We got an unexpected rain storm in West Sacramento yesterday. It promptly caused power outages and the cable television system to break down. Speaking of breaking down, I am amazed with the difference between the voice and data networks the telephone company maintains. Here in SBC land, an outage to the voice network of several hours, whether wireless or wireline would be completely unacceptable, yet a data network they maintain goes down frequently without explanation or apology.

The public switched telephone network has always measured outages in minutes or seconds per year, yet with SBC's DSL network, well, the system goes off line for hours at a time.Why don't they have backup procedures installed for this service? Like redundant servers and routers? I understand other telcos across the country have similar problems. It's odd that as we march into the new century, with better and better technologies, that the quality of the telco networks is decreasing, not increasing.

I'm not sure what this will mean in the future, as services and businesses become more and more dependent on the internet and data com. Will we have to provide a backup system ourselves? So that if Pac Bell goes off line I connect to a cable modem, satellite, or other wireless service to keep my business on the net? This hasn't been needed in the past but I can see where it might be needed in the future. How odd.

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I've just posted small sketches of different transmission and switching schemes (internal link). See if they make any sense. :-)

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It might seem easy to compare the growth of the original, wired telephone network to the growth of wireless networks but that isn't the case. Cellular was possible only because a wired telephone network was already in place. Cellular would never have grown the way it did if no connection to the PSTN did not exist, all you would have is a business radio system or citizens' band radio, point to point communications, mobile to mobile customers, all operating within a small geographical area. Useful, but how could it grow beyond a certain point? So to compare the last 17 years of growth in commercial cellular to something else you might contrast it with other services offered during that time, like caller ID, call forwarding, three way calling, and so on. How many people signed up for those services compared to the installed telephone base? Then, how many people signed up for wireless during that time?

The problem is that these services are so dissimilar, and of such varying utility, that comparisons might not teach you anything. It might be more instructive to reach back to the Citizens' Band radio craze of the mid 1970's, to see how many radios were sold within just a few short years, that is, comparing the growth of personal communications back then and now. C.B. radios were wildly popular although they didn't connect to the telephone system unless someone manually patched a call. I've read Bell Labs literature stating that one in ten American vehicles had a two way radio during these years, why wireless folks were surprised by the growth in cellular I do not know. One reason of course was cost, with C.B. radios available at less than a hundred dollars, while cellular radios were well over a thousand. Too many things to research!

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Saw yet another article on how wireless promoters have over promised cellular and that people continue to be mad over the most basic problem, dropped calls. You cannot build out a cellular network, possibly at any price, so much that it will not drop calls. Years ago I read the obvious in The Ericsson Review: developers and wireless carriers needed to allow for dropped calls since broken connections are inevitable in a wireless world. So if you were downloading a file from the office and your call was dropped, well, once back in range the call would connect again and the file would resume downloading at the point it stopped. Let's hope the wireless community spends more money on continuity since they can't guarantee connectivity.

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Modulation is the way we shape a radio wave. Transmission is the way we send information over that shaped radio wave. Huh? Just musing as I revise the digital wireless basics and the cellular telephone basics series. Can't believe how many corrections and additions are necessary. I'm also putting in links to .pdf files of book chapters and pages that may help you understand the subjects I'm discussing better. This may all sound dry but it is standard web site work. My goal is to have helpful .pdf files on each page of my major series; much nicer than links to other web sites which too soon disappear and leave you with a "file not found error" when you click on them. I hate those 404s! Oh, when do you think the cellular radio idea first appeared in print? I say 1945. Check out my reasons at this page and feel free to tell me if you think I'm not correct.

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Download this chapter in .pdf from Professor Noll's Introduction to Telephone Systems. And for a fascinating look at communicating with lasers, on a budget, click here.

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