The birth of wireless lighting control
In the past, it was actually rare to hear professionals say that smart lighting technologies are about to revolutionize the entire industry. Today, however, we experience a fast-changing market awareness caused the recognition of many advantages of wireless solutions of the wired ones and the growing interest in the Internet of Things (IoT). As a result, there is no doubt that high-end lighting control systems are not merely parts of a futuristic dreamscape, but rather ground-breaking solutions getting ready to transform the way lighting is perceived.
Although a couple of years have passed since an early generation of smart lighting products became available on the market, still to this day the majority of them is primarily limited to being proprietary solutions for home use only. The first products to achieve recognition from smart lighting enthusiasts were the Philips Hue LED lights working on ZigBee wireless protocol. They allowed users to turn on and off, to dim or to change the color of lights, which was an important step in making the concept of intelligent lighting a reality. Even though other companies such as Osram, GE, Ikea, Ilumi, and now Sony, continue to introduce their own lines of lighting control products along with a variety of new available options, a lot of them are still considered suitable only for small-scale applications. Therefore, a whole spectrum of commercial spaces remains relatively untouched and there is a reason for it.
WHAT MAKES LIGHTING SMART
That reason lies in the design and the functionality of a smart lighting system as there are differences between smart home solutions and the ones that are prepared for use in larger environments. It is easier to set up and manage a network consisting of twenty or thirty devices distributed in a couple of rooms than operate a large interconnected system including hundreds or maybe thousands of devices performing in an office building or a warehouse. A number of conditions need to be met before we shall classify a particular system as a technically successful wireless lighting control solution prepared to work in large spaces.
First of all, you need lighting devices to exchange information with each other via an appropriate communication protocol. The data has to be quickly transmitted over long distances. Additionally, it would be significantly beneficial if the process consumed as little energy as possible. Secondly, the system requires high-quality sensors in order to be aware of lighting conditions and human presence in a particular location. The better the sensorics, the higher the quality of system performance. Another important aspect is providing both senses of reliability and security to the user. The overall promise of wireless lighting control technologies is to make them better than classic (wired) solutions. And the last general condition is that the system has to guarantee ease-of-use, but never at the expense of system protection. There has to be a balance between these two aspects for the sake of user experience.
Before we take a closer look at all of the above mentioned conditions, we need to focus on the first step - adopting a proper wireless communication protocol. Today, there are a number of possible ones to choose from - Wi-Fi, ZigBee, Z-Wave, Thread and the aforementioned - Bluetooth. Though all of them have strengths, for example, Wi-Fi demonstrates high data transfer rate, Z-Wave guarantees interoperability of its related products, ZigBee operates using a mesh networking topology and Thread delivers a reliable radio performance, it seems that none of the wireless protocols are capable of delivering practical solutions covering all grounds. Or is that really the case?
A SHORT STORY ABOUT BLUETOOTH
The technology having the potential to introduce smart lighting systems to commercial spaces is Bluetooth mesh, a distant relative of a classic Bluetooth wireless technology standard designed back in 1994 by a networking and telecommunications company, Ericsson. Its initial purpose was to enable simple, wireless and point-to-point data exchange between devices. Since the mid 90’s, however, Bluetooth has come about several iterations making it even more efficient and reliable mean of data transport.
An important stage of its evolution came to be in 2010 when the world was first introduced to Bluetooth Smart, better known today as Bluetooth Low Energy (LE) - a more effective, low-energy version of Bluetooth, specifically designed to meet the needs of the future IoT applications. Even though Bluetooth LE provides a fast, efficient and stable wireless communication, it is not perfectly suitable for smart lighting. That is because of the kind of network topology it supports. LE allows for building wireless connections between one central device and several peripheral ones. This solution is proper for connecting headphones, speakers or wearables with a control device. Smart lighting, however, rather than an old-school hub-and-spoke model, requires a different network topology, the one enabling to connect hundreds of devices.
INTRODUCING BLUETOOTH MESH
The original core specification of Bluetooth LE did not include any support for creating mesh networking topologies. Nevertheless, companies such as Silvair decided to build proprietary mesh solutions using Bluetooth LE radio. While it was a challenge to transform a single-hop protocol topology into a multi-hop network, as it turned out the results were very promising.
Because of the activity of IT companies in regard to the development of Bluetooth mesh proprietary solutions, in February 2015 the members of the Bluetooth Special Interest Group (SIG) realized that it would be beneficial to all parties to form a new group consisting of industry professionals improving on their technology. The Bluetooth Mesh Working Group was, therefore, established. After two consecutive years of hard work, Bluetooth mesh was officially adopted as an open standard on July 19, 2017. It was an important step in making Bluetooth mesh networking a solution for many applications such as, for example, lighting.
