On Monday, 12 November 2001 5:44 PM Michael Turner wrote:
>> I have avoided the alphabet soup of wireless networking protocols,
for the most part. I guess it's my past abortive forays into
international telecom standards -- I break out in hives whenever I hear
"ITU" even whispered.
>> I wonder if someone could just point us to some primary sources?
CDMA itself is a Qualcom patented technology, so the authoritive source
is
http://www.qualcomm.com/cdma/
Which interestingly doesn't say much about WCDMA or the other 3G
variants of CDMA.
>> Ericsson and UMT Forum seem to say little more than "this is the
best stuff since sliced bread and pop-up toasters, you just wait".
WCDMA, as a standard, must be pretty big -- it covers a lot of stack
layers, anyway. There can't be any shortage of primacy sources.
The issue with WCDMA is that there are almost infinate variations of
what the standard consists of, they are all based upon CDMA but there
are many ways to squeeze more bandwith out of a given frequency and each
method gets a new acromym OR just gets bundled under the term WCDMA.
Its like engines just get bundled under 8 valve or 16 valve regardless
of whether they have variable valve timing or not, most car owners don't
even care.
In general the differences are so technical that they are irrelevant
unless you are a Telecom provider looking to put up a network, in which
case I'm sure Qualcomm have already contacted you with a very convincing
sales pitch.
>> Rather than having lengthy descriptions of the wrong thing, and
descriptions of the right thing that admit to not really being clear,
how about just pointing to the original descriptions of WCDMA?
Joran gave an excellent description of CDMA, but the description sounded
more like CDMATwo which is NOT Wideband CDMA.
BTW Do any CDMATwo networks actually exist yet ?
I particularly liked the English/Russian/French analogy.
Some picky points.
>> > You can have 10 or 100 channels using the same frequency band, but
your receiver...
1) CDMA actually overlaps precisely 64 channels in a single frequency
band using something called Welsh Codes.
2) CDMA uses a much wider frequency band, so you don't actually get 64
times in the same band given non CDMA technology of the same level of
advancement. Hence 10 is a closer estimate.
In my original response I described TD-WCDMA which I what I understood
FOMA is based upon (and what the stated bandwidth and other attributes
of FOMA would indicate).
It is a genuine variant of WCDMA, and [I believe] most 3G networks plan
impliment their packet vs data handling in this way.
The other variants are
UMTS
CDMA2000
1XMC
1Xtreme
HDR
3XMC
Then each standard may mix frequency ranges, timeslots and overlaps.
The answer to the original question of how Voice and Data are handled at
the same time (which is what most developers may find useful to
understand) was answered by my original response. And Yes it is similar
in concept to the "HIGHER Slot Class" variants of GPRS, Basic GPRS (Slot
Class 1) is just one packet up and one down and I don't think any one
has actually implimented any of the High Slot Class variants yet.
Regards,
David Davies
http://www.intadev.com
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Received on Mon Nov 12 13:49:59 2001