Radio access node, communication terminal and methods performed therein

Abstract

Embodiments herein relate to a communication terminal (10) for handling communication, which communication terminal (10) is being served by a radio access node (12, 13) in a first cell (11) on a carrier of a licensed frequency spectrum and cross-carrier scheduled in a second cell (14) on a carrier of an unlicensed frequency spectrum by the radio access node (12, 13) via the first cell (11). The communication terminal receives an indication that data may be scheduled for the communication terminal (10) on a data channel in the second cell (14). The communication terminal attempts to detect presence of the data channel intended for the communication terminal (10). Then, in case the communication terminal (10) detects presence of the data channel intended for the communication terminal (10), the communication terminal (10) decodes the data channel. In case the communication terminal (10) does not detect presence of the data channel intended for the communication terminal (10), the communication terminal (10) indicates a non-detection of the data channel to the radio access node (12, 13).

1 . A method performed by a communication terminal for handling communication, which communication terminal is being served by a radio access node in a first cell on a carrier of a licensed frequency spectrum and cross-carrier scheduled in a second cell on a carrier of an unlicensed frequency spectrum by the radio access node via the first cell, the method comprising:
 receiving an indication that data may be scheduled for the communication terminal on a data channel in the second cell;   attempting to detect presence of the data channel intended for the communication terminal; and   in case the communication terminal does not detect the presence of the data channel intended for the communication terminal, indicating a non-detection of the data channel to the radio access node.   
     
     
         2 . The method according to  claim 1 , wherein the receiving the indication that data may be scheduled for the communication terminal comprises receiving, on the first cell, control information for the second cell, which control information indicates where in a subframe the data channel is scheduled in the second cell for the communication terminal and wherein the communication terminal attempts to detect the data channel in the subframe. 
     
     
         3 . The method according to  claim 1 , wherein the receiving the indication that data may be scheduled for the communication terminal comprises receiving a reference signal on the second cell that indicates to the communication terminal that the carrier of the unlicensed frequency spectrum has been occupied by the second cell. 
     
     
         4 . The method according to  claim 1 , wherein the attempting to detect presence of the data channel comprises blindly detecting presence of the data channel. 
     
     
         5 . The method according to  claim 1 , wherein the indicating the non-detection comprises indicating a Non-Acknowledgement, NACK, or Discontinuous Transmission, DTX, state on the first cell. 
     
     
         6 . The method according to  claim 1 , wherein the data on the data channel is scheduled with a Demodulation Reference Signal, DMRS, based transmission scheme and wherein the attempting to detect the data channel comprises searching for a DMRS on scheduled Physical Resource Blocks, PRBs; and based on an outcome of the searching judging whether or not the data channel intended for the communication terminal is scheduled in the PRBs. 
     
     
         7 . The method according to  claim 1 , wherein the data on the data channel is scheduled with a Cell Specific Reference Signal based transmission scheme; wherein the attempting to detect the data channel comprises validating allocated Physical Resource Blocks, PRBs, and if the allocated PRBs are consistent with information given in a scheduling Downlink Control Information, DCI, message, to determine the data channel to be detected, and if the allocated PRBs are not consistent with the information given in the scheduling DCI message, the data channel is determined not to be present. 
     
     
         8 . A method performed by a radio access node for handling communication with a communication terminal in a second cell on a carrier of an unlicensed frequency spectrum, wherein resources for communication with the communication terminal in the second cell are cross-carrier scheduled from a first cell on a carrier of a licensed frequency spectrum; the method comprising
 transmitting an indication that data may be scheduled for the communication terminal on a data channel in the second cell.   
     
     
         9 . The method according to  claim 8 , wherein the radio access node is configured to serve the communication terminal in the second cell on the carrier of the unlicensed frequency spectrum, wherein the transmitting the indication that data may be scheduled for the communication terminal comprises transmitting a reference signal on the second cell that indicates to the communication terminal that the carrier of the unlicensed frequency spectrum has been occupied by the second cell. 
     
     
         10 . The method according to  claim 9 , wherein the reference signal further indicates to the communication terminal whether the data channel is present in a subframe transmitted on the second cell or not. 
     
