模糊控制在垂直切换判决算法中的应用

Vertical handoff algorithm based on fuzzy logic control

为了满足用户的各种通信需求,垂直切换判决算法中考虑的因素越来越多,判决因素的增加,使得切换判决所需的时间延长,不能够实现快而有效的切换判决,影响了移动终端的实用性。并行模糊控制系统使得各判决因素同时进行模糊推理且大大减少模糊规则的数量,降低了切换判决的时延。把网络可用带宽、用户移动速度及网络的服务费用作为判决因素进入并行模糊控制系统,通过用户服务类型的不同,对各判决因素动态地计算相应的权值,同时各判决因素通过模糊控制系统的输出值与权值对应相乘相加,从而得到最优的切换目标网络。仿真结果表明,该算法增强了切换的准确性,减少了不必要的切换,增强了系统性能。

In order to meet different needs of users, more and more factors need considering in the vertical handoff algorithm. Hence, time that handoff decision needs prolongs. Fast and efficient handoff decision cannot be achieved and the application of mobile node gets affected. Parallel fuzzy logic makes fuzzy inference on judgment factors at the same time, and decreases the number of fuzzy rules, then reduces the time of handoff decision. This paper chose some judgment factors to pass the parallel fuzzy logic, including network available bandwidth, user＇s moving speed and cost of the network services, calculated the weights of judgment factors according to different service type of the users, and then calculated the score of the candidates networks based on the output of parallel fuzzy logic and the weight. The simulation results show that the proposed algorithm enhances the accuracy of handoff, reduces the unnecessary haudoff, and improves the performance of system,