As different terminals transmit preamble messages (Msg.1) using different RA preamble resources, each terminal will monitor resources with a RAR window. The RAR window covers the duration of the multiple RAR resources corresponding to the used RA preamble resources. For example, based on FIG. 11, the terminal UE1 monitors the RAR window covering the RAR resources (i?2, i?1, i), the terminal UE2 monitors the RAR window covering the RAR resources (i?1, i, i+1), and the terminal UE3 monitors the RAR window covering the RAR resources (i, i+1, i+2). The terminal UE1 receives the RAR on the (i?1)th RAR resource and receives the combined RAR on the i-th RAR resource. The terminals UE1 and the UE2 receive the RAR on the (i?1)th RAR resource and the combined RAR on the i-th RAR resource, and the terminal UE3 receives the combined RAR on the i-th RAR resource.

If all three terminals transmit a preamble message (Msg.1) using a different preamble sequence, the terminals receive multiple RARs. In the embodiment of the present invention, even if the terminal receives a plurality of RARs, the terminal may select a correct RAR for the preamble message transmitted by the terminal based on its own preamble sequence through the second RAR selection procedure in the terminal.

Based on the preamble sequence used by the terminal UE1, the terminal UE1 may immediately recognize that the RAR on the i-th RAR resource is a correct RAR. Similarly, when the terminal UE2 receives the RAR on the (i?1)th RAR resource and receives the combined RAR on the i-th RAR resource, the terminal UE2 may immediately recognize that the combined RAR of the i-th RAR resource is a correct RAR. The terminal UE 3 may also recognize that the combined RAR on the i-th RAR resource is a correct RAR.