> ... I've spoken to people in ETSI who say
>that W-CDMA has 20-30 times more capacity, MHz for MHz, than GSM.
Oh really ? Well, they must have eaten some of those magic mushrooms they
sell in Shibuya on the sidewalk. Not even Qualcomm (CDMA patent owners) are
making any claims that bold anymore. These days if Qualcomm claims anything
above 3 times more spectrum efficiency for CDMA over TDMA based GSM, even
the CDMA friendly engineers call them biased.
>3G voice at 64 Kbits/sec v. GSM voice at 9.6 Kbits/sec works out at
>five-six times more space.
I think you are mixing up a few things here. CDMA voice channels are
variable up to 19.2K and GSM voice channels are 14.4K. Yet most US users
who have been using both technologies agree that GSM overall sounds better
for it's not only the bandwidth but echo cancellation, codecs and other
implementation dependent factors that matter.
Besides, WCDMA was chosen as air interface for 3G not because of voice
capacity but because of data capacity. Data is the only field where WCDMA
really shines over TDMA. In any other field the pros and cons balance each
other out and there is no clear advantage to use one system over the other
from a technology viewpoint.
Major disadvantage of CDMA is that quality degrades with the number of
users on a given cell. This is fine with data as it will simply reduce the
bandwidth per user, but it is very unclear what will happen when this shows
up on voice services. PHS has the best voice quality of any wireless system
in use, but early implementations were such that calls dropped all the
time, and that degradation of quality in the service has caused the numbers
to drop from about 8m (peak) to now 5.7m.
People don't like degradation of quality when it comes to voice.
As far as building up capacity for more users is concerned, the main
reasons why 3G will have more of it are:
- more spectrum
- microcell deployment
Now, that is neither specific to 3G nor to CDMA. More spectrum could have
been allocated to existing network technology such as GSM and micro-cells
are being deployed today for 2G networks in major cities with very high
population density.
>In reality, though, you can do a number of things with that capacity. You
>*can* do mobile data, at up to 384 Kbits/sec real-world. While not many
>applications need that much, 3G is also the only technology that can deliver
>even 64 Kbits/sec - EDGE will not be deployed in Europe and GPRS will only
>very rarely go above 3 times slots in practice: with most operators saying
>they'll only deploy CS2, that comes to a realistic max of 40 Kbits/sec or so
>(in theory).
Again, you are mixing up a few things here too. EDGE has been dropped by
most operators in Europe in favour of 3G, true. But that doesn't mean that
3G is the only technology available that can deliver 64K data. Quite the
opposite is the case. 3G is only available to 4000 odd people in Japan and
a 1000 or so in the Isle of Man, that's 5000 to whom 3G is available right
now. On the other hand EDGE is being commercially used in Japan by KDDI's
PHS network which has 3.6m users, not even mentioning deployment of EDGE in
the US.
That makes EDGE and 64K data at least 900 times more available than 3G data
at any rate.
On the other hand it is expected that EDGE will be deployed by those
networks in Europe who did not get a 3G license and now even by those who
might run out of cash as a result of foolishly overspending on 3G licenses.
Also, EDGE is expected to be widely deployed in the US where the 3G
spectrum has yet to be freed from other occupants and will therefore have
an even later start or may never happen at all.
Also, EDGE is proven technology that works in a commercial context
successfully today. 3G has yet to get there, at this stage 3G is only
experimental. It is therefore simply and outrightly wrong to claim that 3G
is the only technology available that can deliver 64K. It's not the only
one - It's not available yet - and it is not even stable to deliver 64K all
the time yet.
>But from operators' point of view, just as in Japan, 3G is really all about
>voice capcity, at least for the first four or five years.
In Japan yes, in Europe and the US *no*.
> GSM (like PDC) is now effectively full.
PDC yes, GSM *no*.
Keep in mind that PDC, while using the same principle (TDMA) is not
anywhere as spectrum efficient as GSM. GSM has 8 time slots per radio
channel, while PDC has only three. PDC is more like IS54/IS136 in the US,
less like GSM.
> For the leading operators, it is now becoming cheaper
>to deploy 3G (including the licence) than to continue trying to cram more
>capacity into a technology designed for a tenth as many customers - while
>foregoing the additional revenues coming from traffic that GSM simply can't
>carry.
Again, you are quoting 3G hype, which is outrightly wrong. Repeating it
over and over again won't make it anymore true. Fact is that the financial
markets simply don't buy this propaganda anymore which is why the money
supply for cellular companies got tight. And those guys do a lot of
analysis before they throw money at something these days.
The fact remains that CDMA (and 3G with it) is one of the most expensive
technologies around even without the license cost (for various reasons)
while the economy of scale technologies (GSM and PHS) are the most cost
effective ones available. Last time I had to do with this sort of thing a
couple of years ago, a CDMA basestation was a whopping 500K USD, a GSM base
station 150K USD and a PHS base station a few thousand USD. On top of that
3G requires far more base stations than GSM does. So, multiply those
figures by the number of base stations needed to roll-out a network and you
wouldn't repeat that Qualcomm advertising so mindlessly at least not if it
was your investment that pays for the network.
