As understood from the process configuration described above, when the serving eNB and the coordinated eNB each having a transmission device of a downlink system illustrated in FIG. 2 operate according to the scenario 2, the first packet transmission unit 501 performs an operation of transmitting a retransmission data packet 507 in the transmission device on the serving eNB side. On the other hand, in the transmission device on the coordinated eNB side, the second packet transfer unit 503 performs the operation of transmitting a new data packet 508 corresponding to the information transferred from the serving eNB by the packet transfer unit 502.
FIG. 6 is an explanatory view of the coordinated downlink HARQ transmission system for the scenario 3.
First, in FIG. 6 (b), when the new data packet (for example, a new data packet #0) received by the UE enters an erroneous state, the data is transferred through the X2 interface along a corresponding control channel to the coordinated eNB. Then, it is retransmitted from the coordinated eNB simultaneously with a new packet (for example, a new data packet #4) delivered from the serving eNB to the synchronous transmission timing determined by the serving eNB. A similar process is generated with a retransmission packet #5 (or #14) transmitted with a new data packet #9 (or #7).
