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Voice Over IP

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DQI Bureau
New Update

Taken a look at your company's telephone

bills lately? What if you could cut down your telephone bills, particularly for

long-distance calls? That is exactly what Voice over IP (VoIP, in short) promises. It uses

your company's existing computer network and Internet connectivity for voice

communication, instead of using the normal POTS (Plain Old Telephone System) lines. The

network can be a combination of anything, including your LAN/WAN, fiber optic cables,

VSATs, and of course, the Internet, as long as you have IP as one of the protocols.

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How Does It Work?



If you have PCs with a sound card, and software like Cool Talk, NetMeeting or Video Phone,
you are ready to get going. If you are connecting over the Internet, you could use

Internet Phone or similar software. The sound card converts the analog input from a

microphone/telephone handset to digital data. The software then compresses, encodes, and

breaks this data into small 'packets'. These packets are transmitted over an IP network to

the receiving end, where they are put together, decoded, uncompressed to digital form, and

then converted back to analog sound.

On long-distance calls, particularly ISD

calls, you only need to pay for the local calls to your ISP. Similarly, at the other end

also, the called party needs to pay only for a local call. And you are actually talking to

someone half way across the globe! There are many companies, like Micom, who specialize in

providing IP-based telephony services. They have a large set of solutions for easy set-up

and maintenance of such networks.

It Sounds Nice, But What Are The

Drawbacks?




As with any new technology, VoIP also has some drawbacks. The first and foremost being
that IP is a slightly unreliable protocol when transmitting data over large distances and

involving the Internet. Some of the voice 'packets' may get lost or may reach out of order

in which they were sent. With digital data, this does not pose much of a problem, since

the receiving end can always request for the missing data to be sent again and wait for

them to reach before putting all the packets together. With voice, which is real-time,

this cannot be done as the data no longer exists on the sending side either.

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There is, however, a solution for this.

Researchers have pointed out that humans need to hear only 80-90 percent of what is said

to be able to reconstruct the whole data. This means some tolerance comes into play

because of the human factor and some missing data is acceptable.

Another problem faced with VoIP is network

congestion. Normal PSTN line carry 8000 bytes per sec. A 28.8 Kbps modem gives around 3000

bytes per sec. When sending voice over this sort of network, there is bound to be a lot of

congestion and distortion. This is one area in which research is still going on.

Legality is another issue faced by VoIP.

Presently in India, sending voice over VSNL's Internet service is prohibited. However, in

many countries, telephone companies have taken the lead in offering voice over IP

services.

Instead of trying to fight the technology,

phone companies are themselves turning into ISPs to provide these facilities to users. The

day will not be far off when youwill have a smartly dressed sales executive sitting in

front of you, urging you to replace your archaic EPABX with 'state-of-the-art' and cheap

Internet telephony!

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