Research On Energy-efficient Downlink And Uplink Decoupling Strategy In Heterogeneous Network

Heterogeneous network (HetNet) consisting of macro base station(MBS) and other small base station (SBS) is regarded as one of the core technologies of the fifth generation mobile communication system (5G).The related works have proved that the HetNet can fill the holes of coverage, and improve the coverage probability, system throughput, and other key indicators. However, according to the traditional access strategy,which is based on the downlink received signal power (DRP), users are associated with the same BSs both in downlink (DL) and uplink (UL), so system resources cannot be fully utilized. Therefore, DL and UL decoupling (DUDe) is proposed in 5G system.In DUDe, users are connected with proper BSs in DL and UL respectively, which can make full use of resources and improve system throughput, traffic speed, and spectral efficiency. However, there still some problems. For example, some idle BSs in the network generate inefficient energy consumption, and individual demands of different users are not taken into account. In view of these problems, two kinds of energy-efficient DUDe schemes are proposed in this thesis.Firstly, an energy-efficient downlink and uplink decoupling with base station sleep control (DUDS) strategy is proposed. In DL, users are assoicated to the serving BSs according to DL maximum received power,and in UL, users are associated with the nearest BSs. Then the idle SBSs with no user are put into low-power sleep mode. The DUDS strategy can improve the throughput, save energy and enhance system energy efficient(EE).Secondly, a traffic-aware downlink and uplink decoupling (TDUDe)strategy is proposed. Users are divided into high-demand users and low-demand users according to various traffic demands. In DL, different users are connected to the serving BSs with different association biases.In UL, the transmit power of different users is adjusted by the power adaptive method. The proposed method can satisfy the requirements of different users, improve throughput, reduce system energy consumption,and enhance EE.The theoretical expressions of SBS sleeping probability, rate coverage, SINR (signal-to-interference-plus-noise ratio) coverage, and system EE are obtained using the tool of stochastic geometry, and the accuracy of the theory is verified by simulation. The simulation results show that: in the scenario of dense BSs deployment,EE performance with DUDS strategy is improved by 58.0% and 10.3% respectively compared to traditional DRP and DUDe methods, moreover, in the scenario of various user demands, the proposed TDUDe scheme can improve the DL throughput, reduce the energy consumption of the user equipment, and improve the system EE by 7.7% compared to DUDe strategy.