Abstract: IEEE 802.11e provides the mechanism to distinguish the priority for different service flows，compared to other services it improves the priority of real-time services such as VoIP（Voice over Internet Protocol） in WLAN（Wireless Local Area Network），so that its QoS requirement will be satisfied to some extents，because of not providing the different priority between Move Host（MH） and Access Point（AP） in WLAN，the unbalance between uplink and downlink service flow on AP is induced，and then it leads to bottleneck，further more restricts the VoIP capacity.To solve this problem，a new strategy based on the analysis of the capacity of VoIP in WLAN is proposed to improve the switch in capacity of AP’s channel.It usees the length of AP’s queue to estimate whether the network is congested or not，and then modifies the Arbitration Inter-Frame Space（AIFS） of the service flows dynamically，modulates the priority of AP dynamically according to web congestion condition，to weaken the restriction of VoIP capacity caused by bottleneck of AP.The results of simulation show that the proposed scheme can increase VoIP capacity efficiently.

Key words: 802.11e, Wireless Local Area Network（WLAN）, Voice over Internet Protocol（VoIP）, voice capacity

摘要： IEEE 802.11e提供了对不同的业务流进行优先级区分的机制，提高了无线局域网（WLAN）内VoIP等实时业务相对于其他业务流的优先性，从而在一定程度上保障其QoS要求，但并没有对WLAN中移动节点（MH）和接入节点（AP）进行优先级的区分，导致AP处上下行业务流量的不平衡，并造成瓶颈效应，限制了VoIP容量。针对这一问题，在对WLAN中VoIP进行容量分析的基础上，提出一种改进AP信道接入能力的策略。通过对AP中队列长度的检测来判断网络拥塞程度，从而动态调整AP的仲裁帧间间隔（AIFS），以达到根据网络拥塞状况来动态调整AP的优先级，弱化AP的瓶颈效应对VoIP容量制约的目的。仿真结果表明，所提出的改进方案能够有效地提高WLAN中的VoIP容量。

关键词: 802.11e标准, 无线局域网, IP电话, 语音容量