Strategies and Tradeoffs for Coded Cooperation in Wireless Networks

In a wireless network, fading significantly affects the performance, and diversity techniques are used to overcome this issue. Cooperation among nodes provides spatial diversity by means of packet relaying. In coded cooperation, diversity is further enhanced since cooperating nodes transmit different parts of a coded packet on different channels. In this paper we analyze various combinations of coded cooperation with a hybrid automatic retransmission request (HARQ) algorithm. We assume the use of a capacity-achieving code, so that an outage event occurs when the total transmission rate exceeds the channel capacity. We first provide an analysis of the outage probabilities at the various HARQ phases for different cooperative behaviors. In order to better understand the features of the proposed protocols, we model the network operation with simple semi-Markov processes and then we evaluate metrics such as throughput, efficiency, and success probability. More complex cases, such as networks with multiple simultaneous access to the radio resource and queueing aspects, are evaluated by simulation.