The Avenue Link Lite radios can use either licensed or unlicensed frequencies. Sub-6GHz backhaul in some bands can suffer interference from other networks, including some Wi-Fi systems, but it's well suited to dense urban areas, Solheim said. That's because sub-6GHz radios are good at bouncing around buildings and other obstacles to reach a wired-up destination radio that may be around a corner, he said.
DragonWave has also repackaged a higher-frequency backhaul unit, the Avenue Link, to better fit with small-cell installations. It shrank the high-frequency radio by half, to less than nine eight inches square and six inches deep, Solheim said. Also at MWC, DragonWave will introduce the Avenue Site, a small cabinet that can accommodate a base station, backhaul radio, antennas and other components in a unit that's small enough to be mounted on a light pole.
Tarana, also a wireless backhaul specialist, will demonstrate a line of products it announced last week. The AbsoluteAir series can provide a full 75M bps (bit-per-second) backhaul capacity to each small cell in a metropolitan area, the company said. That means carriers can expand their networks to keep up with subscriber demand and enjoy the same backhaul speed each time they add a cell, according to Tarana. The AbsoluteAir products can be deployed in just 15 minutes, the company said. They are in trials at multiple carriers in the U.S. and Europe.
Mobile infrastructure giant Ericsson is updating its Mini-Link small-cell backhaul offerings as part of a broad set of new products coming at MWC. Among the products the company plans to roll out are a microwave backhaul system using the unlicensed 60GHz band and another unit that uses an even higher band at 70-80GHz for 1G bps throughput. China's ZTE also announced small-cell wireless backhaul gear earlier this month, including products that use microwave, Wi-Fi and time-division LTE links.
Look for small cells to start easing mobile bottlenecks first in dense urban areas, where demand is usually highest. The first of those will probably feed off wireless links to the nearest large cell, taking advantage of its fast fiber connection, according to Infonetics. Those wireless links to small cells are likely to use a mix of high-frequency and low-frequency systems depending on the site, Infonetics analyst Michael Howard said. Where macrocells on building roofs don't have line of sight to small cells that are closer to the street, carriers may have to use sub-6GHz non-line-of-sight technology to get around corners.
The obstacles are more than just buildings, but also include trees, rain and wind that blows lampposts around and changes the direction of point-to-point links, said Gubbins of Current Analysis.
"As they deploy small cells in urban canyons ... a toolkit approach is important," Gubbins said.