What is VOIP?

            Voice Over Internet Protocol (VOIP) is a technology that converts analog voice signals to digital signals that are then carried over the Internet and the Public Switched Telephone Network (PSTN) from the caller’s phone to the called party’s phone. Either the caller, or the called party’s phone equipment, must be a VOIP phone to place the call through a VOIP network. VOIP technology can be used to make a call to any telephone number around the world.

 

With a VOIP phone call, the called party can have a Plain Old Telephone System (POTS) landline connection, mobile phone or a VOIP phone, and it won’t make any difference to the VOIP phone that is calling them. The technology allows a call from any phone type (land-line, VOIP or mobile) to any other phone type to be carried over the internet, however, how the call is routed through the internet, PSTN or the wireless telephony infrastructure depends on the service provider’s infrastructure.

 

            To make a VOIP call the caller must have a VOIP enabled device, like an IP phone or a Personal Computer with a microphone, the device must be connected to the Internet, preferably via a broadband connection with at least 256k upload and download speed. Using a broadband connection gives much better voice reception than an analog phone line dial-up modem (Those of us who have been online since the early 90’s remember trying to place internet calls where you had to say “over and out”, and wait for the other person to speak since you couldn’t both talk at once). The broadband Internet connection can be a DSL connection, cable, LAN or high-speed broadband through 2G/3G wireless technologies like GPRS/EDGE/cdmaOne/CDMA2000 or WiFi.

 

VOIP Call

            A VOIP phone consists of an analog-to-digital & vice-versa codec that encodes/decodes the analog voice into/from a stream of binary digits that are then encoded into an IP packet. The IP packet consists of either the called party’s telephone number or an IP/domain name address. The IP packet travels from the VOIP phone, or the Personal Computer from which the voice call is being made, to the nearest gateway where the called party’s telephone number, or the IP/domain name address, is resolved and connected.

 

            If the called party’s number is a VOIP phone telephone number, IP address or a domain name (SIP call), then the packet travels further on the Internet to the gateway point nearest to the called party. If the called party’s VOIP device is a phone or PC connected to the Internet via phone line, then the packet is switched through DSLAM and a PSTN switch to the end device. If the called party’s VOIP device is connected on the LAN/WAN the packet is routed to the user’s end device (PC or IP phone).

 

            If the called party’s number is an analog telephone number, then the packet is switched to a gateway (Media Gateway Controller) that performs the digital to analog conversion and maintains the telephone address routing database. The call is then circuit-switched onto the PSTN network.

 

Refer to the VOIP network diagram at: Nivasgroup.com

 

VOIP Services

            Services available for VOIP devices over a VOIP network can be classified as Customer Premises Equipment (CPE) services or Network Services. CPE services can be further classified by the type of equipment being used: VOIP phone, Personal Computer or Analog Phone.

CPE Services:

Ÿ         Picture Caller ID – A high bandwidth Internet connection and a web camera, or IP videophone, are required to send pictures or video to the called party.

Ÿ         Multi-party Conferencing, Video conferencing is supported with a high-speed Internet connection and a web camera on your PC or IP videophone.

Ÿ         Exchange Server Integration - Contact and calendar functions can be searched from a VOIP phone, there is no need to save all of the phone book and scheduler information in the phone’s memory.

Ÿ         Money Saving - All VOIP calls are cheaper than PSTN or cellular phone calls.

Ÿ         Virtual Access Numbers – A subscriber can get multiple VOIP telephone numbers or domain addresses and configure their current telephone number as the forwarding number. A subscriber can then be contacted through any of their local VOIP telephone numbers or domain addresses and the call is forwarded to the user’s current number or domain address. The advantage of this feature is that a caller can call the local number instead of a long-distance number and save on their bill. E.g. John has the local numbers 732-245-7658 and 609-876-9087 and sets the latter as his current telephone number; calls to the first number will automatically be routed to the second number. The user’s office PC and home PC can both be configured with different domain/email address, that way, calls made to the user’s current domain name or email address will automatically be routed to the correct computer. E.g. john@office.com, john@home.com are the two domain/email addresses, in the evening, John sets john@home.com as the current default address. If anyone calls John at the office, john@office.com, the call will be routed to John’s home PC and John’s home PC will ring.

Ÿ         Selective Call Forwarding - A forwarding address or telephone number can be uniquely configured for each number or address’s origination. E.g. in the previous example, instead of setting the current location of the call to John’s home computer, any calls that come in on a number from the 732 area code can be forwarded to John’s cell phone, while calls from the 609 area code can be forwarded to John’ land-line number at home.

Ÿ         Independent Voice Mail - Voice mail messages can be saved as audio attachments to an e-mail on a PC’s hard disk. This feature does not require voice mails to be saved at the VOIP service provider server; however, the PC & the e-mail client must be online at the time of the call. If the e-mail client is not online, the voice e-mail will be saved on the e-mail server until such time as it can be downloaded with the user’s regular email.

Ÿ         Power over Ethernet - Electrical power is transmitted over a twisted-pair Ethernet cable, along with the data; there is no need for a separate power connection for the Ethernet port device.

 

Network Services:

Ÿ         A VOIP network provides a single infrastructure for voice and data communication, this saves infrastructure installation and maintenance costs for the service provider.

Ÿ         Using analog phone networks connected through VOIP networks will be more reliable and provide better voice reception, reducing maintenance costs and line disturbances.

Ÿ         Multiple subscribers can use network bandwidth simultaneously. This earns more revenue for the service providers and reduces the cost for the subscribers. Packet switching also allows data/voice, from multiple subscribers, to be multiplexed onto the same physical link or wireless channel.

 

VOIP Equipment

 The CPE required for making a VOIP call are:

Ÿ         A Personal Computer with a microphone and VOIP service provider software. Some links to VOIP software are Net2phone, Dialpad, Go2Call, iConnectHere and Skype.

Ÿ         An Internet connection device. The connecting device can be an analog line modem, DSL line modem or mobile phone that can be configured as a modem or a LAN cable.

Ÿ         An analog phone line dial-up modem (56.25 Kbps or 112.5 Kbps) may be external to the PC or an internal PCI card.

Ÿ         An external broadband DSL modem can be used to connect multiple devices, while an internal PCI card cannot be used directly for other devices.

Ÿ         A mobile phone with Bluetooth® wireless technology and Dial-UP Networking profile (DUN) can be configured as a modem to connect to 2G/3G wireless networks for high-speed broadband connections.

Ÿ         A VOIP phone can be connected to a LAN port (RJ-45) on an external modem or LAN.

Ÿ         A VOIP phone can be connected to a LAN port on a PC with the internal modem, or to a PC connected to the Internet via any other means.

Ÿ         A VOIP phone can also be connected directly to an adapter that takes the analog phone line (RJ-11) as an input and has a LAN (RJ-45) port.

Ÿ         VOIP phones with analog phone line (RJ-11) ports are also currently available on the market.

Ÿ         WiFi VOIP phones can be connected to the Internet through any WiFi hotspot.

Ÿ         VOIP enabled PBX systems.

 

 

References

Voice Over IP. Federal Communications Commission. May 05, 2006.  http://www.fcc.gov/voip/

VOIP Features. http://www.voipaction.com/adv_feat.php

Power over Ethernet. http://en.wikipedia.org/wiki/Power_over_Ethernet