BLE and low-power mesh networks - Wirepas

BLE and low-power mesh networks

Author:
Jani Vehkalahti

We get a lot of questions about our technology. How does it work? How can I take it to use? How does it compare to other technologies? So, we put together a series of blogs to help you out.

In this first blog, we answer questions on hardware and especially in relation to Bluetooth Low Energy (BLE) hardware.

Does Wirepas support BLE?

Wirepas Massive does run on BLE chips, such as the nRF52 product family from Nordic Semiconductor and the EFR32 product family from Silicon labs. We share the same physical layer as the BLE hardware. However, Wirepas Massive overwrites the Bluetooth firmware, still keeping the ability to transmit and receive BLE Beacon messages.

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Is this a BLE Mesh?

That’s a great question. Put simply, no, it isn’t. It’s something much more advanced.

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Unlike most mesh connectivity technologies, BLE Mesh does not use routing. It is a so-called flooding mesh, based on repeaters that repeat messages they hear from devices in the network. And those repeaters need to be mains-powered as they consume a lot of energy.

These limitations are acceptable, for example, for pure wireless lighting control where devices are mains-powered and switch command is broadcast to all devices. But the limitations make it completely unsuitable for sensor networks bigger than 100 devices.

Let’s explain. BLE has an inbuilt BLE Beacon advertisement, designed for devices to find each other and make a pair. This same pairing functionality has been repurposed in the BLE Mesh: there are devices that are advertising beacons like low-power sensors and devices receiving and repeating beacon messages including data. To ensure the message is heard at least by someone, the devices repeat the same message typically three times in three channels. In the end, data might also reach a gateway.

When there are many BLE mesh repeater devices in one building, they all impact interference to others. Why? Because communication is not synchronized, and devices are transmitting at the same time. This is a bit like when many people are all shouting in a room – you might only pick up a word here and there.

The problem increases in use cases like occupancy sensoring. Sensors need to transmit movement data over the network. If there is no routing, sensors transmit BLE beacon opportunistically with full power to maximize the possibility for repeaters to receive a signal. When there are 1000 repeaters in the network, basically all of these devices will receive this one sensor message at least once. One BLE beacon transmission is becoming thousands of transmissions. When there are 100 sensors transmitting data continuously, it means over 100,000 repeats to deliver one change of status of each sensor. The more messages, the more interference and the lower the throughput.

BLE Mesh was never designed for these kinds of use case. With careful design, it is possible to have fewer repeaters in the network and limit hop count per message when the beacon message is not traveling to all 1000 repeaters in the networks. Hop count limit leads to islands of devices which all need to have their own gateway. These methods require network planning.

With Wirepas Massive, the firmware has both adaptive routing and adaptive flooding. This means that the network itself is intelligent and makes the right decisions how to carry the message through the network to the gateway. And it can handle tens of thousands of devices in one network without an issue.

In battery-operated sensor networks, each device extends the coverage meaning there is no wired or additional wireless infrastructure required with Wirepas Massive. This is a big difference from a BLE Mesh where the continuous BLE beacon scanning demands mains power for the repeaters. In BLE Mesh, you need to build infrastructure to include mains-powered repeaters – which is costly.

Can I run Wirepas on my existing device?

Wirepas Massive runs on BLE chips. Your hardware is compatible with Wirepas Massive if your product includes any of the following System on Chip (SoC) components:

1. The nRF52 product family from Nordic semiconductor including chips nRF52832, nRF52840 or nRF52833.
2. The EFR32 product family from Silicon labs including components EFR32BG12, EFR32bg21 or EFR32bg22.

There is a great variety of wireless modules that include SoC components compatible with Wirepas Massive. You can find them all on the Wirepas partner product site.

On top of this, a low-power operation requires a 32kHz crystal to maintain high accuracy of the communication. The low-latency mode of Wirepas Massive, designed for mains-powered applications like LED drivers, does not require a 32kHz crystal. If your product does not include the chips or modules, we would recommend you consider redesigning a new hardware version.

From an application software point of view, your application today is most probably developed with the silicon vendor Software Development Kit (SDK). This means that you would need to port your application on the Wirepas SDK. For more information on that, please visit the Wirepas GitHub.

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