4G Americas recently published a whitepaper titled, 5G Spectrum recommendations. What caught my attention was this informative table (below) that listed the status of public proposals for 5G spectrum bands above 6 GHz worldwide.
Picture: Status of public proposals for 5G spectrum bands worldwide. Source: 4G Americas whitepaper. Note that Ka band is being considered by all countries above, except United Kingdom.
One of the main criteria to consider for 5G is to have large amount of contiguous spectrum available, typically at least 500 MHz. Spectrum below 6 GHz would, in many ways, be an ideal choice but there are too many existing services already, making case for the use of spectrum above 6GHz. The next best choice of frequencies would have been the bands between 6 and 11 GHz as the rain fade starts becoming prevalent at frequencies above 11 GHz. That part of the spectrum is also occupied by many existing services.
The Ka band (17.3 GHz – 31 GHz) is often considered as a sweet spot due to availability of large chunks of contiguous spectrum and at the same time not too high a frequency. The Ka band, because of the associated bandwidth availability and smaller equipment sizes, is becoming increasingly important for satellite services such as high density fixed satellite services (FSS). With the aggressive deployment plans for some of these next generation satellite services, there will be a contention between 5G and other existing users/services in these bands. In UK, Ofcom has not considered the Ka band as one of the 5G candidates, which comes as a relief to these existing users/services that make use of these bands but comes as a concern to many involved in the terrestrial mobile Industry seeking to promote global harmonisation for 5G spectrum. Considering that the band already has a co-primary mobile allocation in the ITU Radio Regulations, they feel it is "too early to take the Ka band off the table".
So what happens next? WRC-15 agenda item 10, amongst other topics, will discuss spectrum allocations for possible study that might eventually be suitable for 5G. The UK (via Ofcom's CEPT co-ordinator) will defend the UK position at the ECC CPG meeting in September. There will likely be submissions from other Administrations as well as the current draft European Common Position (ECP) and associated supporting material. The final decision on the European Commission Position will likely be stable by the end of that meeting with the final ECP being ratified very soon afterwards.
During the next four-year ITU Study Period the chosen frequency bands/ranges will be studied from a suitability and coexistence perspective with the results presented at the World Radiocommunication Conference in 2019 (WRC-19). While many players believe that it is too early to rule out the Ka band, everyone is keen to avoid another ITU-R Joint Task Group (JTG) by reducing the frequency bands/ranges to be studied while avoiding bands being removed from consideration. On the face of it, it is difficult to argue against the notion of undertaking studies to investigate the scope for sharing in the Ka band (most popular choice being 28 GHz band) – especially given the co primary allocation for mobile services. However knowing the nature of international discussions on spectrum, one can understand the sensitivity of the satellite community of studies proving to be the 'thin end of the wedge' in undermining their future access to a band which is increasingly important for them.
All bands that are approved as part of agenda item 10 in WRC-15 have to be studied but of course they will not be allocated at that point since the outcome of the studies will only be finalised at WRC-19. Administrations, like the UK (which is represented by Ofcom on behalf of Her Majesty's Government a.k.a. HMG), can choose to ignore a band or bands if they implement their sovereign rights likely via indicating their preference in the footnotes of the ITU-R Radio Regulations.
Administrations generally tend to protect incumbents from harmful interference. The four year study period should allow enough time to study the possibility of harmful interference to other co-primary or existing services but if studies conclude that there is no harmful interference the WRC-19 could identify the band as suitable for IMT and mobile broadband therefore making it more likely to be adopted by 3GPP.
Globally harmonised frequency bands are a priority as there is a need to reduce radio variants. While the Ka (28 GHz to be specific) band may be very attractive for the mobile community, other frequencies like 31 GHz, 40 GHz or even 26 GHz (which lies in Ka band as well but not as attractive) could be considered. Only time will tell.
In an ideal world, different spectrum using services will compete with each other on the basis of their consumer offering rather than on availability of spectrum. However in our non-ideal world, we must rely on the co-operation of all parties. Governments and regulators must place industry stakeholders at the centre of their strategic decisions and ensure proper timescales for industry to respond to regulatory changes. Industry, for its part, should ensure that they continue to innovate and use technology development to surmount challenges such as spectrum sharing.
More information is available for techUK's Communications Infrastructure Programme, Satellite Applications & Services Programme as well as the UK Spectrum Policy Forum, the industry-led sounding board to Ofcom and Government.