P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
Faculty: Mr. Kiran Kumar
Subject: Multimedia Communication
PART
A
Questi
on
Solutio
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Semester: 8th ‘B’
Sub.Code:10EC841
1. With a neat diagram, explain the following terms relating to a
switched telephone network: i) POTS, ii) Local Exchange/end office,
iii) PBX, iv) Mobile switching center, and v) international gateway
exchange.
Switched Telephone Network
• Basic switched telephone service. POTS (plain old telephone
service). 'Switched' means that a subscriber can make a call/switch
to any other telephone that is connected to the total network.
• Telephones located in Home/ Small Business is connected to Local
Exchanges/End Office. Part of PSTN
• Set of telephones located in Large office/site are connected to PBX(
private switching office). It in-turn is connected to PSTN
• Cellular phone networks (handsets) linked by radio access. Switches
used are called Mobile Switching Centers (MSCs). Inturn connected
to a switching office in a PSTN
• International Calls routed to & switched by (IGEs) International
Mar
ks
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
Solutio
n
2.
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gateway exchanges.
Explain ISDN, B-ISDN, ATM, audio-bridge and MCU?
ISDN (Integrated Services Digital Network) is a set of CCITT/ITU
standards for digital transmission of voice, video, data, and other
network services over the traditional circuits of the PSTN. ISDN
offers circuit-switched connections (for either voice or data), and
packet-switched connections (for data), in increments of 64 kbs.
Enhanced ISDNs is also known as broadband ISDN (B-ISDN).
"Broadband" means it can support a bit rate (>2Mbps). All media
types are converted into digital form and integrated together, and the
resulting stream is divided into fixed-sized packets known as cells.
Different multimedia applications generate cell streams of different
rates and hence the rate of transfer of cells through the network
varies. This mode of transmission is known as asynchronous transfer
mode (ATM), uses asynchronous time-division multiplexing.
Audio-bridge :Special purpose Audio conferencing unit, audio bridge
used to support 6-48 participants. Connects two LANS. Used to
schedule call.
MCU: Special purpose unit, multipoint control unit (MCU) is a
centralized conference server for high volume & rate exchange). It
consists of MC & MP. MC: Establish connection with conference
participants on a agreed set of operational parameters like screen
resolution, refresh rate etc. MP: Distribution of information streams
generated during conference (mixing of different media streams,
voice-activated switching, continuous)
3. State the aim of all broadcast TV networks. With an aid of diagrams,
explain how additional services are provided with a cable distribution
network and a satellite/terrestrial broadcast network.
• Aim: Designed to support the diffusion/transmission of analog
television (and radio) programs throughout wide geographical areas.
Example: Cable distribution network : for a town or city, Satellite
network /Terrestrial broadcast network : for larger areas.
• The traffic is taken to be 1-way or asymmetric. But it generally
works with a low bit rate return channel offered by a cable network
for interaction purposes to provide a range of additional services
such as home shopping and games playing. The subscriber accesses
the cable distribution network through a set-top box.
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
Broadcast television networks: (a) cable networks;
(b) satellite/terrestrial broadcast networks.
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
4. Explain the different kind of multimedia applications which involve
multiple media? Give application descriptions for different media.
Solution: Different kinds of multimedia applications are
1. Interpersonal communications involve speech, image, text or video.
In some cases a single medium, in others multiple.
2. Interactive applications over the Internet
3. Entertainment applications
Interpersonal communications
Category
Interpersonal
communications
Media
Speech
Image
Text
Text and images
Speech and video
Text, image, audio
and video
Application descriptions
Telephony, voice-mail,
teleconferencing
Facsimile
Electronic mail
Computer-supported
cooperative working
Video telephoney, video
mail, Videoconferencing
Multimedia electronic
mail,
multiparty video games
etc.
Interactive applications
And
Entertainment Applications
Category
Interactive
applications over
the Internet
Media
Text, image, audio
and video
Entertainment
services
Text, image, audio and
video
Application
Information retrieval
(news, weather, books,
magazines, video games,
product literature etc.)
Electronic commerce
Audio/CD-on-demand
Movie/video-on-demand
Analog and digital
broadcasts
Interactive television
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
PART B
5. A. Explain different media types? Give examples?
B. Explain symmetric and asymmetric information flow in halfduplex
and
full duplex communications? Give examples?
