The importance of powerful communication technology for modern civilization cannot be overemphasized. From responding to major disasters to the daily operation of critical infrastructure, everything depends on the reliable transmission of data and instructions between personnel and assets. Given the expansion of smart cities, smart utility networks, etc., this reliance on resilient communication technology will only increase.
The importance of communication networks for the smooth and secure operation of society has been recognized by authorities and reflected in the requirements for networks used to manage critical infrastructure. For example, in Europe, the network that controls the power grid and other critical infrastructure must be able to operate for at least 24 hours during power outages. This is much longer than the time provided by many commercial cellular communication networks.
In order to achieve this level of elasticity, the European energy industry is promoting the use of low-end frequency bands below 1GHz spectrum. The 3GPP standard now provides privileged access in the 410 and 450MHz frequency bands for low-power wide area LTE communication in voice communication, LTE, LTE-M, and NB IoT.
On a global scale, we are now seeing approximately 400 MHz frequency bands being auctioned off to create private or public networks to support critical communications. Early adopters included Poland, Estonia, Germany, Czech Republic, Netherlands and South Africa, as well as parts of the Middle East and South America. More people in Europe may follow suit.
400 MHz spectrum: three key advantages of critical infrastructure networks
One of the biggest advantages of the 400 MHz spectrum in critical communication environments is its wide range. Most commercial LTE frequencies operate above 700 MHz, with some 5G networks reaching up to 39 GHz. This enables them to provide eye-catching data rates required for applications such as high-quality video streaming. However, the disadvantage is that the signal rapidly decays, resulting in the need for a very dense base station network. Even relatively small countries, such as the Netherlands, require tens of thousands of base stations to fully cover commercial LTE.
The 400 MHz spectrum is located at the other end of the scale. Its longer coverage means a significant reduction in the required number of base stations: in a country as large as the Netherlands, only a few thousand are needed. When it comes to the robust operation of critical infrastructure, maintaining a network of this scale and all necessary power redundancy is easier to manage than using the commercial LTE network mentioned above.
The lower attenuation of signals in the 400 MHz spectrum has a second major advantage: they can penetrate walls and other solid surfaces. This makes the spectrum very suitable for applications such as smart meters, which can be buried underground or in people’s homes.
Thirdly, many countries already have extensive base station infrastructure in the field of supporting the 400-MHz spectrum. This is because it has existed for a long time and has been used in professional analog mobile radio networks and later CDMA based networks. For the latter, its remote coverage is used to provide coverage in remote and sparsely populated areas of the country, including rural Africa and Northern Europe.
Continuously expanding various applications
The opportunity brought by the use of powerful cellular networks in the 400 MHz spectrum is driving great interest in new use cases. For example, Polish engineers are creating a dedicated wireless network to connect millions of smart meters and tens of thousands of control and monitoring systems for wind turbines and other applications.
In Germany, the government has dedicated the spectrum to public utility use. It has been licensed for 450 Connect for the next 20 years, with its main use cases being power grid control, intelligent metering, and voice communication (as a substitute for professional mobile radios).
In the coming years, we are likely to see more uses of the 400 MHz spectrum emerging to support applications that require flexible operation even in the event of power failure. Key growth areas may include intelligent medical monitoring devices, security applications, and smart city technologies, such as traffic control infrastructure.
Design considerations
Devices operating in the 400-MHz spectrum need to be heard by the network. 3GPP allows them to shout louder than other frequency bands, and devices can broadcast at 26 dBm (power level 2) instead of 23 dBm (power level 3).
For engineers who choose to use cellular components in devices operating in the 400-MHz spectrum, there are many things to keep in mind: do you need support for Power Class 2? Does your device need to run on a public or private network, or a combination of both? Do LTE-M or NB IoT still require new 3GPP 14th edition features? If the device may need to run on the LTE spectrum, does it support active antenna tuning to optimize performance? What is its energy demand, and does it provide the “last gasp” function to send the final message in the event of a complete power outage? Considering the importance of the applications it may support, what are the security features of this module?
400 MHz spectrum: Everything will play a crucial role
As digital control and security critical technologies become an increasingly important part of modern society, the demand for highly resilient communication networks will continue to grow. It is not surprising that the 400 MHz spectrum will play a crucial role in this field in the coming years, thanks to its wide coverage, excellent signal penetration ability, and availability of base station networks established in many countries/regions.
