Abstract: A Bluetooth master unit polls a slave unit to enable the slave to resynchronize to the master, by sending POLL packets with sufficient frequency to maintain a connection to the slave, and in the intervals between such packets, sending NULL packets with sufficient frequency to maintain synchronization of the slave. By replacing some POLL packets with NULL packets, since the slave does not have to respond to a NULL packet, it can save some power, and there is reduced interference on other piconets. The frequency of the remaining POLL packets is set according to a Link Supervision Timeout (to avoid having this timer expire and thus keep the Bluetooth Link to the slave alive) and according to the time since the master received the last packet from the slave.

Abstract: A Bluetooth master radio frequency unit addresses a slave radio frequency unit, to enable the slave to resynchronize to the master, by sending poll packets or null packets, the master being arranged to send sufficient null packets to enable the slave to resynchronize, before sending a poll packet, to determine whether the slave has resynchronized. This approach can provide the slave with the same number of synchronization packets as in the simpler algorithms, while allowing the slave to preserve more (transmit) power and still allowing the master to detect whether the slave has resynchronized or not (and thus to update a Link Supervision Timer for example). Notably this is also suitable for use in prescheduling implementations.