Q&A by Mark van der Hoek on 1XRTT/CDMA2000 1X
Q: Whose behind all these crazy names with CDMA?
A. Who is behind EVERYTHING CDMA? :D Qualcomm, of course. It was originally called a 2.5G technology, but Qualcomm muscled the ITU to call it 3G. After all, who wants 2.5 when you can have 3?
A. Coherent detection on the reverse link. Just like the cell sites have a pilot, now the mobiles have a pilot. That enables much better power control on the mobiles, which means greater capacity on the reverse link. Add to that now we have "supplemental channels". Instead of assigning just ONE traffic channel, now we can assign up to 7 to one mobile. The data is fed in parallel across all of them, thus increasing the data throughput. There are also some differences in coding schemes.
Q. Are data rates measured while the cell phone is moving or stationary?
A. Probably stationary.
Q. And do those data rates continue throughout the handoff?
A. No, supplemental channels are not handed off -- just the fundamental channel. However, the supplementals are added back right after handoff, so you shouldn't notice much.
Q. What's the real speed in practice with Vision or Express? 45 to 60 kbs?
A. That's what Verizon claims for Express, and that's what I've heard from folks in the field. Basically really good dial up. Nothing to get excited about, but usable surfing. I suspect those speeds are stationary, though, and don't expect that at the cell edge.