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ContentsContents

Introduction

Early Communication Systems

Cellular Network Basics Cellular Network Generations

Architecture of 1G

Architecture of 2G

Architecture of 3G

Architecture of 4G

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IntroductionIntroduction

Mobile telephone service (MTS) is a type ofservice where mobile radio telephones:

connect people to the public switched telephone

system (PSTN)

other mobile telephones or to other communication

.

MTS uses the concept of Cell to provide for voice

and data communication through out a wide

geographical area and it is popularly called ascellular mobile communication systems

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Mobile TechnologiesMobile Technologies

The key technologies used in cellular mobileradio include:

cellular frequency reuse

Handover

digital modulation

access tec no og esand packet data transmission.

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Frequency reuse is the process of using the same radio

frequencies on radio transmitter sites within a geographic

area that are separated by sufficient distance to causeminimal interference with each other.

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Handover is a process where a mobile radio

operating on a particular channel is reassignedto a new channel.

The process is often used to allow subscribers

to travel throughout the large radio systemcoverage area by switching the calls (handover)

from cell-to-cell (and different channels) with

better coverage for that particular area whenpoor quality conversation is detected.

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Speech compression is a technique for converting

or encoding audio (sound) information so that asmaller amount of information elements or reduced

bandwidth is required to represent, store or transfer

au o s gna s. The speech compression analysis usually removes

redundancy in the digital signal (such as silence

periods) and attempts to ignore patterns that arenot characteristic of the human voice.

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Modulation is the process of changing the amplitude,

frequency, or phase of a radio frequency carrier signal

(a carrier) to change with the information signal (suchas voice or data).

Modulation is the process of changing the amplitude,

frequency, or phase of a radio frequency carrier signal(a carrier) to change with the information signal (such

as voice or data).

Digital modulation is a process where the amplitude,frequency or phase of a carrier signal is varied by the

discrete states (on and off) of a digital signal

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ASK modulation that turns the carrier signal on and off

with the digital signal

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FSK modulation shifts the frequency of the carrier signal according

to the on and off levels of the digital information signal.

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The phase shift modulator changes the phase of the carrier signal

in accordance with the digital information signal.

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QAM combines amplitude and phase of digital signals.

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Access multiplexing is a process used by a

communications system to coordinate and allow more

than one user to access the communication channelswithin the system

There are four basic access-multiplexing technologies

used in wireless systems:Frequency division multiple access (FDMA)

Time division multiple access (TDMA)

Code division multiple access (CDMA)Space division multiple access (SDMA).

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Mobile SystemsMobile Systems

(), .

().

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Cellular Networks GenerationsCellular Networks Generations

It is useful to think of cellular Network/telephony in

terms ofgenerations:

0G: Briefcase-size mobile radio telephones1G: Analogcellular telephony

2G: Digitalcellular telephony

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3G: igh-speeddigital cellular telephony (including videotelephony)

4G: IP-based anytime, anywhere voice, data, and

multimedia telephony at faster data rates than 3G

(to be deployed in 20122015)

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Evolution of Cellular NetworksEvolution of Cellular Networks

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1 2 3 42.5

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1G Mobile Architecture1G Mobile Architecture

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GSMGSM

Abbreviation for Global System for MobileCommunications

Concurrent development in USA and Europe in

the 1980s

The European system was called GSM and

deployed in the early 1990s

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GSM ServicesGSM Services

Voice, 3.1 kHz Short Message Service (SMS) 1985 GSM standard that allows messages of at most 160 chars. (incl.

spaces) to be sent between handsets and other stations

Over 2.4billionpeople use it; multi-billion $ industry

General Packet Radio Service (GPRS) GSM upgrade that provides IP-based packet data transmission up to 114

kbps

Users can simultaneousl make calls and send data

GPRS provides always on Internet access and the Multimedia MessagingService (MMS) whereby users can send rich text, audio, video messages toeach other

Performance degrades as number of users increase

GPRS is an example of 2.5G telephony 2G service similar to 3G

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GSM ChannelsGSM Channels

Physical Channel: Each timeslot on a carrier is referred to as a

physical channel

Logical Channel: Variety of information is transmittedbetween the MS and BTS. Different types of logical channels:

Traffic channel

Control Channel

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GSM FrequenciesGSM Frequencies

Originally designed on 900MHz range, now alsoavailable on 800MHz, 1800MHz and 1900 MHz ranges.

