Section: 6.7 Carrier Aggregation
Content: In case of CA, the multi-carrier nature of the physical layer is only exposed to the MAC layer for which one HARQ entity is required per serving cell as depicted on Figures 6.7-1 and 6.7-2 below: - In both uplink and downlink, there is one independent hybrid-ARQ entity per serving cell and one transport block is generated per assignment/grant per serving cell in the absence of spatial multiplexing. Each transport block and its potential HARQ retransmissions are mapped to a single serving cell. Figure 6.7-1: Layer 2 Structure for DL with CA configured Figure 6.7-2: Layer 2 Structure for UL with CA configured