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Simultaneous Calls

With normal telephony you can have only one telephone call on one telephone line at once. To get more simultaneous calls you have to install - and pay for - more lines.

With Voipfone that all changes. With Voipfone you can have as many calls on your 'line' as you and your equipment can handle.

We can help you work out what you need and how to get the most out of your VoIP service.

There are three prime considerations which dictate both the quality and number of simultaneous calls you can make or receive over your Voipfone service.

Your Internet Connection

Broadband ADSL has a lower bandwidth back up to your ISP than down from them ie it is asymmetrical. Typically, ADSL bandwidth is described as 2 or 8mbs (or increasingly more) which is the down speed.

But because VoIP is symmetrical - a telephone call is, of course, two-way, most people listen as well as talk - the major bottleneck is your upstream bandwidth which is normally only 256 or 398kbs or sometimes 800kbs.

The more bandwidth you have the more simultaneous calls you can achieve and the less interference you will have from your use of other internet applications such as internet browsing, file downloading, FTP or email (see below).

So, as a general principle, always get the fastest ADSL service you can find and afford. A business ADSL service will have a lower contention ratio than a residential one and will be less congested.

Find a good ISP - they are not all equal!

We provide our own voice prioritised ADSL service which is specifically designed for use with our network. If you are looking for a business class, broadband service look here first as we can then control the whole call from your phone into our network. Click here to view the broadband packages available to you.

If you are really heavy users you could also consider buying symmetrical DSL - SDSL. Please contact us if you require this.

Your Use of Your Internet Connection

It's worth pointing out that if you are heavy users of the internet and you wish to make telephone calls over it, something has to give. Unlike downloading a file or sending an email, a telephone call is instant and happens in real time - it cannot be delayed, slowed down or paused.

So if you wish to use both voice and data heavily you need to design your network correctly. If you are finding that your calls suffer from jitter - calls stuttering and breaking up - it is almost certainly being caused by lack of bandwidth as you voice traffic competes with other data traffic for scarce bandwidth.

If you have several people all sharing the same internet connection for voice and data and are using it heavily for both, you should consider separating your voice connection (VoIP) from your data connection (internet, email etc). This means using two ADSL circuits. This also has the benefit of giving you a back-up if one circuit fails. To obtain an even higher level of back-up, use a two different Service Providers.

It is also worth ensuring that your local network wiring is up to scratch - bad internal cabling can lead to all sorts of problems. Avoid using WiFi for VoIP; it works, particularly with devices specifically designed for it, but for PCs and softphones the encryption/decryption process adds complexity and slows things down.

Another option is to change to a codec that uses less bandwidth.

Your Choice of Codec

Since voice and sound are analogue, they need to be converted (or encoded) to a digital format suitable for transmission over the Internet. A codec is an algorithm used to do this job; it codes and decodes a voice conversation.

All VoIP telephones, both softphones and telephones and adapters, use codecs and unless you specify which one, it will use the default codec which for Voipfone is a very high quality one.

There are a variety of different ways this encoding and decoding can be done - many of which utilise compression in order to reduce the required bandwidth of the conversation.

Reducing the bandwidth will reduce the quality of the call somewhat but will enable you to squeeze more simultaneous conversations over your connection. Getting this trade-off right is up to you!

Your choice of codec will radically affect the number of simultaneous conversations over your network so it is worth experimenting with them.

We recommend using two in particular:

  1. G711a This is a very high quality codec which delivers CD quality sound - much better than an ordinary telephone call. But to do this it uses quite a lot of bandwidth - about 90kbs which reduces the number of simultaneous calls to around 3 for a standard 256kbs connection.
  2. GSM This is the codec used by mobile phones and delivers the same sort of quality. It is however, highly efficient which means that you can squeeze 10 or more calls simultaneously up a 256kbs pipe. In use, the GSM codec delivers indistinguishable call quality from an ordinary telephone call.

For guidance, the chart below shows the maximum simultaneous calls theoretically possible over a perfect connection. Bear in mind, that in the old telecoms world, each call requires one line so using a GSM codec can give you the equivalent of up to 13 lines on a standard ADSL connection!

Got a question?

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