The millimetre bands are useless! Are they?

August 30th, 2019, Published in Articles: EngineerIT, Featured: EngineerIT

From the dawn of radio by Marconi and others, some segments of the radio spectrum were declared of no real value. The high frequency (HF) bands (shortwave) first earned this “useless position” because long and medium waves were considered the only frequencies of value. Then, radio amateurs pioneered international communications on shortwave and before long it became the most contested radio frequency spectrum for international broadcasting and radio telephone links used to connect continents. Many decades later, international radio telephony was replaced by optic fibre, submarine cables and radio broadcasting by internet streaming. The pressure on the HF spectrum is something of the past!

Millimetre bands are now following a similar trend, not considered of too much use other than some backhaul links and short distance propriety line of sight networks; and spectrum is now hotly contested for 5G and other communication developments. One wonders where this “in and out for favour” will end. For the World Radio Conference 2023 (WRC23), there is already talk about spectrum in ranges beyond 300 GHz.

The major focus at WRC19, which will be held in Egypt at the end of October 2019, is about frequency allocation for 5G and satellite services. With the emergence of the fibre industry there were mutterings that satellite technology would soon be something of the past. A new organisation, EMEA Satellite Operators Association (ESOA), is of a very different view and believe that satellites will continue to play an important part in communication. ESOA has become very vocal about the importance of affording the same interference protection to satellite services as terrestrial services.

The organisation has pointed out that with the outcome of WRC15, world administrations have given a clear signal that different technologies, fixed and mobile, terrestrial and satellite, will all continue to play a vital role in enabling next generation communications around the world. ESOA warned policymakers to ensure that studies and plans for development of terrestrial 5G, IMT-2020 services and systems are implemented either in the frequency bands currently identified by the ITU for IMT or possibly new bands that might be identified by WRC19. In either case, existing services in the same and adjacent bands must be protected from interference. The use of bands for terrestrial 5G which are not harmonised internationally is not beneficial and would likely cause harm to other services.

As ESOA has no direct participation in WRC19, the organisation has made it its business to attend as many as possible governmental WRC19 preparatory working group meetings to lobby for support. They made a compelling presentation for their call of protection at the Department of Telecommunications and Postal Services (DTPS) WRC19 meeting held in Pretoria in January this year.

If you can’t beat them, join them

ESOA and its members are focused on ensuring that satellite communications be an important part of the 5G network of networks. As 5G standards are being developed and implemented, it is critical to identify the conditions to fulfil in order to ensure a smooth integration of satellites with 5G so that satellite solutions can become an increasingly important part of the 5G ecosystem and deliver the expected value in terms of service ubiquity, continuity, scalability and resilience. Ensuring compatibility of satellite in the 5G value chain through the standards process is, according to ESOA, not negotiable. There is a long history of satellite communications and the use of standards. ESOA put forward conditions for maximising the successful integration of satellite into the 5G infrastructure:

  • Interoperability of satellite network solutions with the 5G network management system allowing a third party (e.g., mobile network operator or service provider) to manage and configure the satellite network resources.
  • Integration of the satellite communications system into the 5G core network to provide secure end-to-end 5G services to and through satellite terminals.
  • Multi-vendor interoperability between elements (e.g., terminals, radio access networks – RAN) of satellite network solutions for 5G.
  • Technology commonality of satellite network solutions with cellular network solutions to benefit from an economy of scale allowing cost reduction and increased product diversity.

Question of safety

No debate about the millimetre wave band is complete without questioning the safety. Given that systems operating in the millimetre spectrum are essentially short-range systems, which means there will be many of them in a network, how safe will we be walking the street of Cape Town or Johannesburg?

One of the major effects of millimetre waves on the human body is skin absorption. Exposure of EM radiation at millimetre waves will cause skin penetration (60 – 90% in extreme cases) due to dielectric properties of human skin cells (during close exposure). However, researchers observed that the 30 – 40% of the incident power will be reflected from skin. Power of the transmitted signal and time of exposure are significant factors in this scenario.

Many researchers found that long term exposure to microwave and millimetre wave radiation is carcinogenic. The impact may not be obvious in very short terms but could cause serious damage to human cells over periods. Long term exposure of microwave and millimetre wave frequency radiation also could affect other living organisms and plants.

The safety aspects will undoubtedly be an ongoing debate with many different views and arguments, perhaps like with the current arguments in the mobile tower debate: “I don’t want a cell tower at my children’s school because its unsafe”, when in reality directly under the tower it is safer than 500 metres away. Is there currently any unemotional proof? More independent scientific research is definitely needed.

Over the past few years there have been many new developments operating in millimetre wave spectrum, the main reason why ITU study groups have been doing frequency sharing studies. It is quite clear that there are many technologies that are looking for a space in the millimetre wave spectrum. Discussion at WRC19 should prove interesting and pave the way forward. Soon the millimetre spectrum may well earn the position as “high demand spectrum”!

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