Call Admission Control In CDMA2000/WLAN Network Based On Position Information

With the fast development of the wireless communications as well as thegrowing user demand, it is always wished that roaming within all kinds of networkswhile enjoying the guaranteed services only with the same mobile terminal, thus,heterogenous networks convergence is a matter of course. As a result, call admissioncontrol becomes the focus of many researchers’ concern. Many call admissioncontrol schemes has been proposed, but most are transparent to the lower layerprotocols. Thus schemes maybe available to more occasions, but they failed toefficiently use the whole resource or uniformly measure resources from differentnetworks due to inadequate consideration of the lower layer protocols specific tosome kind of network. What’s more, the so-called pingpang effect is anotherproblem in call admission control, it increases the system overhead and signalingoverhead due to the unnecessary handoffs.To solve the problems above, in this paper, a call admission control schemebased on user position information is proposed in the context of CDMA2000andWLAN heterogeneous networks with voice and data traffic. To be specific, a novelchannel condition evaluation method specific to CDMA2000/WLAN networks isfirstly proposed. Unlike traditional methods that compare the received signalstrengths directly, it mapped them into bit error rates to judge channel conditionvirtually. Secondly, a novel netowrk load condition evaluation method is proposed touniformly weigh the resourses in the heterogeneous networks. Last, the calladmission scheme is proposed combining them with the user position imformationwhich is composed of a parameter measurer, an admission controller and a decisionexecuter. When a new call or a handoff call arrives, the parameter measurer firstobtains channel and load conditions of available subnetworks as well as the positionand mobility information for the admission controller. The admission controller thendecides whether to admit or reject the call considering both quality of service andload balancing. The decision executer carries out the final actions at last.Simulation results show that proposed scheme can always reduce pingpangeffect while maintaining the quality of service requirements in that it canappropriately admit or reject the users’ admission requests. Also, the proposedscheme can achieve lower blocking rate than conventional algorithms such asreceived signal strength based algorithm or WLAN first algorithm and cansignificantly reduce the handoff dropping rate by effective load balancing.Considering metrics such as new call blocking rate, handoff call dropping rate,pingpang times, load balancing rate and so on, the innovation points lie not only in the deep research on the physical and media access control layer protocols ofCDMA2000and IEEE802.11, coming up with the effective methods of channel andload condition evaluation, but also the proposal of the call admission schemecombining the user mobility information. It is aimed to reduce the pingpang times,blocking rate and dropping rate, increase the load balancing rate while maintainingthe quality of service.