Introduction to Bluetooth 5
May 20, 2018
The latest version of the Bluetooth standard includes a number of enhancements that will be useful for many applications, but perhaps more important for the Internet of Things (IoT).
The main changes discussed in this article are higher speed, greater reach, mesh networks, and better support for advertising and tags. Bluetooth 5 remains compatible with earlier versions and offers better coexistence with other wireless networks. The longer range and higher data rates do not require power but can not be used simultaneously. In other words, Bluetooth 5 allows designers to optimize throughput, range, and power consumption.
Devices that support Bluetooth 5 become available, such as: Although Bluetooth 5 compatibility can be achieved only by supporting errata (in other words, what was wrong or missing in Bluetooth 4.2), it is important search for device support for new Bluetooth features. 5
The Bluetooth 5 Extended Data Rate (EDR) supports higher transmission speeds of up to 2 Mbps without increasing power output. This means that less energy is used to send the same amount of data that battery powered devices can have a longer life or a physically smaller product.
Most devices are Flash-based so they can use this increased speed to perform firmware updates. This is important for security and feature updates, especially for IoT nodes. There are always people looking for new vulnerabilities.
Higher data throughput will also be useful for applications requiring fast response times, such as robotic system control or factory machines. It also allows nodes to collect downloaded data more easily when needed.
Bluetooth 5 has a theoretical range of up to 400 meters for a line of sight, which, in a more realistic environment, should be about 120 meters. This is about four times the range of the previous version with the same power consumption. However, this can only be achieved at lower data rates, so that it is possible to choose between a higher speed or a higher range. For many low power applications, the 500kbps or 125kbps modes provide adequate bandwidth.
At these lower data rates, forward error correction (FEC) is used to improve data recovery from background noise. The effective sensitivity is improved by about 12 dB, four times the range. Importantly, this does not require more output, so the longer reach can be achieved without increasing power consumption.
Bluetooth was originally defined as a star network, where all nodes are connected via a central hub. This limits the size and scope of the network. A large network would require multiple hubs with different communications, possibly wired together, which would increase costs and complexity. Bluetooth 5 supports mesh networking, where all nodes can communicate directly with each other, as shown in Figure 1. Messages can be transferred via intermediate nodes. This extends the network beyond the simple point-to-point wireless connection, offering virtually unlimited coverage and even between buildings.
Mesh networks are already supported by other wireless systems such as Zigbee and have been implemented by some manufacturers of Bluetooth devices with proprietary extensions to the standard. These and other companies have worked with Bluetooth SIG to set the standard mesh.
Bluetooth 5 uses a flood mesh. This means that each packet received by one node will be copied to all other connected nodes until it reaches the destination. This uses the existing analytics and advertising features to send the package. This is a simple but effective way to distribute information about the mesh network. Each package has multiple paths to the destination, which increases reliability. Battery-powered nodes do not need to relay messages, so the battery life is not reduced when they are part of a mesh network.
The controller can be distributed over the network, the Bluetooth SIG using a “scene” in which a user action triggers a cascade of others. For example, if an owner comes home and opens the front door with a smart lock, the other nodes can be informed to turn on the light, turn on the heat, and so on.
Mesh networks are particularly useful for industrial IoT, where a large number of nodes can be distributed throughout the enterprise. For example, it can manage heating, air conditioning, lighting, security, inter-machine communication, monitoring of system status, energy consumption, inventory tracking at the factory and warehouse, and many other applications in sales and manufacturing environments.
The mesh network standard is not specific to Bluetooth 5 and can be added to Bluetooth 4.2 implementations.
Improvement of tags and advertising
Bluetooth 5 offers better support for “connectionless” applications that use working tags without the need to pair with another device.
The enhanced range is useful for tag applications. The increase in speed is not as important as the detection / connection time rather than the raw data rate is generally important. In addition, there are ad extensions that can transmit more data and reduce the risk of overloading advertising channels.
The base broadcast packet size is increased to 255 bytes and the packets can be concatenated to create improved advertising data payloads. This means that the tag can transmit more useful datasets and new types of data.
However, Bluetooth has only three announcement channels, and these may be quickly clogged with ad packs if they all contain large payloads. Ad extensions meet these criteria by using the same three channels for advertising and then using another (non-advertising) channel to transfer data.
A new periodic advertising mode enables synchronized data transfer between devices.
Improvement of coexistence
There are several wireless connectivity solutions, all operating in the 2.4 GHz band, including cordless phones, baby monitors, Wi-Fi, Zigbee and LTE mobile networks. Bluetooth 5 improves coexistence with these. In addition to avoiding the channels already used by Wi-Fi, “slot availability masks” are added to avoid interference with mobile networks. Bluetooth 5 also has an improved channel sequencing algorithm (CSA # 2) to improve the pseudo-randomness of subsequent channel sequencing. This improves operation in the presence of Wi-Fi and other Bluetooth devices.
To enable products that can work flexibly in this environment, silicon manufacturers produce devices that support multiple protocols, such as ANT, LPWAN (802.15m), Zigbee, and others, in a single SoC.
The enhancements to Bluetooth 5 will allow a new set of applications for tags. For example, outlets and exhibits can use tags to automatically record the presence of people and provide information about items viewed by the visitor, including a link with more details or special offers. You can provide navigation information and suggestions on what else you can see. Beacons can also collect feedback by following people to find out where they are going, where they are going, what they are seeing or buying, etc.
Bluetooth 5 will also be able to compete in IoT applications such as Smart Lighting, which are already dominated by alternatives like Zigbee. Bluetooth has the advantage of being already ubiquitous in devices that can be used to control and monitor these applications.