Resource Allocation In Backhaul-Aware Heterogeneous Cellular Networks

In the fifth generation mobile communication(5G)network,heterogeneous cellular network(HCN),in which the macrocells are overlaid with a large number of small cells,is a promising solution to meet the growing demand for the data traffic.In HCNs,the network throughput and users' transmission rates can be significantly improved.However,there are still challenges to tackle,such as inter-cell interference suppression and user's quality of service(QoS)guarantee.In addition,the large number of small cells deployed in macrocells also puts great pressure on the wireless backhaul link.Specifically,the impact of backhauling on network performance is mainly reflected in the backhaul bandwidth allocation and backhaul capacity constraints.In fact,network performance of HCNs is seriously restricted by these two issues.To this end,in this thesis,we focus on resource allocation in backhaul-aware HCN,and optimize the network performance through the spectrum and power allocation.The main contributions are summarized as follows:1.Resource allocation with backhaul capacity constraints in HCNS.In the first part of this thesis,we investigate the joint resource block(RB)and power allocation problem under two different backhaul capacity limitations(small cell backhaul limitation and macrocell base station backhaul limitation).The QoS requirements of users and the cross-tier interference mitigation are also considered.Based on variable substitution and constraint relaxation,this non-convex mixed-integer nonlinear programming(MINLP)problem is converted into a convex optimization one,and the optimal solution is obtained.Based on the optimal solutions,a joint RB and power allocation algorithms are proposed.Numerical results verify the effectiveness of the proposed algorithms and evaluate the impact of different types of backhaul capacity limitations on system performance.2.Joint downlink wireless backhaul bandwidth(WBB)and power allocation.Secondly,considering the backhaul capacity limitation on each small cell,we investigate the problem of joint downlink wireless backhaul bandwidth(WBB)and power allocation in HCNs.We propose a hierarchical two-level approach and decompose the original problem into two independent subproblems: the WBB allocation at the macrocell base station(MBS)and the power allocation at base stations(BSs),so as to obtain the optimal solutions.Furthermore,we develop a distributed algorithm to implement the joint WBB and power allocation,which is aimed to maximize the weighted sum logarithmic utility function.Numerical results verify that the effectiveness of the proposed approach which can achieve maximum the network performance under the weighted coefficient and backhaul capacity limitation.3.Energy efficient resource allocation with different backhaul capacity limitations.In the third part of this thesis,we investigate the optimization problem which jointly allocate resource block and power among users in order to maximize the energy efficiency(EE)of HCN,which takes different types of backhaul capacity constraints and users' QoS requirements into account.By using the Dinkelbach algorithm,variable substitution and constraints relaxation,we convert this fractional programming problem into a convex one and obtain the optimal solutions.Furthermore,we propose a joint resource block and power allocation algorithm.Finally,the numerical results show the effectiveness of the proposed algorithms and evaluate the impact of different types of backhaul capacity limitations on network energy efficiency.