Effective Capacity of Retransmission Schemes - A Recurrence Relation Approach

TL;DR

This paper introduces a unified analytical approach using recurrence relations to precisely evaluate the effective capacity of various retransmission schemes, including HARQ and network-coded ARQ, under different QoS constraints.

Contribution

It presents a novel recurrence relation-based method for exact effective capacity analysis of multiple retransmission schemes, covering cases not addressed before.

Findings

Exact effective capacity expressions for persistent and truncated HARQ.

Closed-form solutions for systems with finite and infinite horizons.

New insights into QoS parameters and their impact on retransmission schemes.

Abstract

We consider the effective capacity performance measure of persistent- and truncated-retransmission schemes that can involve any combination of multiple transmissions per packet, multiple communication modes, or multiple packet communication. We present a structured unified analytical approach, based on a random walk model and recurrence relation formulation, and give exact effective capacity expressions for persistent hybrid automatic repeat request (HARQ) and for truncated-retransmission schemes. For the latter, effective capacity expressions are given for systems with finite (infinite) time horizon on an algebraic (spectral radius-based) form of a special block companion matrix. In contrast to prior HARQ models, assuming infinite time horizon, the proposed method does not involve a non-trivial per case modeling step. We give effective capacity expressions for several important cases that have not been addressed before, e.g. persistent-HARQ, truncated-HARQ, network-coded ARQ (NC-ARQ), two-mode-ARQ, and multilayer-ARQ. We propose an alternative QoS parameter (instead of the commonly used moment generating function parameter) that represents explicitly the target delay and the delay violation probability. This also enables closed-form expressions for many of the studied systems. Moreover, we use the recently proposed matrix-exponential distributed (MED) modeling of wireless fading channels to provide the basis for numerous new effective capacity results for HARQ.