The LTE conversation has so far been about two things: consumer devices supporting LTE, and operators building out LTE networks. Both are important aspects, but they’re not the whole story. The commentary that’s missing is the next layer down. (This is the third in a three-part series. If you haven’t already, be sure to also read part one on consumer benefits, and part two on operator benefits.)
If you’re one of the lucky few using an LTE device on an LTE network, you’re probably getting used to the “new normal” of your faster data speeds, watching video on demand and all that. What you may not have discovered yet is that if you go on holiday to another country, your LTE may not travel with you. That’s a fundamental problem right now: there’s little LTE roaming, because of spectrum fragmentation.
Spectrum fragmentation? It’s a technical mouthful. Let me break it down.
Around the world, the radio frequency that we use to make mobile phone calls varies. In the UK, we use frequencies between 900 MHz and 1800 MHz. In the US, the military uses that band, so consumers are over on 1900 MHz (or 1.9 GHz).
A decade ago, if you tried to make a call in the UK on a US phone, it wouldn't work because the phone wouldn’t have been using the right radio frequency, or spectrum. So, Europeans had to use European phones. Americans had to use American phones. Asians had to use Asian phones. That’s spectrum fragmentation.
In the intervening years, manufacturers have developed “world phones” that work across the various spectrums. Apple’s iPhone is a great example. Before the iPhone 4S, there was only one phone, made on a single production line. Then iPhone 4S incorporated support for 10 different frequencies on both GSM and CDMA networks. It now costs a pretty penny to make calls and get data while you’re roaming, but you can do it—and without having to do anything special. The phone manages the frequencies and your operator makes sure your data plan travels with you.
Today, LTE has this same spectrum fragmentation problem. For example, a major UK broadcaster currently uses the same frequency as North American LTE networks (2100 MHz). When Canadians with LTE visit London, they can’t use 2100 MHz because EE, the only 4G provider in the UK, is over on 1800MHz. So, they’ll have to upload that video of the Buckingham Palace changing of the guard on 3G, which will take quite a bit longer than what they’re used to back home.
LTE spectrums are so fragmented globally that there’s no way one phone could possibly work everywhere. That’s why the iPhone 5 comes in three models with three different chip sets. All three support the global services of the 4S. Each of the three support 4G LTE in either Asia, Europe or the US. On the other hand, note that Google’s Nexus 4 doesn’t support LTE, and Google says the reason is that it doesn’t want to have to support all the frequencies.
The fact that Apple and other manufacturers are starting to solve the fragmentation problem is good news for LTE. When Apple introduced its first LTE mobile device—the “4G” iPad—it only worked on a handful of operators in North America. Today the iPhone 5 works on over 60 operators across the world. So increasingly, you’ll be able to connect to LTE networks when you travel.
The spectrum fragmentation is one issue. Another is whether or not mobile operators have the technical ability to offer LTE roaming services. If your operator doesn’t support LTE roaming, then you won’t be able to do it no matter what phone you use.
The build-out of high-speed LTE networks is different from that of earlier technologies. LTE uses a completely new signaling protocol, called Diameter. Completely above and beyond the SS7 MAP that 2G / 3G mobile networks use, Diameter requires mobile operators to establish new roaming connections. As operators launch LTE networks over the coming years, each one will have to set up new roaming connectivity. Effectively, the work operators have done over the last 10 years to upgrade to 2G and 3G will need to be repeated.
In fact, there’s a whole backend infrastructure improvement required to make this improvement. SAP Mobile Services (my employer) is working with operators now to upgrade their networks and make it happen.
Global LTE: we’re getting closer, but we haven’t yet arrived.