Which communication technologies to choose for your Smart Street Lighting project?
Smart Cities are already here and everyone feels the vibe. But the increasing IoT ambitions have generated a surge in communication technologies, and things have quickly become confusing. There are tens of communication standards, open or proprietary, that you can choose from. And with everyone claiming they are the best, what are your options?
This article will help answer the following questions:
What types of radio communication technologies are typically used with connected outdoor lighting projects?
What are their advantages?
In what type of environment do they perform best?
Why should you know more about communication technologies?
Your city is about to begin the process of modernizing the public lighting service. The most practical first step is switching to LED lamps and for good reason. They are more efficient and last longer, considerably reduce energy consumption and operation costs, bringing benefits for the community and municipality, while being environmentally friendly.
If you’re thinking about LED lighting, it might be the right time to also consider a smart lighting control system to help you take full advantage of smart public lighting. You’ve heard the news and potential benefits, you’ve seen cities getting smarter, maybe you have already a city management solution in place.
A modern lighting system ensures remote and automated control of street lights, whether for each individual lamp or for a segment. It’s pretty simple in principle: it generally includes a lamp controller, a remote management software (CMS) and a telecommunications technology to enable the transmission of information between hardware and software.
But as soon as you start digging for information, things get complicated. Moreover, a 10 year investment needs to be carefully planned. It’s the future of your own city at stake, right? We have prepared a series of articles to help you better understand the principles of street lighting control, its future and the implications with smart city projects.
What you need to consider, when choosing the communication technology for your smart street lighting project
Choosing a communication technology or a combination of them is one of the first decisions you will have to make when opting for a smart public lighting system. This decision could be vital for your project because it influences the parameters and success of the final result. Therefore, you need to make sure that the communication technology fits the lighting system architecture, the geography of the deployment area, urban density, your future development plans and your overall expectations:
Lighting system architecture: there are many questions that need to be answered when implementing a connected street lighting system (what kind of street lamps you have, how can they connect to streetlight controllers etc.), but as far as communication goes, the most important is ‘how are the lamps placed’. The actual grid architecture significantly influences the choice of communications: e.g. do you have any tunnels? Is it a linear architecture (as in a highway?) etc.
Geography of the deployment area needs to be considered, as some communications technologies thrive on open space (e.g. flat terrain), but have difficulties when they face hill or mountain areas.
Urban density is also essential: buildings in general and high rise buildings in particular flat out block certain communication technologies, making them almost impossible to use. Furthermore, a crowded public RF frequency can negatively affect the communication technologies that use it.
Future development. There are at least three factors that influence the future of your connected lighting implementation: proprietary connectivity will restrict your option for future system development; the communication itself should have a reliable future (high adoption rate), so you will have replacement parts and support for the foreseeable future; last but not least, interoperability is a big plus, adding future-proof and flexibility.
Overall expectations. Do you need real-time malfunctions alerts and notifications? How many unexpected schedule changes do you need over time? Do you expect to switch on and off the lights instantaneously or is a delay acceptable? Do you plan to implement adaptive lighting (street lighting linked to motion sensors that anticipate traffic)? Some technologies provide these features, others are struggling.
As there are tens of existing communication technologies that connect controllers to the CMS and, even though they all act as binders for the entire street lighting infrastructure, these technologies are pretty diverse from a technical perspective. Plus, most providers only employ a limited number of technologies that are compatible with their solution.
With the right communication technology (or the right combination of communication technologies), the system reaches its maximum potential and the municipality, the inhabitants and the environment can take advantage of all its benefits (energy saving, reduced power and maintenance costs, improved security and overall quality of life, reduced pollution etc.). The know-how you will gain from this article will give you an advantage in the preliminary discussions and in choosing the right provider for your project.
Evaluation criteria for choosing a suitable communication technology
How do street lighting controllers communicate? Although wired communications technologies (like PowerLine Communications / PLC) are sometimes used in street lighting projects, radio is widely preferred. So even if LonWorks has successfully defined a reliable PLC communication standard used for smart lighting projects, the intrinsic characteristics of IoT radio communication technologies have come ahead (low power consumption, mobility, flexibility and diversity).
