Research On Energy Saving Control In The WiMAX

In recent years, as a result of special advantage and extensive marketing foreground, Broadband Wireless Access has become a hot point technology. IEEE802.16e standard is a Broadband Wireless Access Metropolitan Area Network standard for mobility in the WiMAX’s family. As a part of this standard, Mobile Subscriber Station (MSS) is mainly charged by the battery, and the energy in the battery is constraint. For this reason, how to lower the energy consumption and extend the time keeping the MSS active are both important researches. Sleep mode is a necessary function in MSS, and it can manage limited energy and extend the using time of MSS. In such a condition, study on the sleep mode is an important issue for energy saving in the MSS.In this paper, we study the energy saving of the MSS in the sleep mode. According to the definition of three different power saving classes in IEEE802.16e standard: Power Saving Class A is recommended for connections of best-effort (BE) and non-real-time variable rate (NRT-VR) traffic; Power Saving Class B is recommended for connections of unsolicited grant service (UGS) and real-time variable rate (RT-VR) traffic and Power Saving Class C is recommended for multicast connections as well as for management operations, we have modeled for all power saving classes and deduced the formulas of the mean energy consumption, the energy saving ratio and the mean packet delay. Through simulation, we compare the Power Saving Classes in some aspects such as traffic pattern, efficiency and so on. It is a stable foundation for our analyzing the sleep mode in the following.Based on Power Saving Class A, we analyze four cases in the sleep mode in detail by modeling, and deduce three formulas: the mean energy consumption, the mean packet delay and the mean sleep time. By means of NS2 simulation, we give charts of the mean energy consumption and the mean packet delay versus the traffic rate. Results show that a larger initial window size has a larger packet delay and larger energy consumption in the sleep mode. In 802.16e, the initial sleep window’s size of the sleep mode is fixed, the window can not be revised according to the different traffic pattern, and the standard algorithm in 802.16e that deals with sleep mode energy consumption does not address the problem of varying traffic rates. So we propose an adaptive sleep mode interval control algorithm for 802.16e in this paper, which takes into account the traffic pattern to minimize energy consumption. In order to reduce the mean energy consumption and the mean packet delay in the sleep mode, our algorithm dynamically adapts the initial window’s size of the next sleep time when the MSS come in the sleep mode. Simulations show that our proposed algorithm for sleep mode saves substantial amount of energy at lower traffic and almost same at higher traffic as compared to 802.16e, and the mean packet delay using our algorithm will gain the same performance improving. Results reveal that the optimization of sleep mode leads to remarkable effect in saving the energy at lower traffic.