GSM最最简易的基础,一看就懂

Antenna Arrangement
BTS
Ø Each TRx has 8 TDMA channels by: carry Gohel & signalling. to Sanjay Voice Prepare
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Base Station Controller (BSC)
Ø BSC controls several BTSs. Ø BSC manages channel allocation, & Handover of calls from one BTS to another BTS. Ø BSC is connected to MSC via A interface. Ø Transmission rate on A I/f is 2 Mbps (G.703). Ø Interface between BSC & BTS is called A’bis I/f. Ø BSC has database for all of its BTS’s parameters. Ø BSC provides path from MS to MSC. BSC
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SIM is a removable module goes into the mobile handset. Each SIM has unique number called International Mobile Subscriber Identity (IMSI). It has built in Micro-computer & memory into it. It contains the ROM of 6 to 16KB,RAM of 128 to 256 bytes and EEPROM of 3 to 8KB
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Operation & Maintenance Centre (OMC)
OMC Ø All the network elements are connected to OMC. Ø OMC monitors health of all network elements & carry out maintenance operation, if required. Ø OMC link to BTSs are via parent BSC. Ø OMC keeps records of all the faults occurred. Ø OMC can also do Traffic analysis. Ø OMC may prepares MIS Report for the network.
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Home Location Register (HLR)
MSC HLR
Ø All Subscribers data is stored in HLR. Ø It has permanent data base of all the registered subscribers. Ø HLR has series of numbers for all subscribers.
wk.baidu.com
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Global System for Mobile
Ø New rapidly expanding & successful technology.
Ø Fully Digitized technology for better speech quality. Ø Available in almost every part of the world. Ø Fully compatible with existing Fixed Line Network. Ø Single number operation with World wide Roaming. Ø Very well defined interfaces makes truly open system
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Call Processing in GSM … 1
Mobile Originated Call
BTS
BSC
MSC
PSTN N/W
Ø Mobile originated calls goes to BTS first & then to BSC. Ø BSC forwards this call to MSC. Ø MSC does authentication & call routing as per dialed digits. Ø If it the call to another mobile subscriber then the process for that call is same as Mobile Terminated Call as shown in next slide.
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Equipment Identity Register (EIR)
MSC EIR
Ø All subscriber's mobile handset data is stored in EIR. Ø MSC asks mobile to send it IMEI & then checks it with data available in EIR. Ø EIR has different classification for mobile handsets like, White list, Grey list & Black list. Ø According to category the MS can make calls or can be stopped from making calls.
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MSC
Visiting Location Register (VLR)
MSC VLR
Ø Active Subscriber is registered in VLR. Ø It has temporary data base of all the active subscribers used for their call routing. Ø HLR validates subscriber before registration. Ø MSC ask VLR before routing incoming call.
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Base Transceiver Station (BTS)
Ø BTS has a set of Transceivers to talk to MS. Ø One BTS covers one or more than one cell. Ø Capacity of BTS depends on no of Transceivers. Ø BTS is connected to BSC via A’bis interface. Ø Transmission rate on A’bis is 2 Mbps (G.703). Ø Interface between MS & BTS is called Air I/f. Ø Transmission rate on Air interface is 13 Kbps. Ø BTS controls RF parameters of MS.
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Mobile Switching Centre (MSC)
Ø MSC is heart of the entire network connecting Fixed line network to Mobile network. Ø MSC manages all call related functions and Billing information. Ø MSC is connected to HLR & VLR for subscriber identification & routing incoming calls. Ø MSC capacity is in terms of no of subscribers. Ø MSC is connected to BSC at one end and Fixed Line network on other end. Ø Call Detail Record (CDR) is generated for each & every call in the MSC.
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Authentication Centre (AUC)
MSC HLR AUC
Ø Authentication is a process to verify the subscriber SIM. Ø Secret data & verification algorithm are stored in to the AUC. Ø AUC & HLR combined to authenticate the subscribers. Ø Subscriber authentication can be done on every call, if required.
Ø Encryption of user information
Ø Available versions, GSM 900, 1800 & 1900
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GSM Network Architecture
OMC
SMSC BTS 1 HLR BTS 3 BSC MSC VLR VMSC EIR AUC
NSS BTS 2 BSS
PSTN N/W
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Mobile Station (MS)
Ø Mobile Station consist of two units Mobile Hand set Subscriber Identity Module
Mobile Hand set is one of the most complicated GSM device. It provides user the access to the Network. Each handset has unique identity no. called IMEI.
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VMSC & SMSC
MSC SMSC VMSC
Ø Voice Mail Service Centre : To provide Voice Mail service. Ø It has database for all the VMS subscribers & also stores voice messages for them. Ø Short Message Service Centre : To provide text message service. Ø To send short messages from mobile to another mobile subscriber. Messages can also be sent by Manual Terminal connected to SMSC.
BTS 1
BTS 3
BTS 2
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GSM-900 System Specifications
Ø Frequency Range : 890 MHz to 915 MHz for Uplink 935 MHz to 960 MHz for Downlink. Ø Uses FDM / TDMA technology for Downlink / Uplink. Ø 124 Reusable Spot frequencies of 200 kHz bandwidth each. Ø Each Spot Frequency carries 8 Time slots for Traffic/Signalling. Ø Separate Logical Signalling & Traffic channels. Ø Compatible to ISDN & PSPDN.