Adaptive incremental-redundancy transmission for tactical packet radio systems

A low-complexity protocol for the adaptation of incremental-redundancy transmission is described and evaluated for use in tactical packet radio systems that must communicate over channels with fading and other time-varying propagation losses. The protocol responds to variations in channel attenuation by adjusting the number of binary code symbols that are punctured in the first transmission for a packet and saved for subsequent transmissions if they are needed. The protocol relies on simple statistics from the receiver to provide the necessary control information for adapting the amount of puncturing or the rate of the code that is employed from one packet to the next. No channel measurements, parameter estimates, pilot symbols, or training are needed. The protocol´s throughput performance is evaluated for dynamic channels that are modeled by finite-state Markov chains. Performance benchmarks are obtained from hypothetical ideal protocols that are given perfect channel-state information and are told all the parameters of the channel model. We demonstrate that the new adaptive protocol performs nearly as well as the hypothetical ideal protocols even though the adaptive protocol is given no channel-state information and no information about the channel model or its parameters.