An apparatus of a Fifth Generation NodeB (gNB) to operate in a License Assisted Access (LAA) system configures a transmission initiation time interval contention window size (CWS) of N number of subframes between Category 4 Listen Before Talk (LBT) uplink (UL) transmissions by a user equipment (UE) operating in the LAA system, and a memory to store a value of N which can have a value 6 or greater or 10 or greater. An apparatus of a UE to operate in an LAA system decodes a configuration from the gNB of a transmission initiation time interval contention CWS of N number of subframes between Category 4 LBT UL transmissions in the LAA system. The CWS is increased to a next higher value when an UL grant or an autonomous UL (AUL) downlink feedback indicator (DFI) is not received before the expiration of a timer.