AN ADAPTTVE HYBRID ARQ ALGORITHM FOR RADIO CHANNELS

摘要

An hybrid automatic repeat request in which the transmitter can encode data packets by one of several codes is considered.An algorithm is presented by which the transmitter selects,,based on the past transmissions and scknowledgments,the code for each packet.According to the algorithm,the transmitter assesses the channel conditions by sending packets encoded by high-rate code and changes to the higher rate whenever a probing packet is received successfully.Negative scknowledgments for packets at a given code rate causes the transmitter to switch to lower rate code.A probabilistic model to ascertain throughput of the algorithm is presented,and its numerical results show that it performs well under a wide range of channel error rates.