In article <463a6fc6$0$16267$88260bb3@free.teranews.com>,
Todd Allcock <elecconnec@AmericaOnLine.com> wrote:
>At 03 May 2007 14:46:22 -0500 Todd H. wrote:
>
>> FWIW, none of my Cingular TDMA phones did the gallopy thing.
>>
>> Well, except for the GAIT phone I had, which was TMDA, GSM, and AMPS,
>> with which came a change to the GSM based network as primary.
>
>
>IIRC, however, my TDMA phones made a different noise through my PC
>speakers (but far less often- I wonder if the TDMA system was less
>"concerned" with keeping up with who was camping on the network than GSM
>is. In fact, now that I think of it, my TDMA phones didn't "chatter"
>over the speakers until they received a call (ironically, therefore, my
>PC would "ring" before the phone did!)
>
>
>--
>Posted via a free Usenet account from http://www.teranews.com
>
Date: 11 Mar 94 21:34:21 EST
From: Stewart Fist <100033.2...@CompuServe.COM>
Subject: GSM and TDMA Problems
John Sims <j...@fs.com.au> asks about the problems with GSM.
They are pretty much the same as with all TDMA systems, including the
TDMA now being introduced into the USA -- and they'll be worse with
DECT and DCS1800 which are designed to be used indoors in large
offices.
You can look at these problems in a number of different ways and at a
number of different levels. The primary problem is that they were
introduced in competition to perfectly good analog cellular networks,
and they failed to provide any real customer advantages. A system
needs to be better than the one it replaces. The magical name
'digital' doesn't carry much weight with customers after a while.
Coverage area is another major problem, and here the American TDMA has
a better solution than GSM because it emphasised dual-mode handsets
with analog providing coverage where digital wasn't available. GSM
didn't do this, so in most nations with the system (except Germany)
you are limited to a very small coverage area, and a very limited
range of base-stations, often with minimal equipment, and with great
holes in the cells. Drop outs on the Sydney GSM networks seem to
range between 40% and up to 80% for a car crossing the city.
Sound quality in all digital systems seems to be consistent, but only
'acceptable'. While good static-free reception extends to the
boundaries of the cell, they do all suffer from a staccato-like effect
when driving down tree-line corridors (especially after dew or rain)
and they drop the link precipitously, without warning, at the
boundary. This is not how consumers think a phone system should
behave.
Within buildings, they have many more penetration and Rayleigh-fading
problems than analog also. Range of a GSM cell, at present is limited
to 35kms, which is too small for Australia, but this will be fixed in
1996 by slot-stealing.
GSM and TDMA base stations also need to radiate from higher points for
good coverage, but if they do that, they then interfere with other
cells. Capacity is set by the amount of general R/F interference
being introduced, and generally they seem to be only getting two to
three-times that of AMPS.
International roaming was the big story behind GSM, and it is
certainly important to 2% of European owners who daily drive across
the Continent. However AMPS is a far better system if an Australian
wants International roaming, because it is used in New Zealand,
Australia, most of Asia, and the America's. What we needed for good
international roaming was a dual-mode AMPS/TACS handset (and the
difference is really only in the R/F stage, so this would have been
easy to do).
The main problems are the R/F interference effects, and these are
common to all TDMA systems (including the new DECT and DCS-1800) and
they are cumulative -- so we see only a few signs of the problems now,
but like automobile pollution growth in cities, it will get worse as
the population of users grows. There are four main problems here:
1. General R/F pollution. Any system that switches its R/F
transmitter on and off rapidly (GSM does it 217 times a second, TDMA
does it 50 times) will scatter EMI throughout the adjacent radio
spectrum. And the sharper the edge of the switch power (on and off),
the wider the band of hash it scatters. These sets need a 3-5MHz
guard-band between them and analog AMPS channels,and they try to ramp
up the power, and still they scatter crap into nearby television
broadcast bands. We've never had anything that generates EMI like a
GSM handset before in these bands. We need large numbers of them like
we need a hole in the head.
2. Audio-Hz interference. The on-off cycle of transmission power will
be read by any analog circuit nearby (with any rectification or
asymmetrical circuits) as an intrusive audio tone of 217Hz, and the
two major harmonics above. This buzz intrudes into hearing aids at
distances up to 30 metres, and is often intolerable at 2 metres. It
also gets into cassette recorder, wireline systems, and into modems as
a carrier tone.
3. Digital byte intrusions. In digital circuits, where the track on a
circuit board is about the length of a GSM antenna, the on-off cycle
of transmission power is often being read as a data-byte. If only one
GSM handset is operating in a vicinity, it will pulse in the first (of
eight) slots in a frame, and so produce a 1000 0000 byte at 217 bytes
(1736 bits) a second. This can also be read as 1100 0000, 0000 0000
at 3.4kbit/s, or 1110 0000 etc. at 5.2kbit/s (and so on).
When two or more handsets are working in the same location, they are
all synchronised to the same base-station (same or different
channels). So amplitude effects (same slot, different channels) are
cumulative: the fact that they may be using different channels is
immaterial, so the range of interference can increase. A number of
handsets will combine to create what amounts to random number
generation (they are also frequency hopping) of power pulses in
digital control circuits nearby.
This seems to hit some electronic equipment (laserprinters, modems,
PCs, TV controllers, possibly air-bag triggers) hard, and have wierd,
and often un-reproducable effects. The randomness seems to be the
problem in detecting what caused some 'event'. It is virtually
impossible to reproduce the conditions.
This is why some people report no problems at all, others say it
knocks out their Powerbook or modem or multiplexer, occasionally, or
every time. Obviously some equipment is far more susceptible than
others -- but not just in terms of needing EMI shielding.
4. The last EMI problems is the remote possibility (and I stress
'remote possibility') that the pulsation of the microwaves can create
a different type, or order, of health problems to analog. Analog is
expected to only have a 'brain and eye-lens' heating effect (but not
everyone is convinced about this).
Digital TDMA introduces a new factor. It is known for instance, that
some enzyme reactions in chemical processes are sped up enormously
when hit by pulsating R/F, but no one seems to know why. This needs a
lot more research, but is no reason for panic. However, it can't be
dismissed, like may technophiles seem to do.
The real problem with both GSM and American TDMA is the way in which
all these problems were kept secret, and the systems were rolled out
slowly and quietly without anyone admitting problems until the press
started shouting. When they play these sorts of games, they have only
themselves to blame when the press reacts strongly and shouts 'foul'
especially when it is likely to be hearing-impaired people who suffer
in office environments.
Later, problems were reluctantly admitted, but always the admission
was associated with "Don't worry, well fix it!" which is just another
of their lies. Most of these problems are intrinsic in time-division
power pulsing.
More recently the tactic has changed once again: now they blame the
lack of shielding on hearing-aids and other electronic equipment, and
want to boost the standard of immunity, rather than reduce their own
emissions.
It's the smoke-stack blaming inefficiencies in gas-masks for the
problems. ETSI is its own worst enemy.
You Tube Video on Cingular/AT&T Speaker Destruction Issue 
Linear Mode
