Ok, so here’s a bit for all you techies out there – or a bit to make you totally confused!! Its about where cellsites fit in to the overall picture of mobile comms – boring eh! The mobile network is made up of several components:
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BTS |
Base Transciever Station (eg Cellsite!) |
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BSC |
Base Station Controller |
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MSC |
Mobile Switching Centre |
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HLR |
Home Location Register |
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VLR |
Visitor Location Register |
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EIR |
Equipment Identity Register |
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AUC |
Authentication Centre |
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NMC |
Network Management Centre |
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OMC |
Operations Management Centre |
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PSTN |
Public Switched Telephone Network |
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PLMN |
Public Land Mobile Network. |
Here’s how they appear in the system
BTS – Base Transceiver Station
Each of the cells in the network has a BTS or Cellsite working on a dedicated set of radio channels. These channels are different in adjacent cells to avoid interference. The job of the BTS (cellsite) is to provide both transmission and reception within its own cell. This is what we love, and what this site is dedicated to!
BSC – Base Station Controller
The BTS’s (cellsites) are grouped together and controlled by a Base Station Controller. This is also known as the BSS or Base Station System. This BSC has an important role ensuring that us users can move freely from one cell to another with no loss in signal strength
MSC – Mobile Switching Centre
The Base Station Systems are in turn grouped together. The groups are controlled by the MSC. This is the heart of the system, having the following tasks:
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It routes calls to and from handsets |
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It controls the setup and ending of calls |
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It provides data for billing and accounting |
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It acts as the link between mobile and public networks |
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It controls “handoff” between itself and other NMC’s
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HLR/VLR/EIR/AUC
These are kind of “behind the scenes” bits. The GSM system uses 2 databases. The HLR and VLR. These work with call processing and provide info to the NMC about
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Subscription Level |
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Additional Services available to the User |
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The User Location |
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HLR deals with UK customers eg “Home” |
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VLR deals with roaming customers in the UK eg “Visitors” |
EIR Equipment Identity Register
The EIR is a centralised database used to validate the IMEI or serial number on your phone. The database is remotely accessed by the NMC and has 3 main parts.
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A White List comtaining IMEIs that are known to have been given to valid mobiles |
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A Grey List of those that have problems and need to be traced |
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A Black List of those reported stolen or that should be denied service |
AUC – Authentication Centre
The AUC handles all security for each subscriber. For each user to gain access to the system, the correct response must be given to a random number generated by the AUC.
confused?? Nearly there!
OMC/NMC Operations & Network Management Centres
(aka Heaven!)
The OMC
manages a particular region of the network,
deals with daily operations and
is used by network operators
The NMC
Oversees the whole of the network
Carries out global network management
Is employed on long term planning
Is used by network managers and planners
