BLE - avoiding radio conflict

[gaminn]

Hi, I have two BLE centrals and one BLE peripheral. Both centrals are in range of the peripheral and both want to connect to the peripheral at exactly same time. What central will be succesfull? Is it possible that the connection couldn't be established (e.g. centrals will jam each other when both try to extablish the connection at the same time)

How in general are radio conflicts solved by BLE and nrf51?

[FormerMember]

If the RSSI received from the two centrals is approximately the same, there will be interference between the signals, and the CRC check will fail. In that case the peripheral will continue to advertise, and the two centrals will get a connection_failed_to_establish error.

If the difference in RSSI from the two centrals is larger than 10 dB, the peripheral will connect to the central with the strongest signal, see the nRF51822 Product Specification, chapter 8.5.5 (co-channel interference)

Note that it is very unlikely that two centrals send a connect request to the same peripheral at the very same time. An advertising device advertises on channel 37, 38, and 39 each connection interval.