In the past decades, cooperative communications schemes have gained significant attention in wireless networks. The cooperative scheme leads to longer transmission time which can considerably degrade the system performance. We evaluate the saturation throughput and saturation delay of the Markov chain model with direct/cooperative schemes to support QoS in WLANs. Simulation results show that differentiating the contention window size is better than differentiating the arbitration interframe space in terms of throughput and delay.