In spite of the fanfare when mmWave first became a topic, a few questionable technology choices by early deployers have left mmWave with a less-than-polished reputation – particularly among US carriers. And mmWave is undoubtedly a technology with its limitations: for example, Verizon’s high-capacity network of hotspots left customers with a very mixed experience when users moved in and out of mmWave coverage areas.
In terms of the physics, mmWave’s propagation characteristics are significantly different from microwave frequency bands in terms of path loss, diffraction and blockage, rain attenuation, atmospheric absorption, and even loss due to trees/foliage. The propagation and range of the mmWave links means it’s most at home in urban/dense urban environments but even there, locating nodes can be tricky and require careful siting in optimal locations – a challenge that should not be underestimated.
From a network and end user perspective, there are other well-rehearsed limitations with mmWave: the ecosystem is evolving but network vendors have yet to show a consistent commitment to these bands to ensure operators have healthy options in terms of suppliers and solutions. Further, in terms of end user devices, making mmWave links to mobile platforms work properly can be tricky in certain environments.
As further evidence of its challenges, as part of our involvement in AutoAir (a UK government project for connected and autonomous vehicles) Real Wireless experts demonstrated the challenges of sustaining a consistent throughput using mmWave to a high-speed vehicle.
With this many limitations and technical hurdles how can MNOs and other service providers make the best use of mmWave deployments as part of a 5G solution? Viable solutions can be and have been deployed and if the requirements are properly assessed mmWave deployments do suit certain use cases and applications. It’s important to understand what you’re implementing and why: take indoor coverage for example, mmWave looks like a good solution on paper, but in factories, with significant presence of metals the reflections and the constant movement of machinery blocking the line-of-sight can cause issues for mmWave.
mmWave is very compatible with indoor wireless solutions for large venues where, with their significant footfall, capacity can be a concern, particularly in airports or sports stadiums. mmWave is a better bet for venues where users/equipment remain static for a period of time (fixed wireless access [FWA], backhauling, indoor venues).
Then again, for some when it comes to planning 5G it’s worth bearing in mind that not all mobile network operators (MNOs) have access to the mid-band spectrum they need and mmWave could be the only viable option to serve extremely high traffic areas. The challenge then is that repeaters of some kind become important and such unfortunates find that at this point in time their options are extremely limited.
The other important aspect is regulators need to consider carefully how to release spectrum and to whom if MNOs are to deliver the 5G availability that governments, consumers and even regional bodies such as the EU are demanding. And SDOs need to fight the corner for the operators in this context.
Our study in the Spectrum Policy Forum shows that with the abundance of spectrum in these bands different use case/sharing combinations across public and private networking sectors can be supported. The UK market is taking a lead in evaluating the options.
With FWA network planning, C-band spectrum (4 – 8GHz, or in the US, just around 4 GHz) can make sense, but for certain locations mmWave might be more applicable. C-band spectrum has historically been used for satellite transmissions. The allocations in the C-band are also subject to discussion in WRC-23 where the approach varies from region to region. Unlike C-band, 26 GHz band benefits from IMT identification globally, giving significant confidence to equipment manufacturers and 5G service providers.
Real Wireless experts have advised governments on spectrum policy and conducted a number of technology feasibility and spectrum studies on mmWave and we continue to advise on a number of successful implementations:
- Study for National Infra Council on priority spectrum for 5G – including mmWave
- Planning and result processing for the mmWave deployment in AutoAir
- Spectrum policy forum mmWave sharing study
- We have explored major use cases being considered for mmWave spectrum bands and explored licensing models to minimise the interference and maximise the usage. With this in mind, we presented a radical approach to licensing the 26 GHz band to the UK Spectrum Policy Forum. We note that Ofcom is planning to follow an approach in line with our recommendations.
- We are also currently advising a Tier 1 MNO in the Middle East on spectrum acquisition and optimum deployment strategies. This includes making the best use of mmWave spectrum.
- Multiple studies into mmWave connectivity to trains
- mmWave spectrum strategy for GSMA – looking at telco needs and the threat of satellite
During these engagements, we gathered significant experience related to the challenges and opportunities of mmWave spectrum band usage and deployments. We look forward to working with spectrum users to help maximise the return on investments and policymakers to help make the best use of the spectrum.
