US Patent No. 9,622,237

METHOD, APPARATUS, AND SYSTEM FOR CHANNEL ACCESS IN UNLICENSED BAND


Patent No. 9,622,237
Issue Date April 11, 2017
Title Method, Apparatus, And System For Channel Access In Unlicensed Band
Inventorship Minseok Noh, Seoul (KR)
Jinsam Kwak, Uiwang-si (KR)
Juhyung Son, Uiwang-si (KR)
Assignee WILUS INSTITUTE OF STANDARDS AND TECHNOLOGY INC., Seoul (KR)

Claim of US Patent No. 9,622,237

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.