The controversy over Apple's iPad 3 not working on Australian LTE networks may be just one signal of problems ahead for international LTE roaming.
LTE spectrum: How much do the big carriers have?
Apple said Tuesday it would give refunds to Australian owners of the iPad 3 if they were disappointed that the tablet couldn't tap into LTE in that country. The company had come under fire from Australia's competition authority for promoting the iPad 3 as a 4G device even though it's not compatible with any Australian LTE networks. iPad owners there have no option but to rely on 3G.
That case involves consumers using a foreign-designed product in their home market, but it reflects a looming problem for travelers who want fast services in other countries, according to industry analysts: The scramble for spectrum to feed mobile-data appetites is fragmenting the frequencies used for LTE. This is likely to make international roaming harder and relegate some users to slower speeds than they are used to at home.
In the age of 2G, four bands were enough to qualify a handset as a "world phone." The 850MHz, 900MHz, 1800MHz and 1900MHz bands were used by most carriers in Europe, Asia and the Americas, or at least those on the globally dominant GSM standard. With 3G, roaming remained fairly simple at least in Europe, where the European Union prescribed certain bands for the new mobile data technology. But elsewhere in the world, frequencies started to diverge as carriers deployed 3G.
Even now, some 3G subscribers have to fall back to slower standards such as EDGE when they leave their home countries. "It happens all the time," said analyst Avi Greengart of Current Analysis. For example, a "world phone" equipped for both the CDMA and GSM standards may not leave you stranded without Internet access, but it's no guarantee of consistent speed, he said.
Now, individual European countries want to reuse some of their 2G and 3G spectrum for LTE, and many other bands are being adopted elsewhere in the world for the new technology. In the U.S., Verizon Wireless and AT&T bought 700MHz spectrum for their 4G networks, Clearwire plans to deploy LTE on 2.5GHz, and more new solutions are being explored all the time. The 3GPP (Third-Generation Partnership Project) standard for LTE specifies more than 30 different frequency bands in which the technology can be deployed, though not all of those will necessarily be used, according to the 4G Americas industry group.
Even discounting bands that are only used for a single, isolated network, that still leaves a long list of frequencies, said analyst Peter Jarich, also of Current Analysis.
"If we start with this assumption that operators need more spectrum, then you end up with fragmentation," Jarich said. "The one is just going to follow from the other."
Two forms of LTE
Adding to the complexity, LTE can be implemented in two different variants, which use either paired spectrum bands (FD or frequency-division) or a unified band (TD or time-division). Which one a carrier will use depends on what kind of frequencies it can get. On top of that, many of the LTE networks set to come on line aren't built yet, and some of those don't even have frequencies assigned.
"It's going to be a problem for quite some time," said Tolaga Research analyst Phil Marshall. There are simply too many possible combinations of LTE variants and locally assigned frequencies to practically sell mobile devices that work with all of them, Marshall said.
While it's theoretically possible to build a phone, tablet or portable hotspot that could be used on all the LTE networks in the world, the task grows more difficult as bands are added, Greengart of Current Analysis said. In addition to including many radios, the universal device would have to have an antenna that could be tuned well to all those LTE frequencies. Plus, high-end handhelds today include Wi-Fi and Bluetooth as well. "That's an awful lot of frequency bands and antennas," Greengart said.
Qualcomm says its Gobi 4G/LTE modem chipset supports most of the frequencies being used for LTE, and it is up to manufacturers to decide which bands to support in a given device. The second generation of the chipset will support all the LTE bands, as well as 2G and 3G bands, in the 3GPP standard, Qualcomm said. The greater challenge in designing multi-frequency devices is fitting in the radio-frequency components for each band, according to Qualcomm.
Handset makers and carriers aren't focused on making devices to run on all the world's LTE networks, Greengart said. "They're interested in the least expensive device that works on their network and, in some cases, works on common networks that their customers demand compatibility with."
The way out
Over time, mobile operators may be able to settle on one or two frequency bands available in most countries to allow LTE roaming, Jarich said. Two possibilities might be TD-LTE in the 2.3GHz or 2.5GHz bands, he said. But a carrier in each country would have to build and operate a network to make that solution a reality.
The better answer for global high-speed roaming may come from Wi-Fi, Jarich said. Cellular carriers and Wi-Fi hotspot operators are working on making it easier for phones and tablets to roam between mobile and Wi-Fi networks worldwide. The GSM (Global System for Mobile Communications) Association and the Wireless Broadband Alliance (WBA) said earlier this year they expect to have a framework available within nine months to make roaming to Wi-Fi as smooth as it is between cellular networks.
Wi-Fi, which runs on unlicensed frequencies that are fairly consistent around the world, with a few exceptions, can offer even more speed than LTE. The new roaming techniques will also improve the security of hotspots, the GSMA and WBA said. But they cautioned that easy roaming may take a few years to be rolled out.