Bursty transmission and glue pouring: on wireless channels with overhead costs

Power efficiency is a capital issue in the study of mobile wireless nodes owing to constraints on their battery size and weight. In practice, especially for low-power nodes, it is often the case that the power consumed for non-transmission processes is not always negligible. In this paper, we consider the channels with a special form of overhead: a processing energy cost whenever a non-zero signal is transmitted. We show that under certain conditions, achieving the capacity of such channels requires intermittent, or `bursty´, transmissions. Thus, an optimal sleeping schedule can be specified for wireless nodes to achieve the optimal power efficiency. We show that in the low SNR regime, there is a simple relation between the optimal burstiness and the overhead cost: one should use a fraction of the available degrees of freedom at an SNR level of radic2epsiv, where epsiv is the normalized overhead energy cost. We extend this result to use bursty Gaussian transmissions in multiple parallel channels with different noise levels. Our result can be intuitively interpreted as a ´glue pouring´ process, generalizing the wellknown water pouring solution. We then use this approach to compute the achievable rate region of the multiple access channel with overhead cost.