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Oh. Sorry.

TDMA: Time Division Multiple Access 3x Frequency Re-use CDMA: Code Division Multiple Access 20x Frequency Re-use

Refers, basically, to how cellular carriers squeeze multiple phones onto one “circuit” (which is actually a frequency/modulation). The difference is essentially describes how the economics of the business are mitigated by technology.

TDM essentially slices up the analog signal using Pulse Code Modulation from a bunch of phones and interleaves them with one another, and transmits the signal from each as barely perceptible chopped up bits of sound (as though you were talking to someone through a desk fan) expressed as Zeros and Ones.

CDM very simply encodes and then compresses (this is the key) the voice using a digital CODEC right on the phone and sends the signal over the network as Zeros and Ones. This increases the number of phones per frequency by 3x.

Thus CDM is more natively “digital” and better-suited to handling bursty data traffic like internet. And because there’s less bandwidth used on each frequency by any given handset, you get more bang for the buck. This increases the number of phones per frequency by 20x.

It’s basically like the difference between a CD and a DVD. Why can you get so much more data onto the same physical media with DVD? Compression!


At 10:30 AM 18/05/00 -0700, you wrote:>Ian wrote:
>”CDMA carriers will now be able to dance circles around the TDMA guys until
>TDMA guys implement WAP, which is more expensive on TDMA than on CDMA (for
>reasons which should be obvious).”
>—–Original Message—–
>From: Ian Andrew Bell [mailto:ian [at] cafe [dot] net]
>Sent: Wednesday, May 17, 2000 9:34 PM
>To: foib [at] ianbell [dot] com
>Subject: @F: AT&T Slammed on Wireless Data
>AT&T launched PocketNet a few days ago, which is CDPD-based. Sprint has
>been offering free WAP access for months now (I have a Sprint mobile now in
>the US) for free in some packages, with unrestricted web access.
>You can even surf to on your phone and it parses
>quite well into WAP!
>This Gartner report slams AT&T, and shows how companies that made the jump
>to digital networks early (and implemented crappy TDMA) are now going to
>pay the price for not really thinking through the notion of
>”Digital”. Because of the greater efficiencies and reduced costs, CDMA
>carriers will now be able to dance circles around the TDMA guys until the
>TDMA guys implement WAP, which is more expensive on TDMA than on CDMA (for
>reasons which should be obvious).
>Wednesday May 17 06:00 PM EDT
>Commentary: AT&T PocketNet–when “free” is still too expensive
>By Gartner Viewpoint, CNET
>See news story: AT&T Wireless offers free phone-based Net access
>By Robert Egan, Gartner Analyst
>As a competitive response to Sprint, AT&T’s effort falls short in several
>First, PocketNet is a far cry from the Sprint service today, or from other
>competitive wireless Internet services. For one, it limits people to 40
>selected sites (out of more than 100,000 wireless-friendly sites) unless
>they want to pay extra fees. Through an untested business plan, this
>”sticky” strategy may bring advertising and other revenue to AT&T and its
>business partners, but it needlessly restricts customer choice in a service
>that should be highly personalized.
>The “free” service includes access only to these selected sites and the
>customer’s “personal Web page.” In addition to wider Web access, email and
>fax service will cost customers from $6.99 to $14.99 over and above their
>regular airtime and other wireless charges. (To be clear about the term
>”free,” AT&T does charge for airtime while Internet services are used, as
>do Sprint and other wireless providers.)
>AT&T has been unable to attract equipment suppliers to build phones for its
>offering, so customers have only two models to choose from, whereas
>Sprint’s Internet service is supported on many more phones. This is in part
>a penance AT&T is paying for its decision to use TDMA (time division
>multiple access) technology, which is unsuited to data transmission,
>instead of the more modern, robust technology used by Sprint.
>The same constraint limits AT&T to markets that support the CDPD (cellular
>digital packet data) protocol, which covers only about half the United
>Therefore, the sheer numbers tip the balance toward Sprint:
>* Sprint’s more modern data protocols are supported by almost twice
> as many points of presence as AT&T’s.
>* Sprint offers 10 times the number of handset models that support
> its data services.
>* Sprint customers can access 3,000 times as many Web sites for the
> same (“free”) price.
>Gartner predicts that AT&T will not be able to fully benefit from the
>ongoing rapid expansion of wireless data services until it begins to more
>accurately meet its customers’ needs and modernizes its underlying
>technology, which will probably take until 2002.
>Entire contents, Copyright © 2000 Gartner Group, Inc. All rights reserved.
>The information contained herein represents Gartner’s initial commentary
>and analysis and has been obtained from sources believed to be reliable.
>Positions taken are subject to change as more information becomes available
>and further analysis is undertaken. Gartner disclaims all warranties as to
>the accuracy, completeness or adequacy of the information. Gartner shall
>have no liability for errors, omissions or inadequacies in the information
>contained herein or for interpretations thereof.