Investigation On Network Selection And Joint Call Heterogeneous Wireless Networsks

With the rapid development of wireless communication technology,a variety ofnew wireless access technologies emerge one after another, such as traditional2G/3Gcellular networks, WiMAX, WLAN, WPAN, etc.The different wireless accesstechnologies provide different bandwidth, coverage area, Mobility support and qualityof service etc.There is no single network can meet the service requirements of all users,the future network must be a heterogeneous environment integrating different wirelessaccess technologies.This paper firstly analyzes the existing network selection algorithm’s shortcoming,and proposes a self-adaptive wireless network selection scheme based on the accessdecision threshold.In this paper, we periodically accommodate the best access decisionthreshold through solving the problem of the global network performance optimization,which jointly consider the distribution of the whole users’ mobility characteristics andnetwork load conditions,and guide the user’s access option based on this value.Simulation results show that the algorithm is better than the traditional networkselection algorithm which reduces the blocking probability and the handover rate, andimprove the overall network performance.In the heterogeneous network environment, multiple networks often overlap ingeographic coverage, and users in different regions obtain different QoS. To addressthe problem, we propose an call admission control algorithm based on the call typedifferentiation. Considering the handoff priority as the major premise, new calls indifferent regions are treated differently in order to guarantee the QoS fairness.In this paper, we distinguish the different types of call priority through setting upmultiple access threshold. And the call admission control problem is modeled as anoptimum problem aiming to minimize the blocking probability in the whole network,inconsidering QoS fairness factors and the call dropping probalility constraint. Finally,We analyzed the system model using the Markov chain model, and determine theoptimal access threshold according to the arrival of the business.