Research On Vertical Handoff Method Based On Internet Connectivity Monitoring

With the widely use of smart phones,there are a variety of mobile operating systems,including Android,iOS,Windows and BlackBerry,in the current market.Among those systems,the Android takes the largest share.Currently,the Android system has occupied 87%of the mobile phone operation System market.Currently,the most widely used network access mode for Android is it can only use a network interface at one time,when the Android smartphone is in the WiFi environment,the system will detect the availability of WiFi networks,first,Android System connected to the WiFi access point to complete the link layer configuration,Then it will run the network protocol stack configuration to obtain IP address,when the smart phone connect to WiFi hotspot,In the usage stage,WiFi module will dynamically update the WiFi availability status,but its update rules are based on the link layer Attribute,and no longer determine the WiFi connection after the first jump of the Internet connectivity;in WiFi mode,if the WiFi access point is lost connection with Internet,Android system will remain in WiFi mode without handoff to the cellular data model,thus causing troubles to users.Therefore,there is a strong need for a effective and automatic handoff mechanism between WiFi and cellular data networks,so that it can have a strong network connectivity.This thesis designs an adaptive,efficient vertical handoff method that enables Android smartphones to vertical handoff between WiFi and cellular networks for reliable Internet connectivity.When using a WiFi network,the system uses active detection and passive measurement methods to monitor the Internet connectivity of WiFi networks.For the detection of mobile phones in cellular data mode,two algorithms,namely,dormant adaptive detection algorithm and variable heartbeat detection algorithm,are designed to detect Internet connectivity.In the vertical handoff technology,this article implements a technology that can open the cellular data network interface and WiFi interface in the Android system at the same time,so that the WiFi interface can be opened without interrupting the cellular data connection while the system is in the cellular data mode Internet connectivity,the experimental results of this thesis show that when the system is in WiFi mode,if the Internet connection after the first hop of the WiFi connection is disconnected,the system can quickly handoff to the cellular data network mode.When the system is in the cellular data network,variable heartbeat algorithm,can quickly detect the current environment,WiFi network to restore Internet connectivity,so that the system can quickly handoff from the cellular data mode to WiFi mode;through the proposed vertical handoff method,smart phones can get more stable Internet connectivity.