US Patent No. 9,900,908

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


Patent No. 9,900,908
Issue Date February 20, 2018
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. 9,900,908

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 hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for downlink channel transmission(s) of the
specific cell assigned by a control channel transmitted on another cell;

determining a contention window based on HARQ-ACK value(s) of the HARQ-ACK feedback, wherein when a ratio of negative acknowledgement
(NACK) of the HARQ-ACK value(s) is equal to or more than a reference value, the contention window is increased to a next higher
allowed value, and when the ratio of the NACK of the HARQ-ACK value(s) is less than the reference value, the contention window
is reset to a minimum value, and wherein when the HARQ-ACK value(s) includes discontinuous transmission (DTX), the DTX is
ignored for determining the contention window,

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.