WHY TO MESH IT UP
But why lighting? What makes mesh networking technology, an IT and telecommunication based solution, perfect for this particular segment? As a matter of fact, when the Bluetooth Mesh Working Group was originally formed, several of the issues group members were aiming to deal with were strictly connected with smart lighting environment. The reason why Bluetooth mesh is commonly associated with lighting is that it enables us to use lighting infrastructures to their full potential. Those infrastructures, however, can be valuable as a foundation for applications beyond lighting control. We are all surrounded by lights and they are all connected to an energy source. Therefore there is no need for additional hardware or wiring as an entire mesh network consisting of thousands of connected devices is already at one’s fingertips.
A DISRUPTIVE MESH
Bluetooth mesh empowers software developers to create lighting control systems that are reliable, secure, easy to install and, later on, simple to control. In comparison with other protocols, Bluetooth provides desirable solutions for some of the more difficult aspects of wireless lighting control. Starting with the commissioning of a smart lighting network, Bluetooth is far ahead with its capabilities. Because protocols such as Wi-Fi, ZigBee and Thread do not provide precise device detection, adding a new one to the network is a strenuous challenge.
In the case of Thread, for example, a new device needs to be commissioned with the use of a network gateway. Therefore a phone or a tablet which an installer uses to add devices via a gateway is unable to define the distance between itself and any device located on site. Besides, the way the devices are labeled may be totally irregular and their distribution in a space can be as random as their names. In other words, it is the commissioner who has to define which device out of, for example, twenty thousand similar ones is the one to be commissioned, where it is located and then - he or she has to add it step-by-step. In order to build a full lighting infrastructure, the installer has to follow the same pattern when approaching every new device. Some Thread devices may use other protocols such as Bluetooth to go through the commissioning process. But then, why would you need Thread?
Bluetooth mesh, on the other hand, uses RSSI (Received Signal Strength Indication) and it detects any device’s signal strength. Therefore, a smartphone plays the role of a gateway. Thus, all it takes is to stand under a given luminaire with a Bluetooth compatible (therefore any) smartphone and the commissioning app will spot it in a matter of seconds. Then, you simply press one button and voila - it instantly becomes a part of the network. No gateways, no additional tasks. Because of this function, better known as proximity sensing, the commissioning process of an entire building takes hours instead of days.
Bluetooth mesh guarantees that a network setup in a large commercial space will be able to operate efficiently thanks to its higher data transfer rate which is essential as any given task has to be completed as fast as possible. Otherwise, smart lighting system would not seem so smart. Currently, one of the slowest available protocols is Z-Wave, having a maximum throughput of 100 kbit/s. The protocols using 802.15.4 radio, such as ZigBee or Thread, operate at the transfer rate of 250 kbit/s, which is a significant improvement. Bluetooth, however, provides 1 Mbit/s data transfer rate, which is a dramatic advancement. Therefore, it is the fastest low-energy radio currently available. Of course, Wi-Fi’s speed can be much higher than that, but it is not a low-power technology. Wi-Fi is an extremely hungry beast, therefore it is not applicable to smart building infrastructures.
High-density wireless networks operate by having a multitude of transmitters randomly accessing the shared radio frequency at all times. To reduce the number of collisions, data packets must be transmitted fast and need to be small. To improve the range, you can use a different message relaying technique. In Z-Wave, ZigBee and Thread, each message is being led by a specific path, hopping from one node to another, while on its way to final destination. This is called a routing technique. Bluetooth, however, uses a managed flooding technique which allows for sending information to every device in range. This way the nodes, the devices of a mesh network, are broadcasting a given piece of information which can be propagated across the entire network and relevant nodes will respond to it as soon as they receive it. A single piece of information in Bluetooth occupies less than 400µs in the shared radio spectrum, which means that during one second it is possible to accommodate more than 2,500 of such messages. Other low-power wireless protocols do not even come close. It takes around 4 ms, for example, to deliver a message in a ZigBee network, which is ten times more than in the case of Bluetooth. It is all caused by the size of data packets. Bluetooth’s managed flooding technique of message relaying and small data packets improve on the scalability of the entire network as it is easier to maneuver data across the connected infrastructure in such conditions. This is one of the reasons why Bluetooth mesh is perfect for operating in large commercial spaces. But there is more.
With a fully commissioned system, we expect it to perform without any defects. High data transfer rate and improved scalability are at the core of providing a reliable and solid groundwork, but one can build much more on it. Another asset of Bluetooth mesh is an ability to send information between nodes using the ICN concept-like (Information-centric networking) publish-subscribe model. It means that a message containing operational data is never sent to each node individually, but rather a device can create a post that is visible to all others. This provides fast and stable communication between the nodes and reduces the number of data packet collisions even more. These and other advancements are there to guarantee that lighting anomalies, such as for example popcorn effect (when lights do not turn on and off unanimously, but rather start flashing and popping until they reach a required state) will never take place. Additionally, in Bluetooth mesh networks there is no single point of failure. A deficiency of one device never impacts the others. As a matter of fact, the system can inform you about a light about to go off, so you could replace it before that happens.
