Re: IMTS vs MTS was 1965 mobile phone on "Get Smart" [telecom]

hancock4@xxxxxxxxxxxx wrote:
Today many public safety units are converting to digital radios from
analog. However, there have been many newspaper reports of digital
radios failing in critical situations due to dead spots, apparently a
digital signal is harder to receive than the older analog signals.

I'm guessing that this has more to do with the frequencies typically used for
a given type of signal and not specifically analog vs. digital. The older
analog channels - which operated at lower frequencies - propagated better in
city environments than devices built to use recently-available higher
frequencies. I also believe that this is part of the reason why the
government wants some of the relatively low (by today's standards)
frequencies from analog television broadcasts for public safety use.

There may also be issues of capacity, where a sufficient number of responders
using all the different 'trunks' fill the available bandwidth.

I'm not sure what the advtg of digital over analog is in public safety
applications (saving bandwidth?). But one capabiltiy lacking today is
optional common channels between police, fire, and rescue which often
work on isolated networks. That is, a policeman can't communicate
with a fireman, rather, he has to relay messages through the
dispatchers.

Yes, they're looking for more bandwidth (or, more specifically, more virtual
channels in a digital stream than they could have fit frequency-based
physical channels in the band available before. And, yet, in retrospect it
seems obvious that having all these responders on different channels can be a
disadvantage when co-ordinating responses to larger events and potentially
dangerous if, say, firefighters can't tell ambulance attendants that a
building is about to collapse.

If I recall correctly, some of these devices have the ability to switch to
other services' channels, and perhaps some even have the ability to tap into
multiple (all?) channels simultaneously. This would be extremely useful in
the "get out, the building's coming down!" scenario.

I can't help but wonder if the old Bell Labs of the Bell System was
still in full strength that R&D in this field, particularly in
applying a sound technology, the state of the art would be improved.
Bell Labs took time to develop new technology, but they tested the
heck out of everything in actual service and debugged it accordingly.

I believe that you hit the nail on the head in the latter half of that
paragraph: there's no shortage of bright people working on leading edge
technology but it feels like the results are often brought to market
half-baked, slapped together as quickly and as cheaply as possible with
little regard to quality, usability, versatility, durability, and a whole lot
of other descriptive words we wish we could use more often. Business
considerations, usually driven by the need for short term financial gains,
seem to dominate the technology development field.

--

Geoffrey Welsh <Geoffrey [dot] Welsh [at] bigfoot [dot] com>


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