Microwave backhaul technology is now able to support 10 Gbps, and it’s well prepared to support the evolution of LTE and introduction of 5G networks, according a white paper (PDF) published by Ericsson.
As capacity needs have grown, the use of backhaul spectrum has shifted toward higher frequencies where larger channel bandwidths are more easily found, the paper noted. The attractiveness of the 70/80 GHz band is rapidly increasing, offering extremely wide bandwidth at a generally low spectrum fee, enabling capacities in the order of 10 Gbps or more over distances of a few kilometers.
Microwave backhaul hasn’t always been the first choice of some operators, but in the U.S., Clearwire in particular championed the use of microwave for backhaul. That company, which was acquired by Sprint in 2013, used microwave backhaul for 90 percent of its connections in its WiMAX network. More recently, Sprint CTO John Saw, who previously was with Clearwire, said he was confident that with a backhaul strategy of dark fiber and microwave radio and small cells being surgical and precise, “we can have a very low cost and efficient backhaul plan.”
Just last week, DragonWave saw its shares more than double in value after announcing that Sprint had selected its microwave backhaul equipment for network deployment as part of the company's densification and optimization strategy. Sprint will use DragonWave's microwave backhaul equipment as part of its strategy to densify its network through small cells and other solutions.
"Microwave backhaul is a cost-efficient, reliable alternative when used in the right ring structures, and it's a key part of the extension of our overall toolkit as we work to provide customers with more consistent coverage, better reliability, and even faster data speeds,” Gunther Ottendorfer, COO of Technology at Sprint, said in a press release.
In its white paper, of which The Mobile Network published excerpts here, Ericsson said the performance of microwave backhaul has evolved continuously with new and enhanced technologies and features that make even better use of available spectrum. “Microwave backhaul technology will continue to evolve and be able to handle 100 percent of all radio access sites’ capacity needs, today and towards 2025,” the paper stated.
Globally, even though the main growth is in the higher bands, some of the lower bands are also growing in popularity – 6 and 11 GHz, for example – due to local regulations, underutilization and good propagation properties in high rain rate regions. However, the band with the highest growth is E-band, or 70/80 GHz, the report stated. “After just a few years, there is now a substantial installed base with a solid footprint, and the band’s growth is accelerating,” it said.
Operators can also look forward to using the E-band spectrum to lower their spectrum fees. The paper pointed to Poland as one example, where the spectrum fee in E-band is 4 to 10 times lower than it is for the traditional bands. That’s had a dramatic effect on which frequencies are used. Existing links in traditional bands are being replaced by E-band links, and over just three years, “the E-band share of all installed microwave links has gone from 0 percent to 9 percent,” the paper stated. The same pattern was also seen in other Eastern European countries and markets where E-band spectrum fees are low.
Looking to the future, the industry also has an interest in the use of frequencies above 100 GHz for fixed microwave, which could enable the next leap in capacity toward 100 Gbps, over hop distances of up to a kilometer, supporting many different applications and use cases, according to Ericsson. Technologies are being investigated and regulatory studies are examining channel arrangements and deployment scenarios in the 92–114.5 GHz and 130–174.7 GHz frequency ranges, commonly referred to as the W and D-band for microwave backhaul.