Transcript
Figure 1.1 Telephone networks: (a) network components; (b) digital transmission using modems; (c) multiple services via an H-S modem. (a)
Radio access
Analog access circute
Home/small business
National PSTNs
LE
PSTN
GMSC
IGE
IGE
PSTN
IGE
LE
Cellular phone network
Digital interconnection circuits PBX
Private site-wide telephone network
Analog access circuit PSTN = public switched telephone network GMSC = gateway mobile switching center IGE = international gateway exchange (b)
LE = local exchange/end office PBX = private branch exchange
Digital streams Analog access circuits
Digital device
Modem
Modem
PSTN
(c) Low bit rate telephone channel
Analog access circuit
H-S modem PSTN
Digital device
H-S modem STB
High bit rate channel
H-S = high-speed
Server
STB = set-top box
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Figure 1.2 A selection of the network types connected to the Internet.
Enterprise–wide private network/intranet
Site LAN
Site LAN
Server computer
Site LAN
Inter-site backbone network
Site LAN
Desktop PC or workstation
G/W
Global Internet backbone network Home
Desktop PC/workstation
G/W
Access via the PSTN with modems or the ISDN
G/W
Site/campus LAN
Internet service provider (ISP) network
Server computer
Small business LAN = local area network ISDN = integrated services digital network
G/W = gateway
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Figure 1.3 Broadcast television networks: (a) cable networks; (b) satellite/terrestrial broadcast networks.
(a)
PSTN
Cable head-end
Cable distribution network
STB
The Internet
(b)
Satellite (or terrestrial) broadcast network
STB
Program source
PSTN
The Internet STB = set-top box with integral modem
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Figure 1.4 Alternative services provided by an ISDN.
Digital subscriber line (DSL) p × 64 kbps switched channel
Single 128 kbps switched channel
Aggregation electronics Two independent
Integrated services digital network (ISDN)
Single 1.5/2.0 Mbps channel (primary rate access)
64 kbps channels (basic rate access)
p × 64 kbps switched channel
Single 64 kbps switched channel Conventional analog phone = network termination equipment
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Figure 1.5 Example of an ATM broadband multiservice network.
High-speed LAN
U
IW
IW
U
ATM LAN
U
IW
IW
U
ATM MAN
ATM LAN
High-speed LAN
ATM = asynchronous transfer mode LAN = local area network MAN = metropolitan area network IWU = interworking unit
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Figure 1.6 Speech-only interpersonal communications: public and private switched telephone networks.
Analog or digital access circuits
Voicemail server
Audio bridge
Cellular phone network
PSTN or ISDN
Private site-wide telephone network Voicemail server
Audio bridge
PBX
PSTN = Public switched telephone network PBX = Private branch exchange
ISDN = Integrated services digital networrk
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Figure 1.7 Telephony over the Internet.
Site/campus LAN
Internet service provider (ISP) network
Global Internet Packet G/W
Packet G/W
Telephony G/W
Telephony G/W
Packet-mode
Packet-mode Telephony G/W
Circuit-mode
Circuit-mode
PSTN/ISDN G/W = gateway
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Figure 1.8 Image-only interpersonal communications: facsimile (fax) examples.
PSTN or ISDN
Fax machine Analog or digital access circuits PC fax
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Figure 1.9 Text-only electronic mail: (a) email transfer examples; (b) example email message format.
(a) Enterprise-wide private network/intranet
Email server
G/W
Global Internet Home
Access via either a PSTN (with modems) or an ISDN G/W
G/W
Email server
Small business
Email server
Internet service provider (ISP) network
G/W = gateway (b) Control: Bin, Reply, Forward, Send etc. From: Name and address of sender To: Name and address of recipient Cc: List of other recipients (optional) Subject: Title of mail (optional) Date: Day, date and time mail sent
Header fields
Body, possibly with a file attachment
Body/Message content
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Site/campus LAN
Desktop PCs
Figure 1.10 Text-and-image computer-supported cooperative working (CSCW).
Change notification
Update control
Shared whiteboard program
Enterprise-wide private network, LAN or the Internet
Shared whiteboard/workspace
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Figure 1.11 Speech-and-video interpersonal communications: (a) two-party video telephone call; (b) videoconferencing using an MCU; (c) videoconferencing using a broadcast network.
(a) PSTN/ISDN/Internet/LAN/enterprise network Multimedia PC/workstation with video camera, microphone and speakers
Two-way simultaneous integrated speech-and-video information stream (b) PSTN/ISDN/enterprise network
Multipoint control unit (MCU)
Two-way simultaneous integrated speech-and-video information streams (c) LAN/Internet
Two-way simultaneous integrated speech-and-video information streams to/from all parties
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Figure 1.12 Speech-and-video interpersonal communications: (a) remote lecture; (b) multiparty (group) videoconferencing.
