2000: The Evolution of 1x Evolution: From HDR to 1xEV-DO and 1xEV-DV
A few articles from the archives ....
>> Dedicated to Data
>> HDR Offers Service Providers the Data speeds for Evolution to 3G
Chris Goldman
Wireless Review
Oct 15, 2000
wirelessreview.com
also:
tin.le.org
In the drive to accelerate wireless-data throughput, technologists have turned speed and spectral efficiency into an art form. And in the case of high data rate (HDR), Qualcomm is the Picasso of proficiency, the Van Gogh of velocity. Qualcomm's patented HDR technology was approved this summer by the CDMA Development Group (CDG) as Phase I of 1XEV - a 3G technology with a peak data rate of 2.4Mb/s on a data-only channel. (Phase II will encompass data and voice improvements, but has yet to be decided.) Sprint PCS and Verizon Wireless are conducting trials of HDR-based solutions, as are KDDI in Japan and KT Freetel in Korea.
This 3G advancement will enable networks to efficiently carry next-generation data services and mobile Internet applications to subscribers. Vendors are providing HDR primarily as a channel-card upgrade that along with new software will allow providers to build on their current 1X investments, hence the name "1XEV," for evolution.
The business case is clear: 1XEV uses current 1X equipment as a springboard to faster data rates and saves providers money and spectrum along the way.
Talking 'Bout an Evolution
When the wireless industry first started talking about transmitting more than voice across digital networks, speeds were incredibly slow - around 14.4kb/s using the IS-95A standard, which evolved to IS-95B (64.4kb/s) and then 1X - also called 1XRTT (144kb/s).
The benefits provided by these standards included doubling voice capacity and increasing data rates. And the market is eagerly anticipating the 2001 roll-out of 144kb/s networks by major providers.
But engineers at Qualcomm decided there were still problems to be solved, said Kimberly Kleber, director of product marketing for HDR.
"What Qualcomm started looking at was the voice channel that is being shared as a data channel," Kleber said. "And the question that came to some of our engineers then was, 'How can we get a higher data speed than what is going to be achieved in this shared 1X mode?' and 'How can we ensure higher data speeds?' The engineers started really focusing on the fact that when you separate voice and data, you have certain benefits. You're no longer concerned about latency requirements of voice. Digital has done a great job of making sure the voice quality is maintained. But in doing that, the overhead that's required for that channel to maintain that voice quality essentially degrades the ability to handle data efficiently and optimally. With HDR, what happens is we take a dedicated 1.25MHz channel, a narrowband channel, and optimize it for packet data. By optimizing it for packet data, we could then allow the channel to burst to any single user at a given instant and send the full power of that sector."
The bursts are sent in 1.67ms packets at the peak rate of 2.4Mb/s, Kleber said. Average throughput rates are closer to 1Mb/s, according to service providers testing the technology.
"You don't get data that fast sitting at a desk," Kleber said. "It's a compelling technology. And HDR is a technology that can bring this wireless-Internet revolution quicker."
A big reason is spectral efficiency. By transmitting at data rates of 2.4Mb/s over the 1.25MHz of spectrum, providers avoid having to upgrade to a wideband 5MHz channel, Kleber explained.
The 1XEV technology is being tested now and should begin deployment in late 2001 or 2002, she said.
Provider Proving Ground
Over the last two years, Sprint PCS has found through trials that 1XRTT will yield a tenfold increase in data rates - from 14.4kb/s to 144kb/s - as well as improved voice capacity and battery performance on handsets.
The provider plans to roll out 1XRTT at the end of 2001, according to Oliver Valente, Sprint PCS CTO.
"What 1XEV will do is take us to the next plateau of data, which is up to 2.4Mb/s," Valente said. "1XEV is based on HDR, and we had HDR in our labs a year ago and liked what we saw. But we had issues with making sure it fit nicely with the 1X evolution path, in terms of upgradeability to our network.
Rather than installing all new radio infrastructure, which was what was originally envisioned with HDR, Sprint PCS needed a more cost-effective upgrade, he said.