MESH SECURITY SERVICE
As for the system security, all of the leading low-power wireless communication protocols are using an AES-128 data encryption standard as to this day there is no practical method to crack it. As a matter of fact, even if it were possible, making a tool designed specifically to breach AES-128 protected system would cost more than one could possibly gain from theft. Nevertheless, it does not change the fact that connected lighting may become subject to cybercriminals’ attacks. That is why Bluetooth puts much emphasis on authentication - a security measure preventing unauthorized access to the network infrastructure. Any device has to be sure that it receives commands from an authorized source, be it a smartphone or a switch. What is more, it must be ensured that the integrity of the exchanged data remains unaffected on its way to its recipient. Unless that happens, any control messages are ignored. Authentication is also crucial for the onboarding process as it prevents third parties or Trojan horses from hacking a device on its way to becoming a part of the network. Due to the upcoming IoT services, providing such security measures is essential.
Before the exchanged data gets to be authenticated, network devices must first exchange authentication keys. That is why it is extremely important to provide a secure delivery of those keys. Otherwise, third unauthorized parties can break into the system. This is exactly what happened with ZigBee devices that were presented during the Black Hat USA 2015 conference. Even though ZigBee empowered products were using AES-128 data encryption standard and also dealt with three authentication types, it was proven that they were vulnerable to hacker attacks.
There are several ways to provide a secure key management and distribution between a provisioning device such as, for example, a smartphone and a new device that is to be added to the network. Yet, Bluetooth mesh specification defines what seems the most reliable solution currently available. It deals with having an assigned pair of security keys consisting of a public key and a private key. Each device has its own pair. A smartphone, however, gains access to the public key of the new device via an out-of-band reliable source, for example, a web page belonging to the device manufacturer enabled by an https protocol. Therefore, the key exchange process goes only one way - from the provisioner to the device. A smartphone is the only one to send its public key and then the two devices respectively use a key exchange algorithm to calculate a secret number based on their private and public keys. That secret number is then used to compute security keys. If they match - that new device becomes a part of the network and it can be further commissioned to perform specific tasks. From this point, the communication with other nodes is encrypted and secured with device, network and application keys.
Building managers are aware of the fact that every network device stores sensitive information and they really care about the security of data. This is why there is a need for carefully prepared procedures for the activities of key transferring and assuring secure key backup. A fair amount of precaution combined with security measures provided by the technology will make it close to impossible for an unauthorized person to access this kind of information.
THE MESH IS NOW OPEN
The Bluetooth Mesh Working Group’s goal was to create a mesh standard so that the technology could become a universally applicable solution for building automation. The standard is now open and all Bluetooth mesh specifications are available online to any of the interested parties as currently the emphasis is being laid on cross-vendor interoperability. Therefore, every company can become a member of Bluetooth SIG and can develop systems prepared to possibly become an officially qualified Bluetooth mesh firmware. Of course, any software developer may add certain proprietary functions to its products which will become extra assets in regard to, for example, lighting control strategies. However, having that basic operational layer ready to use in any combination of luminaires or sensors is what truly matters.
MESH TO THE FUTURE
Bluetooth mesh delivers a complete solution for low-power, robust, secure and interoperable mesh networking. Therefore, its design is perfect for lighting applications. Because network nodes are aware of their own and other nodes’ performance, they can easily support advanced lighting control strategies including occupancy sensing, daylight harvesting, and time scheduling. The system was also built with the Internet of Things concept in mind, therefore it sets the ground for the upcoming IoT services such as asset tracking, occupancy analytics, space utilization and many others to come.
While the entire industry is anxiously waiting for the global implementation of smart lighting control systems, we believe that thanks to Bluetooth mesh technology we as Silvair are right on the verge of making this happen. 2018 is said to be a year of ground-breaking innovations in regard to the lighting segment. Therefore, be sure to expect more coverage in the upcoming months.
"Commercial smart lighting has emerged as one of the most promising segments of the IoT, but to date there has simply been no global wireless communication standard capable of addressing all the challenges awaiting there. I see Bluetooth Mesh as a technology perfectly designed for connected lights, and a powerful enabler for an entire range of new services, products and business models in the lighting sector. We are extremely excited to take part in this process of technology transition." says Simon Slupik, CTO of Silvair and the chair of the Mesh Working Group at Bluetooth SIG.