The general observation is that what CDMA really gains in capacity (that
which hasn't been made up for by advance in GSM and TDMA technology) is
then more than compensated for by the reduced cost of economies of scale of
GSM (and PHS).
>Wher will this extra traffic come from? What we're now seeing across Europe
>is migration of voice traffic off fixed networks onto mobile networks. GSM
>can't handle that - 3G can.
Yet another 3G myth. GSM, allocated only a fraction of the extra spectrum
allocated now for 3G, would be able to handle all the voice traffic you can
possibly think of. Deployment of microcells in high population density
areas is upping capacity without any extra spectrum and advances in
adaptive antenna array and shift phase modulation technology can do the
trick as well.
Public PHS in Japan is dimensioned for 30 million users. This was the
forecast for 2020 in 1994 - don't laugh at it just yet, because they also
forecasted 6m for 2000 in 1994 and that was pretty accurate. PHS with it's
dynamic channel allocation and spectrum shared by all the networks in
combination with microcell architecture make it the most spectrum efficient
technology deployed today.
There are plenty of alternatives to 3G - and most of those alternatives are
far more cost effective than 3G. As I said in my previous post, the only
reason for 3G is that the industry got a bit drunk of their overwhelming
GSM success, felt invincible and reached for the stars. Now, as more and
more people are sobering up it becomes apparent that 3G isn't necessarily
the best thing to throw money at.
>Incidentally, PHS wasn't rejected because it competed with DECT! DECT was
>rejected too!
I wasn't talking about public PHS at all. I was talking about cordless.
>Why would I buy a cordless phone when I can get a proper mobile?
The idea was to have a mobile/cordless hybrid phone that automatically
"roams" between public networks (GSM) when you are on the road and
"private" networks (home base station, office base stations) when you are
inside.
For that the Europeans adopted DECT as a standard and the cost of DECT is
so outrageous (because it hasn't got the economies of scale GSM or PHS
have) that only very few applications justify the cost for a hybrid
handset. The only serious user of that hybrid GSM/DECT technology today is
the military, they can afford to spend 2 or 3000 dollars on the outfit, but
only because it comes with end-to-end voice encryption.
However, the idea is still sound and it has therefore made its way into 4G.
The example of PHS in Japan, and also DoCoMo's Doccimo service shows that
the concept of hybrid wireless/cordless for outdoors/indoors usage is
valid. Unlike video telephony and downloading video clips onto a phone,
this is an application that has a *sustained* demand. Unlike video
telephony and downloading video clips it is also an application that is
equally valuable for home *and* office use.
What I was hinting at was that if Europe was to revive that hybrid concept
and choose PHS for the cordless side, then the economies of scale of PHS
would guarantee a cheap hybrid GSM/PHS solution that would more likely
appeal to users so that they buy new handsets (and home base stations, too)
than 3G will. It may also coerce cordless only buyers who haven't lgot a
mobile yet into buying a hybrid and go wireless moving the saturation limit
further up a bit.
My father, for example, uses his prepaid mobile only when he is spending
the day in his garden-shed in a city garden colony. Any other time the
mobile is switched off and often he has to search a number of drawers
before he even finds his mobile. Give him a cheap wireless/cordless hybrid
phone and he would use the mobile more regularly. With mobile penetration
reaching saturation now, the remaining non-users are likely to have a phone
usage pattern similar to my father.
Hybrid wireless/cordless would also be helpful to deploy office and home
based high speed mobile data via the cordless side (i.e. PHS). This would
be far more cost effective than 3G, once because of economies of scale and
twice because it only needs to be deployed where it is needed. The fact is
in most places you don't need high bandwidth.
The fact that Japan and a few other countries have public PHS only
increases the possibilities but isn't really essential. Although, it would
be a likely bestseller if you'd be able to roam with a hybrid GSM/PHS
handset between Japan and the rest of the world. It remains to be seen
whether 3G can deliver roaming as advertised, because Europe is likely to
delay 3G deployment and DoCoMo's 3G is being rolled-out while the 3GPP
standards are still being amended, causing DoCoMo's network to be
incompatible enough to make roaming difficult again, just as bad as the
KDDI roaming solution that requires a special handset and is often only one
way etc etc etc.
As far as fast data goes, it is more likely that this market will be taken
by WLAN and 3G will be too late for it. WLAN is yet another 3G alternative
that is again far more cost effective and it is much faster today than 3G
will ever be.
No matter how you look at it, unless you have all your money locked up in
Qualcomm shares, 3G doesn't seem such a terrific idea after all. Really
sorry to dis-illution a few folks and I realise that it is particularly
hard to swallow for the engineering crowd, but those are the facts. Better
face the facts now than another Iridium later.
kind regards
benjamin
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Received on Wed Jul 25 19:20:46 2001