Why the 400-MHz Spectrum is Perfect for Critical Communication

Article By : Ludger Boeggering and Samuele Falcomer, u-blox

With long ranges, excellent signal penetration, and many base station networks already in place, the 400-MHz spectrum forms the ideal foundation for applications requiring highly resilient communication.

It’s hard to overstate the importance of robust communication technology to modern civilization. Everything from responding to major disasters to the day-to-day operation of critical infrastructure relies on people and assets being able to send data and instructions to one another reliably. And this reliance on resilient communication tech is only going to increase, given the expansion of smart cities, smart utility networks, and the like.

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The importance of communication networks to the smooth and safe running of society has been recognized by authorities and is reflected in the requirements for the networks used to manage critical infrastructure. For example, in Europe, the networks controlling power grids and other critical infrastructure must be capable of remaining operational for a minimum of 24 hours when there’s a power outage. This is significantly longer than what many commercial cellular communication networks offer.

To achieve this level of resilience, the European energy industry pushed for the adoption of bands at the lower end of the sub-1-GHz spectrum. 3GPP standards now provide privileged access to the 410- and 450-MHz frequency bands for low-power wide-area LTE communication, across voice communication, LTE, LTE-M, and NB-IoT.

Globally, we’re now seeing the frequency bands at about 400 MHz being auctioned off for the purposes of creating private or public networks to underpin critical communications. The early adopters include Poland, Estonia, Germany, the Czech Republic, the Netherlands, and South Africa, as well as parts of the Middle East and South America. More in Europe are likely to follow.

400-MHz spectrum: three key benefits for critical infrastructure networks

One of the greatest advantages of the 400-MHz spectrum, in the context of critical communications, is its extensive range. The majority of commercial LTE bands operate above 700 MHz, with some 5G networks as high as 39 GHz. This enables them to deliver the headline-grabbing data rates required for applications such as high-quality video streaming. The drawback, however, is that signals rapidly attenuate, resulting in the need for very dense networks of base stations. Even a relatively small country, such as the Netherlands, requires tens of thousands of base stations to get blanket coverage of commercial LTE.

The 400-MHz spectrum sits at the opposite end of the scale. Its longer ranges mean significantly fewer base stations are required: just a few thousand in a country the size of the Netherlands. When it comes to the robust operation of critical infrastructure, maintaining a network of this size, with all the necessary power redundancy, is much more manageable than it would be with the commercial LTE network described above.

The lower attenuation of signals in the 400-MHz spectrum has a second major advantage: They can penetrate through walls and other solid surfaces. This makes the spectrum ideal for applications such as smart utility meters, which can be buried in the ground or inside people’s homes.

Third, many countries already have extensive base station infrastructure in the field that supports the 400-MHz spectrum. This is because it’s been around a long time, having been used for professional analog mobile radio networks and later CDMA-based networks. With the latter, its long range was used to provide coverage in remote and lightly populated parts of countries, including in rural Africa and northern Europe.

An ever-expanding variety of applications

The opportunities presented by robust cellular networks using frequency bands in the 400-MHz spectrum are driving enormous interest in new use cases. For instance, engineers in Poland are creating a private wireless network to link up millions of smart meters and tens of thousands of control and monitoring systems used with wind turbines and other applications.

In Germany, the government has dedicated the spectrum to utilities usage. It’s licensed to 450 Connect for the next 20 years, with the main use cases being grid control, smart metering and voice communications (as a replacement for professional mobile radio).

It’s very likely we’ll see many more uses of the 400-MHz spectrum emerge over the coming years to support applications in which resilient operation, even in the event of a power failure, is essential. Among key growth areas are likely to be smart health-care monitoring equipment, security applications, and smart city-technology, such as traffic-control infrastructure.

Design considerations

Devices operating in the 400-MHz spectrum need to make themselves heard by the network. 3GPP allows them to “shout louder” than is permitted in other frequency bands, with devices able to broadcast at 26dBm (Power Class 2), as opposed to 23dBm (Power Class 3).

For engineers selecting cellular components for use in devices that will operate in the 400-MHz spectrum, there are various things to keep in mind: Do you require support for Power Class 2? Will your device need to operate on public or private networks, or both? Might it also require new 3GPP release 14 features for LTE-M and/or NB-IoT? If the device may need to operate across the LTE spectrum, does it support active antenna tuning to optimize performance? What are its energy requirements, and does it offer a “last gasp” function to send a final message in the event of a complete power outage? And given the criticality of the application it’s likely to be supporting, what are the module’s security capabilities?

The 400-MHz spectrum: all set to play a key role

With digitally controlled, safety-critical technology forming an increasingly important part of modern societies, demand for exceptionally resilient communication networks will continue to grow. With its extensive ranges, excellent signal penetration, and the availability of established base station networks in many countries, it’s unsurprising that the 400-MHz spectrum is shaping up to play a key role in this space over the coming years.

This article was originally published on EE Times Europe.

Ludger Boeggering is senior principal application Marketing, Energy and Industry 4.0, at u-blox.

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