCs for increasing unavailable interval, which is defined as the intersections of the sleep windows of all the PSCs. However, the power saving mechanisms of the current IEEE 802.16e standard are designed to take no consideration of the harmonization among PSCs. First, we analyze the performance of power saving mechanism using a discretetime Markov chain (DTMC) technique. The proposed analytical model considers poisson packet arrival, waiting time for power saving mode and etc. when two PSCs are used simultaneously. We validate the proposed model by comparing numerical analysis with simulation results. Also, to consider a practical system, we assume that the traffic for PSC I and PSC II is each generated according to traffic characteristic. By comparing simulation results and numerical results, we prove that the power consumption of the MS increases as many PSCs are used simultaneously. Secondly, when the multiple PSCs are used, we propose a sleep window control scheme that increases the unavailable interval to reduce the power consumption. In the proposed mechanism, we harmonize sleep window between PSC I (III) and PSC II for increasing unavailable interval. The proposed scheme adjusts the timing of the sleep window of PSC I (III) to maximize the unavailable interval of MSs. We model and analyze the performances of a proposed scheme and a conventional scheme. The proposed analytical model considers power consumption and response delay under a poisson pack...