Wednesday, May 1, 2013

Review: Signals: The Science of Telecommunications

Signals: The Science of Telecommunications
Signals: The Science of Telecommunications by John Robinson Pierce

My rating: 3 of 5 stars

The most shocking thing I've learned from this book: the technology that makes phone number portability possible has existed in widespread deployment for USA customers since 1983!

That's it. The following association and implication of this statement is not within the book, but one I came to with information from other sources, including study of my own phone service billing, so permit this little digression:


This technology was developed and activated long-ago by phone companies to satisfy their internal needs. It has side benefits for external customers of phone service, who could from a technical standpoint access a portability feature. No providers actually made this capability available to subscribers back then.

In the 1990s, as cellular phones drove demand by subscribers to change service providers or service locations, these consumers increasingly desired to keep an old numbers. Eventually, this resulted in government regulations to "force" providers to make subscriber phone numbers portable. The new law compensated providers for their effort by legislating a number-portability tax, which feeds a subsidy program paying providers back for the administrative and technology overhead they insisted would be required to comply with the portability mandate.

This being the case...why are USA subscribers STILL paying federal line taxes to "pay" for the "hardship" phone companies say exists today. In fact, why were USA subscribers EVER paying this tax? The capability was already extant!

The truth is, since at least 1983 (before the portability laws) this capability has been an existing core property of national network! All subscriber lines are referred to by internal network numbers, and have separate external numbers (the number you dial). The association between these two numbers is established inside the phone network, by editing the switching databases in the part of the network your phone is attached to. This is something your chosen service provider must do to establish your service, regardless whether you wanted to port over an old number or were willing to accept an assignment of a new one.

This gives the phone companies the greatest internal flexibility, which is why they implemented it. For their needs. But WE subscribers pay for it, not by private company charges to our phone bills, where competition would work to bring about the best available price, but through legislatively mandated taxation, which works independent of market forces and where, years and decades now since implementation of this network function, we're STILL paying at a fixed rate; as though the supporting switch gear was just installed, and as if new switch gear today wasn't more feature-rich at a lower marginal cost like all other technology we buy.

The galling thing for me is that this is a capability that pre-existed the taxation, and was already necessarily factored into rate-structure for service. Because we foolishly allowed the government to make mandatory, a capability that from a technical standpoint was already available, we end up with a slightly less efficient and unreasonably more expensive system.


The book is not very deep, and aimed at curious individuals who know rather little about the field, and may have little interest in anything beyond acquiring a grand overview.

Curious and technically or mathematically adept people who are otherwise unaware of the field will gain entry points for followup to deeper learning.

I gather the authors were famous titans of comm technology's previous era. I found this a pleasantly easy reading introduction to the world of communications signals, with an early focus on the dawn of radio, and a later concentration on the development of telephone technology.

It's old enough that quite a lot has changed since the book was published. From the perspective of 1990, it's very interesting indeed to read the authors' forcasts for the future. Most of this turned out to be nearly spot-on. We have indeed gone almost entirely digital; optical fiber trunk lines are preferred both locally and internationally.

It's also interesting to read about past technologies that predated the wide adoption and development of internet services, that filled a niche and enjoyed some popularity in some countries for a while. Like videotext in the UK and France (especially France).

With videotext, the driver was a desire for interactivity with high-bandwidth content (video and graphics), but with only low-bandwidth channels available (analog modems). The solution there was to have the low-bandwidth channel control and high-bandwidth broadcast. You got some interactivity in the ability to select amongst a limited set of high-bandwidth object, essentially controlling your receiver to preset to you only the desired objects, and have the others coming over the TV broadcast filtered and discarded.

The future seems to be video-on-demand, delivered via the internet. And while access to fully interactive bandwidth has increased several orders of magnitude for most people, that bandwidth still is not yet wide enough in most cases for efficient service. E.g. it doesn't yet make sense to try to stream HD video content from a server direct to an end user device in most situations.

Yet with proliferation of smart cell-phones, etc., more people are coming to expect and demand access to high-bandwidth services beyond basic phone and low-bitrate web interactivity. They want to treat it like just another TV, and the devices themselves are capable of a good viewing experience, if only the content can be delivered.

We've made the internet work with high-bandwidth media by proliferating caching servers to disparate locations. I don't have data, but there might be more caching data centers online now than commercial broadcast TV transmitters.

In the future, we might want to re-examine neglected multicast technology as a means to get more service to more endpoints out of limited bandwidth channels.

This serves as an entry point into new realms of discussion, far afield from the book, so I end here.

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