IP Phones

After signing up with a VoIP service provider you need to get a phone which connects to the Internet. Some providers will include an IP phone as part of their package but other plans specify that you supply your own equipment. IP phones have an Ethernet jack that plug into the router of your broadband Internet connection. Ethernet connectors are similar to regular phone connectors but about twice as wide.

If you want to use a traditional analog phone set with VoIP you can get an ATA (Analog Telephone Adapter) — a small box which contains the hardware and software necessary to convert your voice into digital data and send it over the Internet. The ATA has an Ethernet connector and a regular phone plug connector.

The advantage of using an ATA is that you don’t have to buy new phones — just plug in the phone you are currently using, either wired or wireless. An IP phone, however, is more convenient for taking advantage of many of the extra features that are included free with your VoIP account — call display, call routing, call forwarding, voicemail and many others. You can still use these features with an ATA, but you may need to configure your VoIP account at the service provider’s web site.

There are many IP phones on the market ranging from simple residential phones to complex phone terminals designed for business use. Even basic models, however, have an LCD display for caller ID and phone configuration. More advanced models may have features like speakerphones, headset interfaces, customized rings, and programmable keys which allow you to quickly access certain functions of the phone.

Do you want to go wireless? Although you can’t yet get the freedom of a cellular phone with VoIP, you can still use wireless phones within an IEEE 802.11b wireless network. These phones are suitable for residence, campus and enterprise use.

Besides being cheaper, included in the basic service package are things like call waiting, call display, and call forwarding. You can take advantage of all of these features with an IP phone. When your phone rings, the LCD screen displays the caller information. You can choose to accept the call or redirect it to voicemail or an error message.

Rather than manually routing each individual call, you can set up rules for certain types of calls. For example, anonymous calls could be routed to your voicemail, or calls from someone you wish to avoid could be routed to an error message. Calls can also be forwarded to an outside number.

Some VoIP services operate the same as traditional phone services. Call waiting, for example, allows you to take a second call if you are already using the phone line. When another call comes in you hear a short beep and you can switch between the two calls by pushing a button.

If you wish to keep your calls anonymous you can block your caller ID. This way, when you are calling somebody with call display, your name or phone number will not be shown. This feature can be set for all of your calls or just for selected ones.

If you do not wish to be disturbed, you can route all calls to your voicemail or to a message saying that you are unavailable. With this setting, your phone will not ring until you reset it.

A very handy feature of IP phones is the ability to store names and phone numbers. You can scroll through the phone book or set shortcut keys to commonly called numbers. Every call that comes in can be automatically added to your phone book and you can easily edit or delete numbers at any time.


The Internet Protocol Suite As Applied To VoIP.

All data travelling over the Internet is made up of packets that contain a payload as well as extra information that determine where and how that payload will be delivered. In VoIP the payload is the actual voice data. The packet also consists of several other ‘layers’ that aid in the speedy delivery of the data which allows real time conversations to take place over the Internet.

The Internet Protocol Suite (IPS) is composed of 5 layers which encapsulate the actual payload. The layers contain information about how the payload is to be delivered – for example, if all the data has to be delivered or not – and how it will be treated on delivery. There are three layers that make connections between computers and two physical layers that data must pass through en route to its destination. These physical layers are part of the computer.

The top layer of the IPS is the Application Layer. The VoIP soft-phone controls the Application Layer – in VoIP a common application layer is SIP (Session Initiation Protocol). It specifies the type of connection the caller wants to make (voice, video or instant messaging for example), and identifies the other party with a unique number similar to an IP address (the 4 part number that identifies every computer on the Internet).

The Transport Layer in any Internet connection determines the format for delivering data. Web pages usually use TCP (Transmission Control Protocol) which guarantees data delivery – sometimes at the expense of speed. VoIP depends more on speed than data integrity, so TCP is not usually used. Instead RTP (Real-time Transport Protocol) in conjunction with UDP (User Datagram Protocol) are used to control data flow. RTP identifies the payload and provides sequencing information so that the data can be reassembled correctly when it reaches its destination. UDP provides a fast method of delivery but by itself cannot determine data sequence or delivery information.

Next is the Network Layer, which for the Internet (and other networks) is the Internet Protocol (IP). IP is used to set up a path, but offers no guarantees for data delivery or integrity. For dependable data delivery the upper layers (transport and application) are needed.

The two physical layers of the Internet Protocol Suite are the Data Link layer and the Physical layer. Ethernet is used as the Data Link layer in VoIP. It provides a means to transmit data reliably by controlling and synchronizing the flow. The physical layer provides the pathway that transmits bits to the Data Link layer. In VoIP the physical layer is the twisted-pair cable that connects the network card, routers, modems, Analog Telephone Adaptors (ATAs) and IP phones.

If we follow the data path of a voice packet, it originates in the sound card which converts the voice into digital data. The audio stream is compressed by the Voice Over Internet Protocol software and divided up into packets which contain information about where the data is to be delivered. This data is transmitted from the computer to the Internet through the twisted-pair cable attached to the modem.

