Research On Uplink Power Control In LTE-A Relay Heterogeneous Networks

The relay heterogeneous network technology is regarded as one of the key technologies of the LTE-A system.It can increase the system capacity,expand the area coverage,provide better QoS for users,and prolong the battery life of the User Equipments(UEs).Due to the different size of the Inter-Site-Distance(ISD)of different scenarios in LTE-A relay heterogeneous networks,and the channel conditions of different links are distinct in the same scenario,the key factors affecting the system performance cannot be generalized.The traditional LTE-A uplink power control scheme just adopts the standardized Open Loop Power Control(OLPC)algorithm,but the key factors that affect the system performance are not considered in different scenarios.In order to fully exploit the advantages of LTE-A relay heterogeneous networks,we firstly analyze the key factors that affect the system performance under different scenarios,and then put forward the corresponding uplink power control strategies for different scenarios,which improve the performance of LTE-A relay heterogeneous networks.The main works are as follows:(1)For urban scenario,under the conditions of the relay links are ideal,with the aim of increasing the capacity of the urban scenario and decreasing the Inter-Cell Interference(ICI)and Cross-Tier Interference(CTI)of the receiving nodes,a Closed Loop Power Control(CLPC)strategy which is based on the interference coordination is introduced.For the Macro-cell UEs(MUEs),a CLPC algorithm which is based on the ICI and path loss is proposed.Similarly,for the Relay-cell UEs(RUEs),a CLPC algorithm which is based on the CTI and path loss is presented.Simulation results show that the proposed strategies can not only keep the receiver dynamic range on a certain level,but also increase the system capacity and improve the utilization of the UEs' battery.(2)For suburban scenario,under the conditions of the relay links are ideal,in order to enlarge the coverage of the suburban scene and improve the fairness of the user services over the cell area,a combined power control strategy is put forward.Firstly,according to the path loss threshold,the suburban cell area is divided into different regions.Then,for the area of good channel conditions,a CLPC algorithm based on path loss is introduced.For the region with poor channel conditions,an OLPC scheme which is based on the Fractional Power Control(FPC)and the Adaptive Transmission Bandwidth(ATB)technology is proposed.It is demonstrated by simulations that the proposed power control strategies can significantly increase the data rates of the cell edge users,improve the fairness of the user services,and prolong the life of the UE's battery.(3)For both urban scenario and suburban scenario,under the conditions of the relay links are not ideal,with the aim of reducing the complexity of the computation and improving the adaptability of the Power Control(PC)to the network and environment,an automatic power optimization strategy based on Chaotic-Simulated Annealing is proposed.Firstly,the PC parameters of all the links which affect the system performance are analyzed under different scenarios.Then,with the performance steered concept,the corresponding performance criterias for different scenarios are proposed.Finally,with the aim of maximizing the performance criterion,the power control parameters are optimized by using Chaotic-Simulated Annealing algorithm for all links.Simulation results show that compared with the manual optimization and the Taguchi's algorithm the proposed automatic power optimization strategy can not only provide similar performance,but also reduce the computational complexity dramatically and enhance the abilities of adapting to the network and environment obviously.