SR-ARQ delay statistics on N-state Markov channels with finite round trip delay

In this paper the packet delay statistics of a fully reliable Selective Repeat (SR) ARQ scheme is investigated. A N-State Discrete Time Markov Channel model is used to describe the packet error process and the channel round trip delay is considered to be finite, i.e., ACK/NACK messages are received at the transmitted m channel slots after the packet transmission is started. The ARQ packet delay statistics is evaluated by means of an exact analysis by jointly tracking packets errors and channel state evolution. Furthermore, a procedure to derive a Markov Channel description of a Rayleigh fading process is presented and the delay statistics obtained from the Markovian analysis is compared with the ones estimated by simulation of the ARQ protocol over the actual fading process. Some discussion on the accuracy of the delay statistics obtained from the Markov Channel representation of the actual fading process is finally reported.