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How Bluetooth Mesh Impacts IoT Design

July 21, 2017
New networking enhancement lets Bluetooth continue its reign as the top wireless technology.

Bluetooth is the oldest and most widely used short-range wireless technology today. With billions of chips sold during its 20-plus years of existence, Bluetooth is found in an impressive array of other products. Now with the addition of its new mesh option, Bluetooth is ready to continue its dominance of the short-range space.

Bluetooth Applications

How many Bluetooth devices do you own? I counted a dozen between my wife and myself. Every smartphone has one. Most hands-free automobile infotainment systems have one. In addition, Bluetooth dominates the wireless audio market with its ubiquitous radios in speakers, headphones, and hearing aids. Tablets and laptops have Bluetooth and many use wireless keyboards and mice. Smart and fitness watches include it. Bluetooth is also found in many medical devices like heart rate monitors. Furthermore, its unique broadcast capability makes it a leading choice in the growing beacon market. Bluetooth also competes in the Internet of things (IoT) space, finding its presence in toys and voice control products like Amazon Alexa and Google Home. Smart-home devices like thermostats, security, and lighting systems incorporate Bluetooth. Now, Bluetooth gets ready to find its way into more IoT products with the introduction of the Bluetooth Mesh standard.

Bluetooth Mesh Overview

Bluetooth Mesh is an enhancement to the popular Bluetooth Low Energy (BLE) standard 4.0 and higher. It is now an alternate choice for those designing large networks. The basic communications method of Bluetooth is a device-to-device, point-to-point, or master-to-slave topology where two units “pair” and exchange data. The Bluetooth standard offers a limited networking option called “piconets” for connecting up to seven devices. Multiple piconets can then be connected to form a “scatternet.” These options are not widely used and they could not be easily designed into systems needing hundreds or thousands of nodes. Now with the Mesh option, Bluetooth can compete with other mesh-capable standards such as ZigBee, Dust Networks (Linear Technology/Analog Devices), Thread, Wi-Fi, and others.

Bluetooth Mesh can address large networking systems. Building automation is a good example. It can be used to monitor and control lighting (Fig. 1), security, and heating/cooling systems. And Bluetooth Mesh may find its way into industrial systems to implement large sensor networks. Another new application is asset tracking systems that locate items in large complex environments. The mesh feature opens the door to other uses.

Bluetooth Mesh can automate and manage large building lighting systems.

The Mesh Networking Concept

Mesh networks are interconnections of a large number of monitor or control nodes spread out over a large area. It is a many-to-many (m:m) topology. The nodes are not only individual monitor or control points but also may be repeaters or relays as well as gateways or routers that provide connections to external LANs or the internet. Individual nodes communicate over short distances with those nearby nodes. Yet any node can talk to any other node even if it is not adjacent. This ability is implemented such that communications packets are passed from node to node allowing large distances to be covered in multiple short-range wireless hops. This mesh arrangement is very reliable in that if one node fails, data can still be transmitted over multiple alternate paths. This makes the mesh a self-healing ad hoc network.

Bluetooth Mesh Details

The key to mesh networking is the addition of the management software layers to an already proven wireless physical layer. It is a full-stack solution that affects all networking layers physical through application. This addition provides the four main reasons why a mesh topology is chosen for a new network. These are reliability, scalability, security, and interoperability.

Reliability. Bluetooth Mesh nodes all talk directly to one another rather than through some central gateway or router. There is no single point of failure. Bluetooth Mesh uses what is called managed flood message relay architecture to ensure true multipath communications.

Scalability. Bluetooth Mesh permits the building of very large networks of hundreds of nodes up to a maximum of 32,000 nodes. Networks are easily sized by adding new nodes as needed or decommissioning nodes if required. A node is added by “provisioning”, a process of providing it with an encryption key called a NetKey. The new standard uses a publish/subscribe approach to the managed flood message relay architecture that facilitates the building of large networks.

Security. Built-in security and privacy are a key part of Bluetooth Mesh. A two-layer encryption and authentication process protects all inter-node communications. Provisioning uses 256-bit elliptical curve encryption.

Interoperability. Multi-vendor interoperability is assured, meaning that products from different vendors work together.

For more details on how this sophisticated new network option works, go to the Bluetooth SIG site.

Pervasive Is an Understatement

Bluetooth Mesh will greatly expand the adoption of the Bluetooth standard. In addition, legacy Bluetooth and Bluetooth Low Energy standards will continue to grow as new IoT and other applications are identified. Despite its complexity, the standard maintained by the Bluetooth Special Interest Group (SIG) provides plenty of support that includes testing and certification and access to common applications software units called profiles. And there are a dozen or more chip and module manufacturers with ready-to-go products. One example is Qualcomm’s CSRmesh devices. Its QCA4020 is a tri-mode SoC that supports BLE 5, Wi-Fi, and 802.15.4-based standards like ZigBee and Thread. The QCA4024 integrates BLE 5 and 802.15.4. Another vendor that supports Bluetooth mesh is Silicon Labs with their Blue Gecko products.

Now a new era begins. Bluetooth Mesh will help this versatile standard to continue its leadership position in the short-range wireless space. ABI Research forecasts annual Bluetooth device shipments will reach over 5.5 billion by 2022 boosted by mesh networking and other recent improvements in range, throughput and broadcast capacity.

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