Through standards discussions with other providers and vendors, an agreement was reached on the most effective way to bridge HDR into the 1X evolution path, Valente said.
"The goal is to try and have it standardized by the end of the year and start seeing commercial products in '02 some time," he said.
In order to maximize its investment in 1X infrastructure, Sprint PCS is using a multicarrier-base-station approach for its 1XEV solution.
Qualcomm's Kleber explained that a vendor such as Lucent can take an existing multicarrier base station and install both 1X and HDR channel cards, thus housing both types of technology.
Ed Chao, Lucent senior manager for 3G CDMA data, said this is exactly how the company upgrades its Flexent base station, which Sprint currently is using for 1X and will continue to use for 1XEV.
"Upgrading is very simple," Chao said. "We use the existing shelves and add a channel card - a simple card upgrade as well as some software in the same base station."
Although Sprint now is committed to 1XEV, the decision was not always clear, Valente said.
"Qualcomm was the one that initially developed HDR," he said. "But there were some competing proposals put on the table by Motorola with 1Xtreme. We liked a lot of those ideas, but we really have sort of put those in a second phase of 1XEV. It hadn't been as developed as HDR. We were concerned that if we focused on 1Xtreme that we would lose time to market. What we've said is we liked a lot of those concepts and are trying to incorporate those into the next generation, which is beyond 1XEV. We've worked with Qualcomm, Lucent, Nortel, Motorola, Samsung, Ericsson, just to name a few of the vendors involved in these discussions to date."
Beyond HDR
Phase II of the CDG's standards process will determine what technology will encompass both data and voice, hence one of its working names, 1XDV. However, the technology that will be chosen for Phase II is far from decided, according to Qualcomm's Kleber.
"Phase II, at this point, is being evaluated and doesn't have a solution yet," she said. "(The CDG) is evaluating 1Xtreme or LAS-CDMA (large area synchronized-CDMA) or an evolution of HDR. There will be a technology that will fill this Phase II, which will be totally new. And Phase II is intended to give you high data speeds and voice."
"Right now, Motorola, Nokia and others are positioning their technology proposals as the eventual baseline for the DV technology, the second phase," said Neal Campbell, Motorola director of CDMA product operations, adding that the DV phase is scheduled for a draft standard for May of next year. Motorola's proposed 1Xtreme technology will be considered along with others - many of which reach data speeds of 5Mb/s or faster.
"The DO (data only) space will allow for 600kb/s average data rates with peak rates of better than 2Mb/s," Campbell said. "For the DV proposals - at least I can speak of (1Xtreme) and the LinkAir (LAS-CDMA) technology - those proposals are trialing and proposing to get to 5Mb/s peak data rates with average data rates of 1Mb/s."
According to LinkAir, which conducted a trial call on LAS-CDMA Aug. 15 in Beijing, the technology offers 20 times the voice coverage of existing 2G networks, while increasing data speeds to 5.53Mb/s. LAS-CDMA is compatible with GSM and CDMA networks, as well as the major international 3G standards. And LinkAir refers to it as a bridge standard between 3G and 4G.
As with 1XEV, the Phase II solution - whether it ends up being 1Xtreme or LAS-CDMA - could be installed on existing 1X multicarrier base stations, needing only a channel card and software upgrade.
Although existing network infrastructure can be leveraged for Phase II, providers likely will need additional spectrum, Campbell said.
"When you look at the data rates (5Mb/s) that we are proposing on such a narrow channel (1.25MHz), you do start asking yourself, 'What is the viability or necessity for a 5MHz-wide channel for wireless communications?'" Campbell said. "If we can play out these data rates of 5Mb/s peak and 1Mb/s average that we believe is quite possible, my guess is what we will start to see is a move to greater spectrum trunks, from 1.25MHz carriers to the wider carriers to further increase the capacity and capabilities."
Wireless data's broad popularity remains to be shown, however. Only time will tell what technology truly will match consumer demand. <<
>> Taking CDMA's Scenic Route To 3G Services
Mark Dziatkiewicz
Wireless Week
November 20, 2000
wirelessweek.com
Taking a trip often involves choosing between a direct highway route or the scenic back roads. Both ways get you there eventually, but the out-of-the-way path can open your eyes to sights and experiences you would otherwise miss.
