| 1. IntroductionThe mobile communications system has come through the transition from the first generation which is analogue mobile communications system to the third generation which is developed very well now. TD-SCDMA is a king of 3G which has been operated by China Mobile.But compared with 2G network that has developed for 10 years which is perfect, the mature degree of TD-SCDMA is much lower. On the side, the conflict between the increasing request of user in data service and the limited resource is more and more outstanding. So it becomes our subject which uses limited resources to provide higher quality services to users and make them feel better to the services.Radio resource management (RRM) can use limited wireless resources more reasonable and more effectively, it includes power control, handover, call admission control (CAC), congestion control and groupwise attemperat. CAC is used to prevent the decline of the quality of service (QoS) for the user in existence, or the overcast area of the cell lower than the programming area because of too many users accessed. From the point of user sensible degree (USD), it is more important that keep the blocking rate and dropping rate of real time connection low than ensure the performance of non-real time services because of the multi-service characteristics of 3G. So we can use CAC arithmetics to protect the performance of real time service to improve USD.There is re-connection phenomenon in the cellular mobile networks, it means that some users will always choose to re-connection after being blocked or stopped because the wireless network resources is limited and the users are locomotory. Re-connection phenomenon, which has a significant negative impact on the network performance, is non-neglectable. We reserve guard channel (GC) beforehand for re-connection, upgrade it's priority to prevent that users couldn't get in after called many times, or it will infect USD seriously.2. Re-connection Priority Fixed Multi-Threshold Call Admission Control (R-FMCAC)We divide the services of TD-SCDMA into two types based on the different QoS request of services in 3G: Class I is real time connection, Class II is non-real time connection. Class II can temporarily save the data on some network node (eg. node B) when the network is crowd, and can be transferred at a lower rate. So we don't consider the re-connection and handover of Class II, and set their priority at lowest position. At the same time, we divide Class I connection requests into four parts: new call request in the cell, re-connection of new call request, handover request, and re-connection of handover request. We set handover requests and re-connection of handover requests of Class I have the highest priority, these requests will be rejected only when all of the channels in the cell have been used; the second is re-connection of new call request of Class I, they will be rejected when there are more than N r (include N r) channels used, otherwise they will be accepted; the third is new call request of Class I, they will be rejected when there are more than N n (include N n) channels used, otherwise they will be accepted; the last is call request of Class II, they will be rejected when there are more than N II (include N II) channels used, otherwise they will be accepted.This paper compared R-FMCAC with the arithmetic without re-connection priority, the simulation indicate that: R-FMCAC make the re-connection priority access come true, improve the service accessibility and retainability, heighten the USD. But the system resource is fixed, so the decline of the re-connection blocking rate will cause the blocking rate of lower priority services rise a little for cost.3. Dynamic Re-connection priority Dynamic Multi-Threshold Call Admission Control (R-DMCAC)This paper dynamic adjust the thresholds of each service based on call blocking rate and handover dropping rate which are system level indications, and try to further improve the performance of highest priority service, at the same time, give attention to the higher priority service.We adjust the service thresholds from high priority to low. For the Nth service who has the highest priority, it's service thresholds is fixed, as: TTH N = THN=C.When we adjust the ith (1≤i |
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