Research On Wireless Resource Management Strategy In Heterogeneous Networks (HetNet)

With the popularity of smart phones, tablet PCs and other intelligent terminals and the rapid development of mobile Internet technology, the explosive growth of wireless data services facilitates the upgrade and replacement of wireless communication system. Traditional cellular structure of wireless networks is facing the change from voice services to data services, from circuit switching to packet switching, from homogeneous to a high-density and various forms network, HetNet (Heterogeneous Network) technology is becoming a hot topic in both academia and industry. Apparently, by a significant increase in low-power base stations to obtain a large cell division gain, HetNet has been greatly enhancing the throughput of wireless networks. However, the difference between base station transmitting power levels leads to large differences in the service user number of various types of cells, causing serious inter-cell load imbalance problem. How to balance the load between different types of cells and to improve resource utilization of the wireless network is a major problem faced by HetNet on the way of practical process. In the background of HetNet research topics of3GPP (3rd Generation Partnership Project) standardization meetings, closely focusing on Multi-flow&Multi-carrier HetNet technology, this thesis conducted research on radio resource management strategies in HetNet, in order to carry out load control of different types of cells.On the one hand, a user association strategy in Multi-flow&Multi-carrier HetNet is studied to achieve inter-cell load control. Firstly, a joint optimization model of multi-carriers’ joint user association is established, which could be solved to guide the selection of serving cells. Since the original optimization problem is non-convex and difficult to solve, this thesis skillfully transformed it to a series of interrelated sub-optimization problem. The original problem is solved by solving each cell’s sub-problem iteratively, through which a Multi-flow&Multi-carrier HetNet user association (MHUA) algorithm is proposed finally.On the other hand, a cooperative resource allocation strategy in Multi-flow&Multi-carrier HetNet is studied to achieve further inter-cell load control. A weighted proportional fairness (WPF) algorithm is introduced for scheduling in each cell and a multi-cell scheduling weight joint optimization model is set up for multi-cell cooperative scheduling. Through a series of decomposition and conversion of the complex multi-variable original optimization problem, this thesis theoretically proved the optimal scheduling weight could be obtained by an iterative water-filling strategy, on the basis of which a Multi-flow&Multi-carrier HetNet cooperative scheduling (MHCS) algorithm is proposed at last.In the end, using a simulation model from3GPP (3rd Generation Partnership Project) standardization proposal, the MHUA and the MHCS algorithm are simulated comprehensively. Simulation results indicate that these two algorithms both have high performance gain, with a difference that the former raises cell edge users’ throughput more obviously and the latter enhances cell average throughput more clearly. Since these two algorithms conduct cell load control through serving cell selecting and cooperative scheduling respectively, having different time scale and wireless resource allocation granularity, the combination of these two algorithms all together could constitute a multi-dimensional integrated radio resource management strategy, which not only boosts the cell average throughput, but also significantly improves the cell edge users’throughput and user rate fairness.