Separate Uplink and Downlink frequencies

One example channel on the 1800 MHz frequency band, whereRF carriers are space every 200 MHz

1710 1880 1805 1785

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GS A hiGS A hi

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GSM ArchitectureGSM Architecture

M bil S i (MS)M bil S i (MS)

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Mobile Station (MS)Mobile Station (MS)

MS is the users handset and has two parts Mobile EquipmentRadio equipment

User interface

Processing capability and memory required for varioustasks Call signalling

Encryption

SMS

Equipment IMEI number

Subscriber Identity Module

S b ib Id tit M d lS b ib Id tit M d l

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Subscriber Identity ModuleSubscriber Identity Module

A small smart card Encryption codes needed to identify the subscriber

Subscriber IMSI number

Subscribers own information (telephone directory) Third party applications (banking etc.)

Can also be used in other systems besides GSM, e.g., some

access po n s accep ase user au en ca on

B St ti S b tB St ti S b t

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Base Station SubsystemBase Station Subsystem

Transcoding Rate and Adaptation Unit (TRAU)Performs coding between the 64kbps PCM coding used inthe backbone network and the 13 kbps coding used for theMobile Station (MS)

Base Station Controller (BSC)Controls the channel (time slot) allocation implemented

by the BTSes

anages e an overs w n area

Knows which mobile stations are within the cell andinforms the MSC/VLR about this

Base Transceiver System (BTS)

Controls several transmittersEach transmitter has 8 time slots, some used for signaling,

on a specific frequency

N t k d S it hi S b tN t k d S it hi S b t

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Network and Switching SubsystemNetwork and Switching Subsystem

The backbone of a GSM network is a telephone network withadditional cellular network capabilities

Mobile Switching Center (MSC) An typical telephony exchange (ISDN exchange) which supports

mobile communications

Visitor Location Register (VLR)

A database, part of the MSC

Contains the location of the active Mobile Stations Gateway Mobile Switching Center (GMSC)

Links the system to PSTN and other operators

Home Location Register (HLR)

Contain subscriber information, including authentication information inAuthentication Center (AuC)

Equipment Identity Register (EIR) International Mobile Station Equipment Identity (IMEI) codes for e.g.,

blacklisting stolen phones

Home Location RegisterHome Location Register

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Home Location RegisterHome Location Register

One database per operator Contains all the permanent subscriber information MSISDN (Mobile Subscriber ISDN number) is the telephone

number of the subscriber

International Mobile Subscriber Identity (IMSI) is a 15 digit codeused to identify the subscriber It incorporates a country code and operator code

IMSI code is used to link the MSISDN number to the subscribers

Charging information Services available to the customer

Also the subscribers present Location Area Code, which refersto the MSC, which can connect to the MS.

Other SystemsOther Systems

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Other SystemsOther Systems

Operations Support System The management network for the whole GSM network

Usually vendor dependent

Very loosely specified in the GSM standards

Value added services Voice mail Call forwarding

Group calls

Short Message Service Center Stores and forwards the SMS messages Like an E-mail server

Required to operate the SMS services

Location UpdatesLocation Updates

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Location UpdatesLocation Updates

The cells overlap and usually a mobile station cansee several transceivers (BTSes)

The MS monitors the identifier for the BSC

controlling the cells When the mobile station reaches a new BSCs

,

The update is forwarded to the MSC, entered intothe VLR, the old BSC is notified and anacknowledgement is passed back

Handoff (Handover)Handoff (Handover)

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Handoff (Handover)Handoff (Handover)

When a call is in process, the changes in locationneed special processing

Within a BSS, the BSC, which knows the current

radio link configuration (including feedbacks fromthe MS), prepares an available channel in the newBTS

The MS is told to switch over to the new BTS This is called a hard handoff

In a soft handoff, the MS is connected to two BTSessimultaneously

RoamingRoaming

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RoamingRoaming

When a MS enters another operators network, it canbe allowed to use the services of this operator

