Tom:

I just read an article at http://www.privateline.com/PCS/

mobilephonepictures.htm, which I assume you wrote. As far as I am aware, the last IMTS/MTS mobile system left in North America is run by Bell/Aliant Telecom in Newfoundland, Canada. This system is also slated to be de-commissioned in August of 2002, thereby ending a long history of this technology. In conversation with a past IMTS supplier, Glenayre, a few years ago, they indicated that the only other IMTS system that they were aware of still in operation was in Asia (Cambodia or somewhere). Naturally, I stand to be corrected on this info.

In Newfoundland, our mobile switch is a Glenayre GL1200 (6 side by side units) and the mobile units used were mostly a combination of Novatel VTR74, VTR84, and VTR2084 radios, Glenayre GL2020, 2040, 2021, and 4040 units. Being a landscape with some remote areas difficult to service with cellular, the old IMTS will be missed by some users.

Gerald Rose

Editor's note. You can read the paperwork Aliant filed to decommission this service by clicking here. It is in Word format.

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Tom:

The vocoders in cellular are quite different from those in the PSTN, so a big difference is to be expected. Voice quality was never the objective in going to digital. Capacity was the objective. Also, the error correction in digital cellular is speed sensitive, due to the different types of radio frequency fading that predominates at different speeds. Vocoders used in digital cellular (or PCS) are very different in their operation from the A/D conversion used in CDs. It is a predictive process, and intended to maximize the bandwidth efficiency rather than providing superb voice quality. . ."

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Tom:

We purchased Sprint PCS service to replace our land line long distance. During the month of February, we used the phone at home, almost always getting a signal -- but a very weak signal. So far in the month of March, we have not been able to get a signal at home. The phone does work if we move closer to a tower and it seem to be working the same as other identical phones on the same service. So I do not think the problem is with the phone. Because our signal was weak, I suspect that some variable has caused us to loose the signal. Sprint claims they do not have any equipment problems in the area. We have had a wide range of weather conditions in early march, cold, warm, cloudy, clear etc. But similar conditions in February. What variables could cause us to no longer get a signal?

Mark van der Hoek replies:

Loading will do it with CDMA. If they are borderline when the system is loaded at one level, more loading (more usage) could send them over the edge. Weather conditions could too. If he's in an area of the country where trees have leafed out during that time period, that could do it. I knew an engineer in Minneapolis who had two sets of system parameters, one for winter, one for summer. Each spring and fall he had to make the judgment as to when to switch the parameters. Or somebody may have built a building that is affecting the signal. Even if it's not a direct obstruction, it could affect the multipath patterns enough to ace him out.

Any of these things could push a borderline reception over the edge. Best thing to do is for him to continue to scream at Sprint. He laid his problem out clearly enough that even customer service people should be able to grasp it, but he'll have to be a squeaky wheel.

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