From the moderated Q thread, long but a must read.
Putting the C in TDMA?
by BETSY HARTER
Wireless Review, Jan 1, 2001
Is cdma2000 the best 3G route for TDMA carriers?
Wireless carriers always have had an abundance of choices when it comes to network technology. The many paths to 3G open up even more choices, especially for TDMA carriers.
The path to 3G for GSM and CDMA carriers has pretty much been laid out. Most GSM carriers agree their best option is to deploy GPRS as a 2.5G solution then move to UMTS, also known as wideband CDMA (WCDMA), while CDMA carriers are evolving to cdma2000 1X for 3G. For TDMA carriers, however, the path is not set in stone.
A carrier with a 2G TDMA network today can implement GPRS as a 2.5G solution, then move to enhanced data rates for GSM evolution (EDGE). After EDGE, it can move to WCDMA, which the GSM Alliance backs, or to cdma2000 1X, a technology advocated by the CDMA Development Group (CDG). UWCC advises that TDMA carriers can skip GPRS and go right to EDGE for 3G services. They also recently endorsed WCDMA as an additional 3G option.
Recently, the CDMA faction has launched a campaign advocating that a TDMA carrier's most direct route to 3G is straight to cdma2000 1X, and it has hinted that some TDMA carriers already have chosen that route. Moreover, the group is pushing for a global convergence of 3G technologies. However, U.S. TDMA providers, notably AT&T Wireless and Cingular Wireless, say the "straight shot to cdma2000 1X" theory does not hold water, and they doubt the possibility of the three technologies ever finding commonality.
TDMA 3G Activity Despite the CDMA camp's push for TDMA carriers to move to cdma2000 1X technology, North America's two largest TDMA-based carriers have chosen otherwise. At the end of November, AT&T Wireless said it will overlay a GSM/GPRS platform to its existing nationwide network beginning early this year. The company's existing spectrum licenses, along with its partners and affiliates, will permit installation of UMTS in more than 70 of the country's top 100 markets in 2003 and 2004, even before additional spectrum for new markets is added to the portfolio.
At the end of the year, AT&T Wireless will deploy 3G EDGE, extending the technology to most of its markets by the end of 2002. Sometime in 2002, when equipment and devices become available, the company will deploy WCDMA. The upgrades will be transparent to existing customers because the new network will not replace its TDMA and CDPD networks. These networks will continue to be supported, maintained and expanded as needed, the company said.
Cingular Wireless has chosen a similar route to AT&T Wireless. Kris Rinne, Cingular vice president, technology & product realization, said the company currently has circuit-switched data with WAP capability in Chicago; Dallas; Tulsa, OK; Washington/Baltimore and parts of California and Nevada. It will continue to expand that network across the country into the first half of 2001 so that circuit-switched data with WAP covers GSM and TDMA properties.
"Currently, we have GPRS capabilities in field testing in California and Nevada," Rinne said. "We will be launching that in first quarter of this year. With GPRS, we are building the applications and our expertise as far as managing those backbone networks and the core network associated with that."
Rinne said Cingular is in the process of completing RFPs from infrastructure and handset vendors for EDGE, a migration path for both its TDMA and GSM markets. It plans to have EDGE in the labs by the first half of the year, field trials in 4Q01, and launch the technology throughout 2002. After EDGE, Cingular's plan is for WCDMA.
"I think about this in two components: the RF network and then the core backbone network," Rinne said. "In the core backbone network, there is a clear migration path forward as standards are being completed from EDGE to WCDMA, so we would have the advantage of global roaming capability, global inter-operability and leveraging the R&D that the application community will have in that area. On the radio infrastructure side, that is going to be driven more by market demand and spectrum."
Rinne said Cingular has studied cdma2000 1X, but it does not have any plans for that path.
Cdma2000 1X for TDMA Operators? Although TDMA giants AT&T Wireless and Cingular Wireless have sided with WCDMA, there still is a possibility that other TDMA carriers will go with cdma2000 1X for 3G.
"We have worked with a couple of TDMA carriers in the United States just recently that we have not announced yet, but three or four of them have said they are moving in that (cdma2000 1X) direction," said Mark Tharby, Nortel Networks vice president, wireless Internet solutions marketing. "So there are TDMA customers that will be moving to the CDMA space."
Jim Takach, CDG director of advanced programs, added that TDMA operators in Brazil are considering a transition to cdma2000 1X for 3G.
"We want to tell this story that it is quite feasible for a TDMA operator to migrate to 1X," he said.
In early November, Lehman Brothers said Nextel is considering cdma2000 1X, and BellSouth International in Brazil is considering migrating to cdma2000 1X.
The CDMA sect advertises several advantages to cdma2000 1X for TDMA carriers, including spectrum efficiency and cost savings. And, the CDMA side says the paths chosen by AT&T Wireless and Cingular Wireless require huge investments in software and hardware, which a cdma2000 path avoids. However, neither the CDG nor CDMA vendors gave out hard numbers on how much money TDMA carriers can save by going the cdma2000 route.
