An apparatus for use in a user equipment comprising: radio control circuitry adapted to demodulate and decode a data transmission from an evolved node B, eNB,; and processing circuitry, coupled with the radio control circuitry, the processing circuitry to: receive the data transmission from the radio control circuitry; and generate acknowledgment feedback based on whether the data transmission was properly demodulated and decoded; wherein the radio control circuitry is further adapted to control radio-frequency circuitry adapted to determine whether a physical channel in an unlicensed shared medium is unoccupied, and transmit the acknowledgment feedback to the eNB over the physical channel in the unlicensed shared medium when the physical channel is unoccupied according to the determination; characterized in that the acknowledgment feedback includes a feedback process number to facilitate matching the acknowledgment feedback to the data transmission; and the processing circuitry is adapted to: determine a transmission window based on a fixed timing relation when a first subframe of the plurality of subframes is determined to be unoccupied, the fixed timing relation being a predefined transmit time for transmitting the acknowledgment feedback according to a reception time of the received data transmission; and select the first subframe when the first subframe is determined to be unoccupied, expand the transmission window when the first subframe is determined to be occupied, and select the second subframe of the plurality of subframes that is within the expanded transmission window for transmitting the acknowledgment feedback; and the radio control circuitry is adapted to control the radio-frequency circuitry adapted to transmit the acknowledgment feedback over the selected one of the first subframe and the second subframe during the transmission window. radio control circuitry adapted to demodulate and decode a data transmission from an evolved node B, eNB,; and processing circuitry, coupled with the radio control circuitry, the processing circuitry to: receive the data transmission from the radio control circuitry; and generate acknowledgment feedback based on whether the data transmission was properly demodulated and decoded; receive the data transmission from the radio control circuitry; and generate acknowledgment feedback based on whether the data transmission was properly demodulated and decoded; wherein the radio control circuitry is further adapted to control radio-frequency circuitry adapted to determine whether a physical channel in an unlicensed shared medium is unoccupied, and transmit the acknowledgment feedback to the eNB over the physical channel in the unlicensed shared medium when the physical channel is unoccupied according to the determination; characterized in that the acknowledgment feedback includes a feedback process number to facilitate matching the acknowledgment feedback to the data transmission; and the processing circuitry is adapted to: determine a transmission window based on a fixed timing relation when a first subframe of the plurality of subframes is determined to be unoccupied, the fixed timing relation being a predefined transmit time for transmitting the acknowledgment feedback according to a reception time of the received data transmission; and select the first subframe when the first subframe is determined to be unoccupied, expand the transmission window when the first subframe is determined to be occupied, and select the second subframe of the plurality of subframes that is within the expanded transmission window for transmitting the acknowledgment feedback; and determine a transmission window based on a fixed timing relation when a first subframe of the plurality of subframes is determined to be unoccupied, the fixed timing relation being a predefined transmit time for transmitting the acknowledgment feedback according to a reception time of the received data transmission; and select the first subframe when the first subframe is determined to be unoccupied, expand the transmission window when the first subframe is determined to be occupied, and select the second subframe of the plurality of subframes that is within the expanded transmission window for transmitting the acknowledgment feedback; and the radio control circuitry is adapted to control the radio-frequency circuitry adapted to transmit the acknowledgment feedback over the selected one of the first subframe and the second subframe during the transmission window.