| With the ever-increasing number of smart terminals and the development of mobile Internet, mobile data traffic has been increasing explosively. This trend has resulted in tremendous pressure on mobile network, which not only forces the evolution of air interface technologies but also pushes the transition of network deployment from traditional homogeneous networks consisting of macro eNBs to heterogeneous network consisting of eNBs with various transimitting power. The3GPP LTE/LTE-Advanced radio access technology has been identified as a candidate for the Fourth Generation Mobile Communication. So far, the standardization of LTE-Advanced has entered the stage of Rel-12, when researchers focus more on the optimization of heterogeneous network containing low power eNBs.Backhaul plays a crucial role in Mobile Communication Systems, especially in heterogeneous networks containing vast number of low power eNBs. Both of Carrier Aggregation and Coordinated Multiple Point Transmission and Reception proposed during3GPP Rel-10/11phase which need tight cooperation between nodes only adapt to ideal backhaul deployment scenarios. As to non-ideal backhaul deployment scenarios proposed during the latest3GPP Rel-12phase, data split and aggregation must be implemented at the higher layer. Dual Connectivity which achieves data split and aggregation at PDCP layer has been identified as an alternative technique to cope with non-ideal backhaul deployment scenarios.Deployment scenarios of Dual Connectivity were analyzed and Dual Connectivity was analyzed from the view of its architecture design which achieves the separation of U-Plane and C-Plane; Technology details of U-Plane/C-Plane were studied, solutions which could be applied to Dual Connectivity were proposed including activation and de-activation, uplink timing advance and random access, etc, the procedures of secondary cell addition, modification and release were proposed, meanwhile, an enhanced handover procedure was proposed; Dual Connectivity simulation platform was built, the validity of Dual Connectivity was proved from the view of throughput; Cell association scheme in Dual Connectivity deployment scenarios was studied, a creative dynamic bias setting solution was proposed which could make the network change the bias value adaptively according to its load level, thus achieving the purpose of load balancing and improvement of network resource utilization ratio. |
