Performance Evaluation of Multiple-Relay Cooperative ARQ Strategies for Mobile Networks

In cooperative automatic repeat request (C-ARQ) protocols, one or more nodes can act as relays, collaborating in the frame retransmission process between a sender and a destination node. In the framework of a broadband mobile access network, we consider a relay enhanced cell where the sender represents the base station, and an undefined number of relays can cooperate with a single user (destination). In this paper we present a Markov model complemented with a reward model to analyze the throughput performance and the efficiency in the bandwidth utilization at the base station, highlighting a clear tradeoff between them. Both performance metrics are balanced by means of a multi-objective optimization algorithm resulting in a retransmission strategy for the access node that notably improves the bandwidth efficiency while maintaining the throughput very close to its maximum. The benefits of the proposed approach are evaluated in two scenarios. In the first one, the relays are part of the network infrastructure. In the second one, the relays are cooperative users.