figure 1.1 telephone networks: (a) network components; (b...

Figure 1.1 Telephone networks: (a) network components; (b)digital transmission using modems; (c) multiple services via anH-S modem.

© Pearson Education Limited 2001

STB

GMSC IGEIGE IGE

National PSTNsAnalog accesscircute

Radio access(a)

Digital interconnectioncircuits

Cellular phonenetwork

PBXPrivate site-wide

telephone network

Analog access circuit

PSTN = public switched telephone networkGMSC = gateway mobile switching centerIGE = international gateway exchange

LE = local exchange/end officePBX = private branch exchange

(b)

PSTNPSTN

LE

LE

Home/smallbusiness

PSTNModemDigitaldevice Modem Digital

device

Analog access circuits

Digital streams

H-Smodem

Server

H-Smodem

Low bit ratetelephone channel

High bit ratechannel

Analog accesscircuit

PSTN

(c)

H-S = high-speed STB = set-top box

Figure 1.2 A selection of the network types connected to theInternet.


G/W

SiteLAN

SiteLAN

SiteLAN

SiteLAN

Inter-sitebackbonenetwork

Enterprise–wide private network/intranet

Desktop PC or workstationServer computer

G/W

Global Internetbackbone network

G/W

Internet serviceprovider (ISP) network

Access via thePSTN with modems

or the ISDN

Home

Small business

Desktop PC/workstation

Server computer

Site/campusLAN

LAN = local area networkISDN = integrated services digital network

G/W = gateway

Figure 1.3 Broadcast television networks: (a) cable networks;(b) satellite/terrestrial broadcast networks.


Cablehead-end

Cabledistributionnetwork

PSTN

TheInternet

STB

(a)

Programsource

PSTNSTB

(b)

TheInternet

Satellite (or terrestrial)broadcast network

STB = set-top box with integral modem

Figure 1.4 Alternative services provided by an ISDN.


Integrated servicesdigital network

(ISDN)

Digital subscriber line(DSL)

Single 128kbpsswitched channel

Aggregation electronics

p × 64kbpsswitched channel

Single 64kbpsswitched channel

Conventional analog phone

Single 1.5/2.0 Mbps channel(primary rate access)

p × 64kbpsswitched channel

64kbps channels(basic rate access)

Two independent

= network termination equipment

Figure 1.5 Example of an ATM broadband multiservice network.


ATMMAN

High-speedLAN

IWU

ATMLAN

ATMLAN

High-speedLAN

IWUIW

U

IWU

MAN = metropolitan area networkIWU = interworking unit

ATM = asynchronous transfer mode LAN = local area network

Figure 1.6 Speech-only interpersonal communications: publicand private switched telephone networks.


Voice-mail

server

Audiobridge

Voice-mail

server

Audiobridge

PBX

Analog or digitalaccess circuits

Cellularphone network PSTN or ISDN

Private site-widetelephone network

PSTN = Public switched telephone networkPBX = Private branch exchange

ISDN = Integrated services digital networrk

Figure 1.7 Telephony over the Internet.


Packet-mode

Circuit-mode

Packet-mode

Circuit-mode

PSTN/ISDNG/W = gateway

PacketG/W

TelephonyG/W

Global Internet

PacketG/W

Site/campus LANInternet service provider

(ISP) network

TelephonyG/W

TelephonyG/W

Figure 1.8 Image-only interpersonal communications: facsimile(fax) examples.


PC fax

Fax machine

Analog or digital access circuits

PSTN or ISDN

Figure 1.9 Text-only electronic mail: (a) email transferexamples; (b) example email message format.


DesktopPCs

Enterprise-wide private network/intranet

Emailserver

Emailserver

Emailserver

G/WG/W

G/W

Global Internet

Site/campus LANInternet service provider (ISP) network

Home

Small business

Access via either a PSTN(with modems) or an ISDN

G/W = gateway

(b)

(a)

From: Name and address of senderTo: Name and address of recipientCc: List of other recipients (optional)Subject: Title of mail (optional)Date: Day, date and time mail sent

Control: Bin, Reply, Forward, Send etc.

Body, possibly with a file attachment

Header fields

Body/Message content

Figure 1.10 Text-and-image computer-supported cooperativeworking (CSCW).


Shared whiteboard/workspace

Enterprise-wide private network,LAN or the Internet

Shared whiteboardprogram

Updatecontrol

Changenotification

Figure 1.11 Speech-and-video interpersonal communications:(a) two-party video telephone call; (b) videoconferencing usingan MCU; (c) videoconferencing using a broadcast network.


PSTN/ISDN/Internet/LAN/enterprise network

Two-way simultaneous integratedspeech-and-video information stream

(a)

PSTN/ISDN/enterprise network

Two-way simultaneous integratedspeech-and-video information streams

Multipointcontrol

unit (MCU)

(b)

LAN/Internet

Two-way simultaneous integratedspeech-and-video information streams

to/from all parties

(c)

Multimedia PC/workstationwith video camera,

microphone and speakers

Figure 1.12 Speech-and-video interpersonal communications:(a) remote lecture; (b) multiparty (group) videoconferencing.