Depending on the coverage, there are radio communication technologies for smart street lighting suitable for short-range and long-range networks. Another differentiation is made based on whether the radio spectrum is licensed or unlicensed and whether the network is private or public. As far as the network architecture goes, there are two main types: mesh and star topology. All these attributes contribute towards creating communication technologies that, separately or combined, become a suitable solution for specific infrastructure conditions.
In a star topology, the devices are organised around the central controller known as a gateway or hub. With node-to-hub connection, star topology works efficiently, for example, in linear networks. Because endpoints operate independently of each other, if a device fails or a cable is disconnected, the rest of the network remains unaffected.
However, all communications depend on one device – the gateway. To avoid this vulnerability, system operators install more base stations to create the redundancy (a node always has access to several gateways).
Even though gateways can be costly, star networks normally require only a few, which means that implementation could be more cost effective. However, this is not always the case, as the infrastructure, density and geography could increase the number of base stations required for ideal signal coverage.
A mesh network works by sending data along the fastest route from one device (node) to another as all devices are either directly or indirectly connected. A node serves as both an endpoint that captures and transmits its own data, as well as a repeater that relays data from other nodes.
With device-to-device connection, MESH networks can have a self-healing nature. Lighting control nodes are able to switch easily through the mesh topology, from one router to another, creating multiple routes for data to travel if a device fails. With more devices, the network becomes more robust and secure (having as a weaker point in linear architectures, where redundancy requirements are not always met). However, the bitrate is usually quite high, which makes it suitable for various infrastructures (even with higher data transmission rates, like video applications). Mesh technologies are most suitable for follow-me lighting setups.
Licensed or unlicensed radio frequency
Depending on the type of frequency range used by a specific technology, networks can be licensed or unlicensed.
Licensed frequencies are employed by specialised national agencies or directly by mobile network operators that pay for the licensed frequency spectrum and manage and maintain the network. Cellular networks use licensed (reserved) frequencies, where the communication technology is standardized and proven, with very low risk of interference. They are usually public networks, with carrier-grade reliability and security, which means less hustle for the user, but usually comes with an added monthly or yearly access cost.
On the other hand, unlicensed communication frequencies are free to be used by anyone. There is no need to obtain special agreements to create or access the networks. If an unlicensed frequency is approved in the country of use and the network is compliant with the existing standards, anyone can use this frequency to create their private network in any given location.
Most RF mesh and LPWAN networks use unlicensed frequencies. For example, LoRaWAN uses 868MHz in Europe or 915 MHz in North America. The use of unlicensed radio frequencies gives more freedom of choice to the system operator, creating the possibility to own private networks, yet it also means more hustle for the user as the network must be installed and maintained.
Furthermore, as anyone can access the frequency, it is not unusual (especially in high density urban areas) to experience crowded frequencies. Too many people or applications using the same frequencies can result in radio interference. Such interferences usually cannot compromise the payload integrity, but they can delay or even block the payload delivery, which can translate into delayed smart lighting system reactions and functionality.
Open standard or proprietary communication
Is open communication and availability for integration essential to a new street lighting control project? As smart lighting concepts were introduced, among the first companies to develop such solutions were the lamp manufacturers. Most of them proposed proprietary communications as a means to protect their research efforts, intellectual property and market position.
However, smart lighting by itself brings only limited benefits to a municipality. Smart lighting investments were soon continued by an IoT and smart city revolution, as each smart application fuels new smart city concepts and expectations. Dozens of IoT communication technologies emerged over a few years. And the entire sector became so dynamic and complex that no one company could keep the pace by itself.
Furthermore, it is a very uncomfortable position for any city manager to engage a 10 year investment in a public utility control system that uses proprietary communications, especially in such a dynamic context. What happens when you need to evolve your system? But when you wish to synergistically integrate more services, like adaptive lighting, weather sensor information or CCTV? What if your communication system or the company itself do not stand the test of time and become obsolete in a few years?
In this context, smart city ecosystems were created and provided a sustainable platform the IoT revolution. Groups of companies with a shared vision have created technical interoperability standards to encourage open communication and interaction between systems, bringing freedom for research and development, as well as for city managers and communities. Today, in a matter of years, even if proprietary communication technologies still exist, most manufacturers have developed interoperability standards (whether at hardware or software level) to adapt.
