Wireless Local Area Network (WLAN) mesh network technologies represent a promising architecture for future communications to achieve a ubiquitous wireless access environment. Voice over Internet Protocol (VoIP) is an attractive application in WLAN mesh networks since it can extend the service coverage area. However, due to a large required packet overhead for voice packets and packet collisions, the number of simultaneous VoIP calls that can be supported in a WLAN mesh network is limited. The Transmission Opportunity (TXOP) mechanism, which is defined in the IEEE802.11e standard, potentially improves the overhead issue by transmitting multiple packets per random backoff. However, the TXOP mechanism does not work appropriately since the number of packets in a transmission queue may not be sufficient to transmit multiple frames using the TXOP mechanism. In this report, we propose a novel TXOP mechanism for VoIP communications in WLAN mesh networks. In the proposed method, the starting time of the TXOP transmission is adaptively delayed according to the user requirement for the delay and monitored delay inside the mesh network. Simulation results show that the number of simultaneous voice calls that can be dealt with can be improved by approximately 50.
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