VoIP and Bandwidth

How much bandwidth do you need for VoIP?

Laptop computer with cable forming a bar chart
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Bandwidth is interchangeably used with connection speed, although technically they are not exactly the same. Bandwidth is, in fact, a range of frequencies through which data is transmitted. The same principles apply to radio, TV and data transmission. A large bandwidth ‘range’ means that more data are transmitted at one point in time, and thus at greater speed. Although we will be using the two terms interchangeably here, technically bandwidth is not connection speed, although they are used interchangeably by most Internet users. 

Measuring Bandwidth

Bandwidth is measured in Hertz (Hz), or MegaHertz (MHz) because Hertz are counted in millions. One MHz is one million Hz. Connection speed (technically called the bit rate) is measured in Kilobits per second (kbps). It is simply a measure of how many bits are transmitted in one second. We're going to use kbps or Mbps to refer to transmission speed from now on because that’s what every service provider talks about when referring to the speed they offer. One Mbps is one thousand kbps.

You can have an idea of how good or bad your connection speed is and whether it is suitable for VoIP by performing online connection tests.

Bandwidth Cost

For most people using the Internet as a communication medium, bandwidth happens to be the most expensive requirement, because it is recurring. For voice communication, the bandwidth requirements are more important, since voice is a type of data that is bulkier than conventional text. This implies that the greater the connection speed, the better the voice quality you can get. Today, a broadband connection is common and getting cheaper and cheaper.

Broadband is an unlimited connection (24 hours a day and for as much as you want to use up) at a speed much higher than that of dial-up’s 56 kbps. Most providers give at least 512 kbps today, which is largely sufficient for VoIP communication. This is the case for developed countries and regions. For other places, some users are still restricted to low connection speed at high prices.

Common Bandwidths

Let’s have a look at some typical bandwidth associated with popular communication devices and technologies.

Technology Speed Use in VoIP
Dial-Up (modem) Up to 56 kbps Not suitable
ISDN Up to 128 kbps Suitable, for fixed and dedicated service
ADSL Up to several Mbps One of the best WAN technologies, but provides no mobility
Wireless technologies (e.g. WiFi, WiMax, GPRS, CDMA) Up to several Mbps Some technologies are suitable while some are limited by distance and signal quality. They are the mobile alternatives to ADSL.
LAN (e.g Ethernet) Up to thousands of Mbps (Gbps) The best, but limited to the length of wires which can be short in most cases.
Cable 1 to 6 Mbps High speed but limits mobility. Is suitable is you don't have to move.

Bandwidth and Apps 

VoIP apps on your mobile device consume bandwidth differently. This is based on the codecs they use to encode data for transmission and on other technical considerations. Skype, for instance, is among the common VoIP apps that consume more data or bandwidth per minute of communication, as it offers HD voice. So, while the quality is much better, you will need higher bandwidth and spend more in terms of megabytes. This is fine on WiFi, but you have to be mindful about it when using your mobile data.