Dead zones could impede LTE roaming

Mike DanoThe pending introduction of LTE in the 700 MHz band in the United States sets the stage for a headache of massive proportions for RF engineers charged with ensuring interoperability among 2G, 3G and 4G systems.

As Martyn Roetter, an independent telecommunications consultant based in Boston, pointed out, Verizon Wireless' (NYSE:VZ) forthcoming 700 MHz LTE network will pile onto a veritable spectrum soup spanning GSM/WCDMA at 850, 900, 1800, 1900 and 2100 MHz; AWS throughout the Americas (except Brazil and Uruguay); 790-862 MHz in Europe and other UHF variants elsewhere; 2.6 GHz (FDD and TDD) in Europe and elsewhere; 2.3 GHz in China, Korea and India--and the list goes on (and it doesn't include the radios needed to run Bluetooth, WiFi and GPS).

"Multi-mode, multi-frequency terminals are required or highly desirable in any scenario for mobile broadband," Roetter wrote to me in extensive comments on the topic (the full text of Roetter's statement to me is here). "It is not affordable to roll out new mobile broadband services rapidly to cover entire countries. Hence there is an inevitable need to support fallback to legacy technologies with wider existing coverage. So the real question is how many should be supported, and whether all small markets can or should be accommodated."

Software Defined Radios in the future may help alleviate the need for network equipment and handset makers to support seemingly dozens of wireless spectrum bands, but that technology isn't expected to hit the scene anytime soon. Thus, vendors will need to continue to weigh the number of spectrum bands they want to support with the size, price and battery life they want to provide in their devices.

It's a difficult balance--and it's one that has taken on new meaning in the race to build out LTE technology in the 700 MHz band. A group of smaller carriers (including MetroPCS (NYSE:PCS), U.S. Cellular and Cox Communications) is urging the FCC to require network and handset vendors to build LTE equipment that can work across the four different spectrum band classes that crisscross the 700 MHz band. These carriers argue they will be unable to build out their 700 MHz holdings because the 700 MHz spectrum Verizon and AT&T Mobility (NYSE:T) plan to use for their respective LTE buildouts is different from the A Block 700 MHz spectrum purchased by a number of smaller carriers.

It's an issue that delves into the heart of competition in the U.S. wireless market, and reaches into areas including public-safety broadband networks and data roaming. Check out my special report on the topic here.

Ultimately, I'm not sure how the FCC will come down on the issue, but I would be surprised if the agency issued a controversial decision on what is, in the big picture, a relatively obscure issue. But that doesn't mean it's an issue that should be ignored.

Roetter concluded: "I tend to be biased in favor the 'little guys' and am inherently skeptical of the motives and sincerity of very large organizations. But in this case for the most part I agree with the 'big guys' who say that a mandate in favor of full-spectrum 700 MHz LTE equipment is not justified." --Mike