BLE advertisement frame successful exchange rate in scenarios with many advertising devices

ble_frame_collisions.md

This is based on my partial knowledge of radio networks, and on very incomplete knowledge of the BLE stack.

AFAIK BLE scans in short intervals on one of 3 channels. With >50 devices in advertisement mode it may be hard to get non-colliding frames to the receiver.

• I don’t think Bluetooth LE was designed to have hundreds of devices in discoverable mode sending out garbage identity frames.
• Increasing the radio wake time may not be a solution either because you end up with flat batteries too quickly.

Protocol

• 3 advertising channels;
• scanning device listens to one for the discovery window(?);
• advertising device hops to 1-3(?) and broadcasts the advertisment frame.

References

• discovery latency model, https://codeocean.com/capsule/6248988/tree/v1
• DOS attacks on beacons, "Breaking BLE Beacons For Fun But Mostly Profit" http://www.sharcs-project.eu/m/documents/papers/a04-kolias.pdf