According to some embodiments, a method for use in a
user equipment (UE) of managing a listen-before-talk (LBT) contention window size comprises receiving scheduling for a current burst of contiguous uplink subframes. For each
subframe the scheduling comprises an associated
hybrid automatic repeat request (HARQ)
process identifier and a new data indicator (NDI). The method determines a reference
subframe based on a previously-scheduled burst of contiguous uplink subframes. The reference
subframe is associated with a reference HARQ
process identifier. When the UE determines the HARQ
process identifier associated with a subframe of the current scheduled burst of contiguous uplink subframes matches the reference HARQ process identifier and the NDI indicates new data, the method resets the LBT contention window. When the reference HARQ process identifier matches, but the associated NDI indicates a
retransmission, or the HARQ process identifier does not match, the method increments the LBT contention window. According to another embodiment, a method is presented for performing
uplink transmission according to LBT type and LBT priority class. According to a further embodiment, the contention window size for a UK is determined and sent to the UK.