Private or public network
Depending on whether an operator handles the communication network or not, communication technology can be public (operated by a telecom company and commercially available for a fee to anyone interested) or private (operated by the street lighting provider or another business, only for their own private use and not commercially available to others).
Public networks are installed and maintained by telecom operators (usually over licenced frequencies, but there are examples of public networks over open frequencies – like Sigfox). Cellular technologies like 3G or 4G are the most used and visible example of a public network: handled by an operator who is in charge of network maintenance and making sure that the network is secured and functional at all times (carrier grade security and functionality). This takes quite some responsibility off the user. Also, it rarely requires installation fees. However, the user usually needs to pay for a monthly or yearly subscription to the network operator.
Private networks, on the other hand, are operated directly by the municipality or the street lighting provider. This means, for example, that street lighting data is restricted, allowing for closed systems, unconnected to the Internet. Private networks require a plethora of skills and responsibilities: network planning, installation, maintenance and security – that must be performed by the lighting provider. These networks usually use unlicensed frequencies, which expose them to the risk of crowded frequencies and interference issues. Furthermore, while installation costs are higher and users have to ensure the network maintenance themselves, they eliminate the cost of having to pay for a subscription.
Communication networks can cover various ranges, depending on the distance at which nodes can communicate with other nodes and gateways. A network can usually connect a limited number of devices to a gateway and has a maximum distance where they can still communicate. These are important criteria to evaluate when choosing a communication technology for your street lighting project as it could impact the functionality of the entire system.
The theoretical limits can be extraordinary for the latest communication technologies. These have been optimised for propagation and better immunity to interference, so that some can cover tens if not hundreds of kilometers, while a single gateway (depending on the technology) can handle up to 15000 devices from different applications. Of course, in practice, redundant planning is recommended, so this analysis will talk about the average limits that can be taken into account for deployments.
Cellular networks: can have unlimited range and penetration, depending on the coverage of mobile network operators, they are pretty much omnipresent, and can include an unlimited number of devices. However, the comfort of the omni-presence comes with a tax on the energy consumption and the price of the connectivity.
In a cellular network, two-way data communication occurs between streetlights and the CMS. Each streetlight is connected to an operator’s public cellular network, each device communicating through the network, but rarely directly with each other.
Long-range networks: can cover up to 3-15 kilometres and can connect as many as 5000 devices to a single gateway (in the context of street lighting control). To comply with IoT requirements, they typically function on long range and low power, which is why they are called low-power wide area networks (LPWAN).
LPWANs are preferred by solutions providers when designing IoT or smart city systems because they are well suited to the specific needs of machine-to-machine (M2M) communication. These networks are suitable for use cases that require devices to send small amounts of data periodically over networks that span for very long ranges and lack a reliable power source for recharging. LPWA networks can allow IoT devices to operate reliably for up to 10 years on a single battery.
A LPWAN may be used to create a private wireless device network (needs careful radio planning), but may also be a service or infrastructure offered by a third party, allowing the owners of sensors to deploy them in the field without investing in gateway technology.
Short-range networks: such as RF mesh or WiFi have a maximum node-to-node distance of 200-300 meters and can comprise around 200 devices. The network reliability increases the more nodes there are installed. Streetlights are about 50 meters apart.
In a mesh network, adjacent streetlights can share data with one another via network nodes. The information gathered from the nodes is then sent to the street lighting software through the gateway, using a wireless cellular connection or a wired connection via Ethernet LAN or fiber.
Communication technologies at a glance
|Short Range MESH||Long Range RF||IoT Cellular||Classic Cellular|
Essential network attributes for lighting systems
Cellular networks are extremely reliable. Network operators already have the experience of several generations of standardised technology proven over years of operations with many different types of connected devices (carrier-grade).
RF mesh and LPWAN networks, even though generally reliable, tend to get an abundance of traffic that can affect the performance and slow down the network. However, there are ways to overcome these drawbacks and improve network reliability. MESH networks, for instance, not only have the capacity to self heal, but also become more reliable with higher node density. Similarly, LPWAN’s reliability can be increased by creating communication redundancy between nodes and gateways (the more gateways, the better). It is worth to mention that, even with a redundant planning of the gateways, 1km range non-line-of-sight can be considered.
