Random linear packet coding: Joint power and rate control

Random linear packet coding is considered for channels that experience fading and have long propagation delay, such as the underwater acoustic channels. Previously, we employed power control (adjusting the transmission power according to the channel gain) and rate control (adjusting the number of coded packets according to the channel gain) to counteract the effects of fading. For such policies, it was shown that there exists an optimal number of coded packets (when employing power control) or optimal transmission power (when employing rate control) for which the energy required per bit of information transmitted is minimized. In this paper, we present a strategy to jointly optimize the transmission power and the number of coded packets. We present two optimization criteria, i.e., (a) minimizing the average energy per bit for transmission and (b) maximizing the throughput. Given the statistics of the channel, we compute the average energy per bit and the average throughput under each criterion, to make a choice based on the desired tradeoff. In applications with limited power, minimizing the average energy per bit will be the guiding principle, while in time-critical applications maximizing the average throughput will dictate the choice.