The data packets may take several different routes to their destination because of the ever-changing conditions of the Internet. On arrival, the voice data has to be reassembled in the correct order and converted to an analog signal which the receiving party can hear. All this should happen in less than half a second no matter where in the world the two parties are located.


The Nitty-Gritty Of VoIP

In order to use VoIP, both parties need a broadband connection. This is a high-speed Internet connection usually provided by a cable or DSL modem. Broadband modems are usually used to connect computers to the Internet, but in the case of VoIP, computers are not necessary.

The simplest form of VoIP is a computer-to-computer voice connection. All that is required for this type of connection is a computer, a headset consisting of earphones and microphone, and VoIP software. Most software packages are free and allow you to connect to any computer running the same software. There is no charge for this type of connection and calls can be made to anywhere in the world.

VoIP software can also be used to connect to land-line phones — that is, phones which are not connected directly to the Internet. This type of call is usually not free but the cost is quite a bit lower than what your telephone company charges. Some VoIP services also allow you to make calls to cellular phones.

The only time that both parties need a particular VoIP software package is when they are making computer-to-computer calls. Parties receiving land-line or cellular calls do not need any extra equipment or software.

VoIP Transmissions

VoIP is based on digital data transmission. The first step in any VoIP call is to convert the analog signal of the human voice into digital data. This is done within an Analog-to-Digital Converter (ADC) that divides an analog signal into discrete steps which are represented by numbers. The next step is to compress the audio data using a codec (enCOder/DECoder) which significantly reduces the amount of digital data while maintaining audio quality.

The compressed digital data can now be sent over the Internet. The data stream must be divided into packets which, besides containing the audio data, also have information concerning their destination and their place in the data stream.

All data that is sent over the Internet is encapsulated in ‘layers’ which aid in its proper delivery. For example, web pages may use the Internet Protocol (IP) network layer to specify destination and origin addresses, the Transmission Control Protocol (TCP) transport layer to create a connection between two computers and the Hyper Text Transfer Protocol (HTTP) as an application layer to allow the Web browser to display the web page correctly.

Most VoIP uses a transport layer called User Datagram Protocol (UDP) which is faster than TCP. A commonly used application layer is Real-time Transmission Protocol (RTP) — originally developed for delivering audio and video over the Internet. RTP provides information about the sequence of the data packets so they can be reconstructed in the correct order at their destination.

RTP also has the ability to drop packets if they do not arrive within a certain amount of time. This is necessary for telephone conversations because if the telephone software waited for every packet of information to arrive before reassembling it there would be unacceptable delays in the audio stream.

Even though some of the packets are dropped, there is usually still enough information to make the conversation legible. The number of packets that will be dropped depends on the speed of your Internet connection in the distance between the two parties.

Once the voice data has arrived at its destination, it is reassembled in the correct order and converted back from digital to analog.


The Future Of VoIP

With all the advantages of VoIP there is still one drawback — it cannot give you total wireless phone communication the way that cell phones do. Cell phones and VoIP seem to be two separate worlds. True – you can have wireless Internet connections (including VoIP) with Wi-Fi hot spots, but they are of no use to your cellar phone – or are they?

In fact, dual mode phones are already on the market. A few companies (including Motorola) have introduced cell phones which automatically switch to VoIP when they detect a WiFi hotspot. This type of device is sure to be popular with consumers who will benefit from the reduced costs of VoIP, but it is likely to be less than enthusiastically adopted by cellular phone companies who stand to lose considerable profits if the numbers of cell phone calls are reduced.

Industry analysts, however, predict this kind of service will be widespread within the next five years. Cellular phone companies will have no choice but to offer plans which combine VoIP and cellular otherwise they will lose business to companies that step in to fill the void.

The next step after cell/VoIP integration might be the replacement of cell networks with wireless VoIP. A new wireless technology called WiMax is in the works – city-wide wireless networks that operate at much faster speeds than what is available today. Such a network would allow anyone in its range to use a VoIP wireless phone. This technology could also be used to transmit video and audio possibly replacing or augmenting services like video rentals and radio.

WiMax is currently in the testing stage with more than 100 trials taking place around the world. It sounds like a great idea, but it may cause disruptions within a number of industries including movie theatres, DVD distributors and traditional phone companies such as Globex Telecom— all of which stand to lose if this technology becomes common place.

It’s pretty hard to hold back technological innovation, though. New technology usually presents challenges (and opportunities) to existing industries. The phone companies and entertainment industries will face a challenge but could potentially thrive in the new WiMax environment if they find the proper niche. For example, faster broadband will likely make VoIP video phones a common item. There could be many other unforeseen applications to this new technology.

Another future trend to watch out for is the possibility of free Internet telephony. After all, we do not pay for regular data transmission over the Internet, so why are we paying VoIP service providers $15 or $20 per month? Voice data is the same as any other data that travels over the Internet. Some observers predict that as VoIP gains wider acceptance and is more universally adopted, monthly fees for telephone service will disappear.

Of course, there would still be a charge for the basic Internet connection, but if bandwidth continues to grow, a single Internet connection could be used for telephone, television, as well as e-mail and surfing the net.