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July 26, 2011

Reader Question: What Does the End of the PSTN Mean for DSL?

Customers are abandoning the PSTN (Public Switched Telephone Network) for wireless and VoIP communication. The TAC (Technical Advisory Council) to the FCC (Federal Communication Commission) has recommended that the FCC set a date certain to end government mandates for PSTN use and the ever-increasing subsidies which support it. Knowing that the loss of government subsidy means the effective end of the PSTN, readers ask what the demise of the PSTN will mean to DSL (Digital Subscriber Loop), which is delivered over the same copper infrastructure as the PSTN and usually sold by the same companies which sell you PSTN. (Sorry for all the acronyms).

Good question. The answer is important since, according to the OECD, almost 58% of wireline connections to the Internet worldwide at the end of 2010 were DSL; this number is twice as great as the number of cable modem connections and almost five times the number of fiber or local area network connections. Broadband, either wireless or wireline, is essential to replace and supplement the functionality we decreasingly get from the PSTN. Obviously we can't afford to lose a huge share of our broadband connections at the same time as the PSTN fades into oblivion.

Here are some speculations on what might happen to DSL absent the PSTN; the possibilities aren't mutually exclusive and different things may happen in rural and urban areas, for example. Note that removing the requirement that the existing copper carry analog voice is an engineering opportunity to use the copper more effectively for digital data – including digital voice.

A successor to DSL which uses the same copper wires may be developed and provide much higher bandwidth at lower cost and greater distances than DSL does today. DSL was developed under the constraint that it had to operate in the same copper pairs as analog voice without requiring that ordinary phones be changed in any way; that's a pretty severe constraint. If a successor technology (which I'm sure people are working on) can use the full bandwidth available in the copper, it may be fully competitive with cable-based products. Perhaps this successor product would also travel greater distances without signal degradation so that it could be a large part of the answer to filling the remaining gaps in US broadband coverage – the copper wires do, in fact, already go almost everywhere. This may be wishful thinking but is not an absurd hope. The requirement that PSTN still be served is holding back the development of successors to DSL.

The growing number of unused copper pairs in the telephony plant might be bonded together so that more than one pair serves each subscriber or into some sort of local area network. The number of PSTN lines in use is already down by 50% from its peak so lots of pairs are available. The objective of this bonding is to deliver greater bandwidth over greater distances at competitive prices.

The prime space on utility poles now occupied by the copper wire can be reused for fiber or coaxial cable. A substantial part of the cost of extending cable or fiber service to a new area is "make ready" – replacing poles which either don't have the room or the strength for yet one more line. If the copper comes down, something else can go up in its place without nearly as much need for expensive pole replacement.

Carriers do make money selling DSL – generally without subsidy. The income from DSL or its successor may be enough to keep the copper network in place, particularly in rural areas. Even in that case, though, it would be much more efficient to have an all-digital data network on the copper and use VoIP over that data network than to insist that analog voice (PSTN) occupy a big part of the transmission spectrum.

Better data transmission including cheaper and higher quality voice over existing infrastructure is another reason NOT to artificially perpetuate the life of the PSTN with subsidies and mandates.

Scheduling note: It's still possible to sign up for a workshop in Washington, DC this coming Thursday, July 28, on the future of the PSTN. Agenda and signup at telecom2018.com.

Related posts:

Telecom 2018 Guest Post by Dan Berninger

Reader Objection: The PSTN is Better than Wireless or VoIP

TAC to FCC: Set a Date Certain for the End of the PSTN

The Ugly End of the Phone Network

Planning for the Ugly End of the Phone Network

States Should Deregulate ALL Phone Services – Not Regulate New Ones

Whom Do We Regulate when the Phone Monopolies Are Gone?

Whom Do We Regulate when the Phone Monopolies Are Gone? – Universal Access

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