Adaptive Vertical Handover For Heterogeneous Wireless Networks Based On Preset Expectations

In recent years,the rapid development of communication technologies and high-quality required mobile services have led to the widespread attention and research of heterogeneous networks formed by the convergence of various wireless communication technologies(including 3G,4G,WLAN,WiMAX and LTE-A).Vertical handover is the most critical technology for the mobile management of heterogeneous networks,affecting the experience degree of mobile terminals.Network ranking,as the core link of network selection,determines whether the terminal can access the optimal network and achieve seamless handover.Therefore,the network ranking problem has become a hot topic of the research of heterogeneous networks.Network parameter attribute normalization processing and attribute weight normalization calculation are two important processes of network selection algorithm,and most network selection algorithms involve the fusion calculation of multiple network attributes and parameter weights.When the mobile terminal moves from area A to area B,it is bound to cause an increase or decrease of the network.Then,the network ranking calculated according to the above normalization method is inevitably unreliable.In addition,considering that the power consumption of different services varies greatly within a certain period of time,the research on the power and service types of heterogeneous networks is relatively small,the joint modulation of power and service types can improve the utilization of wireless resources and enhance the accuracy of network sorting.In view of the above deficiencies,this paper proposes an adaptive switching algorithm based on preset expectation value adopting Technique for order Preference by similarity To Ideal Solution(TOPSIS).The TOPSIS algorithm is one of the typical multi-attribute vertical over algorithms.It not only considers the basic network attributes and user preference parameters,but also is more suitable for solving network ranking problems.The algorithm uses five network attributes: power consumption,bandwidth,delay,signal strength and network cost.Four kinds of representative services are selected and the power is divided intomultiple threshold levels for joint modulation.The preset expectation value is introduced instead of the network attribute normalization and the process of parameter weight calculation.The mobile terminal can adaptively select an appropriate expected value for network ranking calculation according to the power and service level.Finally,according to the research content of this paper,two sets of network simulation scenarios are built on the OPNET network simulation platform: LTE-WLAN simulation scenario and LTE-UMTS-WLAN simulation scenario.At the same time,the algorithm proposed in this paper is simulated and verified.The related simulation data show that the adaptive vertical over algorithm based on the preset expectation value of TOPSIS in this paper can avoid unreliable network ranking and reduce unnecessary network switching,and improve the endurance of mobile terminals and the utilization of wireless resources.