Các Bene t ® chính cho các thuê bao di động mà tiêu chuẩn quốc tế của GSM đã mang lại là họ có thể di chuyển tự do không chỉ trong mạng gia đình của họ mà còn trong các mạng GSM quốc tế và đồng thời họ thậm chí có thể được truy cập vào các dịch vụ đặc biệt họ đăng ký ± nhà ở được cung cấp có những thỏa thuận giữa các nhà khai thác. Các chức năng cần thiết cho chuyển vùng này miễn phí được gọi là chuyển vùng hoặc các chức năng. | 8 GSM Switching Services and Protocols . Second Edition. Jôrg Eberspâcher Hans-Jorg Vogel and Christian Bettstetter Copyright 2001 John Wiley Sons Ltd Print ISBN 0-471-49903-X Online ISBN 0-470-84174-5 Roaming and Switching Mobile Application Part Interfaces The main benefit for the mobile subscribers that the international standardization of GSM has brought is that they can move freely not only within their home networks but also in international GSM networks and that at the same time they can even get access to the special services they subscribed to at home - provided there are agreements between the operators. The functions needed for this free roaming are called roaming or mobility functions. They rely mostly on the GSM-specific extension of the Signalling System Number 7 SS 7 . The Mobile Application Part MAP procedures relevant for roaming are first the Location Registration Update IMSI Attach Detach requesting subscriber data for call setup and paging. In addition the MAP contains functions and procedures for the control of supplementary services and handover for subscriber management for IMEI management for authentication and identification management as well as for the user data transport of the Short Message Service. MAP entities for roaming services reside in the MSC HLR and VLR. The corresponding MAP interfaces are defined as B MSC-VLR C MSC-HLR D HLR-VLR E MSC-MSC and G VLR-VLR Figure . At the subscriber interface the MAP functions correspond to the functions of Mobility Management MM . the MM messages and procedures of the Um interface are translated into the MAP protocols in the MSC. The most important functions of GSM Mobility Management are Location Registration with the PLMN and Location Updating to report the current location of an MS as well as the identification and authentication of subscribers. These actions are closely interrelated. During registration into a GSM network during the location updating procedure and also during the
