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By Patrick Durand Worldwide Technical Director, Future Lighting Solutions
The infrastructure in buildings is usually designed to last for decades. This is no different for lighting equipment. When a building owner or manager decides to invest in a lighting control system, they need to have confidence that their decision is going to be the right one not just for the next one or two years, but for the next decade or more. But today the rate at which new technologies are being introduced causes many building managers to say, ‘It is best to wait until the technology landscape matures and a single technology wins.’
In fact, there is no need to delay investments in lighting controls. With a future-proof lighting control system, the building manager’s concern about obsolescence is eliminated. The idea sounds simple, but how can it be implemented?
A basic installation is comprised of a switch, a sensor/controller and nothing more. There should be no gateway, neither for commissioning nor for controlling. The system does however need to provide the option to add a gateway. But in this case, the gateway is just a protocol translator. It is not like a ZigBee® gateway in a large installation, in which the gateway manages the network. In this system, the failure of the main gateway potentially breaks the entire system.
The future-proof lighting control gateway, by contrast, is simply a bridge between a wireless protocol and a building management system such as BACnet or KNX, or a cloud-based system. In future it could even bridge to a technology that is yet to be invented.
A simple, optional protocol translator gateway gives the user the choice of what to do and when. If, during the initial installation of a lighting control system, the building manager is not ready for any complexity and just wants the switch and the controller, the wireless technology just needs to support these requirements, as shown in Figure 1.
But, if two years later the building is upgraded and a BACnet buildingautomation system is installed, the lighting controls can easily be integrated with it, whether the system is supplied by Schneider, Siemens, Johnson Control, Honeywell or any other manufacturer. There will be no need to change any part of the initial installation of wireless luminaires and switches: all that is required is the addition of a small number of protocoltranslator gateways to translate and forward data from the wireless protocol to the BACnet protocol.
Then, if five years later the building manager realizes that he/she can no longer achieve his/her objectives with BACnet and wants to migrate to a cloud-based system, he/she can simply change the small number of BACnet gateways to cloud-based gateways. This is a future-proof solution.
The topology of a wireless system is the key element of a future-proof lighting control installation. If it supports point-to-point and point-tomulti- point topologies, the switch or sensor communicates directly to the controller, which is the wireless device that provides the control signal to the LED driver.
Fig. 1: A future-proof lighting control architecture
EnOcean and Bluetooth wireless are the main standard technologies that support this type of topology, as shown in Figure 2.
Fig. 2: Network topologies for lighting control
A new Qualified Bluetooth Mesh standard was also released in July 2017: this provides for a mesh of nodes which can forward data to other nodes between the wireless switch/sensor and the wireless controller. Although the accurate term for the Bluetooth Mesh topology is many-tomany, one can still think of Bluetooth Mesh as supporting the point-topoint topology with the added benefit of being able to extend the range and reliability of the wireless network via meshing.
Technically, there are significant differences between the Bluetooth Low Energy (BLE) and Bluetooth Mesh standards, they both use the same radio chip or radio module. The ability of Qualified Bluetooth Mesh to relay data sets the two standards apart. Furthermore, for BLE, security is optional whereas for Bluetooth Mesh, security is mandatory. The Bluetooth Mesh standard actually incorporates the entire BLE functionality, which allows existing mobile devices with BLE to directly connect to and control a Bluetooth Mesh network. And since gateways are optional devices in a Bluetooth Mesh network, and can act as a protocol translator between Bluetooth Mesh and a building automation system or a cloud service, Bluetooth Mesh can enable future-proof lighting-control systems.
While the choice between EnOcean and Bluetooth Mesh is a question of personal preference, both systems have advantages and drawbacks. EnOcean is already installed in over 400,000 buildings. It is a mature protocol, widely adopted in HVAC and in lighting control. Another advantage of EnOcean is that it operates in the sub-GHz frequency range: its wireless signals can travel through walls further than the Bluetooth 2.4GHz signals, and there’s no risk of interference with any of the 2.4GHz wireless systems in noisy urban environments.
On the other hand, the benefit of Bluetooth over EnOcean is that it is supported by every mobile device, so that they can directly communicate with the Bluetooth Mesh controller. This greatly simplifies the commissioning process. The other major benefit of Bluetooth technology is that it supports over-the-air updates, giving it a future-proofing advantage over EnOcean. Finally, there is the cost advantage of Bluetooth Mesh, since there are multiple Bluetooth radio and module vendors while there is only a single formal vendor of the EnOcean radio and modules.
Cost is the biggest barrier to the mainstream adoption of wireless lighting-control solutions. What the lighting industry needs are control solutions that are so cost-effective that lighting OEMs integrate a wireless controller in the luminaire regardless of whether the end user will immediately use its capabilities. The scale and presence of Bluetooth means that its mesh derivative is the only technology with a realistic chance of meeting both the cost and futureproofing requirements of mainstream lighting-control solutions.
Security is a mandatory part of the Bluetooth Mesh standard: all mesh messages are encrypted and authenticated. There are three types of security keys in Qualified Bluetooth Mesh. The first is the network key, which is required for a lighting node to join and send a message that will propagate through the mesh network.
Furthermore, it is possible to create sub-networks or zones, each with its own network key: this enables the operator to limit the authority of a user to control lights only in his/ her office but not for other offices in the building.
The second type of key is an application key, so that a user who only has the right to control lights cannot also control the HVAC or other building systems.
