(Global System for Mobile Communications Essays

(Global System for Mobile Communications Essays (Global System for Mobile Communications Essay (Global System for Mobile Communications Essay GSM Architecture of the GSM System GSM-elements interfaces System Architecture: Radio Subsystem Mobile Station (MS) Mobile Station (MS) Block Diagram of BTS with TRX Block Diagram of BTS Contd. Transmitter/Receiver Module – The TRX consists of a low-frequency part for digital signal processing and a high-frequency part for GMSK modulation and demodulation. The operations and maintenance (OM) module – connected directly to the BSC by means of a specifically assigned OM channel. That allows the OM module to process the commands from the BSC or the MSC directly into the BTS and to report the results – OM module provides a human-machine interface (HMI), which allows for local control of the BTS. BTS BSC Block Diagram of BSC BSC Contd†¦. Terminal Control Elements (TCEs) – Abis-Interface Terminal Control Elements Abis-TCEs are to set up LAPD connections toward the BTS peers, the transfer of signaling data, and last- but not lea st- the transparent transfer of payload. – A-Interface Terminal Control Elements The connection of a BSC to the MSC is established via the A-TCEs. A-TCEs is setting up and operating the SS7/SCCP connection toward the MSC. BSC Contd†¦. Database (DB) – maintenance status of the whole BSS, the quality of the radio resources and terrestrial resources, and so on are dynamically administrated – BSC database contains the complete BTS operations software for all attached BTSs and all BSS specific information,such as assigned frequencies. BSC Contd†¦. Central Module – One of the major tasks of the BSC is to decide when a handover should take place. The BSC may decide on intra-BTS handover and intraBSC handover without needing the MSC. In contrast, for all BSC external handovers, the BSC needs to involve the MSC. – Handover decision and power control are main tasks of the central module. Transcoding Rate and Adaptation Unit (TRAU) The task of the TRAU is to compress or decompress speech between the MS and the TRAU. – called regular pulse excitation–long term prediction (RPE-LTP) It is able to compress speech from 64 Kbps to 16 Kbps – Fullrate channel (net bit rate with fullrate is 13 Kbps) and to 8 Kbps in the case of a halfrate channel (net bit rate with halfrate is 6. Kbps) Possible Sites for TRAU System Architecture: Network and Switching Subsystem Home Location Register (HLR) Home Location Register manages the mobile subscribers database which stores – subscriber information – part of the mobile location information – International Mobile subscriber Identity – Mobile station ISDN Number It is the subscriber number commonly used – VLR address Vis itor Location Register (VLR) Dynamically stores subscriber information, needed to handle incoming/outgoing calls, which includes, – Mobile Station Roaming Number When a roaming mobile enters an MSC area. This MSC warns the associated VLR of this situation; the mobile enters a registration procedure through which it is assigned a mobile subscriber roaming number (MSRN) – Temporary Mobile Subscriber Identity, if applicable – The location area in which the mobile has been registered – Data related to supplementary service parameters MSC VLR MSC G-MSC The NSS hierarchy The NSS AUC/EIR Authentication Center(s) (AUC) – Providing the authentication key used for authorizing the subscriber access to the associated GSM PLMN. Equipment Identity Register(s) (EIR) – Handling Mobile Station Equipment Identity Equipment Identity Register(s) (EIR) White list: contains all the approved types of mobile stations Black list: contains those IMEIs known to be stolen or to be barred for technical reasons Gray list: allows tracing of the related mobile stations Numbering Arrangement in GSM International Mobile Subscriber Identification number (IMSI) It identifies a unique international universal number of a mobile subscriber, which consists of MCC+MNC+MSIN. ) MCC: country code, 460 2)MNC: network code, 00 or 01 3)MSIN: subscriber identification, H1H2H3H4 9XXXXXX, H1H2H3H4: subscriber registering place H1H2: assigned by the PT Administrative Bureau (operator )to different provinces, to each province H3H4: assigned by each province/city the IMSI of user will be written into the SIM card by specific device and software and be stored into the HLR with other user information. Numbering Arrangement in GSM Mobile Subscriber ISDN Number(MSISDN) It is the subscriber number commonly used. China uses the TDMA independent numbering plan: CC+NDC+ H1H2H3H4 +ABC CC: country code, 86 NDC: network code, 135- 139, 130 H1H2H3H4: HLR identification code ABCD: mobile subscriber number inside each HLR Numbering Arrangement in GSM International Mobile Equipment Identification code (IMEI) It will uniquely identify a mobile station. It is a decimal number of 15 digits. Its structure is: TAC+FAC+SNR+SP TAC=model ratification code, 6 digits FAC=factory assembling code, 2 digits SNR=sequence code, 6 digits SP=reserved, 1 digit Numbering Arrangement in GSM Mobile Subscriber Roaming Number (MSRN) The MSRN is temporarily distributed to the subscriber by the VLR according to the request by the HLR when this subscriber is called. The MSRN is released and can be assigned to other subscriber later. CC + NDC + 00 + M1M2M3 + ABC CC: country code, 86 NDC: mobile network code, 135- 139, 130 M1M2: same as the H2H3 of MSISDN ABC: 000 999 Numbering Arrangement in GSM Temporarily Mobile Subscriber Identification Number (TMSI) To insure the IMSI security, the VLR will assign an unique TMSI number for the accessed subscriber. It is used locally only and is a 4 GSM Mapping Example (DL) GSM Mapping Example (UL) Air Interface Protocols Air Interface Protocols Air Interface Protocols Block diagram of the base scenarios