The analysis of truncated ARQ and HARQ schemes using transition diagrams

In digital communication systems, ARQ and HARQ schemes are employed in order to ensure efficient transmission of information and utilisation of the channel by retransmitting information that has not being received correctly at the receiver. In some applications, however, such as real-time services, the quality of information is degraded if too many retransmission trials are employed for each unit of erroneously received information. The retransmissions are therefore limited leading to truncated ARQ and HARQ schemes. In this study we develop a new method for deriving the expressions for the throughput efficiencies of truncated ARQ and HARQ schemes and investigate how the efficiencies vary with the number of allowed retransmissions. Keywords: ARQ, HARQ, Throughput Efficiency, Truncated ARQ.