SensorMesh™ Frequently Asked Questions
What is the maximum number of mesh nodes?
The mesh specification allows up to 32,767 nodes. The maximum number of hops is 127.
What is the range?
There are three types of range associated with SensorMesh™. There's the inter-node range of 100m that's the maximum distance between nodes. There's also the sensor detection range of between 25m and 100m that depends on the advertising power of the Bluetooth LE device being detected. Finally there's the maximum range for the whole system that's the inter-node range multiplied by the maximum number of hops = 100m x 127 = 12.7Km.
The real-use range can only be determined by experiment because ranges vary considerably depending on the actual environment and blocking. We also have relay nodes for special situations that support an inter-node line-of-sight range (but not sensor detection) up to 500m and hence a theoretical system range of 63Km.
What is the latency?
Bluetooth mesh has been designed to be suitable for applications such as lighting where the latency, the time for the data to travel across the network, needs to be a humanly acceptable delay. In most cases it's between 200 milliseconds and 1 second.
What is the throughput?
Bluetooth mesh is based on Bluetooth 4 that was previously designed for power efficient transfer of small pieces of information, relatively slowly. Mesh only supports of the order of low thousands of bits per sec. Bluetooth Mesh is suited to sending sensor data that doesn't change very often. In practical terms this means that the number of supported sensor devices depends on how often the relay reports a sensor device, which is configurable.
The maximum number of supported sensors is approximately 1.5 x the period in seconds. For example, a 10 second update period supports 15 devices, 60 seconds supports 90, 100 seconds supports 150 devices and 200 seconds supports 300 devices. These figures are in ideal conditions and don't take into account any site specific factors such as wireless interference. Also, as the mesh reaches capacity it becomes congested and end to end communication less reliable. If you need more throughput you should consider gateways instead of mesh.
How are nodes set up?
Nodes are set up using the Nordic nRF Mesh app.
What does the output data of the mesh look like?
The output from the COM port has the format:
<sensor MAC address>,<relay MAC address>,<rssi>,<advertising data>\r\n
The data POSTed by the Windows Service is similar except with "$GPRP," prepended.
Here's an example of the COM PORT output:
SensorMesh™ is a product from BeaconZone Ltd in the United Kingdom.
We are specialists in beacons and solutions.