A quick grasp of Bluetooth mesh network standards and design application basics

To help engineers build innovative IoT products based on Bluetooth wireless technology , Silicon Labs (also known as " core technology " ) has pioneered the industry's complete Bluetooth 5 and Bluetooth mesh network ( Mesh ) hardware and software solutions. Since the Bluetooth mesh network is a new standard, we hope that this article will be reprinted from the Bluetooth SIG blog's "Bluetooth Mesh Networking FAQ" article to help the industry quickly master the Bluetooth mesh network standards and design application basics .

General market problem

Q. What is a Bluetooth® mesh?

A. Bluetooth mesh networks enable many-to-many ( m : m ) device communication and are optimized for creating large device networks. It is ideal for building automation, sensor networks, asset tracking and other IoT solutions that require dozens, hundreds or thousands of devices to communicate with each other .

Q. Where can I use Bluetooth mesh?

A. We expect Bluetooth Mesh to be used in a wide range of markets. We are seeing it in the building automation market, especially commercial lighting solutions and sensor network solutions in multiple markets. It is ideal for IoT solutions that require dozens, hundreds, or thousands of devices to communicate with each other.

Q. Which Bluetooth versions support mesh networks? Can I upgrade my Bluetooth technology with my existing product?

A. The mesh network uses Bluetooth low power ( LE ) and is compatible with core specification versions 4.0 and higher. Only products designed for upgrades can be enhanced in the field to support mesh networks. The scalability is determined by several factors, such as the amount of memory available in the Bluetooth chip.

Q. Why choose a Bluetooth mesh network instead of other low-power wireless mesh network solutions?

A. Bluetooth mesh network brings many key advantages to developers, including:

1. Industrial-grade solutions: Commercial buildings and factory automation are major new market opportunities for low-power mesh networks. These markets require true industrial-grade solutions with the rigorous reliability, scalability and security expectations offered by Bluetooth Mesh .

2. Proven global interoperability: When there is true multi-vendor interoperability, the market can thrive and consumers can confidently use your products with other vendors' products. Bluetooth implements these points:

·        Full stack implementation

·        Interoperability-centered normative approach

·        Time-tested interoperability tools and processes

3. Mature, trustworthy technology: When choosing wireless connectivity technology, your decision criteria should exceed basic speed and requirements, including understanding the added value of technology and the ecosystem support available. Bluetooth is a trusted brand with a global recognition of over 90 %.

With Bluetooth technology, you can bring significant value-added features to your products, such as beacons supporting localized information and asset tracking and finding services. Bluetooth has fostered a mature ecosystem to ensure you find the best technology at the right cost, while at the same time getting the development and testing tools and services you need to bring your products to market.

Q. When is the Bluetooth mesh network available for commercial products?

A. Commercial products with Bluetooth mesh network technology can be seen this year.

Q. What do I need to do to build a Bluetooth mesh network product?

A. To build a Bluetooth mesh network product, you need compatible hardware and software. The Bluetooth mesh network needs to support the underlying Bluetooth LE 4.x or 5.0 stack of GAP Broadcaster and Observer roles to broadcast and scan packets.

To use the Bluetooth mesh protocol on Bluetooth LE , it is recommended that you use the Bluetooth module provider's SDK , which includes the Bluetooth mesh protocol with the corresponding API .

Q. What do I need to do to build a Bluetooth mesh mobile app?

A. To develop a smartphone or tablet application for Bluetooth mesh products, if your mobile operating system provides the appropriate API to enable the application to meet the Bluetooth LE package requirements defined in the Mesh Profile specification , You should use the advertising bearer method. In all cases, advertising bearer is the preferred bearer . Where the advertising bearer cannot be used , you can use the Bluetooth Mesh proxy protocol to enable communication with the mesh network via the proxy node . The proxy protocol can be implemented on top of the standard Bluetooth low energy GAP and GATT APIs .

Q. Will the sensor solution be transferred from Bluetooth broadcast to mesh network?

A. Yes, we expect many sensor solutions to use mesh networks. Its range, data capacity and security features are superior to broadcast, making it ideal for sensor networks.   

Q. Does the Bluetooth mesh network have higher power consumption?

A. No, sensors and similar battery powered devices operate as low power nodes on a Bluetooth mesh network. They only need to wake up at least once every four days, or when they have data transmission, such as temperature readings. This allows for very low power consumption.