     
         11 . The method according to  claim 8 , wherein the data on the data channel is scheduled with a Demodulation Reference Signal, DMRS, based transmission scheme and the transmitting the indication that data may be scheduled for the communication terminal comprises transmitting, on scheduled Physical Resource Blocks, PRBs, a DMRS with a modified pattern that indicates presence of the data channel to the communication terminal. 
     
     
         12 . The method according to  claim 8 , wherein the transmitting the indication that data may be scheduled for the communication terminal comprises transmitting an extra detection Reference Signal, RS, on the second cell when the carrier of the unlicensed frequency spectrum is occupied by the second cell, and wherein the extra detection RS changes form or state to indicate to the communication terminal that the data channel is present. 
     
     
         13 . The method according to  claim 8 , wherein the transmitting the indication that data may be scheduled for the communication terminal comprises performing a Listen Before Talk, LBT, process on the carrier of the unlicensed spectrum and transmitting the indication only when the outcome of the LBT process is that the carrier of the unlicensed frequency spectrum is free. 
     
     
         14 . The method according to  claim 8 , wherein the radio access node is configured to serve the communication terminal in the first cell and to cross-carrier schedule resources for the communication terminal in the second cell via the first cell, wherein the transmitting the indication that data may be scheduled for the communication terminal comprises transmitting, on the first cell, control information for the second cell to the communication terminal, which control information indicates where in a subframe the data channel is scheduled in the second cell for the communication terminal; and wherein the method further comprises
 receiving an indication that the communication terminal has not received the data on the data channel scheduled in the second cell; and   rescheduling the data on the data channel based on the received indication.   
     
     
         15 . A communication terminal for handling communication, which communication terminal is configured to communicate with a radio access node in a first cell on a carrier of a licensed frequency spectrum and to be cross-carrier scheduled in a second cell on a carrier of an unlicensed frequency spectrum by the radio access node via the first cell, the communication terminal being configured to:
 receive an indication that data may be scheduled for the communication terminal on a data channel in the second cell;   attempt to detect presence of the data channel intended for the communication terminal; and   in case the communication terminal does not detect the presence of the data channel intended for the communication terminal, to indicate a non-detection of the data channel to the radio access node.   
     
     
         16 . The communication terminal according to  claim 15 , wherein the communication terminal being configured to receive the indication that data may be scheduled for the communication terminal comprises the communication terminal being configured to receive, on the first cell, control information for the second cell, which control information indicates where in a subframe the data channel is scheduled in the second cell for the communication terminal and where in the communication terminal is further configured to attempt to detect the data channel in the subframe. 
     
     
         17 . The communication terminal according to  claim 15 , wherein the communication terminal being configured to receive the indication that data may be scheduled for the communication terminal comprises the communication terminal being configured to receive a reference signal on the second cell that indicates to the communication terminal that the carrier of the unlicensed frequency spectrum has been occupied by the second cell. 
     
     
         18 . A radio access node for handling communication with a communication terminal, the radio access node being configured to communicate with the communication terminal in a second cell on a carrier of an unlicensed frequency spectrum, wherein resources for communication with the communication terminal in the second cell are cross-carrier scheduled from a first cell on a carrier of a licensed frequency spectrum; the radio access node being configured to
 transmit an indication that data may be scheduled for the communication terminal on a data channel in the second cell.   
     
     
         19 . The radio access node according to  claim 18 , wherein the radio access node is configured to serve the communication terminal in the second cell and wherein the radio access node being configured to transmit the indication that data may be scheduled for the communication terminal comprises the radio access node being configured to transmit a reference signal on the second cell that indicates to the communication terminal that the carrier of the unlicensed frequency spectrum has been occupied by the second cell. 
     
     
         20 . The radio access node according to  claim 18 , wherein the radio access node is configured to serve the communication terminal in the first and second cells and wherein the radio access node being configured to transmit the indication that data may be scheduled for the communication terminal comprises the radio access node being configured to transmit, on the first cell, control information for the second cell, which control information indicates where in a subframe the data channel is scheduled in the second cell for the communication terminal.