Voice Over Internet Protocol: Submitted By

VOICE OVER INTERNET PROTOCOL SUBMITTED BY ASWATHI S. ROLL NO. - 11 July 18, 18,2009 2009

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OBJECTI VE

INTRODUCTION HOW VoIP WORKS? ADVANTAGES AND DISADVANTAGES APPLICATIONS July 18, 2009

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an evergreen technology that goes on July 18, 2009

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• VoIP was born back in the “stone age of the internet ” that is 1995, developed by a team of computer enthusiasts in Israel. • The earliest form of VoIP was Internet phone software. • Over a period of more than a decade several transformation took place and today it is the real VoIP. • This is an evergreen technology in communication and still more modification will make it more and more useful to the world. July 18, 2009

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VoIP definition • Voice over IP (VoIP) is a technology that allows voice conversation to be conducted over the Internet (hence IP,for Internet Protocol) instead of plain old telephone system (POTS).

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• Skype provides VoIP technology. • What makes VoIP an interesting technology is that it is set to revolutionize the way ordinary telephone conversations are conducted!!!! • The main users of VoIP service: • Residential home users • Small Business or Home Office July 18, 2009

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Also known as: • IP telephony. • Internet telephony. • Voice over broadband(VoBB). • Broadband telephony. • Broadband phone.

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How VoIP work???? July 18, 2009

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In simple words, VoIP is …… method for taking analog audio signals, like the kind you hear when you talk on the phone, and turning them into digital data that can be transmitted over the Internet.

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Telephone v/s VoIP  POTS works by setting up a dedicated

channel (or circuit) between two points for the duration of the call. These systems are based on copper wires carrying analog voice data over the dedicated circuits-Circuit Switching.

 Within VoIP, the analog signal is broken in to packets that are delivered to the other end by various routes on the Internet-Packet Switching. July 18, 2009

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How VoIP works????  The first step is conversion of voice to

bits and bytes, otherwise known as digitized.

 Voice is sampled, a process that divides the analog sound into discrete bits of data that are assigned a numerical value.  Once digitized, the data can then easily be compressed. July 18, 2009

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 The digitized and compressed data can the split up into packets of 1500bytes for transmission over the internet.  The packet also contain information about the packets orgin,the intended destination, and a timestamp that allows packet to be reconstructed in correct order.  Once these packets arrive at the destination they are put back together and converted back into analog sound. July 18, 2009

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HOW VOIP WORKS?

 Steps involved …………

1.Conversion of analog voice signal to digital format 2.Compression/translation of the signal into IP packets for transmission over the internet

 Process is reversed at the receiving end. July 18, 2009

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 VoIP systems employ Session control protocols to control the set-up and tear-down of calls.

How does  In addition to IP, VoIP uses the realVoIP carry time protocol (RTP) to help ensure that packets get delivered in a timely out these way  And audio codecs which encode speech steps???

allowing transmission over an IP n/w as digital audio via an audio stream.

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Role of a Codecs in VoIP???  A codec, stands for coder-decoder.  Converts an audio signal into compressed digital form for transmission and then back into an uncompressed audio signal for replay.  VoIP employs encoding schemes and compression technology to reduce the size of the voice packets so they can be transmitted more efficiently. July 18, 2009

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 Codecs accomplish the conversion by sampling the audio signal several thousand times per second.  There are different sampling rates in VoIP depending on the codec being used.  Use the CS-ACELP (conjugate-structure algebraic-code-excited-linear prediction) algorithm to sample, sort, compress and packetize audio data.

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 Annex B is an aspect of CS-ACELP that creates the transmission rule, which basically states "if no one is talking, don't send any data.“  The efficiency created by this rule is one of the greatest ways in which packet switching is superior to circuit switching.  It's Annex B in the CS-ACELP algorithm that's responsible for the above aspect of the VoIP call. July 18, 2009

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Hardware Required  Basically three things are required: • High speed broadband internet connection • Standard home phone (almost anyone will do) • VoIP adapter

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VoIP Software  VoIP software is commonly used to emulate the functions of a telephone using your desktop, laptop, or Pocket PC. This type of arrangement is known as a soft phone.  Skype is probably the most popular VoIP software and is available for free. Windows, Mac, Linux and PocketPC versions available.