(a) ISDN/broadband network
Speech, video and image VS VS Speech only or speech-and-video Videoconferencing studio (b) ISDN/broadband network/ dedicated-circuit network
VS
VS
Videoconferencing studio
VS
Videoconferencing studio
MCU
Videoconferencing studio
VS = Videoconferencing system MCU = Multipoint control unit
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Figure 1.13 Multimedia electronic mail structure.
Mail header Hi Tom If your multimedia mail is working now just click on the following: Speech part Image part
Sent initially
Video part Otherwise the text version is in the attached file. Regards Fred
Speech sequence Image/picture Video clip
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Sent on request
Figure 1.14 Interactions with a World Wide Web server: (a) schematic; (b) hypertext linkages between the pages of a set of documents.
(a)
Internet
Site LAN
ISPs
PCs/workstations with browser software
World Wide Web servers
Intranet
Multimedia information servers (some with transaction capabilities) connected to a site LAN, an intranet, or an ISP network (b) Home page Navigation toolset
Navigation toolset
S
S
Navigation toolset S Hyperlinks
Navigation toolset
= text string containing uniform resource locator (URL)
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Figure 1.15 Interactions with a video server: (a) networking schematic; (b) movie-on-demand; (c) near movie-on-demand. (a)
Movie/video database
PSTN/cable access network
Set-top box with integral high bit rate modem
Low bit rate interaction channel
STB
Video server High bit rate channel for video stream
(b) MOD Subscriber 5
Movie C Movie A
4
Movie B
3
Movie A
2
Movie A
1
Time 1(A)
2(A)
3(B) 4(A)
5(C)
Subscriber (requests)
(c) N-MOD Subscriber 7,8
Movie C
6
Movie A
3,4
Movie B
1,2
Movie A Time 1(A)
2(A)
3(B) 4(A)
5(C)
Subscriber (requests) Playout intervals
MOD = movie-on-demand
N-MOD = near movie-on-demand
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Figure 1.16 Interactive television: (a) cable distribution network; (b) satellite/terrestrial broadcast network.
(a) Cable head-end Telephony call center
PSTN
Cable distribution network
STB
The Internet
Server computer (b) Satellite (or terrestrial) broadcast network
PSTN/ISDN
Telephony call center
STB
TV program source Service provider base station
Satellite interface
Server computer
The Internet Web server
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Figure 1.17 A selection of the terms used with multimedia.
Multimedia terminology
Communication modes
Simplex
Half-duplex
Symmetric
Duplex
Media types
Continuous
Broadcast and Multicast Canstant bit rate
Asymmetric
Communication channels
Synchronous
Asynchronous
Constant bit rate
Variable bit rate
Circuit-switched networks
Packet-switched networks
Connection-oriented
Connectionless
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Block-mode
Variable bit rate
Figure 1.18 Communication modes: (a) unicast; (b) broadcast; (c) multicast.
Communications channel (a) Simplex:
A
B
A Half-duplex:
B
Time
A
Duplex:
A
B
(b) B C Broadcast:
A D E
(c) B C Multicast:
A
D E F
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B, D and F are members of the same multicast group
Figure 1.19 Circuit-switched network schematic.
Circuit through the network set up using the unique number/address of A and B
Circuit-switched network
A
B
Bit rate of the connection determined by the bit rate of the access circuits = subscriber terminal/computer
= switching office/exchange
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Figure 1.20 Packet-switching network principles: (a) connectionoriented; (b) connectionless.
(a) CO packet-switching network VCI2
PSE2 1 2 3
VCI3
VCI1 A
VCI4 1 PSE3 2 3
2 1 PSE1 3
B
1 2 3 PSE4
VCI = virtual circuit identifier PSE = packet-switching exchange
CO = connection-oriented = virtual circuit (b)
Router 2
A
B
CL packet-switching network
A B
A
Router 3
Router 1
B
Router 4
CL = connectionless A, B = full network-wide addresses
= packet information content source address destination address
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IN PSE1 routing table: VCI1/Link1 VCI2/Link2
OUT VCI2/Link2 VCI1/Link1
PSE2 routing table: VCI2/Link1 VCI3/Link3
VCI3/Link3 VCI2/Link1
PSE3 routing table: VCI3/Link1 VCI4/Link2
VCI4/Link2 VCI3/Link1
Figure 1.21 Multipoint conferencing modes of operation: (a) centralized; (b) decentralized; (c) hybrid.