Speech, videoand image

Speech only orspeech-and-video

ISDN/broadband network

(a)

VSVS

ISDN/broadband network/dedicated-circuit network

(b)

Videoconferencingstudio


VideoconferencingstudioVS

VS

MCU


VS = Videoconferencing systemMCU = Multipoint control unit

VS

Figure 1.13 Multimedia electronic mail structure.


Mail header

Hi TomIf your multimedia mail is working now just click on the following:

Sent initially

Otherwise the text version is in the attached file.RegardsFred

Speech part

Image part

Video part

Speech sequence

Image/picture

Video clip

Sent on request

Figure 1.14 Interactions with a World Wide Web server: (a)schematic; (b) hypertext linkages between the pages of a set ofdocuments.


Intranet

ISPsSiteLANPCs/workstations

with browsersoftware

World WideWeb servers

Multimedia information servers (some with transaction capabilities)connected to a site LAN, an intranet, or an ISP network

Internet(a)

(b)

Navigation toolset

S

Navigation toolset

Navigation toolset

S

Home page

Navigation toolset

S

Hyperlinks

= text string containing uniform resource locator (URL)

Figure 1.15 Interactions with a video server: (a) networkingschematic; (b) movie-on-demand; (c) near movie-on-demand.


Low bit rateinteraction channel

High bit rate channelfor video stream

PSTN/cable access network(a)

Videoserver

(b)

Set-top box withintegral high bit

rate modem

Movie/videodatabase

STB

Movie C

Movie A

Movie B

Movie A

Movie A

1(A) 2(A) 3(B) 4(A) 5(C)

Time

Subscriber (requests)

1

2

3

4

5Subscriber

(c)

Movie C

Movie A

Movie B

Movie A

1(A) 2(A) 3(B) 4(A) 5(C)

Time

Subscriber (requests)

1,2

3,4

6

7,8

Subscriber

Playout intervals

MOD = movie-on-demand N-MOD = near movie-on-demand

MOD

N-MOD

Figure 1.16 Interactive television: (a) cable distributionnetwork; (b) satellite/terrestrial broadcast network.


Cable head-end Cabledistribution network

PSTN

TheInternet

(a)

Satelliteinterface

PSTN/ISDN

(b)

Satellite (or terrestrial)broadcast network

TV programsource

Servercomputer

Webserver

STB

Telephonycall center

Service providerbase station

TheInternet

Telephonycall center

STB

Servercomputer

Figure 1.17 A selection of the terms used with multimedia.


ConnectionlessConnection-oriented

Packet-switched networks

Variable bit rate

Asynchronous

Communication channels

Circuit-switched networks

Constant bit rate

Synchronous

AsymmetricSymmetric

DuplexHalf-duplex

Variablebit rate

Continuous

Canstantbit rate

Media types

Block-modeBroadcastand

Multicast

Simplex

Communication modes

Multimedia terminology

Figure 1.18 Communication modes: (a) unicast; (b) broadcast;(c) multicast.


Simplex:

Half-duplex:

Duplex:

(a)

Broadcast:

(b)

Multicast:

(c)

Time

B, D and F aremembers of the samemulticast group

Communications channel

A B

B

B

D

C

E

B

D

C

B

E

F

A

A

A

A

A

Figure 1.19 Circuit-switched network schematic.


A B

Bit rate of the connection determined bythe bit rate of the access circuits

Circuit-switchednetwork

Circuit through the networkset up using the unique

number/address of A and B

= subscriber terminal/computer = switching office/exchange

Figure 1.20 Packet-switching network principles: (a) connection-oriented; (b) connectionless.


A B

CO = connection-oriented = virtual circuit

CO packet-switchingnetwork

PSE4

21 3

21 3PSE2

1 PSE12

32PSE3

1

3

VCI2 VCI3

VCI1 VCI4

VCI = virtual circuit identifierPSE = packet-switching exchange

PSE1routing table: VCI1/Link1

INVCI2/Link2

OUT

VCI2/Link2 VCI1/Link1

PSE2routing table: VCI2/Link1 VCI3/Link3


PSE3routing table: VCI3/Link1 VCI4/Link2


(a)

A B

CL packet-switchingnetwork

Router1

CL = connectionlessA, B = full network-wide addresses

(b)

Router2

Router4

Router3

AB

AB

= packet

information contentsource addressdestination address

Figure 1.21 Multipoint conferencing modes of operation:(a) centralized; (b) decentralized; (c) hybrid.


Conferenceserver

B CA

Circuit-switched network(PSTN/ISDN)

(a)

Conferenceserver

D

C

B

A

= attached terminal/computer

Circuit-switchednetwork

Packet-switched networkwith multicasting

(c)

B CA

Packet-switched networksupporting multicasting(LAN/Internet/Intranet)

(b)

Figure 1.22 Transmission of a constant bit rate stream over apacket-switched network: (a) timing schematic; (b) FIFO bufferoperation.


