Mobile Communications, Access Control And Multi-service Switching Method

As the types of the services carried by the mobile communication networks are becoming more and more varied, the demands for wireless resources are becoming harder to be met too. It is the opening and sharing characters of the wireless channel that make the wireless resources which can be utilized very limited. To improve the efficiency of the wireless resource utilization and provide differentiated services to different types of services and mobile terminal are key problems to be solved by the future mobile communication technologies. To provide solutions to these problems, this dissertation dedicates on research works on the wireless access control technology, network structuring and handoff methods.Firstly, to provide a more efficient access control method, a wireless access control method based on cyclic polling scheme is presented. The efficiency of packet scheduling and resource utilization has been improved. The newly presented method can provide higher system performance stability and better delay QoS for the time-bounded services. When it is implemented in WLAN, the system performance can be improved. The basic idea of the method has also been implemented in access control scheme in WiMAX. The key contributions are· A wireless access control method named busy queue polled only (BQPO) is presented.· The mathematical model of BQPO system and the mean value of message waiting time are explicitly obtained.· The performance of BQPO is simulated and compared with the other scheme. The results show that when the system load is increasing, BQPO can provide higher stability and better delay QoS than the other methods.Secondly, to decouple the relationship between the resource and the signal coverage in the traditional cellular communication system, which makes the networking planning not easy to adapt to the change of the distribution of the network load, the cellular structure base on distributed antenna system is studied in this dissertation. A network structure named Hierarchical Soft Cellular (HSC) which is based on distributed antenna system is presented as a result of the cooperation with International Center for Wireless Collaborative Research. The distributed antenna network can provide seamless signal coverage for cells in different layers. The cell is formed according to the character of the customers it serves. The structure of the cell can be adjusted according to the change of distribution of the system load and the types of terminals it serves. The key contributions are· A network structure named Hierarchical Soft Cellular (HSC) which is based on distributed antenna system is proposed· The network structure has better scalability and services adaptability than the conventional network.· The analytical results of the system capacity, carrier to interference ratio and system access blocking probability show that HSC outperforms the traditional cellular network. The complexity is controllable.A handoff method using position and speed information for handoff decision is presented to serve the HSC. It can provide reliable handoff for the terminals with different speed. The performance of the method is verified in the simulation.Thirdly, how to provide different resource guarantee for different type of services is studied in this dissertation. Sub-channel combining handoff algorithm used in multi-carrier communication system is presented. By combining the sub-channels provide by the serving BS and the target BS, it can provide smooth and reliable handoff for the mobile terminal. The performances of the services with more bandwidth request and the utilization of the system resource are improved. The key contributions areSub-channel combining handoff algorithm used in multi-carrier communication system is presented.· The mathematical model of sub-channel combining handoff algorithm and the key system performance parameters are explicitly obtained.· System performance simulation results show that sub-channel combining handoff algorithm can provide better QoS for the handoff call compared to the other handoff resource allocation algorithm.· Sub-channel combining handoff algorithm can work with the other handoff resource reservation algorithm and improve their performance.Finally, considering the fact that the services which have loose demand on the bandwidth and delay can accept relative long handoff delay and the services which have harsh demand on the bandwidth and delay will be suffered if handoff delay is too long, the handoff initialization algorithm supporting multi-services in cellular network is studied in this dissertation. The information of the QoS demands of the service, the change of the channel quality and the speed of the mobile terminal bearing the service are integrated to adjust the start time of handoff initialization dynamically. It can improve the accuracy of the handoff initialization. The key contributions are· A dynamic handoff initialization algorithm supporting multi-services is presented.· The performance of the algorithm is verified in the system simulation.The analytical results show the dynamic handoff initialization algorithm can reduced the average number of handoffs then produce less control overhead. With low complexity, it can be implemented easily.