to 11.4 MAC aspects of multi-carrier operation Serving Target Serving Target Carrier Carrier Carrier Carrier Control Signaling +AAI_CM-CMD Acknowledgement Control Signaling Primary Carrier Primary Carrier Change Change Active Active Carrier Carrier Active Serving Target Carrier Carrier Carrier Control Signaling AAI_CM-CMD Acknowledgement Primary Carrier Synchronization and Initial Ranging with the Change Target Carrier AAI_CM-IND (Primary Carrier Change) Control Signaling FIGURE 11-10 Primary carrier change scenarios [2] CHAPTER 11 Multi-Carrier Operation determine the target carrier for the MS. If the target carrier is not currently used by the MS, synchronization with the target carrier may be necessary. The AAI_CM-CMD MAC control message for primary carrier change is transmitted on the primary carrier and includes the target primary carrier index, action time, and ranging indicator. The primary-to-secondary carrier switching in multi-carrier mode is only supported for multicast and broadcast services. 11.4.2 Multi-Carrier Handover Multi-carrier handover is defined as the handover procedure between component carriers. A multi- carrier-enabled MS may use the single-carrier handover procedures alternatively perform the multi- carrier handover procedures. If an MS supports multi-carrier aggregation, it is required to use its primary carrier as the reference for serving BS scanning, and to follow the information broadcast in the AAI_SCD message for handover or scanning related operations. The AAI_NBR-ADV message contains neighbor base stations' multi-carrier configuration information to facilitate the mobile station's scanning of neighbor base stations' fully-configured carriers. A multi-carrier capable MS may perform the multi-carrier scanning procedure, which is a scanning procedure extended to multiple RF carriers. In this case, the MS scans the component carriers of neighboring base stations whose information is included in an AAI_NBR-ADV message. The MS may further scan other fully-configured carriers of the s