So it is for CDMA operators on the road to third-generation services. Choice is the operative word for CDMA operators, who are looking for cost-effective, standardized alternatives to reaching their 3G wireless objectives.
The CDMA road to 3G has taken a few turns during the past several months. And while carriers could take the direct route on highway 3xRTT, the scenic route is getting more interesting every day. If speed isn't the only priority, it could just be the best way to go.
Who Wants Dick Tracy?
Third-generation wireless is all about hard-to-believe data rates and outrageous applications like a Dick Tracy video on your wrist. But if 3G services can't be offered cost effectively to the subscriber, does it matter what the technology is capable of?
In May 2000, the CDMA community took steps toward getting more bang from its cdma2000 upgrade bucks by adopting a high-speed data-only addition dubbed 1xEV-DO, or 1x Evolution-Data Only. 1xEV-DO offers most of what 3xRTT does but accomplishes it within the existing 1.25-megahertz CDMA carrier.
For operators, that is a big step toward cost-effective high-speed data because it avoids the hardware/software upgrade changes required with the 5-megahertz carrier of cdma2000 3x. "If the reason to go to 3xRTT is to provide high-speed data, but you can use the same bandwidth with 1xEV-DO and use less spectrum, it will give you a cost advantage," says Yusuke Higashi, CDMA product line manager at Nortel.
1xEV-DO evolved from the Qualcomm High Data Rate proposal proffered in late 1999. HDR demonstrated peak data rates above 1.8 megabits per second in a 1.25-megahertz carrier, but it was a data-only technology.
Motorola, on the other hand, announced its own competing proposal at CTIA 2000. Its technology–1X Plus–offered first phase data rates of 1.38 Mbps peak throughput on a single 1.25-megahertz CDMA carrier, later moving to 5 Mbps in a fixed environment.
In the end, the CDMA community chose the Qualcomm approach with modifications. Time to market and catching the high-speed mobile Internet wave were motivating factors to go with HDR, according to Ed Chao, Lucent's senior manager, 3G and data product management. The opportunity to offer high-speed data rates that met or even exceeded those capable in GSM and TDMA 3G proposals–in a similar time frame and without costly hardware changes–was too good to pass up.
"Qualcomm had been working on [HDR] for over three years," Chao says. "They had been trialing the technology in San Diego and had done a lot of proof of concept." Because Motorola's technology proposal was not as far along, the CDMA Development Group and its members opted for Qualcomm's approach.
But 1xEV-DO isn't an exact clone of HDR. Because HDR was designed for data only, it required a separate CDMA carrier with no voice integration. While the second carrier was something operators were willing to live with in the short term, the lack of voice integration wasn't.
Relying on a separate carrier would have necessitated stand-alone devices on a high-speed data network, separate from the carriers' 1xRTT voice networks. The business case wasn't as appealing to operators, "because if they can't inter-work and communicate there is less value for operators to provide the services," Higashi says.
For that reason, a number of modifications were made in the evolution to 1xEV-DO, including one to increase traffic throughput and another for interoperability with 1xRTT. The latter acknowledges the direction and importance of Motorola's 1X Plus technology.
In an integrated solution, a terminal could offer both voice and data with hand-off capabilities. For example, the subscriber could be involved in a high-speed data session using the 1xEV-DO network when a voice call comes through. The data session then could be handed off to a 1xRTT CDMA carrier so the data session continues and the subscriber picks up the voice call, without involving two separate CDMA carriers.
"The implication is that the high-speed data application in progress might get flow control because 1X only supports a 144 kilobit-per-second data rate vs. the HDR rate," says Phil Hester, director of technical product marketing at Ericsson.
Providing the multiservice capability was an important concession and strategic modification. In some respects it offers the best of both the voice and data worlds. With 1xEV-DO, the separate spectrum allocation takes advantage of data's characteristics to provide maximum efficiency, which is a nod to Qualcomm's original premise. And the inter-working between voice and data reflects the operators' wishes and market realities.
