Patent ID: 9622237
Date: 2017-04-11
CPC Classifications: H04L,H04W

Claim:
1. A method for performing downlink transmission in a specific cell by a base station in a cellular wireless communication system, the method comprising: receiving a plurality of hybrid automatic repeat request acknowledgement (HARQ-ACK) responses for downlink channel transmission(s) of the specific cell assigned by a control channel transmitted on the same specific cell; determining a contention window based on the HARQ-ACK responses; generating a random number N (N≧0) in the determined contention window; and performing the downlink transmission in the specific cell after sensing a channel on the specific cell at least for N slots while the channel on the specific cell is idle, wherein when a ratio of negative acknowledgement (NACK) among the plurality of HARQ-ACK responses is equal to or more than a reference value, the contention window is increased to a next higher allowed value wherein when the ratio of the NACK among the plurality of HARQ-ACK responses is less than the reference value, the contention window is reset to a minimum value, and wherein when the plurality of HARQ-ACK responses include discontinuous transmission (DTX), the DTX is counted as NACK.