by Brian Boyko
Editor, Network Performance Daily

Ars Technica reports that the National Institutes of Health released a study which show that wireless-phone only households are increasing – currently 15.8 percent of households. 

But that’s just part of it – other consumers are switching to VoIP services – gobbling up another 13.8 percent of U.S. households. 

There are certainly economic factors which result in this change - me, I cancelled my landline phone service when I realized I was paying less on a month-to-month basis on my cellphone than I was for a service I barely used.  Since then, I’ve moved around a lot (seven times in the past five years) and keeping the same cellphone instead of canceling and re-enabling service makes a hell of a lot of sense. 

But still – three out of ten consumers?  This is a major shift – and one that’s likely to continue as cellphone and VoIP quality gets better. 

Of course, there will be more demand for VoIP networking in the future – and with it, a need to monitor VoIP quality of experience.  But more than that is the idea that there is an entire infrastructure of phone lines – stretching from sea to shining sea and beyond – that connect the last mile to the local phone exchange. 

It seems like such a waste. 

But wait!  DSL service only uses the 25kHz and above part of the spectrum – 4kHz is reserved for voice.   If landlines are repurposed ONLY for data, with VoIP being another application on the all-data network, that could free up the 4kHz spectrum currently being used.  Maybe we can use that 0-4kHz band for broadband to rural homes – which can clearly get 4kHz data if they can get a phone call. 

This is especially important for rural broadband penetration.  The longer the distance to the exchange, the lower the quality of high bandwidth exchanges – this is why your DSL service gets slower the further you are from your local phone exchange.  But the 4kHz currently used for voice can travel much greater distances – it won’t be as fast as the DSL available in the cities but repurposing the 4kHz bandwidth from voice to data might make a huge difference to getting some minimal broadband to the most rural parts of the world.

Now, this won’t make a whole lot of difference to a person living in the city – DSL works by dividing that 25kHz-and-up portion of the spectrum into 4kHz chunks, each one connecting with a speed equivalent of a modem.  It is the multitude of these channels – hundreds in most cases – that makes DSL speed possible.  Repurposing the broadband of 0-25kHz would result in only six additional channels.  Assigning two for upload and four for download, you’d have speeds of around 14.4kBytes/s (or 115.9kbits/s) upload and 28.8kBytes/s (231.3kbits/s) download.  That’s not much of a speed boost. 

Still, if you’ve been plodding along on a “56.6k” modem, at speeds of 7.2kBytes/s, this would be like an oasis in the desert.  And what about those phone calls?  Well, if you make the same phone calls with VoIP that you were with the standard 0-4kHz landline, it would only take about 20.8kbits/s using the G.723.1 codec – that still leaves you with 80% of your broadband capacity when on the phone – and 100% of your broadband when you’re off it.  For someone whose only current Internet connectivity choice is a modem, currently getting 16% of a theoretical data capacity – and 0% when you’re on the phone – that’s a major improvement.   

What do you think?  It seems reasonable, but there might be a flaw in my math – I did only pass Calc I on my third try.  Let me know if you have something to share in our comments section.