Bluetooth Mesh paves the way to IoT smart lighting (MAGAZINE)

As building owners and operators consider lighting control networks, the SSL industry has built support around the open Bluetooth Mesh standard. RUSS SHARER outlines how interoperability and other features are driving the momentum for mesh-based IoT lighting.

The promise of smart LED lighting controls has been with us for some time but until now, implementing a building-wide control system for lighting has remained a challenge. There have been multiple potential integration strategies, not to mention different requirements and products for retrofits versus new construction. Without a single dominant control technology, lighting control adoption has been slow since no one wants to back the wrong technology. At the same time, the benefits of building-wide lighting control appear too great to ignore. Many of these constraints are being removed as building owners and operators seek to use a robust lighting control infrastructure as the skeleton for a building management system based on the Internet of Things (IoT) or other technologies. The first step, it appears, is the new Bluetooth Mesh common standard that is open and extensible for lighting controls and much more.

According to the US Green Building Council, buildings consume 70% of the electricity load in the United States and account for 39% of CO₂ emissions. Seventeen percent of that energy goes to power lighting. The US Department of Energy estimates that buildings account for 40% of US energy consumption and waste about 30% of what they consume. That adds up to about $100 billion in annual operating costs. This data drives the adoption of smart lighting controls and even intelligent building energy management for the ability to reduce energy consumption in normal day-to-day buildingoperation.

Commercial building managers have begun cutting energy costs by switching to LED lighting. In fact, overall electricity consumption for lighting in an office has dropped from 38% to 17% of total usage between 2003 and 2012 largely thanks to LED retrofits (Fig. 1), and Gartner predicts that adding smart lighting could ultimately result in savings as high as 90%.

FIG. 1. Energy consumption has been significantly reduced with the uptake of LED-based solid-state lighting (SSL) lamp options compared to incandescent and compact fluorescent (CFL) light sources.

Saving energy and money are only the initial benefits for implementing smart lighting controls. With a common standard or language in place, vendors can look beyond lighting controls to building automation and smart cities. Light fixtures hold great promise as on-ramps to the IoT, especially in commercial buildings where they are prevalent, have a reliable power source, and are more evenly spaced than any other type of electrical equipment, including wall sockets. Placing sensors in these light fixtures extends monitoring and control information, offering the potential for control over HVAC, security systems, emergency alerts, and much more. The same is true for city street lights, where street-light sensors can he used to monitor traffic, the weather, and other value-add services for citizens. Lighting control and its associated communications extends infrastructure from single purpose (illumination) to an enabler of multiple applications and services.

Clever lighting graduates to smart lighting

Building intelligence into LED luminaires is the first step to this smart lighting infrastructure. Many solid-state lighting (SSL) fixtures already feature embedded programmability to adjust for light characteristics such as hue, light intensity, dimming, and energy consumption; what Fulham calls “clever” lighting. With embedded programmability, luminaires can be tuned at the factory or in the field to specific output characteristics, and when you add wireless communications you create an intelligent lighting framework. Sensors that provide input into the lighting system completes the smart, controllable lighting network.

There are different ways to approach lighting communications. Hard-wiring luminaires into a central IP-based network is one approach. For new building construction, for example, replacing conventional wiring with 10BASE-T Ethernet cable uses the computer network for DC power and control. LED luminaires can be powered using Power over Ethernet (PoE), the IEEE 802.3 standard that specifies both power and data be transmitted over the same Category 6 network cable. While PoE doesn’t deliver sufficient power for fluorescent lighting, it offers more than enough power for most LED luminaires, and it’s energy efficient when you consider that a direct network connection eliminates the need for AC-to-DC power.

Having a direct connection to LED luminaires gives you complete control; it simplifies commissioning as well as device control. Using the building’s Ethernet network provides central control over power consumption, lighting characteristics, and light levels and can even monitor and moderate heat, all accessed over the secured corporate IT infrastructure by any web-browser equipped device. This same Ethernet infrastructure — when equipped with sensors — provides direction to the luminaires for centralized monitoring of ambient light, temperature, humidity, and occupancy. The data collected by sensors can be extended to other control systems including those for HVAC, window coverings, fire alarms, etc. — the perfect infrastructure for IoT controls.

However, the number of existing commercial buildings greatly outnumbers new construction. New building space only makes up about 7–8% of commercial space each year, and fully half of commercial buildings still in use are at least 60 years old. Replacing existing wiring to accommodate Ethernet-powered intelligent lighting is not practical. In fact, analysts estimate that 50% of the LED luminaire market will be for lighting retrofits through 2025. That’s why the industry is actively assessing wireless alternatives for lighting controlconnectivity.

There are many existing wireless standards for lighting, such as ZigBee, which is supported by the Connected Lighting Alliance. There’s also Zwave for home automation and even Wi-Fi, which is already widely accepted for commercial and residential IT use. The problem is that, when applied to lighting, these standards can only offer proprietary, single-vendorsolutions.

On the other hand, Bluetooth Mesh is gaining market momentum for wireless lighting controls because it is open, delivers the promise of choosing from multiple vendors, and is extensible to cover a variety of lighting installations. Bluetooth is a well-defined and comprehensively-documented standard, so vendors that conform to the standard can guarantee Bluetooth interoperability. For example, every smartphone has Bluetooth built in and, no matter who the manufacturer is, one vendor’s Bluetooth smartphone can communicate with every other smartphone and Bluetooth-enabled device. Adopting Bluetooth Mesh not only guarantees a means to wirelessly connect luminaire sensors, but it also ensures interoperability with other Bluetooth devices.

