WiMax vs. Long Term Evolution: Let the battle begin

GSM carriers widely plan to back LTE, but WiMax will push competitors in the U.S

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"Although LTE is on the GSM track, it really requires new equipment" at base stations, said Lisa Pierce, an analyst at Forrester Research Inc. That means a substantial investment is in store for AT&T and also for Verizon, which has focused on CDMA (Code Division Multiple Access), but partners with Vodafone, a GSM carrier favoring LTE. The cost of a national WiMax network will be billions of dollars, and an expenditure of that much money would not have been possible without the Clearwire-Sprint joint venture.

Uplinks from the user to the cell tower will probably be different in the two technologies. OFDM will be used in WiMax, but a technology called SC-FDMA (Single Carrier-Frequency Division Multiple Access) will be used in LTE, Solis said. SC-FDMA is theoretically designed to work more efficiently with lower-power end-user devices than OFDM is.

Both technologies will be IP-based, which will enable quality-of-service technologies to be applied, although it is not clear whether carriers will offer guarantees of service to business users. The big push for WiMax has been with consumer-based devices so far, and service guarantee considerations have been secondary.

"How much differs between LTE and WiMax remains to be seen, since LTE is not standardized yet," Pierce said. LTE is designed to turn voice and data traffic into packets, which bodes well for unified communications applications, she said. In theory, WiMax will also be able to support voice, but whether it is used for voice "remains to be seen."

The spectrum difference in the U.S.

Both Verizon and AT&T picked up 700 MHz of spectrum in the recent Federal Communications Commission auction, and both carriers said the spectrum will be used for LTE. Meanwhile, Sprint had already been expecting to use its generous holdings of 2.5 GHz spectrum for WiMax. And the Sprint-Clearwire joint venture expects to control about 80% of that spectrum for the WiMax rollout in the U.S.

Since two different bands of spectrum will be employed, WiMax and LTE transmissions will have different physical properties. And that, in turn, will influence the costs of building base stations and the expensive gear inside.

LTE can run on a variety of spectrums, but the lower 700 MHz frequency will provide greater range and better in-building penetration than a higher frequency would, Pierce said. Still, a lower frequency means that boosting the speed of a transmission might require technologies such as compression and the ability to bond channels together to improve performance.

In comparison, since WiMax will use 2.5 GHz spectrum, bits won't be able to travel as far as they would at a lower frequency. And that suggests that WiMax providers will need to "blanket" service areas with base stations to avoid attenuation, which is the loss of a bit's strength as it travels through air or another medium, Pierce said.

Spectrum properties and the physical layout of cell towers and base stations are ongoing concerns of the carriers. At AT&T, engineers are moving forward with LTE after carefully testing WiMax, which is "very good technology," said AT&T spokesman Mark Siegel. "It appears to be very good for fixed mobility, such as a neighborhood or shopping mall, but it's not clear yet how it will perform over wide distances as people are mobile," he said.

Motorola, Intel and others demonstrated mobile WiMax at the CES and the CTIA conferences earlier this year in Las Vegas, driving cars through busy city streets to show connections to WiMax antennas installed for the tests. The WiMax handoff of signals from tower to tower worked the majority of times on two separate runs conducted for Computerworld but failed at least once on each run. Last fall, a boat on the Chicago River made smooth handoffs as it cruised along, allowing video streaming to laptops and handheld prototype devices.

Siegel said AT&T is convinced it can find cost efficiencies with LTE as an upgrade to GSM, allowing it to use its current infrastructure of 48,000 towers and related base station equipment nationally. "By comparison, WiMax has to start from ground zero," he said.

Sprint disputes that characterization, noting it has long held the 2.5 GHz spectrum being used for WiMax, among other basics, including the rights to use its existing cell towers.

The bottom line

For end users, the current debate over WiMax vs. LTE is largely theoretical but is nonetheless important. Technology investors are the most interested now, because billions of dollars being invested today will have clear implications for millions of users in, perhaps, three years.

Analysts see a clear dominance by LTE in a few years. Among other things, it could support global roaming for users of high-speed wireless devices, since so many carriers are bound to adopt it. However, that won't serve every user or every company, Redman noted.

"The bottom line is that one technology will not cover all the user needs for home, office, local or international services," Redman said. "It is still going to be a combination of technologies and developers. WiMax may be one of those, but LTE will predominate."

For users, technology competition should always be considered beneficial, noted Jack Gold, an analyst at J.Gold Associates. "One thing is certain," he said. "The new Clearwire joint venture will spur the other guys to get their act together and get LTE out in the field."

Copyright © 2008 IDG Communications, Inc.

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