Context-awareapplication Layer Handover Within Heterogeneous Networks

With the progress in research and development of wireless networking and communicationtechnologies, more different types of wireless systems (e.g., 2G, 3G, WLAN, and WIMAX) havebeen created.Owning to the excellent performance of individual networks in a particularapplication or scenario, it is realized that the next generation communication systems will be theheterogeneous networks, which intelligently converge the existing wireless systems. Presently, theinterworking of heterogenous network and the opening of business platform have been wellsolved by academia and standardization organization. Vertical handover, as the key controlfunction which is used to provide session continuity across heterogeneous networks, is urgent tobe addressed.Firstly, according to the mobility scenarios and the environment terminals locate, a wirelessheterogeneous converged network model is introduced. Secondly, a context-awareness basednetworks selection scheme is proposed, following with the logical structure and theimplementation. At last the network selection algorithm is presented. The selection may dependon various parameters including the type of the application, the required bandwidth and delay ofapplication, access cost, transmit power, and the user's preferences.However, the existing MADM algorithms only analyze context parameters mathematically,which may make these networks'load unbalanced and some parameters neglected. To solve theseproblems, a fuzzy analytic hierarchy process (FAHP) networks selection algorithm, by using thefuzzy theory, is proposed, and the simulation using MATLAB shows that FAHP algorithm has abetter performance than TOPSIS on load balancing, and could reduce the nonessential handover.Although SIP has been regarded as an attractive candidate to provide mobility managementin heterogeneous converged networks in respect of its flexibility and ease of deployment, itsunacceptably long handoff delays is unbearable for the real-time application.So an optimizedmechanism of application layer is originated for session continuity. In the mechanism, mobilityproxy (MP) could be as user agent, which can cut some standard register procedures to reduce thetime cost during handoff. Also mobility proxy could be as media gateway, which can use dataforwarding or bi-casting mechanism to ensure that the data flow will not be lost.The test on theprototype system shows that this optimization is reasonable and effective.