Investigation On Multimedia Call Admission Control In TD-SCDMA System

The future mobile communication system should support more and more multimedia services, especially the streaming media service has the characteristics of having large data rate, occupying large bandwidth resource, and requiring high real-time, but the resource is relatively limited in wireless multimedia network. Hereby how to efficiently manage and use the wireless resource is one of the most important problems for the service providers. How to support the different QoS requirements of heterogeneous services and utilize the scarce wireless resource efficiently in the situation of error-prone wireless channel is now challenging the wireless communication system. As the important part of the radio resource management, call admission control gets more and more attention.In addition, there are more and more asymmetric traffic emerging in the wireless network, at the same time most of the existing wireless communication systems are symmetrical system. Accordingly the resource should be assigned fairly and reasonably. TD-SCDMA system adopts the technology of time division, thus it can flexibly adjust switch point of slots for uplink and downlink. It also has some outstanding advantages, such as the interference could be controlled, and it can high efficiently support anisomerous data service. Consequently the system could make balance between the system interference and the capacity, and high efficiently support multimedia service. The characteristics of TD-SCDMA result in that its CAC is more complicated than that in traditional CDMA system. First, because the slots between uplink and downlink can be anisomerous, if we differently allocate the slots among the adjacent cells, it will bring cross slot interference, farther make the interference model be more complicated and different from the traditional pure-CDMA network. And then, the admission control needs to consider not only whether one more user can access the network, but also the problem of slot allocation since there may be different interference situation in different time slot.In this thesis the author fully summarizes the former research achievements and put forward a CAC algorithm based on multimedia service of TD-SCDMA system in allusion to the characteristics of TD-SCDMA system. Firstly, aiming at the characteristics of future wireless communication network and according to the definition of the 3GPP, a more realistic modeled traffic is taken into account. Then, base on the different slot allocation situations of the TD-SCDMA system, the interference and capacity of the system are analyzed, farther the system residual capacities of different interference mode are obtained.The existing wireless communication systems are mostly symmetrical systems, therefore the CAC just considers the uplink (or downlink). The multimedia service presents the characteristic of asymmetry and TD-SCDMA system adopts the policy of dynamically adjust slot switch point between the uplink and downlink, thus the CAC in the system must consider both the uplink and the downlink. According to the service distribution instance among cells, we take account of the real bandwidth requirement of multimedia service and the interference model of the system. We have brought forward CAC strategy that adaptively supports anisomerous service. Admission control is based on the characteristic of service, QoS requirement and the residual capacity of the system. This strategy effectively enhances the system resource utilization.