Solution: An Internet media type is a standard identifier used on the
Internet to indicate the type of data that a file contains. The information
flow associated with the different applications can be either continuous or
block mode.
continuous: The information stream is generated by the source
continuously in a time-dependent way and played out directly as it is
received at the destination.
E.g. real-time audio, video.
The source stream can be generated at a constant bit rate (CBR) or a
variable bit rate (VBR). Digitized audio is generated constant bit-rate,
determined by sampled rate & numbers of bits used digitize each sample.
Individual pictures/frames make up a video are generated at constant rate.
Due to compression and variable information variable rate is generated.
Block mode of operation: streaming Mode of operation: downloading The
source information comprises a single block of information that is created
in a time-independent way. E.g. text, image
Half-duplex: info flows in both directions, but alternately ( request made to
remote server and request granted)
Full-duplex: info flows in both directions simultaneously (1-to-1
transmission). Two-way speech and video in video telephony.
In duplex communications, if the flow is in the 2 directions are equal; the
information flow is symmetric (Video Telephony). Otherwise, it's
asymmetric (Web Browsing).(Diagrams)
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
6. With aid of a diagram explain the operation principle of CO packetmode network. Include in your explanation the need for a virtual
connection/circuit, a virtual circuit identifier and a routing table.
Solution. A connection-oriented network comprises of an interconnected
set of packet-switching exchanges (PSEs). Prior to sending any
information, a connection is first set up through the network using address
of source & destination terminals.
The connection utilizes only a variable portion of the bandwidth of each
link and hence it's known as a virtual connection or a virtual circuit (VC).
Connection-oriented packet-switched networks imitate circuit-switched
network. In order for two users to communicate a Virtual circuit or a
Connection has to be first established by the network, then data transfer
takes place. After a connection or virtual circuit is established between two
nodes or application processes, a bit stream may be delivered between the
nodes.
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
VCI used for setting up Virtual circuit. PSE = Source/Destination Address
+ VCI .
PSE determines the input link and outgoing link by using packet destination
address & a free identifier (VCI). Information transfer phase can start with
VC in place. Only VCI is needed in packet header instead of full n/w wide
info.
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
7. In relation to the CL packet-mode network, explain i) best effort
service, ii) store-and-forward delay
Define BER probability of a transmission line/channel. How does it
influence the maximum packet block size of the channel?
Solution: When a packet is forwarded to a PSE/router, it's stored in a
buffer, checked, discarded if there is any problem (due to congestion or
error), or else forwarded to next PSE/router if the outgoing link is available.
Each PSE/router has a routing table and it's used to determine the outgoing
link to which a packet from a particular incoming link should forward. This
mode of operation results in delay, called store-and-forward delay as a
packet has to wait in a PSE/router until the outgoing link is available.
The service offered by a packet-switched network is said to be a best-effort
service as the transmission of a packet is not guaranteed to be successful.
The mean bit error rate (BER) of a channel is the probability of a bit being
corrupted during its transmission across the channel in a defined time
interval. Mean BER of 10⁻⁴ indicates for every 10000 bits transmitted, 1 of
a bit is corrupted.
A packet is declared incorrect if at least one bit is erroneous. Information is
partitioned into blocks during its transmission so as to minimize the
propagation of error. Any blocks containing bit errors will be discarded.
Hence prior to transmission source info is divided into blocks, whose max
size is determined by mean BER of the channel.
Example: for BER 10⁻⁴, block size < < 10000 bits. Otherwise all the blocks
will discarded if block size = 10000. Block of 100 bits may still contain
error, but probability is less.
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
8. With the aid of a diagram explain the meaning of QoS parameters i)
packetization delay ii) mean packet transfer delay iii)jitter. Hence
describe the effects on a constant bit stream rate and how can it be
overcome by buffering?
• Mean packet transfer delay is the summation of the store-andforward delay that a packet experiences when it travels along the
route.
• Packetization delay is the delay incurred at the source to packetize
the information. The larger the size of a packet, the larger the
packetization delay is.
•
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
Question
Marks
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST
Question
Marks
P.E.S. SCHOOL OF ENGINEERING
Hosur Road, ( 1Km Before Electronic City), Bangalore 560100.
Department of E&C
SCHEME AND SOLUTION
FIRST INTERNAL TEST