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Article: 3G Cellular: cdma2000 vs. UMTS

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Article: 3G Cellular: cdma2000 vs. UMTS

Note: This is an archived article that appeared in the Teracom newsletter January 2001, and this article has not been updated to reflect technology developments since then.

Please be assured that our training courses have been updated since the time of this article!

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We've spent a huge amount of time and effort researching and developing Course 120, "Understanding Wireless", collating and distilling knowledge into a high-value-added two-day seminar. One of the main topics in this course is mobility - understanding the idea behind cellular, and tracing the technologies from first generation "analog" to second generation "digital" to third generation or "3G" technologies.
When covering 3G cellular, we find that there are FIVE competing strategies, two of which are worth learning about: CDMA-Multicarrier, a.k.a. cdma2000 1X; and Wideband CDMA (W-CDMA), a.k.a. UMTS.

We also find that there are two main factions:
  - Carriers and equipment manufacturers that use CDMA for second generation are going with     cdma2000 1X for 3G.  This includes carriers like Sprint PCS and manufacturers like Qualcomm.
  - Those that use TDMA/GSM for second generation are loudly pushing Wideband CDMA for 3G.      This includes all the European telecom companies that used to be government Post Telephone     and Telegraph monopolies.
Here's a comparison of the technologies pushed by the two camps:
CDMA and cdma2000 1X TDMA/GSM and W-CDMA
2G CDMA uses radio bands most efficiently.  Both voice and data are communicated in packets over the airlink. 2G TDMA/GSM is not an efficient way to use radio bands.  Capacity is allocated on the airlink whether you're talking or not.  Same for data.
2G CDMA already provides packet data communications. 2G TDMA/GSM carriers will have to deploy a second, parallel infrastructure called GPRS to do packets.  A huge expense to achieve low data rates.
Current 2G CDMA handsets are already compatible with 3G cdma2000 1X.  Same radios, same waveform, pin-compatible chips... basically, a software upgrade for the carrier. There is no forwards nor backwards compatibility between (2G) TDMA/GSM, (2.5G) GPRS and (3G) W-CDMA  - they are completely different technologies.  Carriers and users will have to start over each time almost from scratch... a huge expense.
(3G) cdma2000 1X is highly flexible and backwards-compatible with the frequency bands allocated for second generation CDMA and TDMA/GSM. W-CDMA is not.
  The processing required in the phone for W-CDMA is exponentially higher than that required for cdma2000 1X - meaning higher processor cost and higher power consumption.  People reportedly burnt their hands on the batteries of prototype W-CDMA phones they got so hot because of the power draw!
cdma2000 1X can handle more phone calls and data communications per Hz of radio band than W-CDMA W-CDMA is less efficient.
cdma2000 1X is already in commercial service. W-CDMA might not be ready before 2006.

And there's more (but you'll have to come to the seminar).  With all of this research, and numerous discussions while teaching the course, I still can't think of ONE reason why the TDMA/GSM -> GPRS -> W-CDMA strategy is better than the 2G CDMA -> cdma2000 1X strategy.

Here's the strange thing: people who write articles in newspapers, and many stock analysts believe that TDMA/GSM -> GPRS -> W-CDMA is better than 2G CDMA and cdma2000 1X.


Go figure.

We asked our readers if they could think of a reason why GSM and W-CDMA is better than 2G CDMA and cdma2000 1X. Two brave souls offered a suggestion:

1) European telcos are going to deploy W-CDMA, so it will become a world standard, so it's better. (H.K., Contech Software Ltd.)
- OK... but that's not a technical reason why it's better, that's just repeating the question back...

2) As my Pappy told me, nothing beats cubic inches, except maybe rectangular money. (T.K., Ericsson). 
T. is pointing out that since W-CDMA uses a 5-MHz band vs. cdma2000 1X's backward-compatible 1.25-MHz bands, W-CDMA will have more capacity, particularly for high-speed data. 
- OK... but what if we deploy 3X, i.e. three 1X cdma2000 1X carriers.  Doesn't this get us more capacity in 3.75 MHz than W-CDMA gets in 5 MHz?

 
For more information: Course 120, Understanding Wireless
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