The need for easy-to-install and high-capacity microwave links, argued the CMO, was an industry necessity. Once you take China, South Korea and Japan out of the backhaul equation -- places where there is comparatively high reliance on fiber -- and Huawei thinks about 70% of macro base stations around the world are served in some way by microwave links. Full migration to fiber, then, is not going to happen anytime soon.
“Pushing fibre to serve base stations can be a slow, expensive and sometimes highly impractical way of installing backhaul,” he said. “On the other hand, high capacity 4G base stations and 5G has been developing very fast, so we still need to keep on developing microwave. It’s very important for the entire mobile broadband industry.”
If microwave is to be a viable alternative to fiber -- and offer lengthy product lifecycles -- Zhou said innovation needed to be ongoing. Internet traffic volumes, he pointed out, were growing tenfold every five years. 5G network topologies will also become much more complex than previous generations of mobile network technologies, supporting ‘massive’ Internet of Things. Microwave backhaul will also have to cope with interference-prone environments, in which macro base stations are combined with micro cells, using millimeter (mmWave) spectrum, to provide ‘deeper’ coverage through network densification.
To stimulate faster-paced innovation, and meet these challenges, Huawei moved its microwave R&D team from the fixed-network business -- it now works with R&D teams on wireless base stations. “There’s a lot of crossover, particularly on mmWave spectrum,” said Zhou. “I’m confident you’ll hear a lot more innovation news from us over the next few years.”
“1+2” = more advanced 5G Microwave
At this year’s MWC, Huawei’s microwave innovation focus was firmly on antenna design and modular radio frequency units (RFUs), which came in the shape of its “1+2” 5G Microwave Architecture.
The ‘1’ refers to a single antenna, which can cope with frequencies ranging from 6GHz to 86GHz. The ‘2’ refers to the pair of RFUs that can plug into the antenna. By using carrier aggregation techniques, each RFU -- operating between 6GHz and 42GHz -- can support four channels and crank up to 5Gbps capacity. By plugging two RFUs of this sort into the antenna, capacity can be doubled to 10Gbps. Wireless signals, using this combination, are capable of travelling up to 20km.
The beauty of the”1+2” approach is that it can support different RFU combinations, using different frequencies, to meet different performance parameters that operators might require. The single antenna can support E-band frequencies in the 80GHz range (71GHz–76GHz and 81GHz–86GHz), over which a single RFU can generate 10Gbps capacity. Two E-band RFUs? Capacity then doubles to 20Gbps. There is, however, a trade-off with the greater signal attenuation that comes from frequencies occupying the higher end of the electromagnetic spectrum. E-band distances whittle down to 3km. Another possible combination is a ‘traditional’ RFU (6GHz-42GHz) plugged in alongside an E-band RFU. This supports 20Gbps at a distance of 7km.
By using an ‘all-in-one’ hardware design -- no need for different antenna for different frequencies – Zhou claimed that operators could achieve 50% savings on tower space and engineering costs. The CMO reckoned, too, that it’s well-armed to mitigate signal interference as networks become more dense. He referenced Huawei’s “advanced and innovative algorithm”, CCIC (co-channel interference cancellation), which gives operators greater network-planning flexibility when it comes to antenna placement.
But what about latency? 5G potential in opening up new markets -- from gaming to smart factories -- will depend on sprightly latency times. Will this be threatened by microwave, especially if there are multiple ‘hops’ -- links between antennas – when backhauling traffic? The more hops, the longer the latency times.
“There’s no real latency issue with microwave,” said Zhou. He explained that operators, by using fiber points-of-presence -- as part of a ‘star’ network topology -- can reduce the number of hops needed to backhaul traffic, perhaps to an average of 1.5 for each base station. And by using clever coding and packet-forwarding techniques, Zhou said latency-per-hop could drop from 200~300us to 100~150us, in best case could be as low as 50us per hop.
Automation and regulation
Huawei has a long-term vision of what the Telco network should look like: autonomous, or, as Huawei likes to put it, self-driving autonomous networks. Last year, with that goal in mind, Huawei launched its Network Cloud Engine (NCE).
Zhou said Huawei was in the process of migrating microwave O&M onto the NCE. He anticipated that, once NCE was in full swing, manual configuration of performance parameters related to microwave links could be reduced by 90%. Closed-loop monitoring, in which the network continuously checks and remedies performance issues without the need for human intervention, is something Huawei has already demonstrated in some use cases. Microwave backhaul, anticipated Zhou, will soon benefit from NCE’s closed-loop capabilities.
Renato Lombardi, director of Huawei’s Research Centre in Milan, drew attention to a more immediate problem -- clunky and outdated licensing schemes, and lack of E band spectrum availability in some markets. He was critical of regulators that licensed microwave backhaul spectrum on a link-by-link base, which drives up costs for operators. A better way, he said, was to license spectrum on a regional or national basis. “People sometimes underestimate the importance of backhaul spectrum and focus on the access portion of the network,” he said. “But without wireless backhaul there is no access.”
This blog is sponsored by Huawei.