On the power efficiency of sensory and ad-hoc wireless networks

We consider the power efficiency of a communications channel, i.e., the maximum bit rate that can be achieved per unit power (energy rate). For AWGN channels, it is well known that power efficiency is attained in the low SNR regime where capacity is proportional to the transmit power. In this paper we show that for a sensory wireless network with n nodes, or for an ad-hoc wireless network with n users and up to /spl radic/n transmit/receive pairs, the power efficiency scales at least by a factor of /spl radic/n. In other words, each user in a wireless channel with n nodes can support the same communications rate as a single user system, but by expending only 1/(/spl radic/n) the energy. We also give a description of how to achieve these gains.