lecture 05 ; multimedia communications

8/6/2019 Lecture 05 ; multimedia communications

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Multimedia Communications andService on the Internet

ETE 436

Course Conducted by

Shuvodip Das, Lecturer, PU.

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Multimedia Network: Broadband Multiservice Network

support a wide range of multimediacommunication applications.Bit rate- more than 2 MbpsCalled Broadband ISDN (B-ISDN) .Uses Cell Switching Network .

Cell Switching Network provides

flexibility of using different bit rates fordifferent multimedia applications.

Varying rate of transfer of cells is knownas Asynchronous Transfer Mode(ATM) .B-ISDN consisting of ATM-MAN andATM-LAN.

ATM-MAN is being used as a high-speedbackbone network to interconnect anumber of LANs.

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Multimedia Applications

Interpersonal CommunicationsInteractive Applications over the Internet

Entertainment Applications.Interpersonal Communication:

Interpersonal Communications involvespeech, image, text or video.

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S peech only Interpersonal Communication

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Example: Telephony service inwhich telephones are connectedto PSTN/ISDN/Cellular phonenetwork or a PBX.Telephone call through PC: CTIand software.

Advantages:voice mail and teleconferencingvoice-mail beside telephony.Telephony over the Internet is

also known as packet voice orVoIP.PC connected Internet cancommunicate with to thePSTN/ISDN can communicatethrough telephone gateway.


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W hat is Teleconferencing Call?

Teleconferencing calls involve multipleinterconnected telephones/PCs. Each personcan hear and talk to all of the others involvedin the call. This type of call is known variously

as a conference call or since it involves atelephone network, a teleconferencing call issometimes called Audio Conferencing call. Itrequires a central unit known as an audiobridge which provides the necessary supportto set up a conference call automatically.

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W hat are the procedures of Voice over Internet Protocol (Vo IP)?VoIP involves-PC to PC telephone call andPC to telephone connected in PSTN/ISDN.PC to telephone connected in P STN/ ISD N:

Procedures:PC 1st sends a request to make a call to pre-allocated telephony gateway.

Then gateway verifies the authentication of user to use the service.Gateway requests the source PC the telephone number of the called party.On receipt of this, the source gateway initiates a session (call) with the telephonygateway nearest to the called party using the Internet address of the gateway.The called gateway then initiates a call to the recipient telephone using its

telephone number and the standard call setup procedure of the PSTN/ISDN.When the called party answers then called gateway signals back to the PC user-through the source gateway-then the call can commence.A similar procedure is followed to clear the call on completion.

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Telephony over the Internet

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Text Only Interpersonal CommunicationExample: Electronic mail (email).Network: InternetUser: Home and Business user.Access: Home user: through ISPand PSTN/ISDN.Business user: through LAN andenterprise network .Associated with each networkthere is a set of one or moreserver computers called Email

Server . These serverscollectively contain a mailbox foreach user connected to thatnetwork.

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Text Only InterpersonalCommunication

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Fig: Email message format


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S peech and Video Interpersonal CommunicationExample: V ideo TelephonyHo me use: D edicated video phone service.

Offic e Use: video phone service with a range of other services.R equ ir ement s: two-way communication channel between the two partiesand sufficient bandwidth to support the integrated speech and video.video conferencing requires a central unit called a M ult ip o int C o nt r o l Un i t(M CU) or sometimes called Vid eo C o n f er en ci ng Se rv er.

P r ob lem: For D esktop conferencing, multiple integrated speech and videocommunication channels, one for each participant, would require and BWrequirement is higher.So lut i o n: M CU .Integrated speech and video information stream from each participant is sent

to the MCU which then selects just a single information steam to send toeach participant. For example, with a voice activated MCU, whenever theMCU detects a participant speaking, it relays the information stream fromthat participant to all the other participants. In this way, only a single twoway communication channel between each location and MCU is requiredthereby reducing bandwidth needed.

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S peech and Video Interpersonal Communication

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Fig: Speech and video interpersonal communications:a) 2 party video telephone call

b) video conferencing using an MCU

c)V

ideoconferencing using a broadcast network.


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Interactive Applications over the InternetInternet is also used to support a rangeof interactive applications.E

xample: World Wide Web (WWW)H yperlinks: Each document comprises alinked set of pages and the linkagesbetween the pages. These are pointersor references that refer to either otherpages of the same document or to anyother document within the total web.U niform Resource Locator ( U RL):Unique address. Identifies both thelocation of the server on the Internetwhere the first page of the document is

stored and also the file reference on theserver.H omepage: The first page of adocument.H ypertext Markup Language (MTML):

A standard for writing documents in

WWW.B rowser: Client function. Used to

explore the content of the web.

Fig: Interactions with a Wide WebServer (Schematic)

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Hypertext text linkages between the pages of aset of documents.

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Media Types

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Communication Mode

15C o mmun ic at io n m o d es a) un ic ast b ) b r o a dc ast an d c ) mult ic ast .


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Network Qo SThe operational parameters associated with a

communication channel through a network are knownas the Network Quality of Service (QoS) parameter andcollectively they determine the suitability of thechannel in relation to its use for a particularapplication.Qo S parameters of Circuit Switched Network:QoS parameters associated with a constant bit ratechannel that is setup through a circuit switched

network includes:The bit rateThe mean bit error rate andThe transmission error rate.

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If Probability of BER = PNumber of bits in a block = NThen assuming random error,Probability of a block containing a bit error, PB isgiven by: P B = 1 (1 P)N

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Qo S Parameter of Packet SwitchedNetwork

QoS parameter associated with a packet-switched network includes:The maximum packet sizeThe mean packet transfer rateThe mean packet error rateThe mean packet transfer delayThe worse-case jitter andThe transmission delay.

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Application Qo SThe network QoS parameters define what the particular networkbeing used provides rather than what the applications requires. Theapplication has its QoS parameters associated with it. In anapplication involving images, QoS parameters may include aminimum image resolution and size. On the other hand, applicationsinvolving videos, QoS parameter may include digitizing format and

refresh rate may be defined. The application QoS parameters thatrelate to the network include:The required bit rate or mean packet transfer rate

The maximum startup delay

The maximum end-to-end delayThe maximum delay variation/jitter.The maximum round-trip delay.

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Media Types used in applications

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Network Types

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lecture 05 ; multimedia communications

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