An apparatus comprising: a transmitter configured to transmit data on a carrier to a set of devices in a first transmission burst having a duration of at least one subframe, wherein the set of devices comprises one or more devices; a receiver configured to receive feedback information from each device of the set of devices; and a processor configured to: determine, based on the feedback information, whether interference above a predetermined level exists on the carrier during the first transmission burst at each device of the set of devices; adjust a contention window size based on the determination of whether interference above the predetermined level exists on the carrier during the first transmission burst at each device of the set of devices; and determine a value N between a predetermined minimum contention window size and the adjusted contention window size, wherein the transmitter transmits a second transmission burst on the carrier at least N time slots after the end of the first transmission burst, wherein the duration of each time slot is predetermined; and wherein adjusting the contention window size comprises increasing the contention window size if interference above the predetermined level exists on the carrier during the first transmission burst for more than a predetermined percentage of devices in the set of devices. a transmitter configured to transmit data on a carrier to a set of devices in a first transmission burst having a duration of at least one subframe, wherein the set of devices comprises one or more devices; a receiver configured to receive feedback information from each device of the set of devices; and a processor configured to: determine, based on the feedback information, whether interference above a predetermined level exists on the carrier during the first transmission burst at each device of the set of devices; adjust a contention window size based on the determination of whether interference above the predetermined level exists on the carrier during the first transmission burst at each device of the set of devices; and determine a value N between a predetermined minimum contention window size and the adjusted contention window size, wherein the transmitter transmits a second transmission burst on the carrier at least N time slots after the end of the first transmission burst, wherein the duration of each time slot is predetermined; and wherein adjusting the contention window size comprises increasing the contention window size if interference above the predetermined level exists on the carrier during the first transmission burst for more than a predetermined percentage of devices in the set of devices. determine, based on the feedback information, whether interference above a predetermined level exists on the carrier during the first transmission burst at each device of the set of devices; adjust a contention window size based on the determination of whether interference above the predetermined level exists on the carrier during the first transmission burst at each device of the set of devices; and determine a value N between a predetermined minimum contention window size and the adjusted contention window size, wherein the transmitter transmits a second transmission burst on the carrier at least N time slots after the end of the first transmission burst, wherein the duration of each time slot is predetermined; and