TDMA, CDMA & GSM

[Michael Hayworth]

We currently have AT&T Wireless Digital PCS cellular phones. Their digital
service is horrible. The absolute pits. So much so that their support line
techs have learned to tell people how to set their dual-mode phones to
analog, so that they can actually keep calls connected.

After researching this a little bit, I discovered that AT&T uses TDMA
technology, which I understand is inferior to CDMA technology (though, of
course, AT&T has lengthy arguments for why this isn't true). But I also
understand that most European cellular is GSM.

I mostly understand the differences between TDMA and CDMA. I'm not sure I
understand the differences between those and GSM. I do note that Motorola
has at least one GSM phone in their "US Products" section, so I'm assuming
that someone here in the US also uses GSM. Who would that be?

Of the competing digital alternatives in my area, does anyone know what
technology is used by:
1. Primeco
2. Sprint PCS
3. Nextel

Thanks,

Michael Hayworth

[Ryan Tucker]

On Thu, 30 Apr 1998 09:56:56 -0500, Michael Hayworth <ms...@airmail.net>
spewed:

>I mostly understand the differences between TDMA and CDMA. I'm not sure I
>understand the differences between those and GSM. I do note that Motorola
>has at least one GSM phone in their "US Products" section, so I'm assuming
>that someone here in the US also uses GSM. Who would that be?

GSM is more of a "holistic" standard, which has a large amount of features
for authentication, messenging, call handling, and such over a TDMA air
interface. It's actually much better than TDMA alone, at least in my
experience.

It's used by quite a few carriers in the US... my carrier is VoiceStream,
who covers chunks of the US west of the Mississippi.

>Of the competing digital alternatives in my area, does anyone know what
>technology is used by:
>1. Primeco

CDMA

>2. Sprint PCS

CDMA

>3. Nextel

iDEN

Standard recommendations about using someone other than a wireline or long
distance phone company for your wireless service apply. :-) -rt

--
Ryan Tucker <rtu...@ttgcitn.com> http://www.ttgcitn.com/~rtucker/
UIN: 1976881 VM/Fax: +15157712865 Box 57083, Pleasant Hill IA 50317
If you think the problem is bad now, just wait until we've solved it.
-- Arthur Kasspe

[Roy]

Jeffrey Rhodes wrote:
>
< Most CDMA cellphones can't
> switch to analog unless you pay roaming charges.

LIE

Stay as far away from TDMA as you can and AT&T in particular.

[Rhodes]

Roy wrote in message <35494272...@garlic.com>...

>Jeffrey Rhodes wrote:
>>
>< Most CDMA cellphones can't
>> switch to analog unless you pay roaming charges.
>
>LIE
>

Maybe I got that one wrong. AT&T Wireless Services Digital PCS tri-mode
cellphones at PCS frequencies may have this problem in some areas of the US.

regards, jcr

[Jeffrey Rhodes]

Michael Hayworth wrote:
>
> We currently have AT&T Wireless Digital PCS cellular phones. Their digital
> service is horrible. The absolute pits. So much so that their support line
> techs have learned to tell people how to set their dual-mode phones to
> analog, so that they can actually keep calls connected.
>

Michael,

Let me guess, you use your cellphone mostly in one or two locations.
Maybe you will find another carrier whose cellsites are placed and tuned
more favorable to you, maybe not. For any carrier, there will always be
someone like you who falls into that carrier's RF coverage near gaps.
Churn around between carriers if you like, but don't base your decision
on which digital technology is reputedly the best. How the digital
technology is implemented is more important. Most CDMA cellphones can't

switch to analog unless you pay roaming charges.

GSM and Nextel use TDMA. CDMA has no current data capability. None of
these digital techniques use the IS-136 digital control channel which is
what makes AT&T Wireless Digital PCS the best choice for users who
require business class mobility within the largest RF footprint in North
America. Global roaming is possible via a GSM gateway. Remember, AT&T
Wireless has attracted more subscribers in North America than any other
carrier, not by offering the lowest prices, but by earning a quality
reputation with competitive prices that reflect value.

If you bought a cellular/PCS phone to replace your cordless phone, then
I don't expect you to value the synergies of IS-136. Someday AT&T
Wireless may be able to offer you a home base station that will suit
your needs better. If you truly value mobility, for communications
anytime, anyplace, then I think you will discover that digital
communications vary with location.

Jeffrey Rhodes at jeffrey...@attws.com

[Eagleeye57]

In article
<FAA3005BA69B08F8.1A3BF386...@library-proxy.airnews.net>,
"Michael Hayworth" <ms...@airmail.net> writes:

>We currently have AT&T Wireless Digital PCS cellular phones. Their digital
>service is horrible. The absolute pits. So much so that their support line
>techs have learned to tell people how to set their dual-mode phones to
>analog, so that they can actually keep calls connected.
>

>After researching this a little bit, I discovered that AT&T uses TDMA
>technology, which I understand is inferior to CDMA technology (though, of
>course, AT&T has lengthy arguments for why this isn't true). But I also
>understand that most European cellular is GSM.
>

>I mostly understand the differences between TDMA and CDMA. I'm not sure I
>understand the differences between those and GSM. I do note that Motorola
>has at least one GSM phone in their "US Products" section, so I'm assuming
>that someone here in the US also uses GSM. Who would that be?

