Basic of Telecom

8/2/2019 Basic of Telecom

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Basics Of TelecomInduction Program


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Mobile technology

What is GSM/CDMA/TDMA or difference between Tata indicom,reliance and Airtel, Hutch, !dea

Various mobility technologies GSM / GPRS / UMTS

CDMA CDMA-95, 1xRTT, 1xEVDO

Mostly different on the Radio Interface (how the handset talks overair)

Core network and its components follow similar framework


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You will also learn about

Network Architecture Air interface and core network

GSM network HLR

VLR

MSC (GMSC)

SMSC

EIR

Billing

IN

VAS


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Roaming

Roaming links

Network Architecture


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Telecom Technology Fundamentals


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Basic Telecom Network 2 subscribers

Customer premiseEquipment (Telephone)

Transmission media


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Basic Telecom Network Speech conversion

Speech

Electrical signal

Equivalent to

speech


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Basic Telecom Network7 Subscribers

A mess ?


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Mesh Connection of LEs

LE

LE LE

LE

LE LE

LE

LE Messy !


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Connection of LEs thru Tandem

LE

LE LE

LE

LE LE

LE

LE

Tandem

Exchange


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Switching Network

What is a Switching NW?

That part of a Telecom Network which connects to the Access network

and switches calls to the desired destination (in Access NW) as perdialed digits..


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Switching- Numbering plan

L.E

101

102

103

104

105106

107


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Architecture of a Telecom Network


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Local Exchange Network- Two Exchanges

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L.E

101

102

103

104

105106

10721

L.E

104


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Local Exchange NetworkEight Exchanges

LE

20

LE

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LE

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LE

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LE

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LE

24

LE

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LE

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Tandem

Exchange

Exch. code


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Local Exchange Network

A Network where calls within its boundary are all charged at a Local

call rate is a Short Distance Charging Area (SDCA)

For eg. Pune City is an SDCA


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National Long Distance Network

TAX

TAX

TAX

TAX

LE

LE

LELE

LE

Mumbai

Delhi

Chennai

Kolkott

11

22

33

44


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International Longdistance Network

LE

TAX

TAX TAX

TAX

LE

LE

LE

International Gateway (IGY)

Mumbai

PuneNagpur

Mumbai


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International Telephone Numbering scheme

+ 91 20 6523138

International

Prefix

Country code

(India)

Area code

(Pune)

Subscriber

Number


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GSM- History

1970s- Bell labs invents Cellular Mobile Telephony

1980s- Nordic PTTs implement NMT 450 Cellular systems

1980s- UK implements TACS Cellular Mobile System

1980s- Germany implements C Netz Mobile system


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GSM History- cond

1990- GSM phase 1 specifications frozen

1991- GSM 1800 Mhz specs. Frozen

1992- January - First GSM Operator in Finland

1992 December- 13 Networks in operation


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Mobile Network

Mobile

Switching

Centre (MSC) Home LocationRegister (HLR)

Visitor Location

Register (VLR)

Radio

Base-station

Sub-system

(BSS)

MSC/VLR

MSC/VLR

Radio Network Core Network


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Network Architecture

PSTN

Data Terminal

HLR/

VLR

MSCBSC

OMC(Operation & Maintenance

Center)

OperationTerminal

BTS

HandsetAX.25

A-bis SS7

Network sub-system PSTNRadio

sub-system

Mobile

station

UM

SIMcard


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GSM Building Blocks- Description

DATA Bases

HLR- Home Location Register All Subscriber information

Services, Authentication parameters Location of MS (Mobile Station) MS sends this info vis MSC/VLR to HLR


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VLR- Visitor Location Register Contains info about all MSs in MSC area As soon as MS roams into a new MSC area, VLR requests its HLR for

subscription data. Also its (MSs) HLR is informed about MSs currentlocation

AUC- Authentication Centre AUC provides Authentication parameters & ciphering keys to HLR


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EIR- Equipment Identity Register Contains unique Hardware identity of Mobile equipment (IMEI) EIR checks whether the validity of the equipment.. Type approved, stolen etc..

Stolen and non type approved can be barred

MS- Mobile Station Mobile equipment + SIM (Subscriber Identity Module) SIM contains subscription, Authentication key and other details


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Some Terminology

HPMN Home Public Mobile Network VPMN Visited Public Mobile Network SMSC Short Message Service Center

BSS/OSS Business/Operations Support System GPRS General Packet Radio Service IN Intelligent Network Customers/Subscribers, Out-Roamers, In-Roamers IOT Inter Operator Tariff TAP Transferred Accounting Procedure


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HLR Home Location Register

A master database which stores permanent information onsubscriber irrespective of their location, including

Individual Subscriber Authentication Key (Ki) for each SubscriberIdentity Module (SIM)

Location (VLR)

Services subscribed to

Each IMSI is attached to MSISDN

Integrated and Standalone HLR

Authentication Center (AUC) - Computes auth. triplets

Revenue Leakage?


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VLR Visitor Location Register

Temporarily stores information for mobile subscribers/roamers whoare served/attached to a cell served by a MSC managed by this

VLR

Standalone VLR and Integrated VLR

Stores Location Area of subscriber

Data related to supplementary services Call forwarding, Call barring etc.


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MSC Mobile Switching Center

Also called the Switch

Controls multiple Base Stations; handles voice trunks

Responsible for setting up, routing and supervising calls to and fromthe mobile subscriber

GMSC is a MSC with a capability to: Interface between mobile and other networks

Query the HLR to terminate a call to a subscriber (which MSC/VLR isthe subscriber attached to?)


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GPRS General Packet Radio System

GGSN, SGSN are two network entities SGSN: Similar to VLR

GGSN: Similar to HLR

GRX GPRS Roaming Exchange Similar to SS7 Signaling Interconnect providers

Nearly 30 GRX providers in the world

Peering with each other in Amsterdam

APN Access Point Name Type of URL


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Basic of Telecom

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