Random linear packet coding for half duplex underwater channels

Abstract

Random linear packet coding is considered for underwater acoustic communications in situations where reliability is essential, i.e., where data packet delivery has to be guaranteed with some probability. We develop an adaptive power and rate control strategy for a half duplex acoustic channel in which the receiver can inform the transmitter about the channel state. We consider transmission in cycles, each long enough to conform to the channel’s coherence. In each cycle, the receiver feeds back the channel gain and the noise power, and the transmitter adjusts its settings accordingly. Based on the experimental measurements, we model the channel gain as a log-normally distributed fading process, and provide a system optimization procedure based on a chosen criterion, such as minimum average energy per bit or maximum average throughput. System performance is compared analytically and numerically to that of a non-adaptive system, showing benefits of closed-loop, channel-aware transmission.