Constant bit rateinput stream

Mean packettransfer delay

Constant bitrate output

stream

Receivedpacket stream

Packetizedinput stream

Time

Num

ber o

f bits

inpu

t/ou

tput

TP TBTN

TP = packetization delayTN = mean network packet transfer delay

= transmission delay + mean store-and-forward delayTB = buffering delay at destination (to overcome worst-case jitter)TT = total input-to-output delay

= TP + TN + TBJitter = variation in store-and-forward delay about the mean

(a)

(b)

Input from networkat a variable bit rate

First-in, first-out (FIFO) buffer

Output at a constant bit rate

Effect of late arrivalEffect of early arrival

Defined levelbefore output starts

Figure 1.23 Alternative types of media used in multimediaapplications.


Summary

Media types

Multimedia applications

Images

Digitizeddocuments,

pictures

Computer-generated

Text

Formattedtext

Unformattedtext

Video

Movies,films

Video-clips

Audio

Generalaudio

Speech

Digital formof representation

Analog formof representation

Analog-to-digitalconversion

Text and Image compression(Chapter 3)

Audio and video compression(Chapter 4)

Integrated multimedia information streams

Figure 1.24 Multimedia communication networks.


Multimedia communication networks

Datanetworks

InternetX.25

Telephonenetworks

PBXPSTN

NarrowbandISDN

Broadcast televisionnetworks

Satellite/terrestrialCable

BroadbandISDN

ISPNsLANs Intranets

Multimedia communication services

PSTN = public switched telephone networkPBX = private branch exchangeISDN = integrated services digital network

LANs = local area networksISPNs = internet service provider networks

Figure 1.25 Multimedia communication networks and theirservices.


The Internet

Multimediamail

Email andfile transfers

VideoconferencingSpeech and videotelephony

Information retrievaland electronic

commerce

Telephone networks

Voice-mailTelephony(fixed and mobile)

Access to theInternet

Facsimile(fax)

Entertainment(video-on-demand,

interactive TV)

Videotelephony

Speech andvideoconferencing

Cable networks

CD and video/movieon demand

Analog/digitalaudio andtelevision

Access to thePSTN

Interactive TV Access to theInternet

Satellite and terrestrial broadcast networks

Analog/digital audioand television broadcast

Interactivetelevision

Near video/movie-on-demand

Narrowband ISDN

Video telephonyand conferencing

Digital telephonyand fax

Access to theInternet

LANinterconnection

Broadband ISDN

ATM LANs ATM backbone networksATM MANs

High-speed networkinterconnection

All interpersonal andinteractive applications

Example 1.1


Derive the maximum block size that should be used over a channelwhich has a mean BER probability of 10–4 if the probability of a blockcontaining an error – and hence being discarded – is to be 10–1.

Answer:

PB = 1 – (1 – P )N

Hence 0.1 = 1 – (1 – 10–4)N and N = 950 bits

Alternatively, PB = N × P

Hence 0.1 = N × 10–4 and N = 1000 bits

Example 1.2


Determine the propagation delay associated with the following commu-nication channels:

(i) a connection through a private telephone network of 1km,

(ii) a connection through a PSTN of 200km,

(iii) a connection over a satellite channel of 50000km.

Assume that the velocity of propagation of a signal in the case of (i) and(ii) is 2 × 108 ms–1 and in the case of (iii) 3 × 108 ms–1.

Answer:

Propagation delay Tp = physical separation/velocity of propagation

103(i) Tp = = 5 × 10–6 s

2 × 108

200 × 103(ii) Tp = =10–3 s

2 × 108

5 × 107(iii) Tp = =1.67 × 10–1 s

3 ×108

Example 1.3


A packet-switched network with a worst-case jitter of 10 ms is to be usedfor a number of applications each of which involve a constant bit rateinformation stream. Determine the minimum amount of memory that isrequired at the destination and a suitable packet size for each of the fol-lowing input bit rates. It can be assumed that the mean packet transferrate of the network exceeds the equivalent input bit rate in each case.

(i) 64 kbps

(ii) 256kbps

(iii) 1.5Mbps.

Answer:

(i) At 64kbps, 10ms=640 bitsHence choose a packet size of, say, 800 bits with a FIFO buffer of1600 bits – 2 packets – and start playout of the bitstream after thefirst packet has been received.

(ii) At 256kbps, 10ms=2560 bitsHence choose a packet size of, say, 2800 bits with a FIFO buffer of4800 bits.

(iii) At 1.5Mbps, 10ms=15000 bitsHence choose a packet size of, say, 16 000 bits with a FIFO buffer of32 000 bits.

Notice that if the computed packet size exceeds the network maximumpacket size, then the equivalent number of packets must be sent beforeplayout starts. For example, if the maximum network packet size was8000 bits, then for case (iii) above playout would not start until two pack-ets have been received and the FIFO buffer should hold four packets.

figure 1.1 telephone networks: (a) network components; (b...

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