Selective idling: Experiments in transport layer energy conservation

In this paper we consider the potential of using an aggressive form of ener gy conservation for mobile computing environments. The estimators for the r ound-trip time and round-trip time variance used by TCP are used to direct the transceiver of a mobile node to idle over extended periods of time when packet activity is not anticipated. In addition, we consider data link lay er extensions that provide additional control information allowing the mobi le to be further selective as to when to idle and when to activate the netw ork interface device. Simulations are conducted to examine the performance of the proposed scheme under various levels of congestion in the fixed part of the network, from completely unloaded to fully congested. The simulatio ns reveal that the technique is promising but its effectiveness depends cru cially on the control of the maximum window size used by TCP and on accurat e knowledge of the congestion conditions in the network.