The Conversion of Street Lights into Intelligent Sensor Hubs: Why and How to Do It

 

By: David Shushan, Field Applications Engineer, Future Electronics and François Mirand, Future Lighting Solutions

The controls embedded even in the more sophisticated street lights in operation today have a rather limited scope: they may be used for dimming, according to a schedule or in response to measurements of ambient light; to turn the light on and off; and to support maintenance and repair operations, providing status reports and flagging faults.

In themselves, these are useful functions – but there is potential to do far more and to provide far greater value to the owners and operators of street lights, to pedestrians and road users, and to organizations with commercial or other interests in cities. This is because, in recent months, the technological stars have aligned to enable street lights to be connected easily and cheaply to an internet gateway.

This article explores the potential value to be derived when a city converts every street light into an internet node, and the approaches that street light manufacturers might take to implementing the design of new connected street lights.

 

The Most Valuable Real Estate

Property values are a perennial source of fascination for many people in prosperous societies. In some countries, entire television programs are devoted to the subject of where, why and how to buy a ‘dream home’. When the general public thinks about property prices, it normally has in mind the cost to buy a home or other building. And the more desirable the location, the more expensive the property will be.

But possibly the most valuable pieces of real estate in any city, square centimeter for square centimeter, are the tiny plots in which its street light poles are embedded. It is an interesting thought experiment to imagine how a commercial entity might go about gaining the right to erect 8m high poles, spaced 25m apart along every street and pavement in the whole of a city, and how much it might have to pay to buy the plots of land. Safe to say, the cost would be astronomical. Today, these poles in these fantastically valuable locations already exist – yet their potential is woefully under-used.

A city’s street light poles enjoy prime positions on busy streets filled with pedestrians and vehicles (see Figure 1).

 

Figure. 1. A line of street lights above the rush hour traffic in Atlanta, US. (Image credit: Atlantacitizen under Creative Commons licence.)

 

Elevated, they provide sight lines to a city’s entire network of roads and pavements. And they are exposed to the different air, weather, light and environmental conditions in thousands of known locations.

This real estate has thousands of potential uses if opened up to commercial and research organizations. Using electronics components which are readily available today and which may be integrated into the luminaire’s circuit design, a street light could sense for instance:

• Environmental phenomena such as air quality and the concentration of pollutants, the concentration of pollen, ambient light levels, temperature, humidity, air pressure, noise and more
• The density and flow of traffic
• The density and speed of movement of pedestrians

These measurements may be comprehensive and granular, revealing differences even between one end of a street and another. Each street light’s sensors have a view of the air and the ground in an area with a radius typically of just 10m to 15m. The field of view of each pole is contiguous with the next, and together, all the fields of view could cover almost the entire surface area of a town or city.

This means, for instance, that local medical services could look for correlations between measurements of air quality and admissions to hospital resulting from severe respiratory illness. It will be able to analyze in detail whether a certain level of air quality, or a particular concentration of an airborne pollutant, is associated with a significant increase in hospital admissions.

Another potential use is to measure the volume and speed of movement of pedestrian traffic. Retailers, for instance, highly value locations in which many pedestrians are concentrated in a dense and slow-moving mass. Information from passive infrared (PIR) sensors or hyper-frequency radars, which can detect the presence and movement of bodies, could be analyzed to provide pedestrian traffic data for all the city’s streets, and produce a ranking or score of the relative attractiveness of each pole location for operators of retail outlets.

These two use cases are presented just to show examples of the value which could be derived from the integration of sensor components into street lights connected to the internet. The actual range of data types which could be captured, and the uses to which the data could be put, are only limited by the imagination of their potential users.

 

Wireless Network Technology for Connecting Street Lights

The vision for the role of the street light presented above is ambitious. So what changes have made this new ambition realistic?

The key requirement of the new street light is a connection to the internet: the internet is the world’s open, universal network, and provides a standard protocol by which any computer anywhere can interface to any addressable internet node. In the case of street lights, this means that any permitted system operator globally would be able to draw data from any internet-connected street light to which the owner had granted them access.