Q. Can I use the Bluetooth mesh network to send music to all the speakers in my home?

A. No, wireless audio products (such as speakers) use Bluetooth Basic Rate / Enhanced Data Rate ( BR / EDR ), which is designed for continuous wireless connectivity and optimized for audio streaming. The Bluetooth mesh network uses Bluetooth LE , which is designed for short burst wireless connections and is ideal for many-to-many device messaging.

The mesh network specification is only available for Bluetooth LE and does not support audio streaming.

Q. Does Mesh affect other Bluetooth wireless devices running nearby, such as listening to music?

A. No, you can continue listening to music, syncing your activity tracker, and viewing notifications on your smartwatch in or near the mesh network.

Q. Are there other Bluetooth low energy network topologies available?

Yes, other network topologies that can be used for Bluetooth LE include:

Peer-to-peer : Used to create one-to-one ( 1 : 1 ) device communication, ideal for data transfer, ideal for connected device products such as fitness trackers and health monitors, and

Broadcast : Used to establish one-to-many ( 1 : m ) device communication and optimize localized information sharing. It is ideal for beacon solutions, such as beacon solutions that provide point of interest ( PoI ) information and projects and methods. service.

Information relay problem

Q Why does Bluetooth choose a flood-based message relay method?

A. The managed flooding method for signaling relays best meets the requirements for a simple, reliable and scalable mesh network.

With managed flood messaging , you don't need to create and manage complex routing tables. Even in a routing solution, tables can be automatically generated, so significant network outages can occur.

Managed flood messaging is essentially multi-pathing, ensuring that information arrives at its destination. It is also inherently point-to-point, allowing all nodes to communicate directly with each other. There is no central hub or routing node and there is no single point of failure.

In most mesh network implementations, a large percentage of message traffic is multicast, such as a single light switch in a building that controls dozens or hundreds of lights. The managed flood messaging approach of the Bluetooth network , combined with its publish / subscribe group messaging model, provides extremely efficient messaging for large networks with high performance.

Q. Are all flood-based mesh networks low in power?

A. No, in a simple flood-based mesh network, this can be done, but Bluetooth technology implements a managed flooding method where only the primary power supply node acts as a message relay . Low-power nodes, such as battery-powered sensors, are not responsible for information relay. In a Bluetooth mesh network, a low power node with a button battery can operate for many years.

Q. How does the Bluetooth mesh network handle multicast messages?

Bluetooth Mesh handles multicast traffic using publish / subscribe group messaging.

Half of the address space is assigned to the group address and a message can be sent to the group address. Each node can be configured to subscribe to a group of group addresses and publish messages to a group of group addresses.

For example, a light switch can post an " open " message to a " corridor group " and all lights along the corridor will be subscribed to the same " corridor group " address. However, lights may also be ordered to other groups, such as the “ Underground ” , “ All Lights ” and “ Emergency Exit Routes ” groups.

Bluetooth Mesh also supports virtual addresses, extending the group address by allowing the 128 -bit UUID to act as the destination address. The hash of the Label UUID is used to reduce the overhead of checking the UUID . Each hash value represents millions of different tag UUIDs , increasing the number of potential virtual addresses.

Configuration problem

Q. What is the configuration?

A. Configuration is the process of adding devices to a specified mesh network. It converts the device to a node in the network and includes security key distribution and the creation of a unique ID for the device to be added .

Q. Can I back up my configuration data and restore it?

A. Yes, you can back up the configuration data. This is not defined in the specification, so you can use any backup mechanism you like.

General architectural problem

Q. What is a node?

A node is a configuration device on a Bluetooth mesh network.

Q. How many nodes can I have in a single network?

A. Although the specification allows for the configuration of up to 32,000 nodes, we do not want to implement these numbers quickly in the real world. However, we have seen representative networks of more than 1000 nodes, far greater than other low-power networking technologies on the market today.

Q. Does the Bluetooth mesh network require different types of nodes?

No, the particularity of the Bluetooth mesh network is that all nodes in the network are scattered and can communicate directly with each other.

There is no centralized hub or routing node, so there is no single point of failure. However, in order to accommodate low power nodes, such as battery powered sensors, only some nodes perform message relay functions.

Some nodes take on additional features to support messaging for low-power nodes. This allows a low-power node to remain part of the network, but it can sleep for hours or days at a time until something needs to be reported. Therefore, a low power node using a button battery can operate for many years.

