Operators are eyeing the future, even as they continue to roll out 3G networks.

Of the 3.4 billion mobile subscribers globally, only 10% or so use a 3G network. With all that room for growth in 3G, why has the industry started talking so much about 4G?

During the Mobile World Congress in Barcelona in February, 4G technologies like Long Term Evolution (LTE) and WiMAX were among the top 10 topics for discussion in conference rooms and hallways.

Speaking at MWC, Carl-Henric Svanberg, president and CEO of Ericsson, highlighted the growth opportunities for W-CDMA and its high-speed packet access (HSPA) upgrade, saying there were 180 million W-CDMA subscribers while the number was growing by 6.5 million a month.

“In 2008, Ericsson expects to see 3G/HSPA networks rolled out in Latin America, Middle East, Africa and Russia, with India coming on board by end of the year,” Svanberg said. “Additionally, we see that in the 3G networks that we monitor in Europe data traffic now exceeds voice and accelerates quickly, from between 50% to 1,500% depending on the operator’s strategy.”

Still, all of the major infrastructure vendors and even some carriers were talking about 4G, and especially LTE. Verizon Wireless announced last fall that it would abandon the CDMA evolutionary path and target LTE for the future. Four more of the world’s largest carriers, Vodafone, China Mobile, NTT DoCoMo and AT&T Mobility, also have said LTE is in their future as well.

Expected fixed and mobile broadband growth through 2012.

THE FACES OF LTE
Vodafone has a financial interest in both Verizon Wireless and China Mobile and the three carriers plan to test the technology together. China Mobile will be looking at both frequency division and time division flavors of LTE, the latter because it is expected to deploy TD-SCDMA as a 3G technology this year and would like the backward compatibility.

The basic LTE standard was only approved in late January and is still under final review before becoming part of the upcoming 3GPP Release 8 protocols. Like other air interface technologies couched as 4G, LTE uses orthogonal frequency division multiple access (OFMDA), as well as multiple-in, multiple-out (MIMO) antenna strategies.

Most analysts think it will be at least 2010 and more likely 2011 before LTE equipment starts getting deployed. That’s creates a possible opportunity for another technology some call 4G – WiMAX. WiMAX doesn’t yet have the data rates that LTE (10 Mbps vs. 100 Mbps) but still could provide multimedia applications like video.

Analysts have just started making forecasts for 4G uptake, including LTE, WiMAX and 3GPP2’s Ultra-Mobile Broadband (UMB) fostered by the CDMA community. ABI Research is expecting more than 90 million subscribers for LTE and WiMAX in 2013. Another research firm, Analysys, is suggesting the number of LTE subscribers will hit 400 million by 2015.

Flat architecture of Long Term Evolution (LTE) as well as the system architecture evolution.

WiMAX PUSHING LTE
WiMAX networks are rolling out globally, mostly by greenfield and fixed-line operators. A notable exception is Sprint’s Xohm deployment, which has been in trials in three cities and is expected to soon launch commercially.

The rollout of WiMAX is one of the big reasons many analysts think the LTE vendors and carriers are being more aggressive with launch plans.

“LTE is being pushed along as a result of WiMAX actually being where it is,” says Godfrey Chua, research manager with the analyst firm IDC. He says WiMAX is not necessarily a competitor to LTE as a technology, but that traditional cellular carriers have not shown much interest in WiMAX and want to have a technology roadmap that matches or surpasses WiMAX.

Of course, the traditional GSM carriers also will have another technology evolution before reaching LTE. That’s HSPA+, the next iteration in the W-CDMA/HSPA technology that expects to provide data rates of about 24Mbps to 40 Mbps. HSPA+, also called HSPA Evolved, is expected to be deployed starting in 2010.

UMB, meanwhile, is either a dead technology or will have only a niche role in the future, depending on who you’re talking with. Chua points out that Pat Russo, Alcatel Lucent’s CEO, showed a slide at MWC that showed the technology path of both CDMA EV-DO and UMTS converging on LTE. “When you have the largest CDMA vendor in the world talking about LTE, it’s indicative of where things stand,” he says.

