Bluetooth Smart Mesh — why does it make sense for IoT?
Also known as Bluetooth Low Energy, Bluetooth Smart is an interesting short-range radio technology that could be used for connecting tiny devices into the Internet of Things.
We believe the concept of capillary networks will be important for IoT. By capillary networks, we mean using short-range radio technologies to connect groups of small devices, to the Internet, via capillary gateways and cellular networks.
There are several radio technologies that can be used for capillary networks, more or less suitable, depending on the use case at hand. In this post, we’ll introduce one candidate: Bluetooth Low Energy (BLE).
Bluetooth technology is widely deployed already. ABI research forecasts that by 2018, there will be over 10 billion Bluetooth-enabled devices in the marketplace. BLE provides ultra-low power wireless communication – necessary if we want to connect devices powered by tiny batteries.
Why BLE mesh?
Bluetooth Smart has some constraints when it comes to the network coverage, the transmission range and peer-to-peer communications, which all limit the use cases BLE is suited for.
Multi-hop mesh networking technology can enable Bluetooth Smart to apply in even wider range of use cases. Typical competing short-range wireless technologies such as Zigbee, ANT and WirelessHART support mesh networking. The essential features of Bluetooth Smart determine that its mesh networking will be different from other short-range technologies.
What is BLE mesh?
In general, a wireless mesh network is a network built on a number of fixed and mobile nodes that provide a robust and multi-hop communication for peer-to-peer transmissions. There are some challenges in transforming a single-hop BLE network into a mesh. Take the topology as an example: most off-the-shelf BLE chipsets have Bluetooth version 4.0-compliant firmware implementation. However, version 4.0 inherently has a topology limitation towards peer-to-peer mesh networks: the supported topology called “Piconet” is a master-slave connection network that does not allow multi-hop communications. Since version 4.1, BLE topology introduced “Scatternet” which enables a master node of one or several slave nodes to simultaneously be a slave of another node. The Scatternet absolutely makes the multi-hop connection possible. Yet, it does not inherently change the Piconet-based asymmetric topology model, where a relay node can receive/relay a message in data channels only after establishing a master-slave connection with a corresponding transmitter/receiver. This challenge calls for innovative solutions to overcome these constraints.
Bluetooth Smart Mesh has the late-developing advantage in adopting more pragmatic mesh technologies. Some existing mesh technologies have been flowing into the Bluetooth Smart Mesh. For example, Nordic Semiconductor released a “BLE rebroadcast mesh implementation” at Github. The open source code utilizes an algorithm called Trickle Algorithm. Instead of flooding, Trickle Algorithm, was originally designed for disseminating small data packets, in a wireless sensor network, with controlled sending rate. Since its publication in 2004, it has been primarily implemented and evaluated in IEEE 802.15.4 radio based platforms.
Why does BLE mesh make sense to IoT and the Networked Society?
Short-range radio devices in a capillary network, such as BLE devices, can be connected to the Internet by a capillary gateway. Nevertheless, the short transmission range for such devices with a single-hop network topology prevents the use cases of IoT applications from running over a large number of devices. BLE mesh enables these use cases by providing peer-to-peer and robust multi-hop connectivity for a large number of local BLE devices. This way, IoT application data can be exchanged between any local BLE device and the Internet through the mesh network and a gateway.
Ericsson invented Bluetooth in 1994; this replaced wired communication between the mobile phone and headset. By 2014, Bluetooth had achieved 90% penetration in all mobile phones! Bluetooth Low Energy (BLE), adopted by Bluetooth SIG in 2010, expanded the Bluetooth ecosystem considerably. The original intention of Bluetooth Smart was to provide connectivity between mobile devices or PCs and watches, wireless keyboards, toys, sports sensors and other small, button-cell battery-powered devices by using ultra-low power wireless communication.
Bluetooth SIG has recently announced that work has started for standardization of Bluetooth Low Energy mesh; and a study group has been launched to examine the subject of mesh networks with a view of defining an industry standard Bluetooth mesh protocol. Coincidentally, Bluetooth specification version 4.2 has recently been unveiled with an optional profile, Internet Protocol Support Profile (IPSP), which enables 6LowPAN (over BLE) compatible devices to discover and communicate with each other. Bluetooth SIG has taken a big step by pushing BLE devices to be directly connected with Internet.
The Future of BLE mesh
Thanks to the network coverage of BLE mesh, the capabilities will greatly be extended in many already existing use scenarios. For example, over the mesh network, you can control any light bulb, anywhere in your home, using a key fob or your smartphone, even if there are obstacles in between. The robustness of BLE mesh also makes it a good candidate for wireless communication in special use cases such as surveillance and security.
Together with capillary gateways, BLE mesh will increase the competence of Bluetooth technology in IoT applications such as regulating at-home heating, ventilation and air conditioning systems from comfort mode to energy saving mode when you leave for the office.
The peer-to-peer communication capability of BLE mesh will benefit some emerging applications. As an example, take the “scene” application: an occupancy sensor at the door entry can broadcast your presence at home, then the lights are turned on and music starts playing; when the TV is turned on, the app broadcasts “entering TV scene” so that lights and temperature are automatically adjusted.
We believe that BLE mesh shall extend many existing applications and trigger emerging use cases for BLE technology in the near future.
Wei Shen and Anna Larmo, Ericsson Research