Energy efficiency of IEEE 802.11 DCF under non-saturation conditions

Abstract

E nergy efficiency is an important issue for a mobile communication terminal which operates by a battery. Most of analytical models proposed so far for IEEE 802.11 distributed coordination function (DCF) focus on saturation performance. In this paper, we develop an analytic model to evaluate non-saturation energy consumption of IEEE 802.11 DCF, based on Bianchi's model (2). The model explicitly takes into account both the carrier sensing mechanism and an additional backoff interval after successful frame trans- mission, which can be ignored under saturation conditions. The probability generating function with respect to energy consumption for a frame to be successfully received is derived. Numerical example shows that the energy consumed in overhearing a frame destined to another user occupies the major part if the frame generation probability is greater than some critical value and if the energy required in overhearing is not negligible. If the energy consumption in overhearing can be ignored, most of the energy is wasted in receiving colliding frames. Index Terms— IEEE 802.11 DCF, energy consumption, non-saturation conditions, Markov model, equilibrium point analysis