Aug 23 22:35 2002 from Mark 
Alrigth, here's my take: 
  - CDMA is a Spread Spectrum technique and protocol used by Qualcomm.  It 
 provides pretty darn good bitrate/signal strength ratios. That is, you 
can still get enough bits through with a weak signal to get an inteligible 
audio signal, and when the RF signal is good, you get more bits than other 
techniques which makes the audio quality better. 
  - TDMA (the technique) is actually used by a bunch of different  
protocols.  The protocol that we call TDMA is actually called IS-136.  It 
has a lower bitrate and therefore lower audio signal quality and higher 
latency than CDMA.  It's a North American thing, mainly.  It sucks and is 
being phased out. 
  - GSM uses a similar technique to TDMA (that is, its over the air  
protocol is a Time Division Multiple Access method, like IS-136), but its 
a totally different protocol.  I believe it achieves a better bitrate than 
IS-136, but not quite as good as CDMA.  It has pretty good audio quality, 
but a higher latency than CDMA.  It's used primarily in Europe, but is 
coming to North America (eg: Cingular).  In theory, your GSM phone will 
work "anywhere in the world." 
  - Nextel is another TDMA technology.  It's propritary (Motorola) and is  
only supported by the Nextel network.  It has spiffy features and some 
pretty good rate plans, but the audio quality isn't the best.  (I don't 
like it.  Doesn't deal well with dropped bits.) 
    
  Over-all opinion, In order of preference, I'd choose CDMA, GSM, Nextel,  
TDMA.  The only problem with this list is that TDMA is the only network 
with coverage at my house. 
    
  Now.  On to bands.  In the US, there are two bands in use: Cellular  
(800MHz) and PCS (1.9GHz.)  You as a user probably won't notice any 
difference other than coverage (PCS is relatively new and therefore not 
deployed everywhere.)  There also isn't any Analog on the PCS band, so if 
you have a PCS only phone, it can't fail-back to Analong (called AMPS.  I 
forgot to add it to the list above.) 
    
  A phone that claims to be Tri-Mode is actually: Cellular/AMPS,  
Cellular/Digital, PCS/Digital (where Digital is one of the above 
techniques.)  I haven't seen any phones that do (for example) both GSM and 
CDMA.  They may exist, but I haven't seen them.  There maybe licencing 
problems with doing that, I don't know.  The important thing is that a 
Tri-Mode phone won't get you coverage for more than one digital 
technology.  (Unless there's a phone out there I'm not familiar with.)