Transmission power control for 802.11: a carrier-sense based NAV extension approach

This paper presents a carrier-sense based transmission power control protocol, CSNE-PC, which addresses the energy inefficiency of basic power control protocols (BPC) for IEEE 802.11 based networks. In BPC, RTS and CTS packets are exchanged at full power while data and acknowledgement transmissions are carried out at low power. While being intuitive and simple to implement, BPC´s energy efficiency is significantly degraded by a unique hidden collision problem, which is removed by the approach in this paper. In CSNE-PC, a node measures and analyses its carrier-sense activities for detecting 802.11 CTS packets in the extended neighborhood of carrier sense range. Upon detecting a CTS packet, the node sets or extends its MAC layer NAV and enters into a silence mode for the data packet duration. Unlike BPC, this enables CSNE-PC to control transmission power without having to suffer from additional data collisions. Evaluation of CSNE-PC through simulation demonstrates that under sustainable loading conditions, reduction in combined transmit and receive energy for CSNE-PC can be as high as 38%, and that is while retaining the throughput and delay characteristics of the regular 802.11 protocol