Energy efficiency of TCP in a local wireless environment

The focus of this paper is to analyze the energy consumption performance of various versions of TCP, namely, Tahoe, Reno and NewReno, for bulk data transfer in an environment where channel errors are correlated. We investigate the performance of a single wireless TCP connection by modeling the correlated packet loss/error process (e.g., as induced by a multipath fading channel) as a first-order Markov chain. Based on a unified analytical approach, we compute the throughput and energy performance of various versions of TCP. The main findings of this study are that (1) error correlations significantly affect the energy performance of TCP (consistent with analogous conclusions for throughput), and in particular they result in considerably better performance for Tahoe and NewReno than iid errors, and (2) the congestion control mechanism implemented by TCP does a good job at saving energy as well, by backing off and idling during error bursts. An interesting conclusion is that, unlike throughput, the energy efficiency metric may be very sensitive to the TCP version used and to the choice of the protocol parameters, so that large gains appear possible.