无线局域网下PCF结点切换时的资源预留方案

在无线局域网（WLAN）环境中，对VoIP等实时应用结点在漫游切换时，提前在邻居AP小区进行带宽资源预留是保障其获得持续、一致OoS的主要措施．但是目前的资源预留方法要么计算复杂，不符合WLAN的实际情况；要么效率低下，不能很好地为切换结点提供资源保证．在结合已有的预留算法的基础上，根据WLAN本身的特点，提出了一种PCF结点资源预留方法，使VoIP结点采用PCFAP轮询信道访问方式，通过VoIP结点漫游时发现邻居AP的存在，提前向邻居AP发出资源预留请求，同时邻居AP根据网络状况动态调整预留资源大小．仿真实验结果表明，在不浪费无线带宽资源的条件下，提出的方法相对于其他预留方案能够获得更低的切换连接掉线率．

A Resource Reservation Scheme for PCF Handoff Station in WLAN

To reserve resource at adjacent AP in advance is an important measure for mobile station which runs real-time application such as VoIP when handoff, which can make it have identical QoS as before in wireless LAN. But the present mechanisms either have complicated computing, being not suited for wireless LAN, or have low efficiency, not making reservation well for handoff station. On the basis of the present resource reservation schemes and the wireless LAN 's specialties, a PCF station resource reservation scheme is proposed in this paper, which makes the VoIP real-time station use the PCF mechanism to access the channel. In the proposed scheme, when a mobile finds a new AP, it can request the new adjacent AP to reserve resource for it and at the same time, the adjacent AP also adjusts the size of reserved resource adaptively. Through a simulation to the proposed scheme, it shows that the proposed scheme can make the handoff drop rate more lower than other reservation schemes under the condition of not wasting the wireless bandwidth resource.