Does WCDMA have 32km limit like GSM?

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Greg Alexander - 23 Sep 2004 15:07 GMT

Hi,
I remember reading that the UMTS-3G standard had multiple options for
it's voice and data traffic, in order to bring together 3 separate 2G
systems (including GSM, some japanese standard, and something else).

I use GSM now, but I've found that a CDMA phone works great on my boat
and in the hilly areas around the waterways.

What I'm wondering is if WCDMA shares the coverage characteristics of
GSM, or the characteristics of CDMA handsets (Of course, when the
WCDMA phone falls back to GSM it'll be GSM!). Does it use TDMA (and
have 32km limits?) or CDMA for the voice component?

Thanks for any help!
Greg

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John Navas - 23 Sep 2004 21:32 GMT

>I use GSM now, but I've found that a CDMA phone works great on my boat
>and in the hilly areas around the waterways.

I suspect that's more a matter of tower siting and configuration than of
technology. Here in the San Francisco Bay Area I get good GSM coverage both
on the Bay and for quite a few miles offshore.

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Best regards, HELP FOR CINGULAR GSM & SONY ERICSSON PHONES:
John Navas <http://navasgrp.home.att.net/#Cingular

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matt weber - 24 Sep 2004 02:29 GMT

>Hi,
>I remember reading that the UMTS-3G standard had multiple options for
[quoted text clipped - 11 lines]
>Thanks for any help!
>Greg

WCDMA has no hard distance limits. the 35km limit on GSM comes from
timing issues and need to keep the users in their time assigned slots.

Having said that, you are likely to find that the data rate is pretty
low at 32km from the base. The shannon theorem provides a relationship
between signal ratio, bandwidth and channel capacity. Very bluntly at
the 1 watt a hand held is allowed to put out, you aren't going to get
a broadband data rate at 32km...

TDMA and GSM are examples of Time Division multiple access technology,
they share the frequency, but don't transmit at the same time. CDMA
does, the signals are sorted by the spreading code. It is a digital
analog to synchronous detection. Think of the calculus problem
The intergral of Sin (theta t ) x Sine (alpha t) over time. Unless
alpha and theta are the same, it is zero. CDMA depends upon the fact
that all signal other than one you are interested in have on average,
zero power in the receiver circuit, and will appear as background
noise.

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Greg Alexander - 26 Sep 2004 16:17 GMT

> >What I'm wondering is if WCDMA shares the coverage characteristics of
> >GSM, or the characteristics of CDMA handsets (Of course, when the
> >WCDMA phone falls back to GSM it'll be GSM!). Does it use TDMA (and
> >have 32km limits?) or CDMA for the voice component?

> WCDMA has no hard distance limits. the 35km limit on GSM comes from
> timing issues and need to keep the users in their time assigned slots.
[quoted text clipped - 4 lines]
> the 1 watt a hand held is allowed to put out, you aren't going to get
> a broadband data rate at 32km...

Hi Matt,
Thanks for that. I think WCDMA might not be the go at the moment. I'd
be happy with a full car-phone kit instead of a handheld, but I
haven't seen that option for 3g phones (and I'm not sure if it'd help
much anyway!).

Thanks,
Greg

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