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Methods of connecting to VoIP service providers….

Analog Telephone Adapter(ATA). VoIP phones Internet phone/Digital phone. July 18, 2009

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1.Analog Telephone Adapter.  The simplest and most common way.  The ATA is an analog-to-digital converter.  An ATA is connected b/w an IP network (broadband connection) and a telephone.

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connecting an analog phone to a VoIP provider.

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Working of an ATA.  You pick up the receiver, which sends a signal to the ATA.

 The ATA receives the signal and sends a dial tone. This lets you know that you have a connection to the Internet.  You dial the phone number of the party you wish to talk to. The tones are converted by the ATA into digital data and temporarily stored. July 18, 2009

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 The phone number data is sent in the form of a request to your VoIP company's call processor. The call processor checks it to ensure that it's in a valid format.  The call processor determines to whom to map the phone number. In mapping, the phone number is translated to an IP address.

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1. The soft switch connects the two devices on either end of the call. On the other end, a signal is sent to your friend's ATA, telling it to ask the connected phone to ring. 2. Once your friend picks up the phone, a session is established between your computer and your friend's computer. 3. You talk for a period of time. During the conversation, your system and your friend's system transmit packets back and forth when there is data to be sent. July 18, 2009

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The ATAs at each end translate these packets as they are received and convert them to the analog audio signal that you hear.

 You finish talking and hang up the receiver.  When you hang up, the circuit is closed between your phone and the ATA.  The ATA sends a signal to the soft switch connecting the call, terminating the session. July 18, 2009

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2.VoIP phones.

 These are phones that allow VoIP calls without use of a computer.  They can be connected directly to the IP network (using technologies such as Wi-Fi or Ethernet).  Has e-mail-like IDs for contacts that may be easier to remember than names or phone numbers.

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3.Internet phone

 This is a piece of software that can be installed on a computer.  Allows VoIP calling without a dedicated hardware.  Also known as Soft-phone or Digital phone.  Advantage—ability of having a fixed phone number which you can move to any country or location.

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VoIP: call monitoring

• To analyze and fix call quality issues, a technique called VoIP call monitoring is used. • Also known as quality monitoring (QM). • Mean opinion score (MOS)-measure of quality. • An MOS of 3.5 or above = "good call"

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measured in terms of 1following…. Latency: This is the time delay  

between two ends of a VoIP phone conversation. Jitter: It is latency caused by packets arriving late or in the wrong order Packet loss: Measured as a percentage of lost packets to received packets.

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ADVANTAGES of VoIP

VoIP uses packet switching. You can use the service almost anywhere in the world, as long as there is a high speed internet connection. Provides security through encryption. Provide features such as voicemail, caller ID, call forwarding and more.  Normally you would pay extra for these features with the phone or cellular companies. July 18, 2009

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Disadvantage of VoIP With VoIP, no power means no phone. A stable power source must be created for VoIP. No way to integrate products like Digital video recorders, digital subscription TV services and home security systems with VoIP. VoIP is susceptible to worms, viruses and hacking(but rare).

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Applications of VoIP

Long-distance communication • Allows you to call overseas for free, or at low rates. Web conferencing • Allows several times more participants than traditional web conferencing (up to 60 members).

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Office Intranet • Large offices use a local VoIP network to channel an internet connection throughout the building, creating an efficient and low-cost local intranet. • This can connect all departments to a single unit, replacing the traditional trunk line July 18, 2009

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Business Applications • Popular among businesses because of the potential savings it offers. • Allows owners to conduct board meetings and talk to clients from inside the office. • Provides opportunities for expanding a company's reach to customers.

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Conclusion…..  VoIP is a good way to get a cheap business line for a home-based business that’s available during office hours only.  In short, in future it is likely that a major chunk of calls using regular telephones will be over the internet. As such the VoIP has a very prominent role in this field.

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