AT&T’s (News - Alert) recent request to the Federal Communications Commission to speed up the timetable for shutting down the public switched telephone network is happening at the same time that fourth generation networks are poised to begin displacing the early third generation network.

At least in principle, such transitions have featured new lead applications. When the analog fixed network began to yield to digital switching, rotary dial equipment began to be replaced by devices using DTMF tones. But such enhanced features as caller identification, call waiting and three-way calling were retail features made available because of the transition.

IP telephony is adding integrated messaging, video calling and other features such as presence and virtual identities.

The second generation of mobile networks remained focused on voice services. But third generation networks added e-mail support and Internet access. Nobody can be sure what potential new lead app will develop around fourth generation mobile networks, though some suspect video entertainment is a good candidate.

Others tend to believe personal Wi-Fi hotspots are a possible new lead application as well.

And network generations are not as rare as sometimes seems to be the case.

Mobile networks have gone through distinct generations based on air interface, ranging from the original analog to second generation TDM and then a few flavors of 3G and now a small range of flavors of 4G Long Term Evolution.

Now U.K. regulator Ofcom is referring to "5G," which doesn't yet exist, for spectrum it plans to auction off in 2018, if all goes according to plan. Those frequencies in the 700 MHz band, which by that time will no longer be used to support TV services.

But there is nothing special about the particular frequencies becoming available, only the timing.

Because the spectrum won’t be available till 2018,Ofcom, expects this will be used for the next technology following 4G or LTE (News - Alert), and it is therefore being referred to as “5G”.

It's a fiction at the moment, since the industry has not agreed on what is to follow LTE. Nor is it clear LTE necessarily will need to be superseded by 2018.

Roughly speaking, air interface generations have occurred about every decade, starting about 1980 for first generation, then 1990 for second generation, then 2000 for 3G and now 2010 for fourth generation networks. That implies the fifth generation will start to appear about 2020.

What new lead applications could then develop is anybody’s guess at the moment. We still have no clear understanding of what the new lead apps will be for Long Term Evolution.

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