A system for transmission of feedback information, comprising: a base station; and a user equipment, UE, configured to receive data sent from the base station and transmit feedback information in response to reception of the data; characterized in that the base station is configured to: transmit data to the UE on three carriers; receive encoded feedback information of the three carriers from the UE on a single code channel; wherein the encoded feedback information of the three carriers is encoded Hybrid Automatic Repeat Request-Acknowledgement, HARQ-ACK, signals of the three carriers in response to reception of the data; wherein the encoded HARQ-ACK signals of the three carriers is a codeword into which HARQ-ACK signals of the three carriers mapped according to the following mapping relationship: ACK-DTX-DTX 1 1 1 1 1 1 1 1 1 1 NACK-DTX-DTX 0 0 0 0 0 0 0 0 0 0 DTX-ACK-DTX 1 1 1 1 1 0 0 0 0 0 DTX-NACK-DTX 0 0 0 0 0 1 1 1 1 1 DTX-DTX-ACK 1 1 0 0 0 1 1 0 0 0 DTX-DTX-NACK 0 0 1 1 1 0 0 1 1 1 ACK-ACK-DTX 1 0 1 0 1 0 1 0 1 0 ACK-NACK-DTX 1 1 0 0 1 1 0 0 1 1 NACK-ACK-DTX 0 0 1 1 0 0 1 1 0 0 NACK-NACK-DTX 0 1 0 1 0 1 0 1 0 1 ACK-DTX-ACK 1 0 1 1 0 1 1 0 0 1 ACK-DTX-NACK 0 1 0 1 1 0 1 0 0 1 NACK-DTX-ACK 0 0 0 1 1 1 1 0 1 0 NACK-DTX-NACK 1 0 0 1 1 1 0 1 0 0 DTX-ACK-ACK 0 1 1 1 0 1 0 0 1 0 DTX-ACK-NACK 1 0 1 0 0 1 0 1 1 0 DTX-NACK-ACK 0 1 1 0 0 0 1 0 1 1 DTX-NACK-NACK 0 0 0 0 1 0 1 0 1 1 ACK-ACK-ACK 1 1 0 1 0 0 1 1 1 0 ACK-ACK-NACK 0 1 1 0 1 1 1 1 0 0 ACK-NACK-ACK 1 0 0 1 0 0 0 0 1 1 ACK-NACK-NACK 0 0 1 0 1 1 0 0 0 1 NACK-ACK-ACK 1 1 1 0 0 0 0 1 0 1 NACK-ACK-NACK 0 1 0 0 1 0 0 1 1 0 NACK-NACK-ACK 1 0 0 0 1 0 1 1 0 1 NACK-NACK-NACK 1 1 1 1 0 1 0 1 0 0 wherein DTX represents discontinuous transmission, ACK represents acknowledgement, NACK represents negative acknowledgement. a base station; and a user equipment, UE, configured to receive data sent from the base station and transmit feedback information in response to reception of the data; characterized in that the base station is configured to: transmit data to the UE on three carriers; receive encoded feedback information of the three carriers from the UE on a single code channel; wherein the encoded feedback information of the three carriers is encoded Hybrid Automatic Repeat Request-Acknowledgement, HARQ-ACK, signals of the three carriers in response to reception of the data; wherein the encoded HARQ-ACK signals of the three carriers is a codeword into which HARQ-ACK signals of the three carriers mapped according to the following