Harq operation when tdd cell and fdd cell are included in carrier aggregation

Abstract

One disclosure of the present specification provides a method for operating a HARQ from user equipment (UE). The method comprises the steps of: the UE receiving downlink data from each cell, when at least one TDD-based cell and at least one FDD based cell are established according to carrier aggregation (CA), a specific TDD-based cell is established as a primary cell of the carrier aggregation (CA), and the at least one FDD-based cell is established as a secondary cell of the carrier aggregation (CA); the UE confirming a PUCCH format to be used for transmitting a HARQ ACK/NACK for the downlink data; and the UE determining the number of bits for transmitting the HARQ ACK/NACK when use of the specific PUCCH format for transmitting the HARQ ACK/NACK is confirmed.

What is claimed is: 
     
         1 . A method for performing a hybrid automatic retransmit request (HARQ) operation, the method performed by a user equipment (UE) and comprising:
 transmitting a physical uplink control channel (PUCCH) signal including plural HARQ ACK/NACK bits based on a first PUCCH format;   wherein the UE is configured with at least one time division duplex (TDD)-based cell and at least one frequency division duplex (FDD)-based cell,   wherein the at least one TDD-based cell is configured as a primary cell,   wherein the at least one FDD-based cell is configured as a secondary cell;   wherein a maximum number of cells configured for the UE is limited such that a number of the plural HARQ ACK/NACK bits does not exceed a maximum number of bits allowed in the first PUCCH format based on that an uplink-downlink (UL-DL) configuration of the at least one TDD-based cell configured as the primary cell is one of UL-DL configurations 2, 3 and 4.   
     
     
         2 . The method of  claim 1 , wherein
 if the first PUCCH format includes a PUCCH format 3 so that the allowed maximum number of bits is 20, the maximum number cells is limited.   
     
     
         3 . The method of  claim 1 , wherein the maximum number of the cells is limited based on the UL-DL configuration of at least one TDD-based cell configured as the primary cell is an UL-DL configuration 5. 
     
     
         4 . The method of  claim 1 , further comprising:
 receiving a radio resource control (RRC) signal including a configuration for the first PUCCH format.   
     
     
         5 . A user equipment (UE) for performing a hybrid automatic retransmit request (HARQ) operation, the UE comprising:
 a transceiver configured with at least one time division duplex (TDD)-based cell and at least one frequency division duplex (FDD)-based cell,   wherein the at least one TDD-based cell is configured as a primary cell, and   wherein the at least one FDD-based cell is configured as a secondary cell; and   a processor configured to control the transceiver and transmit a physical uplink control channel (PUCCH) signal including plural HARQ ACK/NACK bits based on a first PUCCH format,   wherein a maximum number of cells configured for the UE is limited such that the number of the plural HARQ ACK/NACK bits does not exceed a maximum number of bits allowed in the first PUCCH format based on that an uplink-downlink (UL-DL) configuration of the at least one TDD-based cell configured as the primary cell is one of UL-DL configurations 2, 3 and 4.   
     
     
         6 . The UE of  claim 5 , wherein
 if the first PUCCH format includes a PUCCH format 3 so that the allowed maximum number of bits is 20, the maximum number cells is limited.   
     
     
         7 . The UE of  claim 5 , wherein the maximum number of the cells is limited based on the UL-DL configuration of at least one TDD-based cell configured as the primary cell is an UL-DL configuration 5. 
     
     
         8 . The UE of  claim 5 , wherein the transceiver is further configured to:
 receive a radio resource control (RRC) signal including a configuration for the PUCCH format.