July 22, 2021

Part 1: There’s only one viable solution for 5G backhaul

It’s pretty simple – network operators need to build more capacity to support active or future planned deployments of 5G. Even operators who don’t see 5G on the horizon yet are facing new capacity demands, whether they have 4G/LTE networks or are delivering rural broadband services using fixed wireless access.

Fiber is not the answer

Operators have the same choice they have had for the past 20 years – deploy fiber or wireless transport technologies. Of course, fiber is more ubiquitous than it was in the early 2000s, but fiber challenges haven’t changed very much. When it’s not already in the ground, fiber is often prohibitively expensive to deploy, either buried or aerial, particularly over challenging terrain or to span rights of way, and fiber is still susceptible to breaks and lengthy disruptions – now even more so with increased development, greater incidence of storms and floods, etc. Recent studies have predicted that between 2021 and 2027 microwave and millimeter-wave will connect more than 60% of the world’s cellular base stations.

Installed Macro and Small Cell Backhaul Links by Technology (GSMA/ABI Research February 2021).

Traditional microwave bands are feeling the pressure

At the same time, using traditional wireless solutions in microwave bands from 6 to 42 GHz has become much tougher for most operators as well. Spectrum is harder to find, is more expensive, and is now also being allocated to new applications such as 5G RAN access and WiFi-6E. Securing cost-effective access to sufficient channels to support high-capacity links of 1 Gbps or above can be hard or even impossible to achieve.

E-Band (80 GHz) helps, but…

The 80 GHz E-Band has taken off in recent years, with more than 150,000 links deployed worldwide to date, with E-Band soon to form up to 25% of the global volume of microwave and millimeter-wave links to be deployed. E-Band solutions have come down in price, so are now a cost-effective choice to support 10 and even 20 Gbps link capacities. The challenge is that E-Band is heavily affected by rain, so achieving high capacity with high availability limits the practical link lengths to less than 3km, or even less than 1km in high rain rate regions like Asia or West Africa.

D and W Band to the rescue? Not yet!

New bands with huge amounts of spectrum in the 100+ GHz range hold the promise of wireless links that can support up to 100 Gbps. However, these bands will have similar (or slightly worse) propagation characteristics as E-Band, so will also be limited to shorter links. This new technology is also in the early stages of introduction, with first prototypes becoming available for trials, but it is likely to be two to three years (or more) before these systems are commercialized, priced for volume deployment, and have Regulatory support to be deployed in most countries. In comparison, it took about 5 years for E-band to reach the stage of widespread global adoption that we see today.

There is really only one answer: Multi-Band

Multi-band combines two mature and cost-effective wireless technologies – the high capacity of E-Band with the high availability of microwave for the most important traffic, all in an integrated solution. Multi-Band enables operators to stretch the reach of 10 Gbps links as far as 10 km in temperate climates, or around 5 km in high rain rate regions. Multi-band delivers the only viable 5G backhaul/mid-haul wireless solution that extends beyond the urban zones out to the sub-urban and even rural applications, where a sizeable proportion of sites are still located.

An Aviat WTM 4800 Multi-Band link supporting 10 Gbps capacity over 10km path in Africa.

Higher Capacity over longer Links, up to 20 km

But what happens if you want high capacity over longer links, even up to 20 km? Until now, the solution for longer high-capacity radio links has been so-called ‘Trunking’ radio solutions, where multiple channels are combined onto the antenna using an external branching/combining unit. These platforms are more costly and difficult to deploy, not to mention the extraordinarily high potential spectrum fees of licensing 6 or even 8 microwave channels.

Extended Distance Multi-Band

Today, instead of having to resort to expensive fiber, operators can take advantage of highly integrated, dual-transceiver radio designs, which can support two narrow E-Band channels with higher system gain, combined with rain resilient microwave bands such as 11 or 13 GHz, to deploy much longer high-capacity paths, with up to 99.999% availability for your most important traffic.