Research On Small Cell Key Technology In Lte-A System

3GPP Long Term Evolution, the forth generation wireless access technology, is being rolled out by many operators worldwide. In order to meet the demond of fast burst of service data, Small Cell has become an important evolution direction in3GPP, since LTE Release10. However, there are also some disadvantages in small cell such as heterogeneous network interference, multi-hop synchronization and inter-site offloading. In this thesis, the key technology of small cell is studied to promote the performance of network. We propose some enhancement techniques such as cross-layer resource allocation, small cell synchronization and dynamic On-Off.This thesis mainly contains three topics:Firstly, resource allocation in Small Cell scenario with mixed traffic is studied. The sub-carriers and power of a base station are allocated to users to maximize energy efficiency, which is measured by utility per Watt. We model the allocation of sub-carriers and power as a mixed integer nonlinear programming (MINLP) problem, which is computationally forbidden. To simplify the solution of the problem, a two-step resource allocation (TSRA) algorithm is proposed. In the first step, the integer variables are transformed into continuous ones and uniform power allocation is assumed. On this basis, sub-carrier allocation is obtained using KKT condition. Then the optimal power allocation is solved by an iterative sub-gradient method in the second step. Simulation results show that our algorithm can provide25%energy efficiency improvement compared to conventional algorithms.Secondly, Small cell dynamic on/off is studied. In order to deal with the problem of overload and interference in the dense deployment of small cell, the classified dormancy scheme is proposed based on user equipment assistant. The inter-cell interference coordination is achieved without the increase of backhaul load. Simulation results show that the algorithm can provide6.75%aggregated throughput improvement and14.87%throughput of cell edge UEs compared to ICIC algorithms in the dense scenario.Thirdly, small cell synchronization enhancement is studied. For the small cells that work in unlicensed-band TDD mode, out of sync with different clusters cause the main interference. We propose the inter-cluster synchronization algorithm based on network listening. High synchronization precision between Small Cell clusters is achieved with few expenditure of control channel.The last part of the thesis summarizes the research of the full text, and discusses futher research directions.