Ericsson unleashes LTE over the Wi-Fi airwaves

Carriers are constantly on the hunt for more 4G spectrum, but the airwaves they need may be right under their noses. Mobile network builder Ericsson has developed a new technology that allows carriers to add Wi-Fi spectrum to their LTE networks, boosting overall capacity and the raw speeds available to our smartphones, tablets and mobile hotspots.

The technology is called License Assisted Access (LAA) and it’s been worked on by wireless networking companies across the mobile industry, but at CES on Monday [company]Ericsson[/company] said it has a version of its small cell in the pipeline that takes advantage of LAA. A small cell is basically a big tower-mounted cell in miniature, and they’re used to surgically insert more capacity the network. By adding LAA to small cells, carriers would be able to amp up data speeds to their customers in the most high-demand places, particularly indoors where most mobile data is consumed.

Small cells would add surgical capacity to the most high demand areas of the network (source: Gigaom / Rani Molla)

Small cells would add surgical capacity to the most high demand areas of the network (source: Gigaom / Rani Molla)

LAA makes use of another LTE technology we’ve been hearing more and more about overseas and at home: carrier aggregation, which bonds together LTE transmissions from different bands. Instead of gluing together two traditional LTE networks over licensed spectrum, LAA tops off the network with any 5GHz unlicensed frequencies that aren’t being used at any given moment.

Basically, LAA will make LTE function under the same principles as Wi-Fi today: Any network can use the airwaves — they just have to coordinate to avoid interfering for one another. That means an LAA small cell will constantly be scanning the unlicensed airwaves looking for free channels. When it finds one it sets up its 4G connection.

Of course, anyone who has ever been in a crowded Wi-Fi environment – for instance, a big tech show like CES – knows that those airwaves can quickly become overcrowded. That’s the inherent limitation of LAA, Ericsson’s head of LTE mobile broadband Eric Parsons explained: since carriers don’t have exclusive access to the unlicensed airwaves they’re never guaranteed any set level of bandwidth.

But Parsons pointed out that an LAA network would never be crippled the same way a Wi-Fi network would because it still has access to the carrier’s underlying LTE network on licensed airwaves.

Let’s use [company]T-Mobile[/company] as an example. Its regular LTE network in Dallas used 20 MHz of its own Advanced Wireless Service spectrum for downlink communications, supporting a theoretical speed of 150 Mbps. That baseline capacity would always be available to T-Mobile’s customers, but with LAA the small cell could add another 20 MHz of unlicensed frequencies to that downlink. Depending on how crowded those airwaves are with Wi-Fi at the moment that additional speed might be as little as few megabits per second, but it could be as great as 150 Mbps, effectively doubling the network’s capacity to 300 Mbps, Parsons said. The network will always serve its licensed airwaves up as a main course, but any additional capacity it gets from LAA will be gravy.

Mobilize 2012 Neville Ray T-Mobile

Neville Ray, CTO, T-Mobile, speaking at Gigaom’s Mobilize conference (c) 2012 Pinar Ozger [email protected]

T-Mobile isn’t just a convenient example, it’s also an active backer of the technology. In a blog post today, T-Mobile CTO Neville Ray said he plans to use LAA in his network designs once the technology matures. When that happens will be hard to say though. While Ericsson said its LAA small cell will be available for commercial network rollouts this year, the mobile industry still has to release mobile phones and devices that can tap these new LTE frequencies.

But once LAA comes, Ray pointed out, mobile carriers would have a powerful new toy to build raw speed into their networks. Look at it this way: They typical LTE network today uses 40 MHz of spectrum. The unlicensed bands have 550 MHz of usable frequencies.