Bharat Shah, Qualcomm director of business development, said one advantage cdma2000 1X offers is that it can be used in existing spectrum. In fact, SK Telecom in South Korea has deployed 1X in its existing spectrum, and Verizon Wireless and Sprint PCS have similar plans. TDMA carriers effectively could do the same thing.
CDG's Takach said 3G systems, in particular cdma2000 1X systems, should be able to be deployed in existing spectrum, including cellular 800MHz, 1.8GHz, 1.9GHz and 1.7GHz.
"A TDMA carrier can do a 1X implementation in a very small amount of spectrum, and operators want to use spectrum as efficiently as possible and do as much as they can in as small an amount of spectrum, rather than spending billions for brand new spectrum or for overlaying your existing network," he said.
CDMA backers scoff at the route AT&T Wireless and Cingular have chosen, calling it circuitous and costly due to the GSM element.
"Cdma2000 is based on the same network that the TDMA system uses today, an IS-41 network, so there would be less of a change for a TDMA operator to go to CDMA, but to go to GSM requires a new network because GSM works on MAP network," said Christine Trimble Qualcomm spokesperson. "Cdma2000 would be an easier upgrade rather than going through what AT&T is doing, which is pretty costly because of all the new equipment."
Shah added that a TDMA operator wanting to migrate to cdma2000 1X only would need to change out the base-station equipment and the base-station controller. He did not specify whether the solution is more or less expensive than a TDMA-GPRS-EDGE-WCDMA path.
"One thing about WCDMA is that it is a GSM MAP network; a TDMA operator migrating to WCDMA has to change that switch to the MSC," he said. "TDMA operators on this path would have to change out the MSC, which requires a lot of software and a big investment."
CDG's Takach said TDMA carriers need to evaluate which path is easier: invest a lot to get to GPRS, then invest a lot to get to maybe EDGE, then invest more to get to CDMA in the form of WCDMA; or transition sooner to CDMA by investing in cdma2000 1X.
One logical flaw with this thinking is that TDMA carriers AT&T Wireless and Cingular Wireless are heading toward WCDMA, not the cdma2000 1X technology that the CDG backs. Lately, the CDMA camp has taken to saying "everyone ultimately is marching toward CDMA, since both WCDMA and cdma2000 1X are based on CDMA."
Andrew Cole, Adventis wireless practice head, pointed out that Qualcomm, for instance, has made it seem as if WCDMA and cdma2000 1X are similar for some time, but there are a number of important differences between the two technologies.
"You could argue the foundation of both is CDMA, which is true, but the protocols are different," he said.
Despite claims that cdma2000 1X is less costly in the long run than AT&T Wireless' chosen route, AT&T maintains that WCDMA is more cost-effective. Ken Woo, AT&T Wireless spokesperson, noted that TDMA and GSM are in the same family of technologies and are modular in nature, so upgrades require pulling out whole radios and putting in new radios.
"You have to put new software in the switch and new additional peripheral materials, but it is not like starting all over again," Woo said.
Cingular's Rinne admitted that many software and hardware changes will be necessary as the company moves forward, but the cdma2000 1X migration path would require a significant change in the company's core network path, something that the GPRS-EDGE-WCDMA path avoids. Rinne outlined the equipment changes that will be necessary as Cingular takes each step toward 3G.
"From the core networks that we have today moving to GPRS, we have added some network elements ... they are the same network elements we will need in the EDGE environment, and they have a clear path forward. On the radio side, for GPRS that was a software change in our GSM environment."
For EDGE in the TDMA environment, Cingular will need new hardware infrastructure on the radio side, but Rinne pointed out that this technology is interoperable with EDGE and will be backwards compatible with GPRS.
"It is additional infrastructure on the radio side but it is using state-of-the-art technology," she said. "Depending on our vendor selection, we would have the capability for software-defined radios or wideband-defined radios that would give maximum flexibility. So even though it is an overlay network, it gives us the state-of-the-art components of that piece of the network."
As the company moves to WCDMA, it will need software changes. Again, depending on its vendor choice, it might be able to use some of the same hardware. However, because EDGE uses a 200kHz channel and WCDMA uses a 2.5MHz channel, some vendor solutions will require hardware modifications.
One advantage to cdma2000 1X that CDMA backers tout is the ability to use the technology in existing spectrum. Adventis' Cole said he does not subscribe to that theory.
"There is a lot of Qualcomm hype involved (in that theory), and we do not think that is the case," he said. "To do 3G properly, you will need extra spectrum. When you start getting a critical mass of subscribers in any given country, you begin to need capacity."
Woo agreed that all carriers will need new spectrum in the long run, so the ability to deploy 1X in a carrier's current spectrum is not an attractive reason to choose the technology.
"In the short term we can work with what we have going up into EDGE without additional spectrum, but long term as the FCC makes more spectrum available, that is something that not just we but all carriers going to 3G, regardless of standards, will need," he said.
