Voicespan

A recent survey by top10.com has named the Kent village of Farningham as the place in the country with the lowest average broadband speed, a mere 1.3Mb/s.

Slow broadband, as anyone who chooses not to live in a large town or city, is a fact of life in Britain. What makes Farningham’s situation so ironic is the the provider of the fastest broadband in the UK, Virgin, chose to trial it’s 50Mb/s service in nearby Ashford.

Stifling decentralisation

Home working and ‘virtual’ businesses, where there is no central office, are growing in popularity. Redundancies are also expected to increase due to the economic situation, which is likely to lead more people into self-employment. All this just increases the need for high quality, high speed broadband from wherever you happen to live.

So we need to wait?

Actually, no. A download speed of 1.3Mb/s, or even less, can support VoIP as long as you take a couple of sensible precautions. Let’s have a closer look.

Firstly, the speed that’s important when considering broadband is not the headline download speed, but actually the upload speed. Why? Well, voice traffic travels two ways. The audio coming in to you is limited by your download speed, and the audio heading out to the other party is limited by your upload speed. But one-way audio doesn’t allow for a very interesting conversation, so we’re limited by the lower of the two speeds.

Now the upload speed of an ADSL connection is slower than the download speed, hence the ‘A’ for ‘Asymmetric’. This actually makes the situation even worse, right? Well, yes, but it’s still not bad enough to stop you using VoIP.

The not-so-tricky maths bit

Lets assume that an ADSL circuit with a 1.3Mb/s download speed has an upload speed of .5 Mb/s, or 500Kb/s. It may be a bit more, but it’s unlikely to be less.

When the analogue audio coming out of your mouth is transferred into ones and zeros so it can be sent across the internet, that signal is compressed. Depending on a few factors, that compression can be fairly light, or quite heavy.

Heavy compression tends to distort voice quality somewhat, so you can end up sounding a bit like a Dalek! Therefore, most phones and phone systems tend to default to a lighter compression to maintain voice quality.

The most common compression has the memorable name of G.711 (also known as ulaw in USA & Japan, and alaw elsewhere). A G.711 signal requires, with overheads, approximately 80-90 Kb/s of bandwidth. So, as you can see, it’s perfectly possible to run one, two, perhaps as much as five telephone conversations over a fairly low-speed broadband circuit.

Is that all?

Unfortunately, life is quite that simple. Low speed broadband can, quite often, be low quality too. ADSL is a shared resource (this is called contention) meaning that you and your neighbours may all be fighting for a share of that 1.3Mb/s.

Even if you have a good enough share of your theoretical maximum bandwidth, within your own network you will have other devices wanting internet access. Your PC or laptop will be pulling down emails, web pages, operating system updates, anti-virus updates, etc. If you use BBC iPlayer then that can really chew up your bandwidth.

The answer is to make sure that your VoIP traffic jumps to the front of the queue every time. This is called Quality of Service (QoS) and can make the difference between crystal clear and choppy, unusable audio. I expanded on this subject in a previous post. Since then we have started trialling a service that guarantees voice quality even over a low bandwidth ADSL circuit that is shared with other services. If you want to find out more about this then drop us a line.

VoIP is not the limiting factor

Ultimately, running your business from a location with slow broadband may not be possible for other reasons. However, VoIP can and does run successfully in many slow broadband areas. As long as a few simple and cheap precautions are taken, there is no reason why your business can’t utilise the benefits of VoIP too, whatever your location.