| 摘要 |
PROBLEM TO BE SOLVED: To avoid the situation in which a user device cannot determine whether an RA response signal received by the user device via a second cell corresponds to an RA preamble signal of the UE where an RA response signal to an RA preamble signal transmitted via a first cell is received via the second cell.SOLUTION: A base station in a communication system in which a random access (RA) response signal to an RA preamble signal transmitted via a first cell is transmitted via a second cell: identifies preamble indexes (PIs) that are unused in the second cell; selects a PI that is different from a PI for use in a first cell as an S cell when the PI for use in the S cell is communicated to a UE for which a second cell is specified as a P cell; communicates the selected PI to the user device located in the second cell; receives an RA preamble signal; and transmits an RA response signal. |
