Modeling the Impact of the MoreData Parameter for Wireless Power-Saving Protocols

In wireless power-saving protocols, one fundamental problem is when a station switches from an awake state to a doze state. The MoreData mechanism has been widely adopted in IEEE 802.11 standards to solve the problem. In this mechanism, when the access point (AP) transmits one buffered packet to a station, it will set the MoreData bit in the Frame Control field of the packet, to notify the station of either keeping awake (i.e., when MoreData = 1) for receiving additional packets or going to sleep (i.e., when MoreData = 0). Although important, few work studied the impact of this bit theoretically. It turns out that theoretically modeling the impact of this bit is by no means easy. Focusing on a polling system, this paper is the first to theoretically model the interaction between this bit setting and others (such as the sleeping interval) and make a trade-off analysis between power consumption and packet delay. Our results show that enabling this bit can reduce the power consumption remarkably, at the cost of slightly increasing the delay; and ignoring this bit might lead to significant analysis errors and inappropriate parameter settings. Extensive simulations verify that our model is very accurate for both homogeneous and heterogeneous settings. This study indicates that when the power-consumption is seriously concerned, we should enable this MoreData mechanism. Furthermore, it is very helpful to provide theoretically guided parameter settings for battery-powered applications.