The third is the device key, which enables the removal of a node from the network, while the network and application keys are retained. This eliminates the risk that a discarded node could be used by a hacker to attack the building network.
Even with security, there are ways for lighting-control vendors to go beyond the standard to differentiate themselves. For example, in an installation of luminaires from multiple luminaire vendors that are all based on Qualified Bluetooth Mesh, it is possible to automatically check in the background whether the node’s firmware contains any vulnerabilities or malware before it is allowed to join the network. No extra hardware devices would be required, as the installer would use the same internetconnected mobile device for this enhanced commissioning process.
Besides Bluetooth, Wi-Fi is also used in all mobile devices. And since Wi- Fi routers are found almost everywhere, it might seem sensible to use this infrastructure. The question is: should this be an alternative strategy? Or should we potentially consider a multi-protocol node to hedge our bets?
From a technical standpoint, it’s possible to have a wireless node that can support multiple protocols: several radio chips support both Bluetooth and Wi-Fi, and other chips support both Bluetooth and 802.15.4 (ZigBee). The difficult part of implementing a lighting-control system, however, is not the hardware but the firmware and software. Support of multiple protocols adds complexity and may render the node incompatible with nodes from other vendors.
It is also important to understand the differences between Bluetooth, Wi-Fi and ZigBee, and not to attempt to employ a riskier multi-protocol node strategy at the luminaire level. Wi-Fi power consumption is higher than than that of BLE or Bluetooth Mesh, and requires a router and Wi-Fi routers are prone to failure. For large ZigBee installations, gateways are required, adding complexity and single points of failure, since the gateways have the task of managing the ZigBee network, as shown in Figure 3.
The winning technology will be the one which has an advantage in cost, simplicity, reliability, scalability and security: Bluetooth Mesh is clearly superior in these respects. One year on from its introduction, the Bluetooth Mesh standard has already been implemented in 65 interoperable products from various vendors; that number is expected to grow exponentially over the next few years. The key now is to build an ecosystem of Bluetooth Mesh solutions as quickly as possible.
A large ecosystem of solutions based on an open interoperable standard such as Qualified Bluetooth Mesh can provide the functions and capabilities required to support any conceivable project specification. The solutions can cover parameters such as:
The benefit of the future-proofing characteristics of Qualified Bluetooth Mesh is that if the end customer is not ready to use the data on the cloud that a system can generate, they do not need to include gateways at the time of installation. If a decision is made at a later date to use the power of the cloud, the option to do so is available by adding low-cost Qualified Bluetooth Mesh gateways.
Some installation proposals deliberately avoid the use of radio frequencies: bus systems operate via a controlling cable, power-line carriers or Powerover- Ethernet (PoE). Marketing promotion of these technologies has suggested that they are more reliable than wireless systems. But are they competitive?
More attention in recent years has been given to PoE than any other wired communication technology for building infrastructure. For a disruptive technology to be successful, it must also embrace or bridge from an existing one. In the case of lighting controls, the most difficult element to change in the short term is the LED driver. Lighting OEMs must have flexibility in their choice of LED driver options: choice over output power, output current, output voltage and form factor.
With PoE, however, traditional LED drivers cannot be used, because there is today a very limited choice of PoE-compatible LED drivers. Furthermore, the PoE switches which power the PoE LED drivers are expensive, and their power output is low, limiting their ability to supply multiple luminaires.
Finally, the operator’s IT department will need to be involved in and supportive of a PoE system, which adds complexity. Since Bluetooth was initially developed to be a reliable cable-replacement technology, for PoE to carve a niche in the lighting control arena, it needs to provide some additional value that draws on its strengths, such as a high data rate. With PoE, luminaires can also process and send audio and video data from and to microphones and speakers and IP cameras, enabling the integration of lighting and security, or enhancing the functionality of a video conference room.
The other wired protocol that is evolving with the needs of the market is DALI, and in particular DALI 2.0. For example, the DALI 2.0 standard has improved the interoperability of the protocol, helping to reduce problems in installation. The upgrade also incorporates the use of occupancy sensing and daylight harvesting. Advanced functionality such as tunable white lighting control from a single DALI address is now also supported by the standard.
But the greatest impact on the lighting OEM and lighting-control markets is the forthcoming release of the DALI driver diagnostic standard which will also include power metering. This will enable all LED driver manufacturers to use a common interface and protocol when developing the next generation of LED drivers.
More and more companies are starting the process of adopting Qualified Bluetooth Mesh. The advantages the protocol will bring to the lighting industry and building automation as a whole are clear. It is an interoperable, low-cost, simple, reliable, scalable and secure standard which has the potential to bring unity and clarity to lighting OEMs, specifiers and building managers.
Qualified Bluetooth Mesh addresses the drawbacks of existing protocols, which had previously induced several new lighting-control equipment vendors to create their own proprietary solutions. This, however, had caused confusion in the lighting industry, leading many lighting OEMs to wait for the dust to settle before investing in the implementation of wireless lighting-control technology.
It will still take a couple of years before the Qualified Bluetooth Mesh ecosystem reaches critical mass. The opportunity cost for lighting OEMs of continuing to wait might be too high, however: competitors might already be investing, and could gain an early-mover advantage.
Now is the time for lighting OEMs to change their mindset, from an attitude of ‘The first duck out of the pond gets shot’, to ‘The early bird gets the worm.’
