 assigned a distinct physical carrier index, whereas in TDD mode each frequency channel with downlink and uplink partitions is designated as a component carrier and is 11.1 Principles of multi-carrier operation Network Layer Scheduling and Radio Resource Management MAC Control Signaling PHY 1 PHY 2 PHY N-1 PHY N (CC1) (CC2) (CCN-1) (CCN) Air-Interface PHY 1 PHY 1 PHY 2 PHY 1 PHY 2 (CC1) (CC1) (CC2) (CC2) (CCN) MAC Control MAC Control Signaling MAC Control Signaling Signaling Scheduling Scheduling Scheduling Network Network Layer Network Layer Layer FIGURE 11-1 The concept of multi-carrier operation assigned a distinct physical carrier index. The physical carrier index is an identifier for all available component carriers across the entire network. The mobile station is not required to support multi- carrier operation in certain device classes. However, if it does support multi-carrier operation, it may receive control and signaling, broadcast, and synchronization channels through a primary component carrier and traffic assignments (or services) may be made on the secondary component carriers. The generalization of the protocol structure to multi-carrier support using a single MAC instance is shown in Figure 11-1. The load balancing functions and component carrier mapping/ assignment are performed via radio resource control and management functional class. The component carriers utilized in a multi-carrier system, from the perspective of a mobile station, can be divided into two categories: Primary component carrier: a standalone carrier through which the MS conducts initial network entry or network re-entry. When supporting multi-carrier operations, an MS only has one primary component carrier. Secondary component carrier: additional carrier(s) which may be assigned to the MS by the BS. All the unicast MAC control messages corresponding to multi-carrier operation are sent to the MS through its primary component carrier. CHAPTER 11 Multi-Carrier Operation Depending on the use case, the component carriers may be co