TK2153 LECTURE 8 Telecommunication UKM

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TK2153 INFORMATION SHARING

LECTURE 8:TELECOMMUNICATION NETWORKProf Dr Abdullah Mohd Zin

*OutlinePublic Service Telephone NetworkMobile Telephone System

*Data CommunicationData communication involves exchanging of data between two computers.To enable two computers to exchange data, they must be connected by a communication medium.mediumhosthost

*Data CommunicationWhat happen if the distance between two hosts if very far?To make direct connection is very expensive.Alternative use existing network.hosthost

*Existing NetworksElectricity network not practicalWater network not practicalTelecommunication networkCable Television Network

*Telecommunication NetworkPublic Service Telephone NetworkMobile Telephone System

Public Switched Telephone NetworkStructure of the Telephone SystemThe Local Loop: Modems, ADSL and WirelessTrunks and MultiplexingSwitching*

Structure of the Telephone System(a) Fully-interconnected network.(b) Centralized switch.(c) Two-level hierarchy.*

Structure of the Telephone System A typical circuit route for a medium-distance call.*

Major Components of the Telephone SystemLocal loopsAnalog twisted pairs going to houses and businessesTrunksDigital fiber optics connecting the switching officesSwitching officesWhere calls are moved from one trunk to another.*

The Local Loop: Modems, ADSL, and WirelessThe use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.*

ModemsA modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information and demodulates the signal to decode the transmitted information. 3 methods of modulation:Amplitude modulationFrequency modulationPhase modulation*

Modems (a) A binary signal (b) Amplitude modulation(c) Frequency modulation(d) Phase modulation

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ModemsMost modem samples at 2400 times/sec.By sending one bit at a time, the normal speed of transmission is 2400 bps.By using 2 bits, the data rate is 4800 bps QPSK (Quadrature Phase Shift Keying).To achieve a better data rate 4 bits are transmitted at one time known as QAM-16 the speed is 9600 bps.QAM-64 involves transmitting 6 bits at a time.

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Modems(a) QPSK. (b) QAM-16. (c) QAM-64.*

ModemsTo reduce errors, TCM (Trellis Code Modulation) is used.V.32 modem standard 4 data bits and 1 parity bit per sample 9600 bps.V.32 bis 6 data bits and 1 parity bit per sample 14400 bps.V.34 12 data bits 28800 bps.V.34 bis 14 data bits 33600 bps.

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Modems(a) V.32 for 9600 bps.(b) V32 bis for 14,400 bps.(a)(b)*

Modem Faster modem can be introduced by using 8 bit per sample with 8000 samples per second.In US, 7 data bits + 1 parity bit 56000 bps.In Europe, 8 data bits 64000 bps.V.90 standard: 33.6 kps from user to ISP and 56 kbps from ISP to user.

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Digital Subscriber LinesTelephone line is meant for voice communication.Wire runs through a filter that attenuates all frequencies below 300Hz and above 3400Hz.xDSL use different kind of switch that does not have this filter.Problem capacity of local loop depends on distance.

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Digital Subscriber LinesBandwidth versus distanced over category 3 UTP for DSL.*

Digital Subscriber LinesOne of the most popular xDSL is called ADSL which allows speeds of as much as 8Mbps downstream and 1Mbps upstream.Telekom Malaysia offers this as a product called streamyx.

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Digital Subscriber LinesA typical ADSL equipment configuration.*

Wireless Local LoopsCheaper option than the traditional twisted pair local loop.MMDS (Multichannel Multipoint Distribution Service)Microwave transmission at frequency of198MHzHave a range of 50kmLDMS (Local Multipoint Distribution Service)Frequency of 1.3GHzHave a range of 2-5km

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Wireless Local LoopsArchitecture of an LMDS system.*

Multiplexing To share many different conversation over a single physical line.3 schemes:Frequency Division MultiplexingWavelength Division MultiplexingTime Division Multiplexing

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Frequency Division Multiplexing(a) The original bandwidths.(b) The bandwidths raised in frequency.(b) The multiplexed channel.*

Wavelength Division MultiplexingUsed for fiber optic line.A number of fiber with different wavelength can be combined onto a single shared fiber. At the end, the beam split up into different wavelength.

