Bluetooth Mesh - reliable networking for lighting and building automation

Bluetooth already has a firm place in audio streaming and fitness wearables. With Bluetooth Mesh, new areas are being added with lighting and building automation.  

Smart home control via smartphone app, side view. Mobile control of IoT and automation of domestic devices with floor plan and icons for the Internet of Things

Bluetooth Mesh is not synonymous with ‘BLE Mesh’. The term BLE Mesh can be seen as an umbrella term for all previous, proprietary approaches to realising a mesh network with the BLE standard. The only thing that Bluetooth Mesh uses from BLE Mesh is the message carrier, the so-called ‘bearer’.

A major advantage is that we carry a perfect user interface around with us every day, which is already Bluetooth Mesh-capable thanks to this commonality with BLE Mesh. This may be convenient, but it has probably also caused some developers headaches during the development of the Bluetooth Mesh standard. Mainly when it comes to protection against unauthorised access. This brings us to the next topic.

Safety has top priority

Security is an extremely important issue in wireless communication, and its seriousness increases with the number of networked nodes and various applications that are supported.

If it is a simple technology that is limited to lighting control and cannot be combined with any other applications, an attack on such a network is associated with a relatively low risk. However, an attack can be devastating if the network is responsible for critical functions such as air conditioning or access systems in addition to lighting control.

However, the trend is moving in precisely this direction: different sectors are increasingly being combined with each other. This is the core idea behind IoT; the aim is to move away from isolated solutions where each application requires its own, isolated communication network.

As the Bluetooth Mesh standard is comparatively young, this aspect could be adequately taken into account right from the start. The newly rolled-out concept resulted in an architecture that is equipped with state-of-the-art security measures from the ground up. The Bluetooth Mesh Profile Standard is open, anyone can view and critically scrutinise it. The Bluetooth SIG also offers a web portal to report any security vulnerabilities found in Bluetooth.

Padlock symbol and internet technology network as a symbol for cyber security network

Other wireless mesh standards that have been on the market for some time have had to grow with setbacks. Security in wireless standards is a tricky subject. There is a lot of information on the Internet, but it should be read with caution.

However, the events are indisputable. Security keys have already been cracked and published on the web in various forums. Product manufacturers have had to scrutinise the security of their own products. If the implementation of security features is not defined as ‘mandatory’ by the standard, the result is a jumble of products with different levels of security.

Bluetooth, on the other hand, has skilfully tackled this problem and successfully eliminated it by firmly anchoring the protection mechanisms in the mesh standard. This means: mandatory implementation, otherwise there is no Bluetooth stamp on the product! However, Bluetooth is not always synonymous with ‘secure’. For example, the BLE standard offers optional security features. In contrast to Mesh, there is the option of weighing up each design. This also makes sense because security usually comes at the expense of convenience and the potential for damage in the event of an attack is much smaller with the traditional point-to-point connection of Bluetooth.

Bluetooth Mesh Technology

Bluetooth Mesh is the choice when it comes to scalability and reliability. Properties that are particularly important for lighting control. The advantages of the mesh network can be utilised particularly when the transmitter and receiver are not in close proximity and messages need to be exchanged over longer distances, e.g. in an office building.

But how does Bluetooth Mesh work? Bluetooth Mesh uses a so-called ‘managed flood message relay’ process. This means that all participants in the network - the nodes - receive the same message and can also forward it. This makes it possible to reach several thousand participants while still guaranteeing high network performance and reliability.

The process can be compared to messaging services from social media. All nodes can send messages to the network (‘publish’) and subscribe to messages (‘subscribe’). All nodes in a group that are interested in the status of the light value, for example, can subscribe to these messages. Sensors, switches and lights communicate directly with each other. The concept of decentralisation eliminates the need for a central control unit, which means that the lighting control system continues to function even if one or more nodes fail.

The efficient data transmission with Bluetooth Mesh reduces the load on the wireless network and guarantees a high level of reliability. The size of the so-called payload of the messages to be transmitted is optimised in order to generate as little radio traffic as possible within the network. For example, if you want to set the light level, it is sufficient to send the command ‘Light Lightness Set’ (2 bytes), the ‘Lightness Level’ (2 bytes) and a ‘Transaction Identifier’ (1 byte: new message or new transmission). If you want to set the lightness level to the maximum, the message then reads: 0x82 4C FF FF 00.

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DALI and Bluetooth Mesh

The standardised wireless protocol of the Bluetooth SIG is used for reliable networking of sensors within a network. Bluetooth technology follows a full-stack approach. This means that technical specifications have been developed from the low-level (radio part) to the high-level (application layer). So-called models have been defined that describe how a sensor or a light should behave. This ensures that a motion detector purchased 30 years ago will still be compatible in the future. Bluetooth provides the necessary qualification tools and thus guarantees global interoperability.

The DALI (Digital Addressable Lighting Interface) standard is widely used to control LED drivers and is therefore the perfect complement to Bluetooth Mesh. The DALI Alliance (DiiA) has published specifications that cover everything from colour control and dimming levels to diagnostic data such as energy consumption and power consumption. Many well-known manufacturers of LED drivers support the standard and therefore guarantee manufacturer-independent compatibility.

The SENSOTEC NET sensors from STEINEL Solutions support both standards: the Bluetooth Mesh from SIG and the DALI standard from DiiA. The sensors interact in a network as a Bluetooth Mesh-to-DALI gateway. This means that applications such as automatic and needs-based lighting control and energy monitoring are possible today. And the infrastructure for new use cases such as asset tracking or indoor navigation is already in place for the future.

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Portrait of the employees who wrote the technical article

‘As the basis for IoT projects, Bluetooth Mesh opens up access to the future and offers countless potential applications in the areas of building automation, intelligent lighting systems and Industry 4.0, to name just a few.’ 

Ronald Reichmuth, hardware and firmware developer & Timon Meier, former hardware and firmware developer at STEINEL Solutions AG