PhyCast: Towards Energy Efficient Packet Overhearing in WiFi Networks

Abstract

WiFi's energy efficiency is a critical issue for battery-powered mobile devices. Since wireless channel has inherent broadcast nature, a non-negligible amount of a device's energy is spent on overhearing useless packets that are not addressed to itself. To resolve packet overhearing problem, most existing schemes are limited to decode data packet or exchange control packet to obtain extra information. In this paper, we propose PhyCast (Physical layer broadCast), a novel communication scheme to embed lightweight information into the front part of data transmission at the physical layer. With PhyCast, the transmitter's neighboring nodes extract information by symbol level energy detection, which does not require receiving and decoding the whole data packet. Therefore, unintended receivers can quickly drop useless packet and switch to a low-power state. The design of PhyCast does not affect the correct decoding of a data packet or sacrifice the normal data throughput. In addition, the communication scheme PhyCast is transparent to the existing WiFi devices, so PhyCast is backward compatible with the 802.11 standard. Our simulation results show that PhyCast achieves significant energy efficiency improvement under various network settings. When a WiFi network includes 15 nodes, PhyCast saves 36.85% energy compared with the 802.11 standard.