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Oops. Let me clarify: CDM = 20x, TDM = 3x.

AT&T and Rogers/Cantel use TDMA. Sprint, Telus, and most others use CDMA.


At 11:04 AM 18/05/00 -0700, Ian Andrew Bell wrote:

>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
>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
> >the
> >TDMA guys implement WAP, which is more expensive on TDMA than on CDMA (for
> >reasons which should be obvious).”
> >
> >Why?
> >
> >—–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).
> >
> >-Ian.
> >
> >—=—
> >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
> >ways.
> >
> >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
> >States.
> >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.
> >

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