Yes, seems I confused UTMS with WCDMA. Noted. Logged.
(I know nobody will read this, but...)
Actually, you were more correct than you think. UMTS
is WCDMA...two names for the same thing. You didn't confuse a thing. (Although, to be accurate, WCDMA really only refers to the air interface while UMTS encompasses WCDMA and a lot more. Think of UMTS as the next-generation version of GSM.)
The reason that people get confused on this subject regularly is because "CDMA" is used both as the name of a technology as well as the name of a specific implementation of that technology...one name for two
different things.
If we wanted to be completely accurate, Verizon doesn't run a "CDMA" network. (Well, they do, but technically so does every single 3G GSM provider out there, too -- including AT&T -- which I'll get to in a minute.) Verizon runs a CDMA2000+EV-DO network. CDMA2000 is the name of a suite of protocols and standards, drafted by Qualcomm, that use CDMA radio encoding. (Incidentally, Qualcomm also "invented" the CDMA radio encoding technology that CDMA2000 is based on.)
"GSM" is analogous to "CDMA2000" -- it, too, is a suite of protocols and standards collected under one umbrella. Originally, GSM networks employed a radio data encoding method called TDMA, which gave each handset a timeslice within which they could transmit. CDMA, on the other hand, through sophisticated engineering, allows all handsets to occupy the same channel at the same time. Thus, CDMA2000's predecessor, called IS-95, was more scalable than the old-school TDMA version of GSM.
The GSM standards body/committee/whatever eventually realized that TDMA technology was running out of steam, and that they needed to base the next version of GSM, called UMTS but also commonly referred to as "3G GSM", on this new and superior CDMA technology. So they did. That's what UMTS is: a next-generation, higher-speed, CDMA version of GSM. Because UMTS uses a wider channel size than CDMA2000 does (5MHz vs. 1.25MHz), it is also called WCDMA, or
Wideband CDMA.
All GSM providers that have deployed a 3G network, like AT&T, are running UMTS/WCDMA networks. Verizon and Sprint run CDMA2000 networks. Even though
both networks utilize CDMA technology, they are still fundamentally incompatible, both at layer 1 (on account of the channel size difference), as well as layer 2 and beyond (data framing is completely different between the two, network authentication and provisioning are totally different, etc.). So two different versions of each phone still need to be manufactured to run on the two different kinds of networks (although universal "world" chipsets with support for CDMA2000, EV-DO, UMTS, and HSPA exist now, so in theory...).
Qualcomm still owns the patents to the root CDMA technology that they invented, though, so...yeah: 3G GSM equipment manufacturers have to pay royalties to Qualcomm. Qualcomm gets a cut of
all 3G action out there, whether based on the CDMA2000 standard that they had a direct hand in developing, or whether based on the competing UMTS standard that employs WCDMA.
All of it is CDMA at it's core. You can bet they're making bank.
(You really should read Steven C. Den Beste's memoirs about the development of CDMA over at
http://www.denbeste.nu/cd_log_entries/2002/10/GSM3G.shtml if you're at all into the history of these kinds of things. Very interesting reading.)
The reason why AT&T's network has "faster data" than Verizon is also a more complex subject than people are making it out to be. First, ironically, the GSM version of 3G -- UMTS -- started out life with a much lower specificed theoretical maximum downlink data rate than the CDMA2K version of 3G (EV-DO): UMTS could only achieve downloads of 384kbit/s, while EV-DO could hit over 2Mbit/s. Eventually, the UMTS spec was extended with the addition of HSPA, which offered not only new modulation techniques that could accomplish up to 14Mbit/s on the downlink, but also offered, compared to EV-DO, much tighter and more efficient scheduling of a shared resource (the downlink channel) amongst all the handsets that are trying to use it at one time, which equals greater potential throughput for everybody, especially on a cell tower that is loaded down with subscribers. EV-DO Revision A got the 3G CDMA2K downlink up to 3Mbit/s, but that obviously can't match the 14Mbit/s that HSPA offers. There is an EV-DO Rev. B out there that, through channel bonding, can achieve downlink speeds similar to HSPA, but A) it seems like the Qualcomm and the 3GPP2 are still playing catch-up with the GSM guys, given that they're about to roll out HSPA+ with a 42Mbit/s theoretical maximum downlink, and B) Verizon has never rolled out EV-DO Rev. B. So, technically, Verizon has an inferior last-mile network (HSPA compared to EV-DO Rev. A is no contest), AND the development of further advancements to EV-DO has fallen behind that of UMTS.
This doesn't even address what the different companies are doing for backhaul to their cellular towers. You could have the fanciest broadcast equipment at your cellular tower, but if you have a teeny-tiny internet connection feeding that tower, you're still going to see slow speeds. And since neither AT&T nor Verizon are about to divulge that kind of information, we'll probably never know who has the superior network core, except perhaps through guesswork based on raw experience.
*whew*,
-- Nathan
