As 5G achieves widespread deployment this year, operators and customers alike are set to soon enjoy a vast range of new experiences, from AR and VR to autonomous vehicles. But this rapid advancement in technology also threatens a new bottleneck: backhaul.
In previous 4G networks, the main considerations and limitations when it came to backhaul were capacity, availability, deployment cost, and long range. Now, new 5G networks bring two new challenges to the fore, in the form of low latency requirements and the high density of the network.
Fibre is able to handle the new technology’s low latency and increased capacity for 5G, but it is also expensive and time consuming or even not viable to deploy. For some areas, such as rural communities and regions with difficult geography (e.g. mountains), fibre is rarely a cost-effective solution.
This is where microwave backhaul technology comes in. In contrast to fibre, it is readily available, has a low deployment time, and is cost-effective.
Microwave already plays a significant role in today’s mobile infrastructure, accounting for about 70% of global base station backhaul for 2G, 3G, and 4G, excluding China, South Korea, and Japan. This reliance is here to stay, with the GSMA estimating that 60% of 5G sites will be backhauled by 2025.
However, microwave is not without its own challenges, especially when it comes to range and, in higher bands, atmospheric phenomena affecting propagation like rain.
Thus, the question is: how can wireless backhaul cope with the demands of 5G?
For Huawei, the answer lies in innovation and tackling the challenges one at a time.
“We need to ensure that microwave and millimetre wave products are equipped with the features to handle the new challenge of 5G,” explained Renato Lombardi, VP of Huawei’s Microwave Product Line.
Overcoming 5G’s pressure on spectrum, site space, and range in the traditional band
One such challenge comes as a result of densification of the 5G network. As network infrastructure complexity increases, changing from tree to star topology, hub sites must cater for an increasing number of different directions. As a result, operator’s spectrum is put under strain from the multi-directional, large bandwidth upgrades required, often ultimately mandating the installation of additional sites to ease the burden.
This year, Huawei has released its SuperHUB Solution, which focusses on urban and suburban areas where hubs with multi-directional links are paramount. Using interference cancellation and mitigation techniques, the spectral efficiency of SuperHUB can be boosted by at least 200%.
Similarly, this year has seen the further development of last year’s 1+2 Microwave solution, expanding its frequency band up to 38GHz, allowing shorter distance links to be covered by this advanced technology.
But perhaps the most impressive innovation is the Point-to-Multi Point solution, which bring RAN technologies like multi-user MIMO and beamforming to the microwave backhaul sphere.
“Point to multipoint is leveraging the beamforming technologies coming from 5G development […] the use of Space Division Multiplexing with strong interference cancellation can provide an improvement of spectrum efficiency of an order of magnitude by a full frequency reuse as done in 5G,” said Lombardi.
Finally, increasing the range of the microwave technologies is also of critical importance. Here, Huawei is developing enhanced line-of-sight MIMO and other technologies which are set to improve range by 50%.
Use of E-band and beyond
Beyond the traditional spectrum ranges for wireless backhaul, the use of E-band (71–86 GHz) has become an exciting alternative in recent years. The development of E-band solutions has been around since the LTE era, with part of its appeal being the low cost of spectrum compared to traditional bandwidths.
“The first E-band prototypes were around more than 10 years ago. But the technology became mature in last five years and has really taken off, after we were able to make operators confident that E-band could be used with predictable performance and availability,” explained Lombardi.
E-band microwave beams are narrow, reducing interference between links and enabling dense site deployment. But this narrow nature of the beams means that E-band antennas become susceptible to environmental disturbances like tower swaying requiring greater stability.
To combat this issue, Huawei has released a smart antenna solution that delivers intelligent tracking of the antenna beam angle, compensating for unwanted movement as a result of atmospheric interference, like wind, and even pole deformation as a result of varying temperatures in more extreme environments. Ultimately, these smart antennas can deliver a six-fold improvement in anti-shake capability, making the signal much more reliable.
Perhaps more impressive still is the immense capacity that wireless solutions within the E-band can achieve. Huawei’s innovative 2T2R E-band solution can reach up to 50 Gbps when coupled with LoS MIMO technology, anticipating the long-term evolution of 5G networks and its demands.
Further development of E-band solutions may be just the start for wireless backhaul. As demand continues to increase, operators will begin to develop solution for even higher frequencies, such as D band and W band.
“We think D-band can mature in a timespan of 3–5 years from now, preparing for massive deployment around 2025,” explained Lombardi.
What’s the future for microwave technology?
It is clear that microwave can hold its own against fibre when it comes to backhaul technology, but can it compete in the long term?
For Lombardi, wireless technology should not be viewed as a rival to fibre, but an essential part of a balanced backhaul infrastructure, especially as a means for combatting the digital divide.
“The digital divide exists not just between developed and less developed countries, but also within developed countries themselves, where rural areas are often unattractive for fibre deployment,” said Lombardi.
“Microwave can play a very important role here. Microwave can cope with the capacity and latency requirements of 5G, and it is particularly convenient for operators in rural areas where we must span long distances to be connected to the core network.”
Some countries in the Middle East are already making good use of E-band spectrum over relatively long distances, with a leading operator already using wireless backhaul for 90% of its wireless base stations including 5G sites
Wireless backhaul has a bright future, but it is up to regulators and national authorities to ensure that operators are incentivised to make use of its innovation. Spectrum efficiency will continue to improve, but a 5G-like spectrum policy is needed to support wireless technology’s evolution, such as block-based or hybrid spectrum assignment.
Innovations in microwave will continue to make it competitive for 5G backhaul for many years to come, but it remains to be seen whether operators will embrace this new technology or potentially overinvest in expensive fibre.