Wireless Backhaul is Not Dead Yet
By Stuart Little, Director of International Product Line Marketing, US
This Halloween, zombies aren’t the only thing coming to life. Evolutions in e-band and multi-band mean wireless will play a crucial role in the rollout of 5G.
5G is coming (and hopefully it won’t be accompanied by White Walkers) and will bring with it tremendous challenges for network operators, and no less critical will be backhaul, where needed capacities will grow from the hundreds of Megabits to multiple Gigabits. In their latest Microwave Outlook (from December 2017), Ericsson forecasts that by 2022 the typical backhaul requirement for a high-capacity radio site will be in the around 1 Gbps, increasing to as much as 5 Gbps towards 2025.
Wireless Backhaul Remains Strong
Wireless will continue to be a critical element for operators around the globe. Expectations of the ubiquity of fiber driving wireless backhaul out of the network have been common since the days when 3G was at the same point as we are today with 5G. Wireless can’t keep pace with capacity demands, fiber will be everywhere, is the common refrain. But the truth is that fiber isn’t and never will be everywhere cost effectively. Far from being an ‘old’ technology left behind, wireless (ie: microwave) still provides connectivity for more than half the world’s base stations, and this share is expected to exceed 65 percent in 2022 (excluding China, Korea, Japan, and Taiwan), again according to Ericsson.
A critical issue for wireless backhaul for 5G will be spectrum availability. Most microwave bands in common use between 6 and 38 GHz around the world are severely congested. New frequencies are often not available or at best only in relatively small channels. But 5G backhaul needs will require very large bandwidths to support capacities up to and above 1Gbps, using existing technologies. On top of this, many millimeter-wave bands, including 24, 26, 39 and 42 GHz, and 57 to 71 GHz V-Band, are all assigned to or are being considered for, 5G access in various parts of the world, removing those bands from potential use for backhaul. This shortage and congestion will drive a significant change in backhaul networks in the next 5 years towards higher frequency bands, where much more spectrum is freely available.
E-Band Growth Projected
One such band is the 70 to 90 GHz band, also known as E-Band. For many years E-Band radios were prohibitively expensive, costing upwards of $20,000 for a single link. Now the latest developments in technology and higher volume production techniques have resulted in link costs falling dramatically. E-Band is now considered the key band for 5G backhaul to take the place of traditional bands between 24 and 42 GHz, enabling high bandwidth links up to several kilometers, with a high degree of frequency re-use that enables highly dense networks. The interest in E-Band from operators is now widespread in all regions, with many new and mature products available on the market that can support up to 10 Gbps in a single radio channel, to the point that E-Band is expected to see a significant growth curve in 2019.
Sky Light Research, in their latest 5-Year Forecast, predicts that the market for E-Band will grow from $225 million in 2017 to nearly $1 billion in 2022, a CAGR of 34%. In contrast Sky Light expects the microwave market (6 to 42 GHz) to remain more or less flat over the same period at a CAGR of just 1.4%. Clearly, there is enormous expectation that E-Band, and to a lesser extent the unlicensed V-Band (60 GHz) will fuel the emergence of 5G networks by enabling cost-effective gigabit transport over wireless.
Beyond 70-90 GHz, there are even higher bands with even more spectrum available, such as W-band (92–114.25GHz) and D-band(130–174.8GHz), where more than 50 GHz of spectrum is available and there is a potential to achieve link capacities up to 100 Gbps. Some early prototypes are beginning to emerge in these bands, and we are seeing customers start to look for information in tenders, but the reality is that there are few devices and components available today, and commercialization of even a first-generation product which would come at a premium price, could be several years away, and even Ericsson does not expect significant usage in these bands until 2025.
The Multi-Band Evolution
Another piece of the 5G backhaul puzzle that has emerged is known as Multi-Band (or Dual-Band, or Band Carrier Aggregation, BCA, etc). This approach effectively extends the reach of high capacity E-Band links by 100% or more, up to 10km, depending on the region and the expected rainfall. Multi-Band combines an E-Band link with a parallel link operating in a traditional microwave band, such as 15, 18 or 23 GHz. Correctly engineered, the E-Band link supports maximum throughput (say 5 or 10 Gbps) for 99.9% of the time (equal to 8.76 hours of outage per year), while for example 1 Gbps of high priority traffic is maintained for 99.999% of the time (5 minutes of outage per year) on the microwave link. Traffic is automatically load balanced/switched between each link using Link Aggregation. The Multi-Band approach is gaining plenty of attention as a way to provide an alternative for 13 to 23 GHz microwave links that are constrained by narrow channel bandwidths and lack of spectrum for multi-channel solutions, to achieve multi-Gigabit links of longer distances than E-Band alone can support, albeit with a lower availability for lower priority traffic.
In terms of commercial solutions, Multi-Band is now in its second generation, with the initial systems that comprised of an E-Band outdoor radio being connected to a standard split-mount microwave terminal via Ethernet and using separate E-Band and Microwave antennas. Traffic aggregation was often performed with less efficient techniques, such as LAG or Layer 2 Link Aggregation. The second generation of Multi-Band systems have now arrived, which support an all-outdoor architecture that eliminates the need for an indoor unit, employing efficient Layer 1 Link Aggregation, and taking advantage of new Dual-Band antennas that combine the mount and feed for the E-Band and microwave radio onto a single reflector. Overall a more elegant and cost-effective solution, reducing four antennas down to two per link, but you still need to purchase, deploy, configure and manage two individual radios per site, radios that are likely not even in the same product family, so will have different practices for deployment, operations and management – not ideal.
With the deployment of 5G you can see that something better will be needed, and if history teaches us any lessons Multi-Band will need to become more integrated, easier to manage (SDN-enabled is a must), and lower overall capital and operational costs. The industry has some time, with 5G rollout expected to really start in earnest during the second half of 2019.
As they say, wireless is not dead yet, quite far from it in fact, and will play a major and crucial role in 5G networks and whatever follows in the future.
If you would like to know more or see how multi-band could work for you contact Aviat.
By Stuart Little, Director of International Product Line Marketing, US