The SCell identifier is allocated by ENB using an RRC control message.
[Method 2 of Mapping Ci and SCell]
When SCells configured with uplinks from among the SCells set in UE are arranged in order from the lower SCell identifier, the SCell with the lowest identifier can correspond to C1 (or C0); the SCell with the second lowest identifier can correspond to C2 (or C1); and the SCell with the nth low identifier corresponds to Cn (or Cn?1). For example, in a state where SCell 1?SCell 10 are set in UE, when SCell 1, SCell 3, and SCell 9 are configured with uplinks, C1 (or C0) corresponds to SCell 1; C2 (or C1) corresponds to SCell 3; and C3 (or C2) corresponds to SCell 9.
When UE selects one of the two mapping methods, it can use an explicit method or implicit method. The explicit method is described as follows. In a process for ENB to configure a PHR in UE, when the ENB signals to the UE along with control information indicating the UE to use method 2 of mapping between Ci and SCell, e.g., when ENB transmits an explicit indicator to the UE in operation 530 shown in