As far as maintenance goes, private networks require a designated technical team which should be taken into consideration when calculating the deployment costs. Cellular and other public networks, on the other hand, are owned by a network operator who is responsible to ensure a fully functioning network at all times. Therefore, in the case of public networks, maintenance is included in the subscription costs.
A private network is built specifically for the user’s needs. If the user is a city, for instance, the network can serve as a communication platform not just for public lighting, but for a wide range of smart city applications. When the network is used for multiple purposes, it becomes feasible to install a large number of nodes as operating costs decrease and become lower than maintenance expenses.
A public network, on the other hand, has no maintenance costs, is homogenous and does not require radio planning. However, any application with more complex communication needs (more frequent, higher bit rate, longer messages) will involve an extra cost from the network operator which can lead to higher operating costs.
Troubleshooting time can also increase. When you own the network, solving any issues depends on your readiness and preparedness. However, when using a public network, in case of any malfunction, you will have to wait longer to know more about the source of the issue and expected resolution time.
Some applications require commands to be executed as soon as they are sent out from the CMS. Cellular networks are great candidates for constant, instantaneous communication, where larger messages reach their final destination immediately after sending. Depending on the communication frequency and payload size, network operator costs can increase significantly.
Yet, wherever there is no need for communication technology to instantly transmit a command (for public lighting, for instance), schedules can be set in place where delays are taken into consideration. In this case, messages are less frequent and operator costs are diminished.
When it comes to expenses, there is always a tradeoff between operating costs. These are influenced, as mentioned before, by the type of network, the ownership over the frequencies, user’s communication requirements, the project size, workforce availability and so on.
As a rule of thumb, cellular connectivity provides the easiest and most covering service (it is called carrier-grade for a reason), but it is also the most expensive. For very large projects, it may be possible to negotiate connectivity prices similar to those of technologies that use unlicensed frequency.
While the open standards that use unlicensed frequencies need more maintenance and attention from the owner of the network, they provide the most flexibility, as the same network can be used to serve countless applications (existing or under development).
The most cost-effective solution has to be calculated taking into account the scope, size and complexity of each project – there is no one right answer.
Cellular technologies come with increased security because they are under the responsibility of professional network operators. They take steps to ensure that consumers are provided with the most secure and reliable communication service by:
- protecting the network infrastructure
- promoting public-private partnership to minimise the risk of hacking
- being clear about what infrastructure operators are responsible for
Private networks also benefit from increased security because they are operated by a singular entity that has exclusive control over the data. These networks function as a closed circuit, with limited access, and do not have to be connected to the Internet, which makes them less prone to malicious interventions.
Most used smart street lighting communication technologies
Cellular communication technologies
Because it can be considered omnipresent, with excellent penetration regardless of the urban density, cellular can be used in almost any project, but it’s a very good choice especially in large cities or other hard to reach places (like tunnels). Often used in combination with other communication technologies, it’s strong point (operator coverage) is also a weakness, as it cannot be used in remote, uncovered areas. Cellular networks are suitable for more frequent commands and faster communication.
LTE-M is a low power wide area (LPWA) technology standard published by 3GPP. It supports IoT through lower device complexity and extended coverage, while allowing the reuse of the LTE installed base. Supported by all major mobile equipment, chipset and module manufacturers, LTE-M networks will co-exist with 2G, 3G, and 4G mobile networks and benefit from all the security and privacy features of carrier-grade networks.
Narrow-Band IoT (NB-IoT) is a narrowband RF communication technology specially designed for the Internet of Things (IoT). It connects devices more simply and efficiently on already established mobile networks and handles small amounts of infrequent 2-way data, securely and reliably. The special focus of this standard is on very low power consumption, excellent penetration coverage and lower component costs, deployed in GSM and LTE regulated frequencies.
GSM is an omnipresent digital cellular technology used for transmitting mobile voice and data, covering more than 90% of the world’s population.
Long-range RF communication technologies
LPWANs are perfect for low density urban or rural areas. They are also suitable for highways, however tunnels might raise some coverage issues. The same applies for areas where communication is impeded by geographical barriers such as hills or mountains. Long-range networks function best when there are less interventions on the operation program.
