How Much Bandwidth Is Needed For VoIP?


There are several benefits of VoIP but whether it’ll work well for your business or not always comes down to the quality of your connection. As you may already now, VoIP requires a good connection. But what is a good connection in the context of VoIP, and how much bandwidth is needed for VoIP?

How much bandwidth is needed for VoIP? At a minimum, you will need dedicated bandwidth of 100Kbps up and down per VoIP call.

The bandwidth that you need for VoIP will differ depending on the number of concurrent calls you intend to make. It will also differ depending on how high you want the call quality to be and the codec that you use. I’ll explain all you need to know about the bandwidth that you need for VoIP in this blog post.

Why Does Bandwidth Matter For VoIP?

The bandwidth of your connection is crucial to how your VoIP telephone system works. So what is bandwidth and why does it matter for VoIP?

Bandwidth is the maximum rate of data transfer possible on your internet connection. So if you have ADSL2+, the maximum bandwidth is 24Mbps. Knowing the bandwidth you get from your internet service provider is really important, because a VoIP telephone system relies on it.

So let’s say you have ADSL2+ and you want to make 5 VoIP calls concurrently. To make 5 concurrent VoIP calls, you need a minimum of 500Kbps dedicated bandwidth upstream and downstream. So you might think that ADSL2+ is enough for VoIP – but it usually isn’t.

It’s important to remember that a VoIP call needs dedicated bandwidth. Unless you’re using your connection for VoIP alone, it’s unlikely that your VoIP calls are going to have the dedicated bandwidth that they need on an ADSL2+ connection.

If you’re running other applications on your connection, they’re all eating up bandwidth as well. That’s why a basic ADSL connection simply won’t suffice for VoIP, even though you initially think it might.

How Much Bandwidth Is Needed For VoIP?

The amount of bandwidth that you need for VoIP really depends on the codec that your system and calls use. As I stated at the beginning of this post, 100kbps down and up of dedicated bandwidth will normally suffice. However, different codecs need different speeds. I’ll talk through what codecs are, how they work, and how much bandwidth each codec needs.

A codec is a piece of software capable of compressing and decompressing a digital stream or a signal for transmission over a data network. A codec can be for audio or video content, with VoIP falling into the first category. A codec is used to convert the digital signal so that it can be delivered and understood by the other user’s telephone system and phone.

Codecs accomplish the conversion by sampling the audio signal several thousand times per second. Let’s take a look at how this works with one of the most popular VoIP codecs. A G.711 codec samples audio at 64,000 times a second. It converts each tiny sample into digitized data and compresses it for transmission. Once the 64,000 samples are reassembled, the human ear cannot detect the little pieces of missing audio between samples. For example, during a phone conversation, it will sound like a continuous stream of audio despite the process handled by the codec.

There are several codecs that are commonly used for VoIP. I’ve listed several of the most popular codecs used for VoIP in this table, as well as the minimum bandwidth they need.

Codecs Commonly Used For VoIP

CodecBandwidth Needed
G.711100Kbps
G.72264Kbps
G.723.16.3Kbps
iLBC15Kbps
Silk6 - 40Kbps
G.72940Kbps

Which VoIP Codec Is The Best?

The codec used on your telephone system is usually decided by your VoIP provider. They will look at your circumstances and then chooses a codec for your business using that information. So for example, if you have a superfast internet connection with plenty of bandwidth for VoIP, your provider will use a codec that uses more bandwidth but ensures higher quality calls. If you have a basic internet connection with little bandwidth, your provider will use a codec that requires less bandwidth. The trade-off here is that the greater the compression of the digital signal, the lower the quality of the audio.

The G.711 codec is the most commonly used VoIP codec. It requires the most bandwidth but also ensures good call quality comparable to an ISDN call.

The most commonly used VoIP codec is the G.711. This codec requires 100Kbps of dedicated bandwidth up and down to work. If you have a very poor internet connection, or you want to make a lot of concurrent calls, your provider might use a different codec to ensure call quality. For example, your provider might use the G.729 codec instead, as it requires less bandwidth. The G.729 codec requires 40Kbps of dedicated bandwidth up and down per call. The trade-off here is, of course, call quality. The call quality when using the G.729 codec is equivalent to a mobile call. On the other hand, the call quality when using the G.711 is the equivalent of a high-quality ISDN call.

So the best codec for your telephone system really comes down to the quality of your connection. If you don’t have a good connection but require numerous concurrent calls, a codec requiring less bandwidth must be used. If you have a high-speed connection, or you don’t need to make many concurrent calls, a codec requiring more bandwidth but ensuring high-quality calls can be used.

Tips For Improving VoIP Call Quality

If the VoIP call quality in your office is very low, it suggests that your connection might be the problem. Here are some easy and relatively cost-effective ways that you can improve your VoIP call quality.

Install A Second Connection Just For VoIP

The more services and users eating up bandwidth, the lower the quality of your VoIP calls. If you’re struggling on your current connection, you can always upgrade to a faster connection. However, this can be very expensive depending on the connection you already have and the upgrade options available in your area. If you cannot afford to upgrade your connection, installing a second connection could be cheaper and ensure VoIP call quality.

There are several businesses providing VoIP for businesses that will install a second data connection as standard when setting up a VoIP telephone system. By using a second connection for your VoIP telephone system, there’s less competition for bandwidth and higher call quality can be guaranteed by using codecs that require the most bandwidth.

Set Up Quality Of Service

If you cannot afford the expense of upgrading your connection or installing an additional one, configuring your network’s quality of service features could help you to get around the issue of poor quality calls.

To ensure that enough bandwidth will be available at all times of the day, you can adjust your network’s Quality of Service features to prioritize VoIP calls above all the other services that are using your connection. Usually, Quality of Service features can be managed at router-level by instructing the router to prioritize VoIP traffic. If this isn’t possible, or you don’t know how, your ISP or VoIP provider should be able to help you out. Your router will then ensure that no matter what, VoIP will have enough bandwidth space.

Sometimes Quality of Service features are only configurable by your internet service provider. If this is the case, contact them and let them know the problems that you are having with VoIP. They will then be able to configure the settings on your network to prioritize your VoIP traffic over anything else.

Check The Basics

Before purchasing or upgrading anything, it’s always a good idea to check the basics to see whether there’s a easier way to overcome your VoIP issues. For example, are your phones up-to-date with the latest firmware? Not having your phones on the latest firmware can really mess with the way your VoIP system works, so make sure you check little things like that before rushing to upgrade to gigabit-capable internet.

Before you rush into anything, it’s always good to check the basics. If you are experiencing issues and you’re unsure why, speaking to your provider is always a good idea. With most business-grade VoIP solutions, your provider is obliged to offer you a high-quality service. If that isn’t what you’re getting, they’ll have to offer solutions and help you resolve your issues with call quality.

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