Exact statistics of ARQ packet delivery delay over Markov channels with finite round- trip delay

In this paper the packet delay statistics of a fully reliable selective-repeat ARQ scheme is investigated. It is assumed that the sender continuously transmits packets whose error process is characterized by means of a two-state discrete time Markov channel. At the receiver these packets are checked for errors and ACK/NACK messages (assumed error-free) are sent back to the sender accordingly. The feedback message is known at the transmitter m channel slots (round-trip delay) after the packet transmission started. An appropriate Markov model has been developed in order to find the exact statistics of the delays experienced by ARQ packets after their first transmission.