The big change which makes it possible today to consider connecting all of a city’s thousands of street lights to the internet is the broadening availability of new Low-Power Wide-Area Networking (LPWAN) technology. Two such technologies are competing for dominance:

• Semtech’s LoRa™ technology consists of RF transceivers embedded into sensors and gateways, providing the ability to capture and transmit data over long range while consuming little power. In addition, the LoRa Alliance™ has developed an open protocol based on LoRa technology called LoRaWAN™ to help ensure the interoperability of all devices and software components on both public and private networks (see Figure 2).
• SIGFOX, a network protocol, implemented in public network infrastructure

 

Figure 2. The architecture of a LoRaWAN™ network providing a connection to the internet for multiple end nodes. (Image credit: LoRa Alliance white paper)

 

What is new is the ability of both LoRa and SIGFOX to provide low datarate, low power, very low cost wireless coverage over wide areas. For instance, the open-space transmitter-to-receiver range of a single LoRa link can be as far as 15km at a low but useful data rate. A single gateway can also provide an interface to as many as 10,000 nodes. This means that all of a mid-sized city’s street lights could be connected to the internet via just one, centrally located LoRa gateway.

LoRa technology may be implemented in a LoRaWAN-based private network, dedicated to street lights alone; this means that the street light operator will pay for the cost of installing LoRa-based sensors and gateways, and setting up and maintaining the network. But through the efforts of the LoRa Alliance, public LoRaWAN networks are springing up in many cities, and some street light operators will be able to piggyback on existing infrastructure, lowering their connection costs even further.

SIGFOX is accessible to users only as a public network, using infrastructure installed by SIGFOX in some countries, and its network operator partners in others.

For both LoRa and SIGFOX, the cost to connect a node and to send and receive signals over the network is remarkably low. Set against the already considerable bill-of-materials and PCB assembly cost and the installation and commissioning cost of a new LED street light, the additional cost to provide internet connectivity via a LoRa or SIGFOX network is almost negligible. The cost/benefit ratio is extraordinarily favorable.

This is not just because of the data-gathering use cases, examples of which were described above. Internet connectivity also provides operating benefits to the owners of the street lights:

• The internet connection allows the street light to upload more detailed, timely and actionable status information than closed lighting-control networks. This allows for more effective preventive maintenance, and reduces the requirement for costly field maintenance.
• Communication via the internet supports more sophisticated control techniques, such as motion-activated lighting, or lighting-on-demand. Such lighting control schemes, triggered by motion sensors on multiple neighboring poles, call for complex interactions between street lights and the control system, interactions which are generally not supported by legacy lighting control networks, but are readily enabled over an internet connection.

 

New Component Requirements

Municipal authorities and commercial organizations, then, can be expected to demand a new generation of internet-connected intelligent LED street lights. What impact will this have on the architecture of street light manufacturers’ products?

The most obvious effect is to increase the number and type of components on the board. Today’s LED street lights are typically comprised of a light engine, optics and a driver. New intelligent street lights will require additional device types:

• Sensors to capture data on parameters such as temperature, gases, humidity, ambient light and so on
• A high-powered microcontroller capable of processing multiple sensor inputs and handling internet-protocol transactions
• An RF system. End-node modules for either LoRa or SIGFOX networks are available from suppliers such as Microchip and MultiTech, providing a complete, certified solution for wireless connectivity (see Figure 3).

 

Figure 3. The MultiConnect® xDot™ USB dongle developer kit for the xDot LoRa module from MultiTech. (Image credit: MultiTech)

 

The specification of these components and their integration into an end-product design will take many lighting-equipment manufacturers into uncharted technical territory. This does not, however, mean that they will lack support or roadmaps to guide them. In fact, the growing strength of the Internet of Things is leading manufacturers of many types of industrial, residential and commercial devices to add wireless networking and sensing capabilities to ‘dumb’ products that were previously unconnected to any network.

Such manufacturers and their industry partners have been able to learn from their experiences, and this knowledge is available through third-party experts such as Future Electronics, a distributor of electronics and lighting technology components. In fact, Future Electronics’ divisional structure, incorporating its Future Connectivity Solutions, Future Lighting Solutions and Future Sensor Solutions operating units, is designed precisely to meet the needs of the new generation of IoT-enabled equipment manufacturers.

The value of adding internet connectivity to street lights, then, is clear, and the component technology is newly available to support it at low cost. With expert support, street light manufacturers may reap the reward of transforming their simple lighting product into an intelligent, internet connected multi-sensor hub which also happens to cast light on a city’s roads and pavements.

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