Rinne said Cingular weighed the option of buying new spectrum against clearing existing spectrum and plans to clear the necessary spectrum by cell splitting to launch its 3G services.
"In our strategy you can dedicate a portion of your spectrum to data and dedicate timeslots to either voice or data; you can sell to the customer and manage QoS (quality of service) on their behalf for data versus voice independently," Rinne said. "In a 1X environment, you are sharing all of that, so the quality of your voice depends on your data usage or vice versa."
In reality, Cole said, for any carrier to do 3G properly, it will have to rip out the guts of its network and give it a significant overhaul. So, when all is said and done, carriers must choose based on which technology they feel is superior, not which will require fewer upgrades.
A Global Standard? Will there ever be global convergence of GSM, TDMA and CDMA technologies? It depends on whom you ask. The CDMA caucus is open to finding commonality among the three technologies, claiming that WCDMA and cdma2000 1X have some commonality already because they both are based on code division.
"If Irwin Jacobs can shake hands with Ericsson, anything is possible," said one CDMA advocate.
Vendors that support all three technologies such as Nortel Networks are not ruling out the idea, either.
"I think a lot of people would like to get to the point of global convergence," Nortel's Tharby said. "The TDMA and GSM space already is moving rapidly to a UMTS future. We will see continued efforts to bring convergence because we have seen that bringing all the markets to bear at one technology level has given operators in Europe competitive cost advantages. So I would think there would be a lot of pressure by the operators to drive to a converged solution in the marketplace."
At the same time, CDMA is popping up in European markets as operators look to differentiate, which brings about competing forces.
However, Adventis' Cole is less enthusiastic that global convergence will occur.
"You will have a time-division camp and a code-division camp, and the two will remain at war with one another, unfortunately," he said.
There is consensus among TDMA carriers that convergence between TDMA, GSM and CDMA is unlikely, even at the 3G level. Chris Pearson, UWCC executive vice president, said the TDMA and GSM communities have been working closely together in the 2G space and beyond. For example, the two groups are working on a TDMA/GSM multitechnology wireless telephone that works on a TDMA system in North America but roams on GSM overseas. In addition, the Third Generation Partnership Project (3GPP) has brought together GSM and TDMA technologies. Because WCDMA and EDGE both work on a GPRS core network and because the two offer similar speeds in the mobile environment, there is a natural reason for the organization to accept the work of both, he said.
"There isn't much chance between the CDMA IS-95 and 2G TDMA finding much commonality," Pearson said. "If you look at cdma2000, which is the IS-95 3G proposal, there are not similarities that are part of EDGE and WCDMA, so CDMA is pretty much on its own."
Cingular's Rinne agreed that GSM and TDMA have a clear migration path together on both the data and voice sides due to cooperation between the UWCC and the GSM Alliance.
"I don't see as clear a path to bringing together the CDMA and the GSM/TDMA communities," she said. "I do see three folding to two, but I don't know that I see it going to one."
Over the last year, the work between the GSM Alliance and the UWCC has effectively brought two of the three competing technologies together, leading the industry to believe that the ongoing war among the three technologies was nearing an end. Rumors of global convergence ran rampant. A recent turn of events, however, shows that there is very little chance that TDMA and GSM sects will extend the olive branch to CDMA.
At the end of November, when AT&T Wireless blew the CDMA community away with its 3G plans (the GSM/GPRS-EDGE-WCDMA route), Qualcomm in turn surprised the industry by responding to the announcement - which some analysts might have interpreted as a negative for Qualcomm - with congratulations rather than disappointment. Qualcomm's spin started another technology brouhaha with its longtime foe.
Qualcomm said in a statement that it "applauded AT&T's decision to embrace CDMA technology and deploy 3G WCDMA networks," adding that "AT&T's plans represent a long-awaited decision in favor of CDMA technology."
The release did not sit well with the TDMA community, particularly AT&T.
"It is a gross misrepresentation of the technology we have chosen," said Ken Woo, AT&T Wireless spokesperson. "Our choice has nothing to do with Qualcomm or Qualcomm CDMA products."
Qualcomm said it has essential patents for the WCDMA standard and has licensed some or all of its essential patents to more than 30 companies to manufacture WCDMA equipment. The company claimed that each licensed manufacturer has agreed to pay Qualcomm the same royalty for WCDMA as that licensed manufacturer is paying for other CDMA standards, including cdmaOne and cdma2000.
"All of the manufacturers I have talked to that are licensing the CDMA are telling us that it is absolutely false that they are paying royalties to Qualcomm for UMTS," Woo said.
Analysts had speculated that AT&T Wireless might possibly choose cdma2000 1X for 3G, but Qualcomm's latest ploy has wiped the radar screen clean of that possibility. When asked if AT&T Wireless would ever go to cdma2000, Woo responded, "Nope. Over our dead bodies collectively."
Although animosity still exists between code-division and time-division camps, wireless carriers would do well to never say never.
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