eters of the VLR, meaning that they do not depend on the subscriber's HPLMN (home PLMN). The VLR-specific parameters can handle: general VLR operations (e.g. VLR cleaning, triplet record, deregistration); security operations (e.g. the use of authentication and IMEI checking); the use of TMSI paging and searching; the support of supplementary services, teleservices and bearer services. The network planner should be familiar with the most important VLR parameters and their effects on network performance, as this constitutes part of the optimisation process. In the example above, the use of TMSI for paging is disabled. This means that the operator is using IMSI for paging purposes. It is not recommended that IMSI is broadcast on the air interface as this could lead to eavesdropping. According to product recommendations, one repaging attempt should be used if TMSI is used for paging but in the case where only IMSI is used, it is recommended that three repaging attempts should be made. The number of repaging attempts may be checked. As an example, unsuccessful paging may cause a high number of clear codes of 0005H, B number busy, and 0012H, no answered call. A thorough study of the VLR and PLMN parameters should be done to ensure proper functioning and better results with paging, location update and the general call answer rate. CS Core Network Optimisation PLMN-Specific Parameters Audit The PLMN-specific parameters control VLR-specific functions that depend on the subscriber's HPLMN. The PLMN-specific parameters can handle: roaming status; IMEI checking parameters; TMSI allocation parameters; authentication and ciphering parameters; advice of charge parameters; equal access parameters. The PLMN parameters enable subscriber and roaming profile management. When a roaming profile is being set for the subscriber, the profile data have to be checked. Whenever creating a profile, it is recommended that a name for the profile be determined SO that profiles can be distinguished from those that have not been used in subscribe