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(e.g., FDD band 29)Figure 21. Mobile Supplemental DL.6.5 HET NET SCENARIOS [9]LTE-A Release 11 introduced the support of multi-site CA by supporting multiple UL Timing Advanceenhanced UL power control for Heterogeneous Networks (HetNet) (Figure 22). In this case, the macrobase station with full coverage could serve as Primary Cell (PCell) providing system information, RRCcontrol signaling and bandwidth limited data transmission, while the small base station would serve localhigh data rate requirements. This CA technique will also be beneficial when macro and picocells areusing dedicated carriers. Fast selection of small cells would be beneficial even for moving users as longas the proximity of the user within the small cell coverage can be detected.Figure 22. LTE-A HetNet Multi-site CA.Nevertheless, there are drawbacks to this functionality. First, tight coordination is assumed betweenmacro/pico layers, requiring a centralized architecture. Furthermore, in the case of UL CA, CA-capableterminals supporting Multiple Timing Advance are required. This will basically require two transmitters inthe terminal, which is a big step in implementation complexity. At least initially, terminals having such4G Americas LTE Carrier Aggregation October 2014 34