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Wavelength Division MultiplexingWavelength division multiplexing.*

Time Division MultiplexingTransmitting digital data over copper wire.Analog data is converted into digital data by a codec (coder-decoder) at 8000 samples persecond.This technique is known as PCM (Pulse Code Modulation).One scheme for using this technique is called T1 carrier.Consist of 24 voice channel multiplexed together.8 bits 7 bits of data + 1 bit control.Data rate of 1.544Mbps.

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Time Division MultiplexingThe T1 carrier (1.544 Mbps).*

Time Division MultiplexingSeveral T1 carriers can be multiplexed into higher order carriers.4 T1 streams can be multiplexed into 1 T2 stream. with 6.312Mbps.7 T2 streams are combined to form T3 stream.6 T3 streams are combined to form T4 stream.

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Time Division MultiplexingMultiplexing T1 streams into higher carriers.*

Time Division Multiplexing SONET and SDHSONET (Synchronous Optical Network) is an optical transmission interface originally proposed by BellCore and standardized by ANSI.A compatible version is called SDH (Synchronous Digital Hierarchy) has been published by ITU-T in Recommendation G.707.To provide specification of high speed data transmission capability of optical fiber.*

Time Division Multiplexing SONET and SDHSONET and SDH multiplex rates.*

The Mobile Telephone SystemFirst-Generation Mobile Phones: Analog VoiceSecond-Generation Mobile Phones: Digital VoiceThird-Generation (3G)/Fourth-Generation (4G) Mobile Phones: Digital Voice and Data

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Advanced Mobile Phone SystemA region is divided into cells.In AMPS, the cells are typically 10-20 km across.Each cell uses some set of frequencies not used by the neighbours.

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Advanced Mobile Phone System(a) Frequencies are not reused in adjacent cells.(b) To add more users, smaller cells can be used.*

Advanced Mobile Phone SystemAt the center of each cell is a base station.The AMPS system uses 832 channels from 832 to 849MHz and 832 channels from 869 to 894MHz.Each channel is 30kHz wide.

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Advanced Mobile Phone SystemThe 832 channels are divided into four categories:Control (base to mobile) to manage the systemPaging (base to mobile) to alert users to calls for themAccess (bidirectional) for call setup and channel assignmentData (bidirectional) for voice, fax, or data

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Advanced Mobile Phone SystemCall management:Each mobile phone has a 32 bit serial number and a 10 digit telephone number.When the phone is switched on, it scans to find the most powerful signal.The phone then broadcast its serial number and its phone number.The base station records the presence of a new customer.

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Advanced Mobile Phone SystemTo make a call:The phone transmit the number to be called.The base station will check whether the number os within its region.Otherwise it will broadcast to other base station.Once it is found, a channel is allocated for the call.

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Second GenerationFour systems:D-AMPSGSMCDMAPDC

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D-AMPS Digital Advanced Mobile Phone SystemFully digitalOperates on a new frequency band: upstream 1850-1910MHz, downstream 1930-1990MHz.Voice signal is digitized by using PCM encoding.

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D-AMPS Digital Advanced Mobile Phone System(a) A D-AMPS channel with three users.(b) A D-AMPS channel with six users.*

GSM Global System for Mobile CommunicationsCellular system, just like AMPS.However, GSM channels are much wider than AMPS (200 kHz compared to 30 kHz).GSM system has 124 channels.

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GSM Global System for Mobile CommunicationsGSM uses 124 frequency channels, each of which uses an eight-slot TDM system*

CDMA Code Division Multiple AccessTotally different from AMPS, D-AMPS and GSM.Instead of dividing the allowed frequency range into a few hundred narrow channels, CDMA allows each station to transmit over the entire frequency spectrum all the time.Multiple simultaneous transmissions are separated using coding theory.

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Third-Generation Mobile Phones: Digital Voice and DataBasic services an IMT-2000 network:High-quality voice transmissionMessaging (replace e-mail, fax, SMS, chat, etc.)Multimedia (music, videos, films, TV, etc.)Internet access (web surfing, w/multimedia.)*

2.5G3G systems took a longer time to be developed.While waiting for it, some operators move towards 2.5G:EDGE (Enhanced Data Rate for GSM Evolution)GPRS (General Packet Radio Service)

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4GFaster than 3G.

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