There has been a great deal of discussion in the press lately about “PSTN Sunset” and it may leave you with the impression that everything is settled when it comes to setting an end date for today’s Public Switched Telephone Network. It is true that if you step back and look at the big picture, the major trends are clear: Carrier PSTN lines have been declining for years, Cable and Internet VoIP is growing, mobile subscriptions are peaking, and social networking is flourishing.

But it’s a leap from these “facts” to “PSTN Sunset,” and most of the articles and blogs never really connect the dots. So I think it’s important to examine the source, which in this case is the FCC’s (News - Alert) Technology Advisory Council (TAC). When you do that, a clearer, more nuanced, and far more interesting picture emerges.

First, some background. The TAC is a group of industry leaders and experts that provides technical advice to the FCC. The TAC mandate is to help the FCC develop informed technology policies. The current TAC was appointed in October 2010, and for the last year it has been studying several important technology issues. For example, one sub-group is tackling IPv6. Another is tackling the “Critical Legacy Transition.” This is where PSTN Sunset is being discussed. The TAC meetings are broadcast on FCC Live, and fully archived, so you can see exactly what the group has been saying about PSTN Sunset. There are a number of popular myths about PSTN Sunset, but the actual TAC proceedings give us the information to understand the reality behind those myths.

Myth no. 1: PSTN, and PSTN Sunset, are clearly defined.

It seems strange to talk about PSTN Sunset, without a clear definition of what is meant by the “PSTN.” But that is pretty much what the press is doing. Are we talking about shutting down the entire PSTN? If not, then exactly what parts of the “PSTN” are we going to “sunset?” Do we mean (E.164) telephone numbers? Mobile phones use E.164 numbers too. Vonage (News - Alert) uses E.164 numbers. Even Skype allows you to use an E.164 number, so that seems unlikely.

Is the PSTN the phone that plugs into the wall? Once again, most VoIP services allow you to use standard telephone sets. Is it the copper wires coming into your home? Those are used for broadband service too, so getting rid of them might not be a good idea either. You can see where I am going with this.

A close look at the numbers referenced by the TAC would suggest that the definition of the Public Switched Telephony Network has more to do with the installed base of TDM Switch technology in the public network. That excludes fixed line service that has migrated to VoIP as deployed by Cable companies, Carrier broadband voice offerings that use FTTP or DSL, and Internet “Over-the-Top” services like Skype (News - Alert) and Vonage. In fact, the same thing is going on in mobile networks, which also use similar TDM technologies in 2G and 3G voice implementations. VoLTE will ultimately displace TDM in wireless networks using 3GPP standard SIP based VoIP technology. Across the industry there’s general agreement that TDM will be retired in the next decade and VoIP will redefine the services scope, cost points and definition of a new Public Services Network.

Myth no. 2: Voice isn’t as relevant anymore - Broadband provides everything you need.

There is truth to the claim that “voice is just another application.” But that does not mean people are not talking on the phone anymore. It certainly does not mean that voice is unimportant. At least it doesn’t look like the FCC views it that way.

In October, the FCC released a Report and Order (R&O) outlining comprehensive reform of the Universal Service Fund (USF) and Intercarrier Compensation (ICC). This document did not propose that USF support be shifted from voice to broadband. Instead, it proposed that the focus be expanded to include voice and broadband. Earlier this year, the FCC issued a Notice of Proposed Rule Making (NPRM) dealing with outage reporting. This proposes to expand the existing requirement for voice outage reporting, to include voice, interconnected VoIP and broadband. In document after document, the FCC is sending the same message: voice is still a critical universal service, but now, broadband is equally important.

Myth no. 3: Everything will go wireless.

The steady growth of wireless is well known. Over half of U.S. broadband subscriptions are mobile. Americans are increasingly cutting the cord, with 30 percent of households only having mobile phone service.

Are we moving inexorably, and en masse, to a world where all communications needs are provided by wireless networks? Reading the blogs, you might think so. But this is not what the TAC is proposing. In the September TAC meeting, the head of the Wireless Access sub-team went out of his way to clarify that wireless was one of a range of technologies that would replace legacy TDM networks. An important TAC objective is to verify that multiple alternative broadband access technologies are available to support the transition from a voice-centric TDM network to an IP-based broadband network.

A closer look at the statistics for mobile substitution in the National Center for Health Statistics1 survey also suggests it is unlikely that everything will move to mobile. True, in some segments of the population, such as unrelated adults living in rented accommodation, wireless substitution is already the norm. However in other segments, such as families living in a home they own, wireless substitution is much lower – below 20 percent.

We see significant geographical differences as well, with affluent, densely populated areas showing the lowest incidence of wireless substitution. Wireless will play an important role, even a critical role, in the transition to a broadband infrastructure. But it is not the only answer. Wired broadband, cable, fiber, satellite and copper all have their own role to play. One size, does not fit all.