Non-Aware Handover Algorithm For Terminals In Software-Defined Wireless Networking

In order to provide faster and more stable services for users,operators usually deploy multiple wireless access points(APs)in public places with strong mobility and high traffic,such as companies,campuses,etc.When users move freely within the coverage area of multiple APs,terminals may handover frequently between APs.Therefore,there are two ways to ensure the continuity of terminal communication and the level of user experience,one is to reduce the terminal handover delay as much as possible,and the other is to select a most suitable AP for handover.Due to the lack of considering the terminal mobility in the protocol 802.11,the issue of AP handover is still a hotspot in the mobile communication field.In order to ensure the continuity of data transmission during AP handover,this thesis studies the scheme of non-aware terminal AP handover and the AP selection algorithm in the software defined wireless network(SDWN).First,a dual-channel alternate AP handover scheme is proposed.During the moving process of terminals,the main channel communicates with the server through its associated AP,while the secondary channel continuously detects to be switched APs.While the performance of the main channel decreasing,the secondary channel associates the candidate AP actively and takes over the task of data transmission between the terminal and the server.Meanwhile,the secondary channel substitutes for the main channel to continue detecting APs.During the handover,the SDWN controller sends the flow entry to the connected SDN switches with its centralized controlling APs,and the terminal can receive data from multiple APs simultaneously.After the handover is completed,the controller updates the flow tables in the switches and only keeps the communication between the terminal and the server through the newly connected AP,thus ensuring the continuous communication between the terminal and the server.Furthermore,to ensure that the switched AP is an AP with better communication services for terminals,the thesis proposes an AP selection algorithm based on ideal point.Firstly,the initial matrix is constructed based on some attributes,such as load,bandwidth and number of terminal connections of each AP in the region.Then,the normalized initial matrix is weighted by the objective assignment method for each attribute,and the positive and negative ideal solutions are calculated.The positive ideal solution is the ideal point.while can be regarded as the most suitable virtual AP for terminal connections.The Euclidean distance between the positive and negative ideal solutions is used to represent their proximity level to the ideal point.Finally,the AP while is near the positive ideal solution and far from the negative ideal solution is chosen as the AP for handover.The effectiveness of the algorithm is verified by experiments based on the network simulator NS3.The experimental results show that the proposed algorithm can guarantee the continuous communication during handover,realize the non-aware terminals handover between multiple APs,and improve the user experience to a certain extent.