Research On Call Admission Control In Heterogeneous Wireless Networks

It is a stirring time for Internet and wireless communication technologies'rapid development during the past ten years. Driven by the expectation to the future communication system that"Whenever, wherever, whoever, whomever and whatever to communicate", heterogeneous wireless networks emerge as the times require. Recently there is a growing interest in this field, bringing some new challenges.The most promising wireless access networks in heterogeneous networks are mobile cellular network and wireless local area networks (WLANs). Because of high cost, limited bandwidth and limited services, the progress of cellular network's evolving is much slower than people's expectation. WLAN gains more and more market because it is cheap, easy to install, providing high-rate data services at the same time. In the future, mobile cellular network will still be the most popular technology for wireless communication, and WLAN will serve as the complement.Call admission control (CAC) as a necessary part in radio resource management has been well researched in recent years, relating to QoS of ongoing and new services directly. However, most of the current CAC schemes in cellular network and WLANs are developed independently. The proposed CAC scheme in this paper is for heterogeneous networks by jointly taking into account heterogeneous networks characteristics, multiple service types, user mobility and vertical handoff.This paper introduces the CAC strategies in mobile cellular network and WLANs, and proposes a joint CAC strategy, which is a two-tier CAC scheme. The first tier is network selection, which selects a preferred network by jointly considering heterogeneous networks characteristics, network traffic load, multiple service types and user mobility. After the preferred network is selected, the second tier entity, i.e., CAC decision in individual network, decides whether to admit the call to the preferred network or not. In order to guarantee system's performance and enhance resource utilization, dynamic bandwidth reservation and dynamic bandwidth allocation schemes are adopted. At last, a simulation platform is established to verify the strategy. The analysis and simulation results validate that this strategy can reduce the average vertical handoff number, guarantee system's performance and take full advantage of radio resource increasing capacity.