Small-cell network architectures have gained significant momentum in 2011 among commercial mobile operators, and the trend is expected to be the basis of many LTE deployments going forward.

Once seen as an afterthought to backfill macro coverage with picocells, small-cell architectures now are becoming a critical piece of new LTE networks, because they are capable of providing higher capacity, greater data throughput and indoor coverage.

The idea is to use multiple network layers — macro cell and small cell — to improve user data rates and network spectral efficiency. It's a story about bringing users closer to a cell site, which makes more capacity available per user.

Big vendors have jumped in the market with new product offerings, some of which still need further development. Alcatel-Lucent announced a miniature base station earlier this year called lightRadio. Huawei is working on microcells, while Ericsson is building integrated antennas and radios to reduce the footprint of equipment. Nokia Siemens Networks recently announced Liquid Radio, which uses distributed antennae and virtualized baseband processing to provide a highly distributed architecture built around small cells and miniature base-station designs.

There are issues with small cells that need to be resolved, however. Namely, costs associated with mounting the thousands of base stations, interference and management and managing the tremendous amount of backhaul traffic that will be generated.

Heterogenous networks — those with small and macro cells — will be part of 3GPP Release 10 of the LTE standard, but network equipment remains several years off, noted Yankee Group analyst Ken Rehbehn in a recent report. "Absent Release 10 features, MNOs (mobile network operators) may fail to get the desired level of integration into the larger radio plan. Compromised interference management and hand-off support will result."

But vendors are determined to get an early start. This week startup Wazco, which describes itself as an LTE solutions developer, has teamed with Interphase, AirHop Communications and DataSoft to develop a multi-sector, small-cell LTE base station.

Called the MetroStorm, the product includes a single, self-contained, integrated enclosure that can host up to four coordinated sectors that can be disguised as a street light. And it is powered by standard interfaces on street lights and power poles.

The small size is accomplished because the sector's power amplifiers are an integral part of the active antenna array, said Mike Nasco, CEO and co-founder of Wazco.

Several MetroStorm base stations can be combined into what is called the MetroStorm Cluster, which operates as a single unit because of AirHop's eSON (enhanced Self Organizing Network) technology and is designed to be deployed over a large area such as a city. SON refers to the ability of an LTE network to self-configure and self-optimize itself through the network lifecycle and is a planned part of the LTE standard.

AirHop's eSON technology is designed to extend SON well beyond the initial set-up phase to include distributed, real-time, intercell coordination capabilities that let neighboring base stations communicate with each other to dynamically manage interference, data throughput and quality of service (QoS), as well as optimize frequency reuse.

“Our architecture is designed to be adjusted often,” Nasco said. “You need to be aware of the UE QoS and who it is attached to, the adjacent frequency interference and what you can do to optimize the experience.”

Interphase's iSpan 36701 baseband module is powering the MetroStorm, while DataSoft is providing RF front-end hardware derived from its RF transceiver portfolio of tunable RF filters, software-defined radio and cognitive radio technologies.

The market can expect to see a host of players, especially femtocell vendors, coming to market with small-architecture solutions for the outdoors. Last week, femtocell vendor Ubiquisys announced an agreement with Texas Instruments to create a new generation of small cells that will combine TI's infrastructure solutions with Ubiquisys' adaptive and self-organizing capabilities to deliver what Ubiquisys calls an adaptive small cell.

The two companies plan to bring to market a range of dual-mode WCDMA/LTE small cells for public-space and metro environments, such as base stations designed for mounting on walls or street infrastructure. The first products are expected during the first half of 2012.