Method for transmitting downlink in unlicensed band

Abstract

A method for performing uplink transmissions in an unlicensed band is discussed. The method includes receiving, by a first user equipment (UE) in a first group from a base station (BS), a first uplink grant for a first uplink transmission in the unlicensed band; receiving, by a second user equipment (UE) in a second group from the BS, a second uplink grant for a second uplink transmission in the unlicensed band; determining, by the first UE in the first group, a first delay time to initiate first clear channel assessment (CCA) in the unlicensed band from a reference time; determining, by the second UE in the second group, a second delay time to initiate second CCA in the unlicensed band from the reference time; checking, by the first UE in the first group, whether a channel is idle by performing the first CCA during a first CCA duration after the first delay time from the reference time; checking, by the second UE in the second group, whether the channel is idle by performing the second CCA during a second CCA duration after the second delay time from the reference time; and performing, by the first and/or second UE, the first and/or second uplink transmission based on the first and/or second uplink grant when the channel is idle.

What is claimed is: 
     
         1 . A method for performing uplink transmissions in an unlicensed band, the method comprising:
 receiving, by a first user equipment (UE) in a first group from a base station (BS), a first uplink grant for a first uplink transmission in the unlicensed band;   receiving, by a second user equipment (UE) in a second group from the BS, a second uplink grant for a second uplink transmission in the unlicensed band;   determining, by the first UE in the first group, a first delay time to initiate first clear channel assessment (CCA) in the unlicensed band from a reference time;   determining, by the second UE in the second group, a second delay time to initiate second CCA in the unlicensed band from the reference time;   checking, by the first UE in the first group, whether a channel is idle by performing the first CCA during a first CCA duration after the first delay time from the reference time;   checking, by the second UE in the second group, whether the channel is idle by performing the second CCA during a second CCA duration after the second delay time from the reference time; and   performing, by the first and/or second UE, the first and/or second uplink transmission based on the first and/or second uplink grant when the channel is idle.   
     
     
         2 . The method of  claim 1 , wherein the second delay time is longer than the first delay time. 
     
     
         3 . The method of  claim 1 , wherein the first uplink grant and second uplink grant are allocated same as a single uplink grant. 
     
     
         4 . The method of  claim 1 , wherein the first delay time is determined based on a parameter specific to the first group, and the second delay time is determined based on a parameter specific to the second group. 
     
     
         5 . The method of  claim 1 , wherein each of the first and second uplink grants comprises information on a parameter used to determine each of the first and second delay times. 
     
     
         6 . The method of  claim 1 , wherein the reference time is a point after a certain period of time from a time when the first or second uplink grant is received. 
     
     
         7 . The method of  claim 1 , wherein the first CCA duration is defined in inverse proportion to the first delay time, and the second CCA duration is defined in inverse proportion to the second delay time. 
     
     
         8 . The method of  claim 1 , wherein the first and/or second uplink transmission is not performed when the channel is busy. 
     
     
         9 . A device for performing uplink transmissions in an unlicensed band, the device comprising:
 a transceiver to transmit and receive a radio signal; and   a processor coupled to the transceiver and configured to:   receive a first uplink grant for a first uplink transmission in the unlicensed band;   receive a second uplink grant for a second uplink transmission in the unlicensed band;   determine a first delay time to initiate first clear channel assessment (CCA) in the unlicensed band from a reference time;   determine a second delay time to initiate second CCA in the unlicensed band from the reference time;   check, whether a channel is idle by performing the first CCA during a first CCA duration after the first delay time from the reference time;   check, whether the channel is idle by performing the second CCA during a second CCA duration after the second delay time from the reference time; and   perform the first and/or second uplink transmission based on the first and/or second uplink grant when the channel is idle.   
     
     
         10 . The device of  claim 9 , wherein the second delay time is longer than the first delay time. 
     
     
         11 . The device of  claim 9 , wherein the first uplink grant and second uplink grant are allocated same as a single uplink grant. 
     
     
         12 . The device of  claim 9 , wherein the first delay time is determined based on a parameter specific to the first group, and the second delay time is determined based on a parameter specific to the second group. 
     
     
         13 . The device of  claim 9 , wherein each of the first and second uplink grants comprises information on a parameter used to determine each of the first and second delay times. 
     
     
         14 . The device of  claim 9 , wherein the reference time is a point after a certain period of time from a time when the first or second uplink grant is received. 
     
     
         15 . The device of  claim 9 , wherein the first CCA duration is defined in inverse proportion to the first delay time, and the second CCA duration is defined in inverse proportion to the second delay time. 
     
     
         16 . The device of  claim 9 , wherein the first and/or second uplink transmission is not performed when the channel is busy.