Category: BluetoothMesh

Bluetooth Mesh, Thread and Zigbee Network Performance

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.

Silicon Labs have a more specific paper on Bluetooth Mesh Network Performance.

Read about Beacons and the Bluetooth Mesh

Bluetooth Mesh and IIoT in Factories and Warehouses

Dialog Semiconductor, the manufacturer of the SoC chip in some beacons, has an informative article on How Bluetooth Mesh and IIoT are Reimagining Factories and Warehouses. It explains how the recent introduction of Bluetooth mesh has created new opportunities in the Industrial Internet of Things (IIoT).

“The manufacturing industry is absolutely ripe for potential with Bluetooth mesh”

IDC

“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.

Read about Beacons and the Bluetooth Mesh

Bluetooth Multi-hop Networks

There’s an in-depth paper by Nicole Todtenberg and Rolf Kraemer on A Survey on Bluetooth Multi-hop Networks. The paper describes the basics of Bluetooth and Bluetooth Mesh.

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.

Read about Beacons and the Bluetooth Mesh

Insights into Bluetooth Mesh

There’s an informative article at LEDs Magazine on Bluetooth Mesh expert addresses questions about connected SSL. The expert is Simon Slupik, CTO of Silvair and chair of the Mesh Working Group at the Bluetooth SIG.

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.

Read about Beacons and the Bluetooth Mesh

Bluetooth Mesh Energy Consumption

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.

This battery is probably a CR2032 battery. Read our post on Beacon Battery Size, Type, Capacity and Life for typical beacons battery sizes and capacities.

Read about Beacons and the Bluetooth Mesh

Bluetooth Mesh Standard Evaluation

There’s recent new research on The Bluetooth Mesh Standard: An Overview and Experimental Evaluation (pdf) by Mathias Baert, Jen Rossey, Adnan Shahid ID and Jeroen Hoebeke of Ghent University.

The paper explains how the Bluetooth Mesh Standard came about to address the problem of the variety of BLE meshing solutions that were not interoperable. It includes a great introduction to Bluetooth LE and Mesh with some statistical and experimental insights into mesh performance.

The authors explain how the choice of the use of advertising advertising at 100% duty cycle for lower end-to-end delay has degraded the low energy advantage of BLE advertising thus limiting the usefulness in power (battery) sensitive applications.

The paper contains some useful insights:

  • The back off mechanism, used to decrease the chance of mesh network collisions, contributes most to the communication delay. However, as they identify, it’s this mechanism that provides reliability and scalability in larger networks. Disabling the backoff mechanism decreases the delay but makes the network less scaleable and robust.
  • Making the network more dense, has a positive effect on the round trip time (RTT). However too a dense network leads to more collisions.
  • Increasing the number of hops needed, making the network more sparse, has a negative effect on the RTT.

“It is clear that there are a lot of factors influencing the communication flows within a Bluetooth Mesh network, requiring more advanced management mechanism for optimizing the performance of the mesh network.”

However, the research had some limitations. Noise was simulated by introducing non-mesh beacons advertising every 20ms. This wasn’t very realistic given that most beacons advertise in the range 100ms to 1000ms. Re-transmit time was considered that complicated calculations – especially as re-transmit is application specific. It wasn’t mentioned that in many mesh sensing applications, unacknowledged messages are acceptable such that there’s no re-transmit. Also, the affect of other mesh network traffic, on the round trip time, wasn’t considered – only one mesh transmission at a time was considered.

Read about Beacons and the Bluetooth Mesh

Provisioning Bluetooth Mesh Devices from Smartphones

We previously mentioned there are currently no app examples of how to provision Bluetooth mesh devices via apps on smartphones. Well, Filip Nowakowski has announced:

Nordic nRF5 SDK for Mesh v2.0.0 Released

Nordic, who provide the System on a Chip (SoC) in many beacons, have released v2 of their Mesh SDK that implements standard Bluetooth Mesh.

The main improvements are around support for Bluetooth GATT. It’s now possible for devices such as commercial beacons or smartphones to participate in the mesh via the GATT Proxy mechanism. It’s also possible for devices such as smartphones to provision new devices via GATT through Provisioning Bearer GATT (PB_GATT) rather than via firmware API or the serial API. Unfortunately, there are currently no app examples so there’s a large learning curve and development mountain to overcome to implement products based on these mechanisms.

Martin Woolley, who works for the Bluetooth organisation as an evangelist, has new slides (PDF – needs login at Google for some reason) from a Bluetooth Mesh talk at DroidConIT. The slides explain many of the mesh concepts. Here’s the slide showing the GATT proxy mechanism:

The documentation for Mesh v2 is on the Nordic web site.