Bluetooth Mesh delivers a robust control network

Built as an extension of the Bluetooth standard created by Ericsson in 1998, Bluetooth Mesh is a wireless radio networking schema created to scale to connect thousands of devices. The Bluetooth Mesh standard offers out-of-the-box connectivity with any Bluetooth device.

Where Bluetooth was originally developed for point-to-point device connections, Bluetooth Mesh operates as a “flood network,” providing simultaneous, many-to-many communications among all devices associated with a network in the vicinity (Fig. 2). Bluetooth Mesh sends every incoming data packet across every outgoing connection to share the data across a lattice of Bluetooth devices. Bluetooth Mesh is scalable and fast (up to 1 Mbit/s), and there is no single point of failure. It’s the mesh topology that makes Bluetooth Mesh robust and reliable, establishing it as a solid communications framework.

FIG. 2. The value of Bluetooth Mesh networks lies in their scalability with extended range, connecting many devices in a multipoint architecture and rerouting communications as needed.

Bluetooth Mesh ensures compatibility as well since the standard is well-defined and products have to be qualified by the Bluetooth SIG. Since Bluetooth Mesh is self-healing, you can add or remove devices without the need for reprogramming, as well as adding or removing devices as needed without disruption. If a device fails or the signal is blocked, the mesh compensates by rerouting the data.

Bluetooth Mesh data packets can be up to 384 bytes, but most messages fit in an 11-byte frame — more than enough for most machine-to-machine, or in this case luminaire-to-
luminaire, communications. The message starts with one byte of opcode (for special messages), then includes 2 bytes for standard messages or 3 bytes for vendor-specific messages. Each Bluetooth message also includes a source and destination address, and sequence numbers to prevent replay attacks.

Bluetooth also brings compatibility with a huge established base of wireless devices. Handheld devices such as smartphones and tablets can be equipped with Bluetooth apps for lighting controls. In addition, inside of a rigorous security framework, other Bluetooth devices can be added to the same mesh network.

One of the advantages of using Bluetooth Mesh for smart lighting is it can support two-way communications. This means the same mesh infrastructure can be used to commission smart lighting solutions and monitor luminaire performance. Once the luminaire sensors are in place, the same infrastructure can be used to monitor other building conditions, like occupancy or temperature, and send back information to a control system.

With two-way communications, sensors can be used to measure ambient light, sending the information back to a control system that would then issue instructions to make the luminaire brighter or dimmer. A sensor that detects presence in a space can not only turn on the light but also signal the HVAC to cool or heat the space, while notifying the security system that someone is in the building and switch the office telephone to available or at least in-office.

Secure as well as stable

As the world becomes more connected, network security becomes a bigger concern. Providing two-way wireless lighting control as part of a building management infrastructure could potentially give hackers access to systems such as building security, as well as provide a back door to access sensitive data on connected business networks.

Bluetooth Mesh has security well covered with encryption and authentication. All Bluetooth communications are encrypted using two decryption keys: 1) network keys that are allocated to a specific network and 2) application keys that relate to a specific function such as turning on a light as opposed to configuring a light. The encryption standard is one of the most advanced on the market, making it virtually impossible to break into a Bluetooth Mesh lighting control grid.

Bluetooth authentication uses a challenge-response schema where each device in the authentication procedure is either a verifier or a claimant; the verifier is seeking to validate device identity and the claimant needs to prove its identity. Verification is made using a Bluetooth link authentication key.

Finally, for additional security, Bluetooth Mesh also can be divided into separate subnets or groups, each with its own cryptography and authentication schemas. The system has been designed to defend itself from attacks such as malicious data transmission repeats and delays, extracting passwords from devices separated from the mesh, and so on.

Bluetooth Mesh enables multiple standards

One of the most confusing parts of Bluetooth Mesh is what software it supports. For this, the standard has options. The Bluetooth Mesh standard does contain not only definitions for the wireless network and mesh but also for the upper level applications that turn lights on and off, and provide dim and tune illumination characteristics. However, a developer can also use the Bluetooth radio and mesh and use a different upper-level software — much like a Wi-Fi network can speak IP or some proprietary machine-to-machine language.

Initially, this may be tricky for smart lighting deployments, since vendors are promoting Bluetooth Mesh networks with standard, proprietary, and IPv6 software. What is important is for the specifier and contractor to be sure they are using a consistent implementation. When looking at the true Bluetooth Mesh standard, it will be documented as SIG qualified or just qualified. Anything else will have limited multivendor interoperability (Fig. 3) — which means the selection of luminaires, sensors, and switches the installation can deploy is much more limited.

FIG. 3. Interoperability characteristics of an open standard such as Bluetooth Mesh are one of the factors boosting its support for IoT applications.

The promise of IoT appears ready to drive demand for wireless lighting controls. With commercial construction limited annually, building managers will rely on Bluetooth Mesh to retrofit lighting control connectivity. Once installed, the luminaires can support various lighting control systems, then move on to empower IoT infrastructure that goes far beyond lighting.

The next step in the evolution of lighting controls will be for manufacturers delivering SIG qualified Bluetooth Mesh-ready luminaires with sensors installed. These will be easy to install and offer a relatively fast return on investment. And once this Bluetooth Mesh framework is in place delivering two-way, machine-to-machine communications, the possibilities offered by smart building controls are endless.