ip.access will be one of the Wi-Fi infrastructure vendors stepping up its game at the Mobile World Congress later this month after the UK-based company announced plans for the E-100, its first combination 3G and 4G small cell, with a Wi-Fi upgrade slot, for enterprises and indoor public spaces such as shopping centres and stadiums.

ip.access, the maker of AT&T's Microcell consumer femtocell, will demonstrate the E-100 in Barcelona and expects to have it in field trials in the first quarter of 2013.

Mobile operators are looking at smaller cells and Wi-Fi to better cover indoor spaces and crowded areas, with Wi-Fi offering the added benefit of taking users off the carrier's scarce licensed spectrum. New technology is emerging for managing these new types of infrastructure in a larger network and for subscribers to shift between different radios invisibly. But exactly how carriers will use smaller cells and Wi-Fi is still emerging.

Mobile World Congress, beginning February 27 in Spain, is expected to become the stage for many debuts in this area. Already, Alcatel-Lucent has announced lightRadio Wi-Fi, a technology to more tightly integrate Wi-Fi with its cellular infrastructure, and will demonstrate it at the show. Last week, Stoke announced an appliance for shifting users on to Wi-Fi hotspots. Earlier this week, BelAir Networks announced performance and management enhancements to its GigXone lineup of small cells and access points. And earlier this week, the femtocell industry group Femto Forum said it would change its name to Small Cell Forum to better reflect the diversity of smaller cells stretching beyond tiny femtocells designed for homes.

"These guys are doing this because they're hearing this from operators," analyst Peter Jarich of Current Analysis said.

The E-100 is a small cell designed for heavier duty than a consumer femtocell. The device is designed to serve as many as 64 subscribers with 4G LTE (Long-Term Evolution) and simultaneously support 32 users with 3G. It will include 3G UMTS (Universal Mobile Telecommunications Service) technologies up to 42Mbps (bits per second) and will be able to offer 150Mbps on LTE, said Andy Tiller, senior vice president of marketing and strategy at ip.access. All the users on the small cell will share those capacities.

The E-100 will have an integrated antenna and a range of about 100 metres, Tiller said. An Ethernet port will provide both wired backhaul and the power to run the unit. Carriers will also be able to implement other types of backhaul as needed, he said.

The add-on Wi-Fi module is intended to give carriers an alternative network and eventually to supplement the capacity of the cellular radio. Carriers have been asking for this type of capability so they can offload traffic from their traditional outdoor network or get it off the cell network altogether, based on the demand for capacity, Tiller said. Using an emerging standard called IP Flow Mobility, the small cell will be able to use the 3G, 4G and Wi-Fi networks in combination for even more capacity, he added. Client devices as well as the cell would need additional software to make that possible.

The E-100 represents a big step up from femtocells such as the AT&T MicroCell, which forms a closed network for just a handful of users in a home, such as a family. Like most other femtocells, the MicroCell is intended primarily to improve indoor voice coverage. Enterprise-class small cells such as the E-100 are designed to add capacity in indoor settings, where outdoor macro cells may not be able to provide good performance.

A small cell with built-in Wi-Fi gives carriers options for how to provide wireless capacity in an enterprise or public venue, Jarich of Current Analysis said.

"It opens up a new model where you can go in and offer the Wi-Fi side of things, and at the same time catch the 3G side of things for yourself," Jarich said. "There's all sorts of stuff you can do when it's all in that one access point."

However, there are still unresolved issues about small cells, Ovum analyst Daryl Schoolar said. For example, it's not yet clear how small cells will communicate with macro cells to prevent interference between them, he said. To simply add mobile data capacity, many carriers will simply use Wi-Fi, he said.

"Small cell runs the risk of being just a little overhyped," Schoolar said.