软件定义无线局域网的切换接入机制

软件定义无线局域网（WLAN）是管理无线网络的一个趋势。针对无线访问接入点（AP）部署密集环境中频繁切换、接入失败等问题，提出了基于惩罚因子的全局关联记忆保留的接入控制的方法。首先，扩展OpenFlow协议；其次，利用扩展数据报文通过AP向控制器报告网络的质量、负载、吞吐量以及利用率等指标；接着，引入变异系数法确定网络指标的系数，然后利用这些指标参数构建AP接入权值；最后，引入全局惩罚因子记录网络中发生频繁来回切换的情况，根据全局记忆保留的惩罚因子修正AP接入权值和发射功率。通过与信号最强接入法和负载均衡接入法的实验对比表明，终端站点（STA）在复杂网络环境中移动时，该方法能有效地降低切换的“乒乓效应”，减少网络的切换次数和切换时延并提高网络切换成功率。与传统信号最强接入法相比，所提方法的切换请求次数减少了21.7%，增强了网络接入性能的稳定性。

Handover access scheme in software-defined wireless local area network

Software-defined Wireless Local Area Network (WLAN) is a trend for managing wireless networks. Aiming at the problems of frequent handover and access failure in AP(Access Point)-intensive environment, an access control method based on global association memory retention of penalty factors was proposed. First, OpenFlow protocol was extended. Second, the extended data messages were used to report network quality, load, throughput, and utilization indicators to the controller through AP. Then, the network index parameters determined by introducing variation coefficient method were used to construct AP access weights. Finally, a global penalty factor was introduced to record frequent back-and-forth handovers in the network, and AP access weights and transmitting powers were modified based on the penalty factor retained by the global memory. Experimental comparison with the strongest signal access method and load balancing access method shows that when the STAtion (STA) moves in a complex network environment, the proposed method can effectively reduce the “ping-pong effect” of the handover, and reduce the number of network handovers and the handover delay, so as to improve the success rate of network handover. Compared with the traditional strongest signal access method, the proposed method has the number of handover requests reduced by 21.7%, which enhances the stability of network access performance.