GSM Mobile Radio System [Compatibility Mode]

8/14/2019 GSM Mobile Radio System [Compatibility Mode]

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GSMMobileRadioSystem


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EMAIL:

[email protected]


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. .

www.google.com

www. ictionary.com

etc


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Introduction to GSM: services provided by a GSM network; GSM network components

inc. T C C G C structure o a G network.

GSM radio interface: principles of TDMA and FDMA; GSM frequency bands; speechprocessing; use of FEC; discontinuous transmission and power control.

Principles of GSM location updating and handover.

Role and provision of GSM control and traffic channels.

Introduction to signalling in a GSM network inc. the role and operation of MAP

signalling. Features a lications and basic o eration of GSM data services inc. GPRS HSCSD

and EDGE.

The components of a mobile Internet service.

Introduction to message services inc. SMS, EMS and XMS.

tructure o a networ ; prov s on o og ca ata an contro c anne s. Mobility in a GPRS network.


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GSM: Properties

digital transmission, integrated data communication

roaming (mobility between different network operators)

good transmission quality (error detection and -correction)

scalable (large number of participants possible)

security mechanisms (authentication, authorization, encryption)

good resource use (frequency and time division multiplex)

inte ration with fixed tele hone network

standard (ETSI, European Telecommunications StandardsInstitute)


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GSM Frequency Bands


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GSM: Structure Operation and Maintenance Center (OMC) - logical, central structure with HLR,

AuC (Authentication Center) - authentication, storage of symmetrical keys,generation of encryption keys

Equipment Identity Register (EIR) - storage of device attributes of allowed, faultyand blocked devices (white, gray, black list)

- ,networks, assigned to one VLR each

Base Station Subsystem (BSS): technical radio center

Base Station Controller (BSC): control center Base Transceiver Station (BTS): radio tower / antenna


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Allocation of different carrier frequencies

Allocation of time slots on the same

frequency to a user


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There is a continuous stream of TDMA

frames between the MS and the BTS.

Each time slot is regarded as a physical

that is 0.557ms long. Information is

transmitted as bursts each TDMA frame

period thus burst is the content of a

physical channel. The burst contains the

payload and security information whichguarantees high data reliability and


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Discontinuous

and Power

control

All voice signals are transmitted the same way in a continuous data stream,t e c anne is occupie even uring si ent interva s its isa vantage is t attransmitting power is used during silent intervals thus wastes MS batterypower. Secondly other users using the same frequency in more distantcells would be disturbed. Therefore, it is necessary to switch off the

sen er t e su scr er s not transm tt ng n ormat on t us t e averageoccupation of the radio link is less than 40%


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GSM Radio Interfaces

MSC - Mobile SwitchingCenter

- ransco er

BSC - Base StationController

BTS - Base Transceiver

Station

The user and signalling data is transported over series of

MS - Mobile Station

interfaces; the A interface connects the MSC to the TC, theA-ter interface connects the TC to the BSC, the A-bisinterface connects the BSC to the BTS while the air


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GSM Radio

(contd)

Each of the interfaces (A, A-ter and A-bis) transmit information for the synchronization of

.

transcoder forwards the SS7 signalling between the MSC and the BSC in time slot 16. The

TRX signalling is transmitted between the BSC and the BTS at bit rates 16, 32 and 64kbps

depending on the producer. O&M alarms are transmitted over the A-ter and A-bis interfaceat 16; 16 or 64kbps respectively or as inband signalling in a traffic channel


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S eech and user data is transmitted

at a data rate of 64kbps over the Ainterface; 16kbps over the A-ter

transcoded speech or rate adapted

data and 16kbps per sub channel overthe A-bis interface. SMS messages

are transmitted via signalling

channels.


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Databases

Home Location Register (HLR), stores data of participants which are registered in anHLR-area

Semi-permanent data:

Call number (Mobile Subscriber International ISDN Number) -MSISDN, e.g.+49/171/333 4444 (country, network, number)

-Country Code (262 for .de) + MNC = Mobile Network Code (01-T-Mobile, 02-Vodafone, 03-eplus, 07-O2) + MSIN = Mobile Subscriber Identification Number

Personal data (name, address, mode of payment)Service profile (call transfer,roam ng- m s e c.

Temporary data:

MSRN (Mobile Subscriber Roaming Number) (country, network, MSC)VLR-address, MSC-address

Authentication Sets of AuC(RAND (128 Bit), SRES (128 Bit), KC(64Bit)) Billing data


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Databases (contd.)

Visitor Location Register (VLR)

local database of each MSC with following data:

IMSI, MSISDN Service profile

Billing and accounting information

TMSI (Temporary Mobile Subscriber Identity) -pseudonym for data

security

LAI (Location Area Identity)

MSC-address, HLR-address


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Data Transmission


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Data transmission - structure


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MAP is a GSM specific

protocol for non-core related

applications between

elements in the NSS. MAP

based communication occurs

between NSS elements in

the absence of a call.


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The example of a location update procedure mentioned previously is notconfined only to the MSC-BSC section, it spans multiple PLMNs. In case

of a first time location update by an international roaming subscriber(where he is not in his home network), the VLR has to get the data from

network.

While a mobile terminated call is being handled, the MSRN has to be

requested from the HLR without routing the call to the HLR.Therefore, for these cases another protocol layer was added to theSS7 called the Mobile Application Part (MAP).

MAP is used for signalling communication between NSS elements.


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Signalling in GSM


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Signalling in GSM

Between the BSC and the BTS, a signalling protocol known as LAP-D(Link Access Protocol for the ISDN "D" channel) is used. This is thesame pro oco a s use n ne wor s e ween e cus omer

and the network. Between the mobile station and the BTS, the same signalling protocol is

radio transmission medium. This protocol is known as LAP-Dm wherethe "m" denotes modified.

The LAP-D message structure is similar to SS7, but it does not supportnetworking capabilities, therefore, it is used for point to pointconnections.

Protocols for Radio Resource (RR) management are passed using- - .

and Connection Management (CM) are passed between the mobilestation and the MSC.


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Documents

GSM Mobile Radio System [Compatibility Mode]