With VoIP, your voice will be transmitted over IP- the Internet Protocol. The first thing you will need is a stable Internet connection, with sufficient bandwidth. Bandwidth is used interchangeably with connection speed although technically they are not exactly the same but we won’t split hairs for the sake of this discussion. A stable connection for voice transmissions would be any Cable circuit or an ADSL connection. ADSL is important because the upload and download speeds need to be identical for voice traffic over DSL to be successful.
There are so many factors affecting voice quality: the broadband connection, bandwidth, hardware, software and the technology itself but the key element of VoIP technology is data compression.
Compression software (called a codec) encodes the voice signals into digital data that it compresses into lighter packets that are then transported over the Internet. At the destination, these packets are decompressed and given their original size (hopefully), and converted back to analog voice again, so that the user can hear.
Picture Captain Kirk standing in his transporter chamber, getting converted into an energy pattern by Scotty, traveling through the ethernet and being reconverted into matter at his destination with all limbs and organs intact. Thus is the journey of a voice packet.
There are 3 standard compression protocols most frequently used in the world of IP business telephone systems:
G.711 typically uses up the most bandwidth because it’s compressed the least- 75kb per second
In contrast, G.723 uses approximately half at about 35kbps
G.729 uses the least at about 21kkbps
One of the most important factors to consider when you build packet voice networks is proper capacity planning. Within capacity planning, bandwidth calculation is an important factor to consider when you design and troubleshoot packet voice networks for good voice quality.