I just bought my wife a PacBell GSM phone ( Motorola 2000e). This is TDMA, but
I understand that they use a better vocoder than European GSM. When she calls
me from the mobile, it's pretty hard to tell that she's not on a landline.

Someone in my company just got a PacBell phone, and he says that the coverage
is better than both Nextel and the analog carriers we've been using.

>Of the competing digital alternatives in my area, does anyone know what
>technology is used by:
>1. Primeco

CDMA, I think, but not 100% sure on that.

>2. Sprint PCS

CDMA. 2 people I know have Sprint PCS phones (Samsung). The phone is nice &
light, and they have some pretty good plans for high volume users, but every
time I talk to them on them, they seem to get cut off. The voice doesn't sound
nearly as good to my ear as my wife's PacBell phone.

>3. Nextel

TDMA. We have a bunch of these at my company. We get a lot of complaints
about coverage here in the L.A. area, and voice quality is probably on a par
with Sprint. The 2-way radio feature though, is fantastic. If you have a use
for it, this can be a very effective and inexpensive way of communicating.

I am well aware of all of the issues regarding CDMA vs. TDMA. On a technical
basis, I know that CDMA is probably superior to TDMA. At the same time though,
there were several isuses I had to consider when buying my wife a phone.
Though roaming is more expensive with Pacbell, we don't expect to do much
travelling. The basic rate of $20 per month gets me 30 anytime minutes, and
500 weekend minutes. You also get numeric paging, caller-id & voice mail.
Can't beat that for such a low priced plan, and the phone was only $50 after
rebate. And you only have to sign for a year.

Technical superiority is only part of the equation. It seems to me that Pac
Bell has done a very good job of utilizing GSM/TDMA technology to create a high
quality service. TDMA vs. CDMA is really not the issue - it's how you use the
technology to build a network.

In my case, Pac Bell was cheaper based on our usage pattern, and at the same
time, I've been very pleased with the quality of the service.

[Bill Walker]

In article <3548AF...@attws.com>, jeffrey...@attws.com wrote:
[...]

> Most CDMA cellphones can't
> switch to analog unless you pay roaming charges.

[...]

Let's clarify this: most 1900 MHz CDMA/800 MHz analog dual-band PCS
phones can't switch to analog unless you pay roaming charges (carriers
using this type of phone include Sprint PCS and PrimeCo), but 800 MHz
CDMA/analog dual-mode cellular phones can switch to analog on their home
networks without paying roaming charges (carriers using this type of phone
include Airtouch, Ameritech, Bell Atlantic, and GTE). And even in the
1900/800 case, it's a business issue, not a technical one.

----------------------------------------------
Bill Walker, QUALCOMM, Inc., San Diego, CA USA
Bill_...@qualcomm.com
Support the anti-spam amendment. Join at <http://www.cauce.org/>

[Jeffrey Rhodes]

Yes, all TDMA 1900MHz cellphones are susceptible to the same business
issue with respect to analog roaming. IS-136 TDMA 1900MHz cellphones may
be able to select Digital PCS at 800MHz to get a better roaming rate.

What, no tri-mode CDMA cellphone? AT&T Wireless Services Digital PCS has
an intelligent roaming capability within IS-136 to select the *right*
frequency that can result in the least roaming charges. That way my
tri-mode IS-136 cellphone can select AWS at 1900MHz in Atlanta or 800MHz
in Seattle.

Are CDMA cellphones unable to use CDMA at different frequencies?

regards, jcr

[John]

Jeffrey Rhodes wrote in message <3548AF...@attws.com>...

>Michael Hayworth wrote:
>>
>> We currently have AT&T Wireless Digital PCS cellular phones. Their
digital
>> service is horrible. The absolute pits. So much so that their support
line
>> techs have learned to tell people how to set their dual-mode phones to
>> analog, so that they can actually keep calls connected.
>>
>

>Most CDMA cellphones can't switch to analog unless you pay >roaming
charges.

Where did you ever hear this?

The technology (CDMA) allows switching to analog and back if implemented
within the same cellular system or same type of technology (traditional
cellular for instance).

The confusion factor has been introduced with the advent of PCS Cellular
(2GHz frequency band) and the desire by the old cellular companies to appear
(at least) to be on top of the technology ladder.

Even though the CDMA technology is basically the same in both the 800MHz
band and the 2GHz band, the difference in the cellular companies is
tremendous.

The "traditional" cellular companies have a built in analog infrastructure
that allows them to switch as the customer goes from one part of their
system to the other and cell site capabilities change. My wife has SBMS
service and although digital is definatly available in the Dallas area,
where I live (some 75 miles outside of Dallas but still part of the same
system) no digital service is offered. She has no problem driving from
Dallas all the way home and carrying on a conversation with the phone and
the cellular company switching her from digital to analog along the way.

On the other hand, I have Sprint PCS service and when I go from Sprint's
digital service to a roaming situation with SBMS, I am dropped and have to
re-initiate the call. Not only does Sprint NOT have an analog system to
switch me to they do not have the equivlant of IS-41 and it's derivitives to
cause the hand off with the other carrier.

[John]

Jeffrey Rhodes wrote in message <354A5D...@attws.com>...

>Are CDMA cellphones unable to use CDMA at different >frequencies?

Currently PCS CDMA cell phones can't.