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VoIP (voice over IP) is one of the real time applications which demand that wireless LAN systems achieve severe quality requirements in terms of delay time, jitter and packet loss. However, it is difficult for CSMA/CA (carrier sense multiple access with collision avoidance) to achieve the service quality demanded by VoIP if voice and data traffic coexist, so some form of priority control is needed. This paper proposes a novel multiple access protocol that allows wireless LANs based on autonomous distributed control to satisfy the VoIP requirements. This new protocol suits both VoIP and data traffic and executes priority control dynamically according to whether the VoIP packet collides with a data packet or another VoIP packet. The results of a theoretical analysis and computer simulations indicate its excellent performance. This proposed protocol reduces the delay time of VoIP packets by 54 to 70% compared with conventional CSMA/CA, even if the traffic load increases, provided that the packet loss probability is less than 3%.