The Design And Implementation Of The Mobility Management System In The CDMA Wireless Location Loop

With the development of telecommunication, and the combination ofCDMA wireless access technology and V5 Interface, CDMA WLL(Wireless Location Loop) will substitute for traditional location loop as theindispensable part in the 3G age. But LE cannot support mobilitymanagement and there is no corresponding information given by V5protocol .Since lack of Mobile Switch Centre which is used to deal with it,the mobility management should be implemented by wireless accessnetwork only.In this paper, we accomplish the design and implementation of the mobilitymanagement system suitable for the CDMA WLL based on the research andanalyses of the CDMA WLL system and mobility management. The systemis composed of HLR (Host Location Register) and VLR (Visitor LocationRegister).This mobility management system does not support the function of roaming,when taking account of not only the capability and coverage of the wirelesssystem but also the actual situation of the telecommunication market allover the world. That is, the MS (Mobile Station) should only be effective inthe home BS but not in others. Because the system needn't to deal withroaming service, it brings the simplicity of the processing flow and lessmemory spaces needed. The mobility system is more stable, effective anduseful as a result. Meanwhile, the compatibility can be mostly ensured asonly adding modules to BSC.The HLR module is a phone number operation and maintenance systembased on Client-Server structure. The major functions of this part areoperating and maintaining the phones' information and sending the basicinformation to VLR module so as to dealing with all kinds of service. Themodule consists of three parts: SMP (Service Management Platform), HLRServer and database. SMP is the part that communicates with the operators,in charge of saving and deleting phone numbers, etc. The HLR Server is aprocess running at background, which is used to send service messagesbetween SMP and VLR and do same work about database maintenance. Allof the phone numbers information is saved in the database. The fundamentalfunction of HLR module includes: saving, deleting, modifying, exporting,searching phone numbers and data synchronization. Besides, wirelessparameter configuration and right management should be taken intoaccount.The VLR module, which runs in the embedded system of the veneer of theBS, is used to deal with authentication, location updating, paging andregistering of MS. The amount of information about phone numbers in theVLR module is limited by the memory and CPU of the veneer, which willinfluence the coverage of the base station system. In order to solve thisproblem, we put forward a solution that dividing the VLR into GVLR(Global VLR) and PVLR (Performance VLR). The VLR module comprisesone GVLR and several PVLRs and the resources of phone numbersinformation are assigned to the corresponding PVLR respectively. GVLRwill be responsible for sending messages to the right PVLR according to thePVLR ID with the MS (the MS is given a PVLR ID automatically whenadding it to the system according to the configuration of the system), andthe PVLR which get the message will then deal with it accordingly. Thusthe capability of the system can be enlarged by simply adding PVLR to it.Because the VLR module resides in the veneer of the BS, there is noinfluence to the normal running of the system even if the BS and the HLRdisconnect. But this will cause another problem that the embedded systemdoes not support existent database system, so in the PVLR system we give away to simulate the database system of the phone information. In this way,it satisfies the need of quick query and storage.In order to restrict and manage to the user's effective region under the singleBS situation and simulate the roaming function in the system, (for example,let some MSs can be used only in the appointed area), the concepts of LACGroup and CELL Group are introduced in the paper. LAC and cell are theregions that are used to separate different places in an area by differentmethods when setting the network up. Here we will group the cells andLACs, and every LAC Group or CELL Group can contains none, one ormore LACs or cells. Set the phone number a LAC Group and a CELLGroup when it is added to the system. After that, taking the advantage of theauthentication control of the VLR, the MS can only be used in the appointedarea but not in other area. The purpose of using both LAC Group and CELLGroup is to meet the different needs of dividing areas.Furthermore, a feasible solution to import OTAPA (Over the Air ParameterAdministration) into the mobility management system of the CDMAwireless access network based on V5 interface is given in this paper. Usingthis technique, the parameters used by MS could be sent in the air.This mobility management system fully takes advantage of the powerfulprocessing capability and coverage region of the 3rd generation BSS,reducing the developing cost, farthest guaranteeing the stability of thesystem and satisfying the request of mobility. The system is suitable fordeveloping countries and regions to setup wireless network. Now it isadopted by ZTE Corporation as a main solution to the CDMA 2000 WLLSystem and works well.