Operator to operator agreements and contracts

Higher billing The MS is identified by the information in the SIM

card and the identification request is forwarded to the

ome operator

The home HLR is updated to reflect the MSs currentlocation

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2 5G Mobile Architecture2 5G Mobile Architecture

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2.5G Mobile Architecture2.5G Mobile Architecture

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3G, 3.5G and 4G (LTE)3G, 3.5G and 4G (LTE)

3G Overview3G Overview

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3G Ove v ew3G Ove v ew

3G is created by ITU-T and is called IMT-2000

MobileTelephoneSystems

Evolution from 2GEvolution from 2G

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Evolution from 2GEvolution from 2G

IS-95 IS-136 & PDCGSM-

GPRS-

2G

EDGEHSCSD

Cdma2000-1xRTT

Cdma2000-1xEV,DV,DO

Cdma2000-3xRTT

W-CDMA

EDGE

TD-SCDMA

3G

2.5G

3GPP3GPP2

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GSM Evolution to 3GGSM Evolution to 3G

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High Speed Circuit Switched DataHigh Speed Circuit Switched DataHigh Speed Circuit Switched DataHigh Speed Circuit Switched Data

Dedicate up to 4 timeslots for data connection ~ 50 kbps

Good for real-time applications c.w. GPRS

Inefficient -> ties up resources, even when nothing sent

Not as popular as GPRS (many skipping HSCSD)

Enhanced Data Rates for Global EvolutionEnhanced Data Rates for Global EvolutionEnhanced Data Rates for Global EvolutionEnhanced Data Rates for Global Evolution

9.6kbps (one timeslot)GSM Data

Also called CSD

GSMGSMGSMGSM

General Packet Radio ServicesGeneral Packet Radio ServicesGeneral Packet Radio ServicesGeneral Packet Radio Services

Data rates up to ~ 115 kbps

Max: 8 timeslots used as any one time

Packet switched; resources not tied up all the time

Contention based. Efficient, but variable delays

GSM / GPRS core network re-used by WCDMA (3G)

GPRSGPRSGPRSGPRS

HSCSDHSCSDHSCSDHSCSD

EDGEEDGEEDGEEDGE

ses mo u at on

3x improvement in data rate on short distancesCan fall back to GMSK for greater distances

Combine with GPRS (EGPRS) ~ 384 kbps

Can also be combined with HSCSD

WCDMAWCDMAWCDMAWCDMA

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UMTS Frequency SpectrumUMTS Frequency Spectrum

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UMTS Band1900-2025 MHz and 2110-2200 MHz for 3G transmission

In the US, 17101755 MHz and 21102155 MHz will be used

instead, as the 1900 MHz band was already used.

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3.5G (HSPA)3.5G (HSPA)

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High Speed Packet Access (HSPA) is an amalgamation of two

mobile telephony protocols, High Speed Downlink Packet Access

(HSDPA) and High Speed Uplink Packet Access (HSUPA), that

extends and improves the performance of existing WCDMA

protocols

.

technology in future. 1xEV-DV already supports most of thefeatures that will be provided in 3.5G. These include:

- Adaptive Modulation and Coding

- Fast Scheduling

- Backward compatibility with 3G

- Enhanced Air Interface

4G (LTE)4G (LTE)

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LTE stands for Long Term Evolution Next Generation mobile broadband technology

Promises data transfer rates of 100 Mbps

Based on UMTS 3G technology

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Advantages of LTEAdvantages of LTE

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Comparison of LTE SpeedComparison of LTE Speed

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Major LTE Radio TechnogiesMajor LTE Radio Technogies

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Uses Orthogonal Frequency DivisionMultiplexing (OFDM) for downlink

Uses Single Carrier Frequency Division Multiple

Access (SC-FDMA) for uplink Uses Multi-input Multi-output(MIMO) for

Reduced power consumption Higher RF power amplifier efficiency (less

battery power used by handsets)

LTE ArchitectureLTE Architecture

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LTE vs UMTSLTE vs UMTS

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Functional changes compared to the currentUMTS architecture

SummarySummary

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ThanksThanks

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