IP: an interesting note on what is PCS really (from Telecom

[David Farber <farber@cis.upenn.edu>]

From: hbaker@netcom.com (Henry Baker)
Subject: Re: Which of the New "PCS" Carriers Really Uses PCS?
Date: Sun, 22 Jun 1997 01:09:14 GMT




In article <telecom17.158.2@telecom-digest.org>, grendel6@ix.netcom.
com wrote:


> Can someone out there (with more patience than I) PLEASE explain whether
> the Sprint Spectrum service here is "real" PCS (like in D.C.) or just
> juiced-up cellular?  Since S/S isn't talking about the technical aspects
> of its service, I assume that they probably AREN'T cutting edge.


It depends upon your definition of "PCS".  One definition of PCS is that
it utilizes 1.9 GHz, while another definition is that it uses digital +
a number of additional features like caller id, short messages, etc.


So far as I know, there are at least three bands:


Nextel is in its own part of the band with push2talk mobile radios
Analog cellular (A & B) is in its own 900 MHz band
"PCS" cellular is in the 1.9GHz band


There are at least four types of modulation:


analog FM (like A&B cellular)
"American" TDMA (includes Nextel's hacked up version) ("American" is my term)
GSM (also TDMA, but is usually considered different from American TDMA)
CDMA (Qualcomm, etc.)


There are a number of voice encoders:


analog (can be almost wireline sometimes)
8 khz GSM (so-called "half-rate") -- relatively poor quality
14 khz GSM (so-called "full-rate") -- better voice quality
14 khz GSM (so-called "enhanced full-rate") -- best voice quality
14 khz CDMA -- about equal to GSM enhanced full-rate quality


The confusion really reigns because Sprint is CDMA with the single
exception of Wash DC, which is GSM.  I think that all of Sprint is 1.9
GHz.


I think that Sprint in DC uses 14khz full-rate GSM, while Pacbell in
Cal uses _enhanced_ full-rate (14khz) voice encoders.  Thus, the voice
quality of pacbell phones should be a bit better than Sprint DC GSM
phones.


Most of the GSM services offer enhanced services, because this is
software that has long been working at 900MHz outside the US.  The
CDMA services and the TDMA services will offer essentially similar
capabilities.  Even the analog cellular people have gotten with the
program, and want to provide short messages, caller id, etc.


The major advantage for digital is better privacy, although unless you
get the best voice encoder systems, you give up a lot in voice
quality.


Oh, and by the way, you'll have a heck of a time finding out the above
information by consulting the various providers' web sites.  They seem to
not want anyone to really know what is going on.  The best place to learn
is to consult some of the trade rags.




[TELECOM Digest Editor's Note: Actually the best place to learn what
is going on is to read this Digest on a regular basis. <grin>  PAT]




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