To improve the media access control mechanism and enhance the performance of largescale wireless LANs, the distributed coordination function of IEEE802.11 standard and two typical improved schemes are studied extensively. Compared with the distributed coordination function, the fast collision resolution mechanism greatly enhances the throughput, but deteriorates the delay jitter and fairness of wireless LANs. The new selfadaptive distributed coordination function markedly improves the delay jitter and fairness performance, while enhancing the throughput of wireless LANs to a certain degree. Hence, with further improvement, the new selfadaptive distributed coordination function is more suitable for largescale wireless LANs for multimedia information transmission.