nor provide the carrier aggregation benefits from dynamic scheduling and load sharing between two carriers. The overall security is managed by MeNodeB, but each eNodeB manages its own ciphering, SO two different security keys are needed at the UE. In Architecture 3C, all the user plane data (i.e. S1-U) are routed via the master eNodeB. The PDCP protocol is only located in the MeNodeB, and only the lower layer protocols (i.e. RLC, MAC) are identical in both eNodeBs. The Architecture 3C provides all the carrier aggregation benefits for throughput increase and can be used when the backhaul between the eNodeBs is good. The security solution is unchanged since the PDCP is only located at MeNodeB and this architecture can be rolled out without any changes in the core network side. Since the user plane data for all bearers arrives first for the macro eNodeB which can then dynamically select between the small cell and macro cell. With this approach also the service interruptions are smaller compared when losing the connection with small cell in Architecture 1A. The UE also gets the increased peak rate even if only a single service is active. The gains as reported in [1] reach up to 90% increased user throughput at lower load levels. The 3GPP Release 12 allows the bearer split on the downlink direction only while the uplink user plane data for each bearer is provided via one cell only, and then forwarded to macro cell. This is foreseen to be extended after Release 12 to enable aggregation benefits in the uplink direction as well as discussed in later section. 4.4 Dual Connectivity Protocol Impacts For the control plane side, the fundamental difference is that the cell serving as the master eNodeB (typically the macro cell) remains as the master of the correction and will send RRC signalling to the UE as well as be the receiving entity for the RRC signalling from the UE. The macro and small cell eNodeBs will enhance control information over the X2 interface. All the RRC measurement reports are provided for the macro eNodeB