CDMA - the hidden 3G secret?

While we in Europe have been auctioning bandwidth, building new standards and starting to roll out our long term third generation wireless strategy, our distant cousins in the US have been quietly working out how to make a quick jump from what they have to something better, and with CDMA2000 1x it looks like in the short term this may well have been the best choice to take.

It's all in a technology..

GSM, the current European standard for mobile communications, uses TDMA technology (time division multiple access) to fit multiple digital streams into a given bandwidth and allowed the progression from Analogue to Digital wireless networks. Most US and Asia Pacific carriers however chose to use IS-95A/B, a standard air interface, which uses CDMA (code division multiple access technology) to achieve the same end. So what's the big deal about that you might ask - well it really evolves around the fact of where are we all heading with our 3G networks..

Any old CDMA.

Unsuprisingly the standards using CDMA are pushing to use an extended version of the CDMA technology called CDMA2000, also known as "1x", then on to 1xEV, and ultimately to 3x to enhance the bandwidth available to them for wireless voice and data transfer.

GSM standard adopters path to 3G however is through GPRS (packet based, IP aware TDMA technology), then to EDGE (new modulation scheme to increase bandwidth but still TDMA technology), and ultimately on to wideband CMDA (WCDMA).

Now, the more observant of you will have noticed that both paths end up at some sort of CDMA based technology. This is where the gain lies for those who already have CDMA technology in place.

First to the post.

For carriers like Sprint, what this means is they can easily role out higher data rate services off the back of their existing CDMA network while still moving towards CDMA2000 3G3x, whereas UMTS carriers will be potentially be delayed while they upgrade frequency allocations, infrastructure and handsets to switch over to W-CDMA and TD-CDMA schemes.

Other future proof planning such as Qualcomm's pin-interoperability between it's IS-95A/B, 1x and 1xEV chips means that the upgrade path for manufacturers is simple, quick and cost effective.

Where are the standards?

One final point worth mentioning is that even though this route is quicker and faster for some carriers to take, the whole point of IMT-2000/UMTS was that it was proposed as an international standard for third generation mobile networks. Universal adoption by all wireless carriers was meant to achieve the same kind of unity that GSM bought for Europe during the second generation of wireless networks. CDMA2000 is primarily a competing technology not selected for an international standard and unluckly the seperation WCDMA and CDMA2000 3G3x brings will mean that complex and expensive handsets will need to be manufactured to cope with both technologies and that ultimately it will be us the consumer that pays the price of this.

Alex Judd
CTO - Skywire & e-conultant

References:
Sprint PCS - http://www.sprintpcs.com/
Qualcomm CDMA technologies - http://www.cdmatech.com/
UMTS Forum - http://www.umts-forum.org/
The Evolution of GSM to UMTS - http://www.mdi-ng.org/es53061/artholley.htm