Bluetooth Mesh expert addresses common questions about connected SSL (MAGAZINE)
Connected lighting and the Internet of Things (IoT) have been key topics for us recently, and we’ve covered the networked solid-state lighting (SSL) trend in feature articles, news, and webcasts. A March webcast presentation was titled “What is the shortest past to advanced lighting control strategies?” Bluetooth Mesh was the focus, and the presenter was Simon Slupik, CTO and co-founder of Silvair and chair of the Mesh Working Group at the Bluetooth SIG (Special Interest Group). That presentation drew far more questions than our time slot that day would allow us to address, so here we will revisit a couple of key questions that were addressed and a number that weren’t. You can still view the original presentation on demand as well.
Q: What makes Bluetooth Mesh a better option for connected lighting relative to Zigbee or other wireless schemes?
Slupik: There are very important reasons why we decided to use Bluetooth for lighting control, and why so many vendors are switching over to Bluetooth Mesh. This technology is more robust than any other wireless technology available today. Bluetooth operates over 40 frequency channels and uses a frequency-hopping scheme that is immune to any interference. It runs well in crowded environments [areas with many active wireless devices using various protocols].
The other fundamental advantage is the low energy advantage. Bluetooth Mesh uses way less energy than other technologies. It enables the use of energy-harvesting technology to power wireless nodes, and it results in much lower standby power consumption in powered nodes. Another area where Bluetooth Mesh is better is security. Finally, Bluetooth offers ease of use, which we should not forget. Ease of use drives how affordable the technology can be and comes from the fact that the technology can be interacted with using a phone. You can make an app that makes all of the commissioning simple.
Q: As Mesh isn’t addressable and is a publish/subscribe methodology, is there an issue with the amount of traffic on a network?
Slupik: From the scalability perspective, it scales very well. It’s actually publish/subscribe and addressable. The addressable modes are used, for instance, in configuring individual devices. For lighting control, it’s mostly about controlling a group of devices. Rarely do you control an individual device. A single message from an occupancy sensor can reach hundreds of nodes if it’s a big room like a ballroom in a hotel. One other reason it functions well is that the control function is not centralized; it’s distributed. There is no radio traffic between controllers and the outputs. The controller is in every light and mainly the only traffic you see is from sensors. From a practical perspective, you can think of a few thousand devices per network.
There is also one principle that improves scalability, and that feature is subnets. You can organize a whole building and partition it into subnets. For example, each floor may be a separate subnet. The function of subnets is to confine the traffic. Traffic from sensors on one floor will not traverse to other floors. Yet the whole building may be on a single network, which means that you may have a single master switch that turns the thing off if needed, or you may have a single monitoring device that collects all of the maintenance data. Networks in the range of a few hundred devices are very easy. Networks that reach 1000 or more nodes require some planning, but it’s not difficult.
Q: Bluetooth was originally a relatively short-range wireless technology. Now Bluetooth Mesh is being promoted as capable of covering an entire commercial building. What is the range and what is required, such as antennas, for maximum range?
Slupik: Everything depends on the hardware used, location, and environment. Bluetooth Mesh is built on the Bluetooth Low Energy specification. In closed spaces such as rooms, the radio range will be around 10–15m. In an open space such as a field outdoors, the radio range could be anywhere from 50–500m, depending mostly on antenna design. Distance limitations should be characterized and documented by fixture manufacturers. An external antenna is not obligatory; however, the best radio performance can be achieved when the antenna is not covered and is properly exposed.
Q: Is Bluetooth Mesh applicable to outdoor applications such as street light control?
Slupik: As mentioned earlier, Bluetooth Mesh is based on Bluetooth Low Energy, which can reach line-of-sight distance of several hundred meters with properly designed antennas. We believe Bluetooth Mesh is capable of serving outdoor applications, but as always, care has to be taken when designing components for outdoor usage. Street light control requires the range of twice the distance between each light in order to achieve minimal redundancy for packet relay in such a linear setup. This type of installation requires properly designed antennas. Bluetooth works better in more rectangular outdoor setups — for example, in parking areas, where multipath mesh delivery assures robustness of the system.
Q: How secure is a Bluetooth Mesh node? How does it combat “bad actor” scenarios, and are there any known vulnerabilities?
Slupik: Bluetooth Mesh provides state-of- the-art security, and the security is not optional. The open nature of the specification allowed it to be analyzed by independent researchers. There are no known protocol vulnerabilities. One option to be considered by product designers is the factory reset option. If a product is to be installed in a hostile environment, the factory reset option should not be exposed or it should be possible to block it at some point. This could also prevent devices from being stolen, as a device that has the factory reset locked can’t be provisioned into any other network. Therefore, it’s going to be useless when stolen.
