Bluetooth Mesh – a secure and reliable network for light and building automation

Bluetooth is already well established in the areas of audio streaming and fitness wearables. With Bluetooth Mesh, new areas are being added with lighting and building automation.

A hand holding a smartphone over icons and a floor plan of a house to symbolise smart home control and the Internet of Things (IoT)

Bluetooth Mesh is not the same as "BLE Mesh". The term BLE Mesh can be considered an umbrella term for all previous, proprietary approaches to implementing a mesh network using the BLE standard. The only thing that Bluetooth Mesh uses from BLE Mesh is the message carrier, the so-called "bearer".

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

Safety is our top priority

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

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

However, the trend is moving in precisely this direction: different industries are increasingly being combined. This is the core idea of IoT: to move away from isolated solutions where each application requires its own, separate communication network.

Since the Bluetooth Mesh Standard is comparatively new, this aspect could be given appropriate consideration right from the start. The newly developed 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 it and critically question it. The Bluetooth SIG also offers a web portal for reporting any security vulnerabilities found in Bluetooth.

Padlock symbol and internet technology network symbolising cyber security network

Other wireless mesh standards that have been on the market for longer have had to cope with setbacks. Security in wireless standards is a tricky subject. There is a lot of information on the internet, but it has to be read with the appropriate caution.

However, the events are indisputable. For example, security keys have already been cracked and published on the web in various forums. Product manufacturers have had to question the security of their own products. If the implementation of the security features is not defined as "mandatory" by the standard, the result is a confusing mix of products with varying degrees of security.

Bluetooth, on the other hand, has tackled this problem skilfully and successfully eliminated it by rigidly anchoring the protective mechanisms in the mesh standard. This means: implementation is mandatory, 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. Unlike Mesh, this provides the option for each design to be considered individually. This also makes sense because security is usually at the expense of convenience and the potential damage from an attack is considerably smaller with the traditional Bluetooth point-to-point connection.

Bluetooth Mesh Technology

Bluetooth Mesh is the right choice when it comes to scalability and reliability. These are particularly important features for a lighting control system. The advantages of a mesh network can be utilised especially when transmitters and receivers are not in close proximity and messages have to be exchanged over long distances, such as in an office building.

But how does Bluetooth Mesh work? Bluetooth Mesh uses a so-called "managed flood message relay" procedure: all participants in the network – the nodes – receive the same message and can forward it. This makes it possible to reach several thousand participants while still guaranteeing a high level of network performance and reliability.

The procedure 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 luminaires communicate directly with each other. The decentralisation concept 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 of Bluetooth Mesh reduces the load on the radio network and guarantees a high level of reliability. The size of the so-called payload of the messages to be transmitted is optimised to generate as little radio traffic as possible within the network. For example, to set the lightness level, it is sufficient to send the command "Lightness Set" (2 bytes), the "Lightness Level" (2 bytes) and a "Transaction Identifier" (1 byte: new message or retransmission). If you want to set the lightness level to maximum, the message is then: 0x82 4C FF FF 00.

DALI and Bluetooth Mesh

The standardised radio protocol of the Bluetooth SIG is used to reliably connect 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, thus guaranteeing global interoperability.

Standardised gateway that allows D4i-certified luminaires to be controlled via a Bluetooth mesh lighting control network

The DALI (Digital Addressable Lighting Interface) standard is widely used to control LED drivers and is therefore the perfect addition to Bluetooth Mesh. The DALI Alliance (DiiA) has published specifications that include colour control, dimming levels and diagnostic data such as energy consumption and power input. Many well-known LED driver manufacturers support the standard, thus guaranteeing 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 makes it possible to use applications such as automatic and demand-based lighting control and energy monitoring today. And the infrastructure for new use cases such as asset tracking or indoor navigation is already in place for the future.

Recommended case studies

✓ SILVAIR: The largest Bluetooth® mesh lighting control installation in the world!
✓ SENSOTEC NET: Intelligent lighting solution for underground and multi-storey car parks

A portrait of the employees who wrote the article.

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

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