Every day we read articles describing how wireless sensor networks will drive change in cities all around the world, bringing connectivity to street furniture, vehicles, utility networks and so on… In particular numerous Smart City enthusiasts regularly praise low power wide area networks (LPWAN, such as LoRa Alliance or Sigfox), to the point that one wonders if they are some kind of magic recipe to make cities smart.
Don’t get me wrong, LPWANs are wonderful tools to connect all kinds of end points throughout the city, especially to collect data for a better monitoring and management of public assets:
- The sensors don’t need much energy to transmit data; they can literally last years on a single battery. Beyond energy efficiency, this means that a city doesn’t need to connect these devices to the grid, making the idea of widespread sensor arrays realistic.
- The investment required to cover a given area is limited compared to cellular networks. Typical LPWAN antennas can cover a radius of 2.5 km in urban areas, and active equipment costs much less than cellular equivalents.
- It’s a low-cost solution to connect your sensors, with a yearly price between €1 and €10 per end point.
Of course, these networks are designed for low bandwidth applications: this is a requirement to preserve the devices’ batteries, but also to operate in such wide ranges.
If however a city was to rely on cellular networks in addition to LPWAN for applications involving heavier content and to connect end users (and therefore their own sensors and wearables), the question of whether fixed networks are of any use to smart cities seems legitimate.
One reason cities will need fixed networks and particularly fiber is obvious: CCTV. It’s sometimes perceived as a ‘second-class’ smart city application, too often associated to the sole surveillance needs. But while surveillance is the primary purpose of CCTV, new algorithms now allow for the real time processing of video streams: cameras can act as super-sensors of the Smart City, to detect traffic congestion, parking lots availability, fires, or even meteorological conditions. But that requires very high definition video carries in real-time, with the requirement of carrying and analyzing considerable volumes of data very fast. No doubt fiber will be needed for that.
Beyond that though, fiber aggregation availability is an insurance for the future:
- With improved battery life and more efficient radio standards, widespread sensors may soon be able to transmit more data. LPWAN antennas may not be able to carry all of this heavier data load going forward.
- Considering that most of the LPWAN networks operate on unlicensed spectrum, how dense will they have to be to avoid interference? Which infrastructure will these higher density networks rely on for backhaul?
- It will always be easier to secure who may ‘listen in’ on the transmitted data on a fixed network. Considering the criticity of some of the municipal data, and the latest news regarding attacks on SCADA networks, there will always be a role for fixed networks in improving security.
- We do not know yet how sustainable the technologies currently being used for LPWAN are: the sector is still being consolidated and new, better solutions may supersede the ones being used today. Having a fixed network as an alternative, or as a foundation on which various wireless networks can be connected, is a safeguard.
I’m not suggesting that cities shouldn’t take a look at low power wide area networks. I actually find it reassuring to see more and more cities thinking about the management of their sensors and data holistically rather than separately for each city department or application. However, I wouldn’t be surprised if the first city-wide IoT networks are set up by cities who have previously invested in fiber networks.