Research On Vertical Handoff Technology In Dynamic 5G Heterogeneous Wireless Networks

In recent years,the rapid growth of smart devices and a variety of new communication technologies has promoted the rapid development of 5G network.Considering that the current network environment is composed of 5G wireless cellular network and other wireless access technologies,the density,heterogeneity and overlapping coverage of networks bring unprecedented challenges to the field of vertical handoff.Therefore,in the highly overlapping network environment,how to get the vertical handoff scheme to maximize the comprehensive performance of the network and select the best service network for the terminal is the focus of the current research.In order to reduce the number of handover failures and alleviate the dropped calls caused by the ultra-high dynamic characteristics of the network,this thesis designs two kinds of vertical handoff schemes based on the fuzziness and randomness in the process of vertical handoff to ensure that the comprehensive performance of the network and the terminal is greatly improved.The main work of this paper is as follows:1.In the ultra-dense heterogeneous wireless network,the traditional vertical handoff algorithm can not describe the fuzziness and randomness of the network state at the same time,so the network performance can not be effectively improved.A vertical handoff algorithm based on the interval type II fuzzy neural network is proposed to solve above problem.Firstly,a two-stage decision system is reconstructed: in the network's prescreening stage,the historical access rate is defined to set the threshold combine with the number of current candidate network sets.According to the received signal strength and the remaining available bandwidth,all the networks within the user's receiving range are preliminarily screened;Then,the delay,packet loss rate and bit error rate of the remaining candidate networks are taken as the inputs of the it2 fnn in the vertical handoff decision stage.The fuzzy logic reasoning is completed by using the structure of the feedforward neural network,and the output decision value is calculated after the training,and the optimal network is selected.Finally,the simulation results show that the algorithm can ensure low time consumption,and effectively reduce the error probability of handoff decision and the number of handoff failures and handoff times.Meanwhile,it can improve the total throughput of networks.2.In order to solve the problem that the drop rate keeps increasing due to the ultra-high dynamic characteristics of ultra-dense heterogeneous wireless networks,and considering the large time cost of previous vertical handoff algorithm based on fuzzy logic correlation,a vertical handoff algorithm based on dynamic rule was proposed.Firstly,5G core access and mobile management functions are used to discover all candidate networks near the terminals.At the same time,the environment awareness ability of self-organized network technology is used to monitor the running status of networks at any time and actively maintain the neighbor relationship table between them.Then,the dynamic fuzzy neural network algorithm is introduced to execute the handover decision,and the network parameters obtained are taken as the input of the system to dynamically generate a rule base that is effective for vertical handoff.After learning,the output decision value is calculated,and the best access network for the terminal is selected.Finally,the simulation results show that the algorithm can significantly alleviate the drop of calls in the process of vertical handoff and reduce the probability of handover failure.Meanwhile,compared with other similar algorithms,it can maintain a lower time cost.