The phase one standard was scheduled for publication at the end of October, enabling field trials in January 2001. Manufacturers suggest commercial deployments will commence during 2002.
Focusing On Phase Two
At the same time, work continues on phase two of 1xEV, where the objective once again is to integrate phase one capabilities on the "same" CDMA carrier while retaining the ability to maintain packet data services on a separate carrier.
Peak data rates get bumped up to 1.25 Mbps in both directions (see chart) with average rates of 600 kbps in a fully loaded system with all users moving at vehicular speed. Phase one provided asymmetric data rates in all categories.
Other objectives in phase two include three modes of traffic delivery–real-time, non-real-time and a mixture of the two–and another doubling of voice service spectral efficiency. But most importantly, the standard should provide graceful evolution from existing CDMA platforms with minimal cost upgrades.
It's a tall order, but since time to market isn't as critical, the requirements have spawned three proposals to date, coming from Motorola, Lucent and LinkAir.
Motorola partnered with Nokia and repackaged 1X Plus as 1XTREME. "Integration of voice and data is the preferred method, so we've refocused our efforts on phase two requirements," says Neal Campbell, director of CDMA product operators for Motorola's Network Solutions Sector.
One of the primary challenges in the integrated approach is packetized voice and handling the basic differences between voice and data. Voice needs a continuous stream while data uses bursts, so allocation issues exist.
Combining both types of traffic within the same bandwidth will require unique approaches in order to achieve cost efficiency while maintaining the necessary voice and data throughput. There seems to be agreement "that integrating voice and data is the right thing to do going forward, but no one is sure of the right way to do it," Nortel's Higashi says.
Motorola could have an early lead with phase two because it's been working for a while on an integrated approach. But still there are a number of requirements that 1XTREME would need to support, "and some of those things are pretty dicey," Ericsson's Hester adds.
Ericsson doesn't have a submission of its own, so it is closely examining what's already on the table. Hester says one of the toughest requirements is to provide backwards compatibility with everything CDMA offers to date. And providing another doubling of voice capacity isn't trivial either.
He indicates that Motorola uses some incredible modulation schemes to achieve its 5 Mbps burst capacity but suggests that throughput often suffers as a result. And there also are concerns about the required proximity between base station and terminal to support these extraordinary data rates.
Nortel isn't bound to any proposal so far either but intends to see the process move forward in a way that is beneficial to everyone. Higashi points out that the current proposals deal with the radio portion only, and that alone "won't give you a cost advantage." The overall network solution is just as important.
Lucent submitted its proposal to the 3GPP2 (third-generation partnership program 2) standards group last month, according to Chao. Lucent was an early Qualcomm HDR supporter and is working closely with Motorola and Nokia to resolve differences between proposals.
The 1xEV-DV dark horse is LinkAir, a startup founded by one of the inventors of CDMA. LinkAir patented LAS-CDMA (large area synchronized-code division multiple access), which provides up to six times greater capacity than that of cdma2000, and the company hopes to position the technology as CDMA's next evolution.
With Internet protocol technology at its core, LAS-CDMA already incorporates 1xEV-DV's integrated voice and data requirements. And based on patented spreading technology, it eliminates the interference-limiting aspects of CDMA technology, according to a company white paper.
It also promises backward compatibility with existing wireless systems such as IS-95, IS-41 and GSM Mobility Application Part. But despite being a more efficient CDMA, some suggest it could have difficulty maintaining the backward and forward compatibility due to the nature of its implementation.
Whatever direction 1xEV-DO takes, it likely will undergo a few iterations before a final solution emerges. But an overall commitment exists on the part of manufacturers and operators to drive CDMA technology forward, while driving costs downward.
No single road exists to implementing 3G technology, particularly for CDMA operators. But sometimes the scenic route is simply the better way to go. <<
The CDMA2000 High Rate Packet Data Air Interface Specification (TIA/EIA/IS-856) published in November 2000 and was subsequently accepted as an ITU IMT-2000 3G standard under the IMT-MC CDMA2000 Release A umbrella (although it is not part of Release A.
qualcomm.com
- Eric - |
