early T310 termination, by introducing a new timer called T312. In short, T312 is started upon TTT expiry if T310 is already running and T312 is not running. RLF is declared when T312 expires, and T312 can be configured for any measurement event. Results from extensive system-level simulations show that by using the new T312, the average interruption time can be decreased by approximately 30% for high-speed users in co-channel HetNet scenarios. Furthermore, the use of eNodeB context fetch can additionally improve the re-establishment success rate by 20-40% depending on the considered scenario. Inter-site Carrier Aggregation with Dual Connectivity 8.3.1 User Data Rates with Inter-site Carrier Aggregation Macro cells with wide coverage area are a great solution for wide coverage and reliable mobility while small cells can boost the data rates and capacity. The target of inter-site carrier aggregation is to combine these two benefits in HetNet deployments. Mobility management is maintained in macro layer while the small cell capacity is aggregated to the user plane for higher throughput. The solution uses dual connectivity (DC) between macro cells and small cells. The concept is illustrated in Figure 8.4 and described in more detail in Chapter 4. This chapter focuses on the performance and usage of inter-site carrier aggregation. The user throughput performance of inter-site carrier aggregation is first studied assuming that the small cells are realized as remote radio heads (RRHs) with centralized baseband processing at the macro, and virtually zero latency fibre-based fronthaul connections between macro and RRHs. This architecture option is already feasible with Release 10 carrier aggre- gation. The best HetNet performance can be obtained by using direct fibre to the small cells but in practice many small cells use non-ideal backhaul, which add the requirement of inde- pendent radio functionalities in the macro and small cell layers. Release 12 inter-site carrier aggregation is designed to work with non-ideal back