CSRMesh uses the company's µEnergy product family, and is a protocol running over Bluetooth Smart. It permits up to 65000 nodes in a single network, and multiple co-existing networks, and CSR intends that it be used in applications such as home automation; it has already been applied to lighting, and will be extended to other functions in the near future.
Asked what Bluetooth can bring to mesh networked systems, CSR’s Rick Walker – senior product marketing manager – says that above all else; it’s the smartphone. Virtually every recent smartphone, he notes, comes ready-equipped with Bluetooth Smart. Any phone can therefore host an app to directly interface with a network of devices, either controlling or collecting data. You do not need any form of gateway or additional hardware between the phone and the network.
CSRMesh is – in contrast to other network technologies that form specific routes through the network – a flood mesh protocol. That is, any device receiving a message either identifies that the message is for itself, or it re-broadcasts the message. CSRmesh does not use full IP addressing but adopts a light weight data structure which enables much lower power and lower processing burden for simple devices.
How does Bluetooth, in the shape of battery-powered nodes, implement a flood-mesh and still contain power such that long battery life is possible? It is, Walker says, all about minimising the time that each node spends “listening” - that is, with its receiver powered up and waiting for a message. In a typical home-automation context originating or repeating a message will be relatively infrequent event and therefore, less significant for battery drain; and CSR says that its µEnergy range already achieves this with low current drain while active. The Mesh protocol needs to maximise the probability of intercepting a transmitted message while minimising wake-to-sleep Rx ratios.