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Will 4G LTE devices ever roam internationally?

The widespread acceptance of 4G LTE was supposed to unite wireless operators around the globe. But the worldwide spectrum crunch is making international roaming a tough problem to solve.

It's true that today iPad owners, along with other 4G LTE smartphone and tablet owners in the U.S., won't be able to roam onto international 4G LTE networks while traveling. But will that change in the future?

When Apple introduced its third-generation iPad last week, it took the wraps off the first Apple device to get 4G LTE, giving the tablet super-fast wireless access on both AT&T and Verizon Wireless, even when Wi-Fi isn't available. But for iPad users taking their devices overseas, 4G LTE access won't be available. For some, this tiny fact may not matter much, since the device will be able to roam on 3G networks that use the HSPA and HSPA+ standards. And the iPad will still be able to access Wi-Fi. But the lack of 4G LTE roaming on the device highlights a fundamental issue with all LTE devices.

The problem is simple: There's not enough spectrum available throughout the world in the same frequencies to make roaming between networks easy or cost effective. So even though most of the world's wireless carriers will finally be operating networks using the same basic technology, they still may not allow for easy international roaming.

"The fragmentation in 4G is driven by spectrum scarcity," said Neville Ray, chief technology officer for T-Mobile USA. "The International Telecommunications Union tried 15 years ago to harmonize the spectrum plan globally, but what works well for one country or region doesn't work well in another region. So we have this patchwork approach."

Fragmentation is a killer
A recent report published by the GSMA's Wireless Intelligence Service predicts that at least 38 different radio frequency combinations may be used in LTE deployments in the next few years. For example, operators in the U.S. are mostly using 700MHz spectrum to build their 4G LTE networks. But in parts of Europe operators are using 2.6 GHz. China is using 2.5 GHz. Japan is using 2.1 GHz. And many markets in Southeast Asia are using 1.8 GHz.

And devices built for one band of radio frequency won't work on a network that uses a different band. In other words a Verizon 4G LTE smartphone that operates on 700MHz spectrum in the U.S. will not operate on TeliaSonera's 4G LTE network in Sweden, which uses spectrum in the 1800MHz band.

There are similar spectrum differences among countries when it comes to 2G and 3G networks. But what's different about the shift toward 4G is the shear number of radios that must be supported to offer roaming. When 2G and 3G spectrum was allocated, regulators in various regions of the world were able to work together to develop more comprehensive spectrum plans that necessitated fewer radios in devices.

But now spectrum in almost every part of the world is harder to come by, which means more radios must be supported in devices to allow for international roaming.

Some experts in the industry say that the lack of cohesive spectrum planning has fragmented the market so much that it will be difficult and expensive for device makers and carriers to ever make roaming from one LTE network to another anywhere in the world as seamless as it is today for mobile subscribers to roam onto 3G networks.

"We'll likely see some LTE roaming between different regions and carriers," said Chris Pearson, president of the industry trade group 4G Americas. "But it won't be worldwide roaming."

But others are more optimistic. Dan Warren, senior technology director for the GSMA, an international trade group promoting GSM technology throughout the world, is confident that technology advancements will prevail and save the day for future LTE device-toting globe trotters.

"It's a nice headline grabber to say the market will be too fragmented," he said. "But I think that's far to pessimistic. It won't be the reality."

Warren thinks that in the future, devices can be built to accommodate the most widely used spectrum bands. Even though there could be close to 40 different frequencies used for LTE around the world, Warren said that this number can be whittled down to between 10 to 15 different bands that are used most widely, and about six or seven bands that might offer global support for roaming.

And he believes that technology is advancing rapidly to get more radio technologies handling more frequencies into devices at a much lower cost.

"What's happening in terms of the number of radio technologies that can be added to a chip is not classic Moore's Law, but it's similar" he said. "There has been a lot of change in the past 9 to 12 months. And we're seeing chipsets go from single and dual frequency to four and five frequencies."

Today's so-called "world" phones already need to operate in about six bands to get access to 2G and 3G networks around the world. To include LTE roaming, wireless devices will need another six or seven frequency bands, Warren estimates. This means that the next generation of truly mobile "world" devices will need at least 12 frequency bands.

The highs and lows of wireless spectrum
Warren said that there is more spectrum available globally at higher frequency bands. For example, he believes that there is a chance that a global band of spectrum for 4G services could be allocated at the 2.6 GHz band or even higher at 3.5 GHz.

The problem is that high frequency spectrum bands need to be paired with lower frequency bands. With higher frequency spectrum, carriers can build more capacity into their networks. But because of the spectrum used in these networks, the range of the network is much smaller than using spectrum at lower frequencies. So the actual cell sites are much smaller.

Also, spectrum at higher frequencies is not ideal for indoor coverage. The reason is that signals at higher frequencies don't propagate as easily through obstacles, such as walls. This makes high-frequency spectrum problematic for in-building coverage.

Spectrum in the lower bands is scarce because it's already been allocated for other purposes. For instance, the 700MHz that U.S. operators are using for LTE was initially allocated for analog TV. The FCC was able to free up spectrum in this band when it forced TV broadcasters to broadcast in digital rather than analog back in 2009. This made more efficient use of spectrum and allowed the FCC to clear a large chunk of spectrum, which it auctioned off in 2007.

The problem the U.S now faces is that the 700MHz block of spectrum its carriers are using for LTE isn't being used outside of North America. Canada is using 700MHz spectrum for LTE. And it looks like Mexico will use it as well. But Europe, Asia, the Middle East, and Africa using different bands. And it's unclear if the rest of Latin America will follow in the U.S.' footsteps.

"American operators using the 700MHz band of spectrum are a little bit isolated," Warren said. "It would be great if they were able to open up more spectrum that could be paired with this spectrum for roaming."

Regulators have tried to do this. But so far their efforts have been unsuccessful. The U.S. government is sitting on spectrum between 1755MHz to 1780MHz that could be paired with unused AWS spectrum in 2150MHz band. But so far, the U.S. Defense Department, which controls this spectrum has not made a move to clear it for commercial wireless broadband use. And in the latest piece of legislation authorizing spectrum auctions, there was no mention of the 1755MHz spectrum.

"The unemployment extension bill that recently passed in the U.S. and was signed by President Obama had some very positive elements in for freeing up unused TV broadcast spectrum," Pearson said. "But we were disappointed that that there was nothing about auctions for the 1755MHz spectrum."

Pearson went on to say, "This spectrum would nicely pair with the already cleared 2150MHz AWS spectrum. In fact there are already 80 devices ready to take advantage of this spectrum combination. And Latin America was ready to follow as well."

3G to the rescue
The good news is that regulators, engineers and wireless operators have some time to figure out some things. For now, there are few LTE networks for current LTE subscribers to even use when they travel. According to market research firm Wireless Intelligence, there are 52 live 4G LTE networks deployed in 30 countries. By contrast, there are 400 3G networks using HSPA.

But as demand for more wireless data around the world increases, more operators are deploying LTE. Still, there are more networks using the next generation of 3G technology known as HSPA+. There are already 159 HSPA+ networks deployed throughout the world in 149 countries, according to Wireless Intelligence. This will likely be the network on which world travelers with advanced devices will roam.

And given that 4G LTE subscribers in the U.S. are used to average download speeds of 12Mbps, roaming onto an HSPA+ network, which can achieve similar data rates, might not even be noticeable.

"When you think of LTE roaming in the near term, it's called HSPA+," Pearson said. "And for most consumers that's probably just fine. It's really about the overall experience rather than the technology. And HSPA and HSPA+ is here today and will be around for a long time."