Its long range, excellent signal penetration, and numerous base station networks in operation make the 400 MHz spectrum ideal for applications that require highly resilient communication.
Ludger Boeggering, Senior Principal Application Marketing, Energy & Industry 4.0 at u-blox and Samuele Falcomer, Principal Product Manager, u-blox Cellular Product Center
It's hard to overestimate the importance of robust communication technology for modern civilization. Everything from major disaster response to the daily operation of critical infrastructure relies on people and assets capable of reliably sending data and instructions to each other. Furthermore this reliance on resilient communication technology is bound to increase due to the spread of smart cities, smart power grids and the like.
The importance of communication networks for the correct and safe functioning of society has been recognized by the authorities and is reflected in the requirements for networks that manage critical infrastructure. For example, in Europe, the networks that control electricity grids and other critical infrastructure must be able to remain operational for a minimum of 24 hours when there is a power outage. This is well beyond what many commercial cellular communications networks can offer.
To achieve this level of resilience, the European energy industry pushed the adoption of spectrum bands below 1 GHz. 3GPP standards currently offer privileged access to the 410 and 450 MHz frequency bands for LTE communication in LPWA networks. (low-power wide-area), voice communication, LTE, LTE-M and NB-IoT.
Around the world we are watching the auction of the frequency bands near 400 MHz in order to create private or public networks that support critical communications. Among the first countries to do so are Poland, Estonia, Germany, the Czech Republic, the Netherlands and South Africa, as well as parts of the Middle East and South America. Other European countries are expected to join them.
400 MHz Spectrum: Three Key Benefits for Critical Infrastructure Networks
One of the biggest advantages of 400 MHz spectrum, in the context of critical communications, is its long range. Most commercial LTE bands operate above 700 MHz, and some 5G networks go up to 39 GHz. This allows them to provide the data rates needed for applications such as high-quality video streaming. However, they have the drawback that the signals attenuate quickly, resulting in the need for very dense networks of base stations. Even a relatively small country like the Netherlands requires tens of thousands of base stations to provide full commercial LTE coverage.
The 400 MHz spectrum is at the opposite end of the scale. Its greater range means that far fewer base stations are needed – just a few thousand bases in a country the size of the Netherlands. When stable operation of critical infrastructure is the goal, maintaining a network of this size, with all its necessary redundancy, is much more manageable with this than with the commercial LTE network described above.
The lower attenuation of signals in the 400 MHz spectrum has a second big advantage: they can pass through walls and other solid surfaces. This makes this spectrum ideal for applications such as smart meters that can be installed underground or inside homes.
Third, many countries already have an extensive infrastructure of base stations supporting the 400 MHz spectrum. This is because it has been in operation for a long time and has been used for PAMR (professional analog mobile radio) networks and later as networks based on CDMA. Finally, its long distance has been used to cover remote and sparsely populated parts of countries such as rural Africa and northern Europe.
An ever-growing range of applications
The opportunities presented by robust cellular networks using frequency bands in the 400 MHz spectrum are generating tremendous interest in new applications. For example, a group of engineers in Poland is creating a private wireless network to connect millions of smart meters and tens of thousands of monitoring and control systems used with wind turbines and other applications.
In Germany, the government has allocated this spectrum to utility companies. It has granted a license to 450 Connect for the next 20 years whose main uses will be the control of the electrical network, smart meters and voice communications (replacing PMR (professional mobile radio)).
It is very likely that in the coming years we will see more examples of 400 MHz spectrum being used in applications where resilient operation is paramount, even in the event of a power outage. Among the main boom areas will surely be smart medical monitoring equipment, security applications and smart city technology 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 “scream louder” than other frequency bands and there are devices capable of transmitting at 26 dBm (Power Class 2) versus 23 dBm (Power Class 3).
Engineers selecting cellular components for devices that will operate in the 400 MHz spectrum must consider several factors. Is Power Class 2 needed? Will your device have to work on public or private networks, or both? Could I require the features of the new 14GPP version 3 for LTE-M and/or NB-IoT? If the device may need to operate on the LTE spectrum, does it allow tuning of active antennas to optimize performance? What are your energy needs? Do you offer a “last breath” feature to send a final message in the event of a total power outage? And given the critical nature of the application you are likely to serve, what are the security capabilities of the module?
The 400 MHz spectrum: everything is ready for it to play a key role
Digitally controlled critical security technology is an increasingly important part of modern societies and the demand for exceptionally resilient communication networks will continue to grow. With its long range, excellent signal penetration, and availability of established base station networks in many countries, it is not surprising that 400 MHz spectrum will play a key role in this environment for years to come.
u-blox has developed the SARA-R540S LTE-M/NB-IoT module for use in this environment. More information on the u-blox website.