LoRaWAN is a Low Power Wide Area Network (LPWAN) specification that targets key requirements of the Internet of Things such as secure bi-directional communication, mobility and localization services. It provides seamless interoperability among smart things without the need of complex local installations and gives back the freedom to the user, developer and businesses, enabling the rollout of Internet of Things.
Sigfox is a cellular style communication technology that provides low power, low data rate and low communication costs for Internet of Things and M2M applications. Sigfox employs Ultra-Narrow Band (UNB) technology, which enables very low transmitter power levels to be used while still being able to maintain a robust data connection, using unlicensed ISM radio bands. The network topology has been designed to provide a scalable, high-capacity network, with very low energy consumption, while maintaining a simple and easy to rollout star-based cell infrastructure.
Short Range Mesh communication technologies
Short range communication technologies are efficient irrespective of density, area remoteness or other geographical challenges. Short range networks are well suited for areas where getting uniform coverage would otherwise require effort and would involve considerable costs. When it comes to linear projects such as highways, careful attention should be paid to the infrastructure challenges.
Wi-SUN (IEEE 802.15.4g RF MESH) is a mesh type RF communication technology proven for years in a range of harsh and remote environments across the globe. Supports the latest IP-based security technologies for device authentication and encrypted communications.
Zigbee creates flexibility for developers & end-users while delivering stellar interoperability. Created on IEEE 802.15.4, using the 2.4GHz band and a self-healing true mesh network; Zigbee has many applications and is widely implemented across the globe.
Cellular networks are the most appropriate when an instant response is expected from the network. Cellular technologies (2G, 3G, 4G) allow nodes to communicate with the gateway in real-time, which makes it possible to execute commands like turning the lights on and off instantly.
Transferring more data requires a higher bit rate. According to the peak data rate, cellular networks such as NB-IoT and LTE-M have the highest uplink (UL) and downlink (DL) rate and can therefore send the largest messages. Mesh can be also used with this purpose.
OTA (over the air) firmware updates depend on the solution deployed for the project, not on the communication technology. So this is good news – any technology supports OTA. There is an advantage for high bit networks that support real-time communication because they allow for faster updates.
The lowest initial investments are for networks handled by operators (cellular, LPWAN, Sigfox). These communication technologies can be easily installed and do not require you to build your own network. They will, however, involve a recurrent license cost. Private networks are more costly to install, they require radio planning. Depending on geography and density, more gateways might be required when building a private network. Moreover, specialised staff is needed for network maintenance.
Communication technologies handled by network operators (cellular, LPWAN, Sigfox) are the quickest to be installed as there is no need for radio planning or building your own network.
Theoretically, private networks have the lowest operating costs as they do not involve extra costs for operator licenses. However, it also depends on the size of the project. A management system used for two or three gateways only could increase expenses.
Cellular networks could be considered the safest, as they are handled and maintained by professional network operators. However, private networks can also be considered safe, as they do not need Internet connection and support closed system installations. Considering that virtually any system can be broken into, this finally depends on your IT security practices and team.
For high density, cellular networks have the best coverage. MESH networks also provide very good results when the connected nodes are dense.
Yes, it is possible to combine communication technologies to make sure there is full coverage and all project needs are met. This depends on the solution provider you choose.
Can I integrate other smart city devices (sensors) on the same communication technology used for smart street lighting?
There is an emerging array of smart city applications (e.g. air quality monitoring, car and people counting, hazard detection etc.) that can be connected to modern RF communication networks. However, with single-purpose networks (proprietary standards that only allow streetlight control), this is usually very limited or not at all available. If you choose open standard communications, there will be a better chance to find a wide array of complementary smart city sensors and actuators, provided by various suppliers.
If I start the smart lighting implementation with one smart lighting solution provider, can I decide to continue with another provider?
This is not an intrinsic characteristic of any communication technology. Although it is somewhat influenced by communication (as choosing an open standard technology will give you more chances to find a compatible solution), it mostly depends on the system itself. If you plan to avoid vendor-locked situations in the long run, it is recommended to choose a solution that encourages interoperability (compatible with an IoT interoperability standard like TALQ and/or available for API connections)