Q. What are the models and attributes?

A. Bluetooth provides a simple and powerful way for developers to describe a node on a Bluetooth mesh network and interact with other nodes. This approach is based on a set of building blocks called models. A model consists of a series of functions with defined functions and behaviors. There are four types of models, including generics, sensors, timing, and illumination. The generic model is the basic building block and defines the standard features of the device, such as the ability to have a simple on / off state. You can combine generic models or use properties to enhance them. The attribute provides additional values ​​for the model.

safe question

Q. How is security handled in a Bluetooth mesh network?

The Bluetooth mesh network is a true industrial grade solution, including its security approach.

Configure devices added to the network with a proven security algorithm. This uses 256 -bit elliptic curves and out-of-band authentication to safely add devices.

All communications require AES-CCM with a 128 -bit key for protection. All grid messages are encrypted and authenticated.

Encryption and authentication are applied to both the network layer and the application layer. All nodes in the network can help relay messages at the network layer without having to read their contents. These content are protected with a separate application key, providing true end-to-end security.

Each message has at least 64 -bit authentication, but for up to 1088 digits of authentication for the longest message .

Models are organized in specifications to trade different users with different security credentials. This allows maintenance personnel to fully control the network configuration while allowing employees to interact.

Replay attacks are prevented by forcing a new serial number on each message sent.

Devices can be blacklisted in the mesh network by using the defined key update process. During configuration, each device calculates a unique device key that only the configurator knows and can update.

Messages protect the identity by obscuring each sent packet and refreshing the privacy. This means that even if you carry a mesh device while walking, people who sniff the grid packets will not be able to track you.

Q. What kind of security attack is designed to prevent Bluetooth mesh network?

Prevent brute force attacks by using 128 -bit keys and at least 64 -bit authentication on each packet .

Replay attacks are prevented by using the new serial number of each packet sent and checking each received packet.

During configuration with out-of-band authentication, ECDH encryption is used to prevent man-in-the-middle attacks.

Use the key refresh process to block spam attacks, allow keys from all remaining devices, and blacklist deleted / damaged devices. Someone disassembled a discarded device and it could not display any security information.

Prevent physically unsafe device attacks by having separate keys for devices in unsecured locations and physically secure locations. This prevents someone from attacking the doorbell and sending a message to unlock the door.

Prevents visitors from attacking by allowing guests and visitors to temporarily access the network using a separate set of keys and restrict access to the network. These guest keys have a limited life span.

Q. Will I lose privacy when using a Bluetooth mesh network?

A. No, each grid packet is obfuscated to protect the identity of the user. An attacker listening to a mesh packet cannot determine which device sent the message because there is no identity value, such as a source or destination address. This confusing information is changed each time a message is relayed, eliminating the ability to track the message flow.

Q. What if my neighbor also has a Bluetooth mesh network?

A. Each mesh grouping includes a small identifier that is used to determine the network to which the mesh group belongs. A device in one mesh network cannot decrypt or authenticate a mesh packet from another mesh network, and it does not relay these messages. Each mesh network is completely isolated.

Reliability problem

Q. How do I know if the nodes on my Bluetooth mesh network are down?

A. A node on the Bluetooth mesh network sends a heartbeat message. In addition, there is a mandatory Health model that allows devices to send fault information. For example, if the device overheats, an " overheat fault " message is sent .

Q. If the node is disconnected, is the traffic affected?

A. No, the node of the message that the relay stops working does not stop the network. Flood message relay creates an inherent self-healing network because messages are sent over multiple routes simultaneously.

other problems

Q. When is the specification available?

A. Bluetooth mesh network specifications and the tools required to qualify Bluetooth products using mesh network support are now available, available at this link: https://

Q. Is the qualification process for the Bluetooth Mesh network specification different from other Bluetooth specifications?

A. No, the process is the same. Core Specification Addendum 6 (CSA 6) introduced a new Bluetooth mesh network terminology, but the product type categories and allows the combination (defined in the Bluetooth Core Specification 0 volume) change, members are still responsible for meeting the eligibility requirements for reference Qualification Program File ( PRD ). To learn more about qualifying new or modified products for Bluetooth Mesh or any other Bluetooth specification, check out the Bluetooth Qualification Process .

Q. Can I use the Bluetooth mesh network to get started with the product today?

A. Yes, if you are ready to comply with Bluetooth Mesh 's new or modified products, please click :

Https://

Q. Can I limit my existing Bluetooth products with Bluetooth Mesh low power?

A. No, existing products cannot support Bluetooth Mesh . However, these products may already have the inherent ability to be added to the mesh network.

Q. Should I know of any brand changes with Bluetooth mesh networks?

A. No, all qualified Bluetooth products continue to use Bluetooth combination markers and / or graphic markers. Click to download the Bluetooth Brand Guide and registered trademark files: https://