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Posted by Howard Eisenhauer on September 7, 2007, 7:31 pm
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On Fri, 7 Sep 2007 02:16:17 +0000 (UTC), johnl@iecc.com (John L)
wrote:
>>Unfortunately its not just a problem of power output, for the systems
>>using GSM there are also timing issues involved that limit the maximum
>>range to about 20 miles. I've been in situations where I've had
>>plenty of signal strength but couln't establish a call due to this
>>distance limitation.
>
>Good point. I hear that the GSM towers on the coast of Brittany in
>France make the TDMA slot size double width so people on ferries out
>in the channel can use them.
>
>R's,
>John
Yup, its called "half rate"- four timeslots/conversations per rf
channel instead of eight. The call quality dose'nt improve, the
regular CODEC remains in use, they just double the "cush space" for
incoming data bursts. Also used along remote highways but it's,
predictably, not as cost effective/profitable as "full rate" cells.
CDMA systems don't suffer from this so much, they have a pretty wide
timing window for the base reciever to lock onto & follow the mobiles
signal. On the other hand they do suffer from "The Mysterious
Shrinking Cell Site Syndrome". CDMA systems like everybody's signal
to arrive at the same level, to do this the systems commands
subscriber's phones to raise & lower thier output power so that the
base station receiver sees everybody the same. If there's someone
close in on a call who's phone's power output can't be commanded any
lower, & you're out in the boonies (with lottsa bars showing on your
screen) & your phone can't be commanded any higher, once the
difference reaches a critical level you'll be denied service. :(.
This can even happen during a call in progress :( :(
I miss my bagphone :(
H.
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