Bluetooth Mesh is a network managed by a provisioner. The provisioner has means of enforcing strong authentication of devices it brings into the network, up to verifying manufacturers’ digital certificates. Implementing strong provisioning policy effectively prevents any bad actors from landing as mesh nodes. If such an actor is discovered after being provisioned, a node blacklisting procedure may be used to force it out of the network.
There are no known security vulnerabilities. This has been confirmed by several scientific research papers published already. As of today, the only known concern is with physical device design. Devices should not use unencrypted external memory to store security keys. If it does, the keys may be retrieved when an attacker gets physical access to a mesh device.
Q: The webcast presentation stressed how Bluetooth Mesh can enable complex SSL control with no gateways or cloud access. But what if someone desires to enable remote access, programmatic network control, data analysis, and more? How do Bluetooth Mesh lighting networks get the data to/from the intranet or Internet?
Slupik: For remote access to the data, there needs to be a device that is both part of a Bluetooth Mesh network and is connected to the cloud. This device could be a mobile phone with a suitable app that enables access to the data, which is stored in the devices and may be transmitted to the cloud infrequently — for example, energy consumption or the last error code. This device could also be a gateway device, which allows for permanent connection between a Bluetooth Mesh lighting system and the cloud. This arrangement enables more advanced functionalities, like occupancy analytics.
Q: Can you address functionality of the Bluetooth Mesh platform? How robust is this system? We’ve seen some installations where the nodes repeatedly get disconnected and don’t speak to each other correctly, which frustrates the end user. And while the standard allows a large number of nodes on a network, what is realistic?
Slupik: The first version of the Bluetooth Mesh specification was designed specifically for professional lighting applications. It addresses multiple industry-specific challenges, delivering all the tools you need to build a wireless system with wire-like reliability and scalability. However, the specification only provides a framework for a wireless control system. Each firmware vendor can implement this framework slightly differently, so the end user experience may vary depending on the implementation. But if done right, a Bluetooth Mesh lighting system works better than any wireless solution you’ve seen before. When visiting our office for the first time, our partners often can’t believe there is wireless communication behind our entire 200-luminaire control system. We hear it’s beyond what they’ve ever imagined as far as wireless controls go. We strongly encourage you to put Bluetooth Mesh to the test and find it all out for yourself.
Q: At the zone setup stage, how does the Silvair commissioning app typically select specific luminaires to make up a zone if there is a large number of luminaires in the area?
Slupik: Zones are defined by a designer in the Silvair cloud platform or can be created in the mobile app. Then, during commissioning, the luminaires are added to each zone. This is done onsite using the mobile app. The app allows for importing floor plans and marking individual zones on them — which makes it easy to locate these zones physically and choose the right devices that should be added to a given zone. In addition, the app includes a slider that you can use to narrow down the list of available devices to those that are nearest to you. This simplifies and accelerates commissioning when there are multiple luminaires in your vicinity.
Q: If power still has to connect to each luminaire, is there worthwhile return on investment (ROI) for installation of a wireless network? Will the investment pay off simply to gain exceptional levels of control and possibly enable data collection? How do we as contractors sell this?
Slupik: A qualified Bluetooth Mesh-based lighting system allows your customers to comply with energy-efficiency codes quickly and easily. In addition, it also gives them a future-proof system that has the potential to deliver significant value that goes way beyond lighting. Have a look at the recent infographic published by the Bluetooth SIG to get an idea of how you might sell this to your customers.
We’ve heard many times that installed lighting control systems fail to reach their advertised potential because either the cost of bringing in a qualified/certified installer is too expensive and the employee who was originally trained to make adjustments has left the company, or the system is proprietary and the company has gone out of business or discontinued support. A qualified Bluetooth Mesh system is cost effective to install. As it doesn’t require any control wiring or central controller, commissioning can be done by anyone with a smartphone, and in larger installations, the contractor can test the system straight away without having to wait for the controls specialist to do the commissioning. In addition, it’s future proof. Not only does the Bluetooth SIG take care that the standard is always backwards compatible, but the devices can easily be updated with additional features and improvements with a smartphone, giving savvy contractors a potential additional revenue stream.
Get to know our expert
SIMON SLUPIK, CTO and co-founder at Silvair, also chairs the Mesh Working Group at the Bluetooth Special Interest Group (SIG), and is the author of the Mesh Model specification that lays the ground for interoperability of multivendor smart lighting systems. A serial entrepreneur with a strong engineering background, Slupik has been positioning Silvair as a provider of a smart lighting control platform as a service, based on interoperable and open standards. He drove the development of Bluetooth mesh networking, elevating smart lighting as the primary application for this wireless technology.