(a) Conference server
Circuit-switched network (PSTN/ISDN)
A
B
C
(b) Packet-switched network supporting multicasting (LAN/Internet/Intranet)
A
B
C
(c) C
A Conference server B
D Circuit-switched network
Packet-switched network with multicasting
= attached terminal/computer
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Figure 1.22 Transmission of a constant bit rate stream over a packet-switched network: (a) timing schematic; (b) FIFO buffer operation.
(a)
Constant bit rate input stream
Mean packet transfer delay
Constant bit rate output stream
Number of bits input/output
Received packet stream
Packetized input stream
TP
TN
Time
TB
TP = packetization delay TN = mean network packet transfer delay = transmission delay + mean store-and-forward delay TB = buffering delay at destination (to overcome worst-case jitter) TT = total input-to-output delay = TP + T N + T B Jitter = variation in store-and-forward delay about the mean First-in, first-out (FIFO) buffer
(b) Input from network at a variable bit rate
Output at a constant bit rate
Effect of early arrival
Effect of late arrival
Defined level before output starts
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Summary
Figure 1.23 Alternative types of media used in multimedia applications.
Multimedia applications Media types
Images
Text
Unformatted text
Formatted text
Computergenerated
Audio
Digitized documents, pictures
Speech
Video
General audio
Digital form of representation
Videoclips
Analog form of representation Analog-to-digital conversion
Text and Image compression (Chapter 3)
Audio and video compression (Chapter 4)
Integrated multimedia information streams
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Movies, films
Figure 1.24 Multimedia communication networks.
Multimedia communication networks
Telephone networks
PSTN
Broadcast television networks
Data networks
PBX
X.25
Internet
LANs
ISPNs
Cable
Narrowband ISDN
Satellite/terrestrial
Intranets
Multimedia communication services PSTN = public switched telephone network PBX = private branch exchange ISDN = integrated services digital network
LANs = local area networks ISPNs = internet service provider networks
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Broadband ISDN
Figure 1.25 Multimedia communication networks and their services.
Telephone networks
Telephony (fixed and mobile)
Voice-mail
Facsimile (fax)
Video telephony
Access to the Internet
Speech and Entertainment videoconferencing (video-on-demand, interactive TV)
The Internet
Email and file transfers
Multimedia mail
Speech and video telephony
Videoconferencing
Information retrieval and electronic commerce
Access to the PSTN
Access to the Internet
Cable networks
Analog/digital audio and television
CD and video/movie on demand
Interactive TV
Satellite and terrestrial broadcast networks
Analog/digital audio and television broadcast
Near video/movieon-demand
Interactive television
Narrowband ISDN
Digital telephony and fax
Video telephony and conferencing
LAN interconnection
Access to the Internet
Broadband ISDN
ATM LANs
ATM MANs
All interpersonal and interactive applications
ATM backbone networks
High-speed network interconnection
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Example 1.1
Derive the maximum block size that should be used over a channel which has a mean BER probability of 10–4 if the probability of a block containing 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
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Example 1.2
Determine the propagation delay associated with the following communication channels: (i) a connection through a private telephone network of 1 km, (ii) a connection through a PSTN of 200 km, (iii) a connection over a satellite channel of 50 000 km. 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 = 5 × 10–6 s 8 2 × 10
(i)
Tp =
(ii)
200 × 103 Tp = = 10–3 s 8 2 × 10
(iii)
5 × 107 Tp = = 1.67 × 10–1 s 3 × 108
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Example 1.3
A packet-switched network with a worst-case jitter of 10 ms is to be used for a number of applications each of which involve a constant bit rate information stream. Determine the minimum amount of memory that is required at the destination and a suitable packet size for each of the following input bit rates. It can be assumed that the mean packet transfer rate of the network exceeds the equivalent input bit rate in each case. (i) 64 kbps (ii) 256 kbps (iii) 1.5 Mbps. Answer: (i) At 64 kbps, 10 ms = 640 bits Hence choose a packet size of, say, 800 bits with a FIFO buffer of 1600 bits – 2 packets – and start playout of the bitstream after the first packet has been received. (ii) At 256 kbps, 10 ms = 2560 bits Hence choose a packet size of, say, 2800 bits with a FIFO buffer of 4800 bits. (iii) At 1.5 Mbps, 10 ms = 15000 bits Hence choose a packet size of, say, 16 000 bits with a FIFO buffer of 32 000 bits. Notice that if the computed packet size exceeds the network maximum packet size, then the equivalent number of packets must be sent before playout starts. For example, if the maximum network packet size was 8000 bits, then for case (iii) above playout would not start until two packets have been received and the FIFO buffer should hold four packets.
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