Allen Nogee, principal analyst for In-Stat on wireless technology and infrastructure, says flatly that “UMB won’t be happening.” He says UMB is a good technology but there are just two few customers available to it now that Verizon Wireless has taken the LTE route.

“UMB requires a large base station change, and if you are going to do that, why not just switch to LTE or WiMAX,” he asks. “Even Qualcomm has made working on the CDMA-to-LTE migration path a priority.

Standardization timeline for 3GPP Long Term Evolution (LTE).

THE MULTIMODAL PLAY
In fact, Qualcomm has joined with Vodafone, Ericsson and Huawei on a forthcoming trial of HSPA+. Vodafone started deploying HSPA last year, with data rates of up to 7.2 Mbps.

Peter Carson, senior director of product management in Qualcomm’s semiconductor group, says access to all these various air interfaces will be done on the device side through multimodal chips. Qualcomm announced in February it was expanding its device and base station chipsets to include LTE along with UMTS and CDMA2000. Carson says the chipsets will allow backward compatibility to legacy UMTS and CDMA2000 networks for carriers that deploy LTE.

Qualcomm’s multimode LTE chipsets will start sampling next year, assuming the 3GPP finalizes the standard.

Carson says Qualcomm hasn’t given up on UMB because few operators have signed commercial contracts for LTE. Meanwhile, he says, 3G technology improvements are going to improve performance for those technologies, especially where spectrum bands are 5 MHz or less.

“We have EV-DO Rev. B and Release 8 for UMTS under way,” he says. “3G isn’t standing still. The bar continues to get raised by 3G. That makes differentiation a challenge even in OFDMA standards.”

Bhikshesvaran: Ericsson has demonstrated LTE with data rates of 160 Mbps.

Qualcomm also has no plans to enter the WiMAX market, but Carson says the company is watching how that technology rolls out.

Arun Bhikshesvaran, Ericsson’s chief technology officer and strategy vice president for North America, says the company has demonstrated LTE with data rates up to 160 Mbps in frequency division duplex (FDD) mode and also recently demonstrated LTE using both FDD and time division duplex (TDD) on the same base station. The company also made what it says was the first demonstration of an end-to-end phone call using LTE, with handsets developed by Ericsson Mobile Platforms.

Bhikshesvaran thinks LTE will be rolled out first in Japan and the United States. He notes the United States isn’t playing second fiddle to anyone in wireless technology, being the first in the world with W-CDMA/HSDPA with AT&T’s launch more than a year ago. LTE could even find a home in a network deployed by winners of the FCC’s ongoing 700 MHz spectrum auction.

During MWC, Vodafone CEO Arun Sarin said WiMAX might somehow find a future in the LTE standards. The two are not compatible now, although Danny Locklear, director of wireless product marketing at Nortel, says there are many similarities, especially in the use of OFDM and MIMO.

Locklear: Industry politics could prevent any LTE/WiMAX compatibility roadmap.

But Locklear thinks any linkup between LTE and WiMAX may be doomed just because of the politics. The GSM/UMTS community needs backward compatibility with LTE, while WiMAX doesn’t have any backward compatibility. He also notes that most traditional cellular carriers are going to opt for LTE, while WiMAX will provide a differentiated mobile offering for greenfield and fixed-line operators.

“We see Sprint as unique,” Locklear says. “Most existing cellular carriers we believe will move to LTE, which will require some level of backward compatibility.”

Will the 2- or 3-year time-to-market advantage for WiMAX delay the deployment of LTE? Locklear thinks not, just because there is such momentum being generated by carriers like Verizon Wireless, Vodafone, DoCoMo, and AT&T. Ericsson’s Bhikshesvaran agrees.

“The momentum behind LTE is extremely powerful now,” he says. “From the 3GPP track, 3GPP2 track and from China. Some of the largest operators in the world are behind it. They represent a significant chunk of consumers and enterprises on wireless today.”