Expressions for the mean transfer delay of generalized M-stage hybrid ARQ protocols

In this paper, we develop expressions for the transfer delay of an M-stage hybrid automatic repeat-request (HARQ) protocol. These generally applicable expressions make no assumptions about the quality of the feedback channel and explicitly account for both feedback errors and their associated delays. Both infinitely repeating and terminated HARQ protocols are considered. Through a series of examples, we demonstrate that these expressions admit earlier results as special cases or applications, while providing additional insight on the contributions of various error and delay terms.