PSTN & ISDN DIALUP

INTERNET ACCESS

Public Switched Telephone Network (PSTN) dialup uses your phone connection to connect your computer to the internet. You need a modem, phone line and a computer for a PSTN dial Up connection.

PSTN DIALUP

Dialup equipment infrastucture for PSTN

Telephony The term telephony refers the technology behind

voice communication it uses analog electrical signal over copper wire.

VoIP This is a technology which allows telephone to be

make over computer networks like the internet.VoIP convert analog signals into digital data packets and support real time , two way transmission of conversation using internet protocol.

Related topics

It allows telephone calls to be made from personal computer.

Choosing abroadband internet ohone service :-

A broadband phone service enables voice telephone calls to work over high-speed Internet connections. Broadband phone services combine your Internet and local telephone subscriptions and share the same IP network.

Internet phone calls( IP phones)

Downloading Skype software allows you to set up your computer for free Internet phone calls. Free Skype downloads are available for Windows, Mac OS X, Linux and Pocket PC. Skype allow offers separate toolbar downloads for Microsoft Internet Explorer and Outlook 

Skype software download

PSTN gateways :- PSTN gateways are third party device that

translate signlling and media between enterprise voice infrastructure or a PSTN or PBX.

SIP trunking:- As an alternative to using PSTN gateways,

you can connect your enterprise voice solution to the PSTN using the the SIP trunking .

PSTN connectivity components

Private branch exchange:- IP-PBX that supports media bypass with a

mediation server . IP-PBX requires stand alone PSTN gateways .( time division multiplexing PBX with standalone gateway.)

The task of building networks and selling services fell to the network operators.

In some countries however the job of providing telephone networks fell to the government as the investment required was very large and the provision of the telephone services increasingly becoming an essential public utility.

PSTN operators

In most countries the central government has a regulator dedicated to the monitoring the provision of PSTN services in that country.

Their task may be for example to ensure that end customer s are not overcharged for services were monopolies exist. They may also regulate the prices charged between the operators to carry each others traffic.

Regulation of the PSTN

Network topology:- The simple meaning of topology is how devices

are connected to each other.

The original concept as that the telephone exchanges are arranged into hierarchy so that if a call can not be handled by the local cluster , it is passed to one higher up for onward routing. This reduced the number of connecting trunks required between operators over long distances and also kept local traffic separate.

Technology in the PSTN

To carry a typical phone call from a calling party to called party , the analog audio signal is digitized at an 8 khz sample rate at the 8 bit pulse code modulation.

The call is carried over the PSTN using a64 kbit/s channel, originally designed by the bell laboratory . the name given to this channel is digital signal 0(DS0) . the DS0 circuit is the basic granularity of the circuit switching in a telephone exchange . a DS0 is also known as the timeslot because DS0 are aggregated in time division multiplexing equipment to form a higher capacity communication links.

Digital channels

It provides a method to route the voice and data traffic between the endpoints ( in a conversation ) from end user to other switching center.

A continous electric current goes through the wires as long as the conversation takes place , until it is closed by one of the participants .

Switching centre know the pieces of information about the other ones, and based on these , they can chose an optimal route for a certain call.

Circuit switching

No antenna. Straight forward , well established

technology. Easy to set up and maintain. Auto dial and auto answer capability. Flexible “AT” command set. Two way communication. Event modification through one or more

stored telephone numbers to provide a timely warning. 

Advantages of PSTN

1.The speed of a typical PSTN modem is 56KBPS. Therefore the speed of the internet connection will be slower than this.

2.During the time you are connected to the internet, you have to pay the telephone charges.

3.While you are connected to the internet you cannot use your telephone to call anyone because you are using that phone line for connecting to the internet. You also will not receive any calls from outside during this time.

DISADVANTAGE S OF PSTN DIALUP

Integrated Services Digital Network (ISDN) dialup uses a higher end digital telephone line to dial up. To use this type of connection you need ISDN telephone line, computer and a ‘Terminal Adapter’.

ISDN DIALUP

Structure of ISDN

ISDN connection reference point

Rate Reference Point (R) R reference point refers to the link between

the TE2 and the TA.

 Terminal Reference Point (T) and System Reference Point (S)

The S/T reference point is the user-network reference point.

The S reference point sits between the TE1/TA and the NT2.

The T reference point is the point between the customer site switching equipment (NT2) and the local loop termination (NT1).

Reference points

The U reference point is the two-wire link between the NT1 and the Line Termination (LT) (or Local Exchange, LE) which handles the termination of the local loop.

V reference pointThe V reference point is that between remote

terminations.

User Reference Point (U)

Basic Rate Interface (BRI) has two B channels and one D channel.

Primary rate interface

Primary Rate Interface (PRI) has either 30 B channels and 1 D channel (MCE1 - UK) or 23 B channels and 1 D channel (MCT1 - USA).

Basic rate interface (BRI)

BRI frame

The bits in the BRI frame are described below: F, FA, N - Synchronisation bits that use line code

violations L - DC line balancing B1, B2 - Bearer 1 and Bearer 2 channels

containing the data E, S, M - Collision Avoidance bits, although 8

devices with sub-addresses can be daisy-chained on a multipoint bus, only one device can talk at a time.

D - Data channel control A - Activation indicator

Bits of the BRI frame

1.While you are connected to internet using ISDN dialup connection you can use your ISDN phone to make phone calls simultaneously.2.When you are making phone calls while connected to the internet then the speed of internet will be 64KBPS.3.If you are using the ISDN phone line just for internet then the speed of internet will be 128KBPS.

ADVANTAGES OF ISDN DIALUP

1.Not every place has ISDN connection.2.Even if your place has this facility, it is expensive to get an ISDN dialup connection from your ISP.3.Not all the ISPs provide ISDN dialup plan.

DISADVANTAGES OF ISDN DIALUP

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