Mobile data traffic is growing…and fast. A new approach aims to seamlessly offload data from carrier networks to Wi-Fi in response to the demand for more bandwidth.

Wireless data use is growing by leaps and bounds. The Cisco Visual Networking Index (Global Mobile Data Traffic Forecast Update 2011-2016) forecasts that worldwide mobile data traffic in 2015 will be 26 times greater than it was in 2010. And while there is considerable controversy about the details of estimates, there's no question that demand is growing much faster than carriers' available bandwidth, even with considerable improvement in efficient use of the airwaves.

One solution is moving a good chunk of the data that currently moves over carrier networks onto Wi-Fi. Today that is much easier said than done. But a new approach called Hotspot 2.0 should make seamless transitions between cell-type networks and Wi-Fi a reality.

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Wi-Fi offload already works well when you are in familiar surroundings. Today's smartphones and tablets are designed to use Wi-Fi when it is available. When a device detects a network on which it is already registered—say your home or office—it automatically connects. Public networks don't work so well, unless they are completely open—and then you face the problems that you don't really know what is on the other end of that network and that all wireless traffic is completely unencrypted.

Hotspot 2.0 (called Passpoint by the Wi-Fi Association and IEE Standard 802.11u by engineers) is designed to make this transition from cell-type networks to Wi-Fi completely seamless. Its big advantage to carriers is that it will  lighten the load on their increasingly overburdened networks while allowing them to control access to private or shared Wi-Fi networks. For users, it means faster and more reliable networks, especially where demand for service is very high.

One thing that has made switching from carrier networks to Wi-Fi difficult is that typically some sort of login process is required. If the network is secured by Wi-Fi Protected  Access, the user needs to know the passphrase. This presents the carrier with the huge problem of distributing passphrases and still makes it all but impossible to restrict access to paying customers. (Wi-Fi is much cheaper to deploy than cell-type networks, but there still is significant cost involved, especially the expense of the "backhaul"—connecting access points to the internet backbone.)

The alternative leaves the access point open, but uses authentication, typically a username and password, to a server to gain access to the internet. This controls access well, but requires a manual login, making the process anything but seamless.

Hotspot 2.0 (see illustration) automates the process. Instead of the user logging in, the phone or other mobile device can identify itself to the network, most often by using the same Subscriber Identity Module (SIM) card used for authentication on the carrier network.  The Wi-Fi network checks with the carrier to make sure the device is authorized before letting it connect to the internet. The process is quick and invisible. (If you care to know about it in a lot more detail, check out this Cisco white paper.

Niels Jonker, chief technology officer for Boingo, a leading operator and aggregator of Wi-Fi networks, says he expects to see Hotspot 2.0 networks start to appear early in 2013. The first installations are likely to be in sports stadiums, where the tightly packed mass of device users often overwhelms the network, especially when everyone tries to send a photo at the same time.  Although the wireless capacity assigned to Wi-Fi is quite small, it is possible to restrict access point coverage to a small area, which allows the same channels to be used over and over. You can also expect to see Hotspot 2.0 installations show up in densely populated urban settings, such as the Times Square area of New York.

Hotspot 2.0 won't solve all the problems of today's wireless networks. Wi-Fi is not designed for rapid handoff between access points, so it's not going to work well in moving vehicles. It's not likely to do much to fill-in coverage dead spots either. But it could go a long way toward solving a growing capacity crunch.

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About Steve Wildstrom @swildstrom

Steve Wildstrom was a veteran technology journalist who wrote the Technology & You column at BusinessWeek.