1. A method performed by a first communication device for adapting a random backoff contention window size, comprising:transmitting a downlink burst to at least one second communication device;
receiving from the second communication device, a plurality of Hybrid Automatic Repeat reQuest, HARQ, feedback values corresponding to a plurality of transmissions in the downlink burst; and
adapting the random backoff contention window size based on the received plurality of HARQ feedback values,
wherein the plurality of HARQ feedback values comprises at least one previously unused HARQ feedback value.