On Call Admission Control In WiMAX And 3G Convergent Network

As a new access technology for Metropolitan Area Networks (MANs), WiMAX can provide the broadband access in "the last mile" for wider areas than Wi-Fi. To fulfill the requirements of QoS and multimedia applications, the IEEE 802.16 standard series define four different scheduling services: Unsolicited Grant Service (UGS), real-time Polling Service (rtPS), non-real-time Polling Service (nrtPS), and Best Effort (BE). The MAC layer of IEEE 802.16 standard specifies QoS service flows, their parameter configuration mechanisms, scheduling service types based on QoS and corresponding bandwidth request/allocation, but the standard leaves some important issues such as access control strategy, QoS parameter mapping and packet scheduling algorithms undefined. These hot problems are expected to be resolved by the researchers. For improving the system efficiency, achieving user fairness, satisfying the QoS requirements of various services, and cooperating with 3G and next generation networks as the part of 4G system, we need to research and implement the access control schemes for WiMAX.In this thesis, in order to guarantee the QoS requirements of various services and improve the wireless resource utilization, the call admission control (CAC) policies in WiMAX networks are proposed based on existing studys.On the one hand, according to the characteristics of WiMAX networks and the QoS requirements of the four different service types in the IEEE 802.16 family standards, the admission control mechanisms for different services are proposed, on the condition that most subscribers can access the network to get high-quality services and meanwhile the QoS requirements of different services are all considered. In the scheme of this thesis, the BS will grant the request of high priority traffic (real-time traffic) connections according to the difference of various priorities of services if it gets connection requests simultaneously. If the bandwidth is not enough for a new high priority traffic accessed, the low priority traffic will be degraded to release bandwidth for it. On the other hand, to guarantee the fairness of the system, a threshold-based scheme is used to ensure the QoS requirements of the non-real-time traffics. In this way, we gain the goals that high-priority services have higher probability of admission; the QoS requirements of different subscribers are considered, and the ratio of system resource utilization is increased and the ratio of congestion is reduced.Another important research of this thesis is about the admission control of WiMAX and 3G convergent network. Along with the development of WiMAX and 3G, the convergent network is the trend of next generation wireless networks. The most sensible position of WiMAX is to provide area supplements and transmission from hotspots. In the control of convergent BS, the data traffic in 3G network can be mapped and vertical handed off to WiMAX network in subscriber station. So the load of 3G network will decrease and more conversational and streaming traffic requests can be accepted. The simulation results show that the block probability is reduced in 3G network, the throughput is increased in the double networks, and the QoS of different traffics can be guaranteed efficiently.