This thesis aims at contributing to the field of cooperative AHNs. The focus of this research is on the relay based MAC layer: design of cooperative MAC protocols, performance modelling, and protocol enhancements. The first contribution of this thesis is dedicated to the modelling of energy consumption which aids MAC protocol developers in the design phase to devise efficient protocols and energy saving solutions. This model can predict energy consumption in an ideal and non-ideal environment. It is shown that using a relay results in not only better throughput but also higher energy efficiency. In the next contribution, we propose an Enhanced relay-enabled Distributed Coordination Function (ErDCF), which uses high data rate nodes to work as relays for the low data rate nodes. ErDCF in saturation achieves higher throughput, lower delay and lower energy consumption as compared to conventional 802.11 Distributed Coordination Function (DCF) in ideal conditions. The performance of ErDCF under non-ideal condition is evaluated and it proves that the gain of ErDCF can still be maintained under reasonable link quality and distance. Finally a multiple relay MAC protocol is proposed and its performance is evaluated. The results confirm the throughput advantage of multiple relays, but they also show that beyond two relays the throughput gain becomes increasingly marginal due to the cost of higher overhead.