Research On Approaches Of Resource Allocation In Heterogeneous Networks

As an important product of the development of mobile communication systems,heterogeneous networks are considered to be one of the important technologies to meet the exponential growth of user data rate requirements,and also the main force to significantly improve network coverage and network capacity.Under the current situation of low frequency spectrum resources,spectrum sharing becomes the main resource reuse form of heterogeneous networks.However,with the spurt of the number of access nodes and the dense deployment of low power nodes,it could trigger the severe problem of interference including intra-tier interference among dense low power nodes and inter-tier interference between low power nodes and the macro base station,which influences the system performance strongly.Consequently,it seriously violates the heterogeneous networks as the original intention of supporting the increasing data rate demand.On the other hand,the energy consumption rate in heterogeneous networks is rising rapidly,which causes the power cost of heterogeneous networks becomes the main factor restricting the operator's profit margin.As an important research topic in the development of wireless mobile networks,resource management technology plays a decisive role in the efficient communication of heterogeneous networks.Therefore,it is expected to become an important technical means to solve the above-mentioned interference problems and energy consumption problems.This dissertation focuses on the interference problem and energy consumption problem of heterogeneous networks.For two heterogeneous networks scenario with Small cells and the relay nodes,this dissertation studies the one-dimensional or Multidimensional resource allocation scheme,which contains the frequency domain,the time domain,the airspace,and the power domain resource allocation.The specific research results are summarized as follows:(1)Spectrum sharing approaches in heterogeneous networks based on interference coordinationFor inter-tier interference problems and intra-tier interference problems in spectrum sharing heterogeneous networks with Small cells,this dissertation considers the contradiction between inter-tier interference mitigation and capacity enhancement of Small cells and the reduction of intra-tier interference and capacity enhancement of heterogeneous networks.To study the effective trade-off between inter-tier interference and Samll cells capacity,and balance the intra-tier interference and heterogeneous networks capacity,this dissertation proposes the spectrum sharing schemes based on inter-tier interference and the intra-tier interference.With considering the multi-objective optimization theory,two multi-objective optimization models are proposed to minimize the maximum inter-tier interference and maximize the Small cells capacity,and minimize the same layer interference and maximize the heterogeneous networks capacity.This dissertation use the heuristic algorithm to solve the corresponding compromise solutions.The simulation results show that the above schemes achieve a trade-off between spectrum multiplexing gain and interference coordination gain under the condition of ensuring the minimum transmission rate of Small cells users.(2)Resource allocation approaches in heterogeneous networks based on energy efficiency optimizationAiming at the interference problem and energy consumption problem in spectrum sharing heterogeneous networks with Small cells,two energy efficiency metrics based on penalty term polynomial and ratio-based energy consumption rate ratio are studied.An energy efficiency power allocation scheme based on interference price and a joint optimization scheme based on sleep strategy are proposed for energy efficiency improvment.Combining the conflict between the energy efficiency enhancement of the macrocell and the improvement of the energy efficiency of Small cells,and the conflict between the energy efficiency of the Small cells and the reduction of the inter-tier interference,two multi-objective optimization models of the above energy efficiency optimization schemes are established.The heuristic algorithm is used to obtain the compromise solutions of the above optimization models.The simulation results show that the dynamic interference price mechanism can effectively control inter-tier interference,improve the energy efficiency of the macrocell and reduce the total energy consumption of heterogeneous networks.In addition,the joint optimization of resources such as spectrum and power combined with the sleep strategy can effectively achieve the reduction of inter-tier interference and the increase of the capacity of Small cells.(3)Resource allocation approaches in heterogeneous networks based on user experience qualityAiming at the energy consumption and user experience problems in spectrum sharing heterogeneous networks with relay nodes,and the bottleneck problem of the performance of the access link and the backhaul link,users in relay cellular network are allowed to select the transmission mode in order to obtain the optimization of the number of relay nodes deployments.Furthermore,this dissertation combines the access link and backhaul link spectrum resources and power allocation to achieve joint optimization of multi-dimensional resources of the access link and the backhaul link.And then users in the relay-aided cooperative system are allowed to share different numbers of subcarriers in each coordinated transmission stage.A joint optimization of multi-dimensional resources is formed with relay selection,multi-carrier pairing and allocation,and power allocation.Considering the tight coupling for the joint optimization of multi-dimensional resources,the contradiction between energy consumption reduction of systems and user experience quality improvement,a multi-objective optimization model is established.And a heuristic algorithm is used to obtain a compromise solution to make a tarde-off between the performance of systems and users.The simulation results show that the proposed resource joint optimization allocation schemes based on user experience quality can achieve an effective compromise between the improvement of user experience quality and the reduction of energy consumption in spectrum sharing heterogeneous networks with relay nodes.(4)A resource allocation approach in heterogeneous networks with hybrid energy suppliesAiming at the energy consumption problem and the fairness of transmission rate in spectrum sharing heterogeneous networks with relay nodes powered by renewable energy,the joint optimization of the spectrum and power resources is studied.Moreover,considering the instability of renewable energy supply,the study of user transmission mode selection not only can ensure the reliability transmission of user services,but also increase the dimension and freedom of resources optimization.Considering the two goals of system fair performance improvement and renewable energy utilization improvement,this dissertation acombines with multi-objective optimization theory and heuristic algorithm for obtaining the target equilibrium solution.The simulation results show that the proposed resource allocation scheme can achieve the user fairness transmission rate and improve the renewable energy utilization rate,thus reducing the energy consumption of the grid.