The paper explains mesh topologies and routing protocols. It describes Bluetooth:
“BLE is presently raising more and more attention and is becoming one of the leading technologies for both IoT-oriented and industrial scenarios”
The authors provide an in-depth introduction to SIG Bluetooth Mesh. (Note that an excellent higher level overview also very recently became available from InsightSIP). The research paper also mentions other Bluetooth mesh implementations such as the draft IETF Bluetooth Mesh for IPv6.
Applications such as smart city, industrial monitoring and smart agriculture are considered and factors such as interoperability and security are mentioned. Finally, the paper compares other protocols such as Thread, ZigBee and LoRaWAN.
There’s an informative video presentation on the Bluetooth SIG web site on Simplifying Multi-Vendor Mesh and Sensor Networks. It provides an introduction to Bluetooth mesh and explains the ways in which it can provide for Industrial IoT (IIoT).
To add to this, Bluetooth Mesh is suitable for use on the factory floor where the environment can be electrically noisy. Standard Bluetooth Mesh uses advertising on several channels rather than (GATT) connections so as to provide for more reliable communication in environments with wireless interference.
Silicon Labs have a useful web site, webinar and slides on “Benchmarking Bluetooth Mesh, Thread, and Zigbee Network Performance”.
The two main measures of performance are throughput, the rate data transfer that can be achieved (in bits per second) and latency, the time taken for data to cross the network.
With a typical implementation of 6+ hops, throughput converges to a similar order of magnitude for all the protocols:
In real use these protocols only support of the order of low thousands of bits (not bytes!) per sec and should therefore only be used for sending small amounts of data that don’t change very often.
For a small payload with 192 nodes, Zigbee has lowest latency and Bluetooth has greatest variation of latency of 20ms to 200ms:
For a larger payload, the Bluetooth latency has a larger range of up to 750ms:
Whether the variation of latency matters depends on your particular solution. Which technology is best depends on what you need to accomplish. For example, in a Bluetooth lighting scenario you might not want some lights to come on immediately and far ones to come on up to a second later. For sensing, the delay usually doesn’t matter.
You also need to consider other factors such as interoperability, scalability, security, reliability and ease of deployment. For example, Zigbee is less scalable and Silicon Labs recommends a maximum of seven hops otherwise the network becomes congested due to re-tries. Bluetooth has especially good interoperability because it is ubiquitous on smartphones and other devices. It also works reliably in industrial situations and has double encryption.
All protocols can be difficult to deploy due to the lack of off-the-shelf general solutions outside specific verticals such as lighting and home automation although our SensorMesh™ is a notable exception.
SensorMesh™ is our technology that allows Standard Bluetooth advertising, such as from beacons, to be relayed across a site using standard Bluetooth Mesh. When used with iBeacon or Eddystone beacons, SensorMesh™ output enables you to determine the location of assets and people to the nearest relay node. When using SensorMesh™ with sensor beacons, you can detect movement, temperature, humidity, air pressure, light, open/closed, close proximity and human proximity (PIR).
Up until now, SensorMesh™ has only been available to end customers taking up our complete solutions. ISVs haven’t been able to take the components and create their own solutions. As previously with BeaconRTLS™, we have used the same strategy of using the technology ourselves, learning how we need to simplify so 3rd parties can use and then updating the product to offer to ISVs.
We have updated SensorMesh™ to remove the gateway box. It was decided it would be too complex to set up for ISVs. Instead we now have a gateway node that sends output to a USB COM Port.
This widens the possibilities for the receiver to be a PC, Linux box, Raspberry Pi, single board computer or any device with a USB port. For customers who need the data to be uploaded, in place of the gateway box functionality that uploaded to a server, we now have an installable Windows 10 Service that takes data from a COM port and uploads it to your server, BeaconServer™ or BeaconRTLS™.
As previously, SensorMesh™ is stand-alone hardware with no subscription and isn’t software as a service (SAAS). You buy the hardware and then there are no ongoing costs. The data stays within your systems.
“The manufacturing industry is absolutely ripe for potential with Bluetooth mesh”
“Industrial sensors and smart buildings among other use cases, are expected to outpace the overall Bluetooth LE market by 3X through 2022”
Research and Markets
The article mentions preventive maintenance, air quality sensing, asset tracking, robot control systems and traditional air conditioning as possible applications for Bluetooth Mesh. However, a key insight is that once a mesh network is in place it can be used for applications beyond those originally envisaged.
The paper goes on to describe connected networks (scatternets) and connectionless networks including some complex topics such as scatternet formation, topology maintenance, optimisation, inter-piconet scheduling and packet forwarding.
While the article explains the use of Bluetooth mesh in the context of lighting, many of the concepts are equally as applicable in other applications of mesh. The article covers robustness, interference immunity, low energy, scalability, antennas and security.
There’s a new paper by Seyed Mahdi Darroudi, Raül Caldera-Sànchez and Carles Gomez of Department of Network Engineering, Universitat Politècnica de Catalunya/Fundació, Spain on Bluetooth Mesh Energy Consumption: A Model.
They set up some experiments to measure current consumption under various parameters:
They found that a sensor device running on a simple 235 mAh battery, sending a data message every 10 secs, can achieve a lifetime of up to 15.6 months.