mapping relationship: ACK-DTX-DTX 1 1 1 1 1 1 1 1 1 1 NACK-DTX-DTX 0 0 0 0 0 0 0 0 0 0 DTX-ACK-DTX 1 1 1 1 1 0 0 0 0 0 DTX-NACK-DTX 0 0 0 0 0 1 1 1 1 1 DTX-DTX-ACK 1 1 0 0 0 1 1 0 0 0 DTX-DTX-NACK 0 0 1 1 1 0 0 1 1 1 ACK-ACK-DTX 1 0 1 0 1 0 1 0 1 0 ACK-NACK-DTX 1 1 0 0 1 1 0 0 1 1 NACK-ACK-DTX 0 0 1 1 0 0 1 1 0 0 NACK-NACK-DTX 0 1 0 1 0 1 0 1 0 1 ACK-DTX-ACK 1 0 1 1 0 1 1 0 0 1 ACK-DTX-NACK 0 1 0 1 1 0 1 0 0 1 NACK-DTX-ACK 0 0 0 1 1 1 1 0 1 0 NACK-DTX-NACK 1 0 0 1 1 1 0 1 0 0 DTX-ACK-ACK 0 1 1 1 0 1 0 0 1 0 DTX-ACK-NACK 1 0 1 0 0 1 0 1 1 0 DTX-NACK-ACK 0 1 1 0 0 0 1 0 1 1 DTX-NACK-NACK 0 0 0 0 1 0 1 0 1 1 ACK-ACK-ACK 1 1 0 1 0 0 1 1 1 0 ACK-ACK-NACK 0 1 1 0 1 1 1 1 0 0 ACK-NACK-ACK 1 0 0 1 0 0 0 0 1 1 ACK-NACK-NACK 0 0 1 0 1 1 0 0 0 1 NACK-ACK-ACK 1 1 1 0 0 0 0 1 0 1 NACK-ACK-NACK 0 1 0 0 1 0 0 1 1 0 NACK-NACK-ACK 1 0 0 0 1 0 1 1 0 1 NACK-NACK-NACK 1 1 1 1 0 1 0 1 0 0 wherein DTX represents discontinuous transmission, ACK represents acknowledgement, NACK represents negative acknowledgement. transmit data to the UE on three carriers; receive encoded feedback information of the three carriers from the UE on a single code channel; wherein the encoded feedback information of the three carriers is encoded Hybrid Automatic Repeat Request-Acknowledgement, HARQ-ACK, signals of the three carriers in response to reception of the data; wherein the encoded HARQ-ACK signals of the three carriers is a codeword into which HARQ-ACK signals of the three carriers mapped according to the following mapping relationship: ACK-DTX-DTX 1 1 1 1 1 1 1 1 1 1 NACK-DTX-DTX 0 0 0 0 0 0 0 0 0 0 DTX-ACK-DTX 1 1 1 1 1 0 0 0 0 0 DTX-NACK-DTX 0 0 0 0 0 1 1 1 1 1 DTX-DTX-ACK 1 1 0 0 0 1 1 0 0 0 DTX-DTX-NACK 0 0 1 1 1 0 0 1 1 1 ACK-ACK-DTX 1 0 1 0 1 0 1 0 1 0 ACK-NACK-DTX 1 1 0 0 1 1 0 0 1 1 NACK-ACK-DTX 0 0 1 1 0 0 1 1 0 0 NACK-NACK-DTX 0 1 0 1 0 1 0 1 0 1 ACK-DTX-ACK 1 0 1 1 0 1 1 0 0 1 ACK-DTX-NACK 0 1 0 1 1 0 1 0 0 1 NACK-DTX-ACK 0 0 0 1 1 1 1 0 1 0 NACK-DTX-NACK 1 0 0 1 1 1 0 1 0 0 DTX-ACK-ACK 0 1 1 1 0 1 0 0 1 0 DTX-ACK-NACK 1 0 1 0 0 1 0 1 1 0 DTX-NACK-ACK 0 1 1 0 0 0 1 0 1 1 DTX-NACK-NACK 0 0 0 0 1 0 1 0 1 1 ACK-ACK-ACK 1 1 0 1 0 0 1 1 1 0 ACK-ACK-NACK 0 1 1 0 1 1 1 1 0 0 ACK-NACK-ACK 1 0 0 1 0 0 0 0 1 1 ACK-NACK-NACK 0 0 1 0 1 1 0 0 0 1 NACK-ACK-ACK 1 1 1 0 0 0 0 1 0 1 NACK-ACK-NACK 0 1 0 0 1 0 0 1 1 0 NACK-NACK-ACK 1 0 0 0 1 0 1 1 0 1 NACK-NACK-NACK 1 1 1 1 0 1 0 1 0 0 wherein DTX represents discontinuous transmission, ACK represents acknowledgement, NACK represents negative acknowledgement.