Research On Radio Resource Management And System Evaluation In Heterogeneous Network

With the rapid growth of the number of mobile users, and the continuous development of the wireless communication technologies in network bandwidth, hardware configurations and software applications, the need for massive multi-media data services is facing an explosion. The future demands from mobile users for ubiquitous communication and higher quality of service can not be satisfied by current system performance. In the beginning of2012, the number of global mobile user has exceeded six billion. Meanwhile, the International Telecommunication Union has formally adopted the LTE-Advanced and802.16m technical specifications as the international standards of IMT-Advanced. Commercial road in the cellular mobile communication system has come to the beyond-3rd Generation era, and gradually move towards the4th Generation era.In the context of4G, the development and evolution of traditional cellular network architecture is facing great challenges. Data services are showing exponential growth and clustered distribution; high frequency band communication shortens the transmission distance; compared to the backbone fiber network, the capacity of radio access network is limited; the energy consumption of the information industry continues to grow, calling for high-density and low-power nodes; physical layer and many other new technologies require the network architecture to be changed. In this context, heterogeneous network is playing a more and more important role in the4G network. By adding new nodes to traditional cellular network, it can improve the system coverage and performance.This thesis focuses on the requirements of development and evolution of cellular network architectures and selects two representative heterogeneous deployments as the main study items, which are Distributed Antenna and Picocell Systems. They are similar but also with key different characteristics. Based on the investigation of the domestic and international research, and considering the main features of the two systems, a series of radio resource management strategies for Distributed Antenna and Picocell Systems are proposed and related system evaluations are made.In Distributed Antenna Systems, precoding based joint transmission can be used by distributed antenna ports. For this topic, firstly the feasibility and performance of a number of linear precoding strategies are evaluated. Since the block diagonalization algorithm shows the good performance, the semi-joint block diagonalization method is proposed for backhaul constraints. We also propose its enhanced algorithm when there is asynchronous interference to interfere with non-ideal factors, to achieve better system performance.When combining the Distributed Antenna Systems with Orthogonal Frequency Division Multiple Acces, the joint resource allocation becomes an important issue. For this part, firstly the problem is formulated to maximize the system spectral efficienc and solved by the Lagrange dual decomposition. In the dual domain, the problem is solved by analytical geometry. Then, the power efficiency is modeled and analyzed. A Proportional Power Allocation method is proposed. When applying this method to the joint problem, it is shown that a considerable part of power can be saved, only with a small loss in spectral efficiency.For a better understanding of Picocell Systems, performance evaluation is studied, including different frequency division, cell range expansion, network topologies, and antenna patterns. From the evaluation, the rules can be obtained for system optimization.A Pico eNB deployment algorithm for the coverage of outdoor hotzone users was presented, to improve the cell edge spectrum efficiency in Picocell Systems. The proposed algorithm joint considers the Pico eNB transmit power, interference, user densities and users’ quality of services. Results show that applying the rules can efficiently balance the load between the hotzone and macro region, and improve the cell edge performance.As for the cell selection in Picocell Systems, traditional cell range expansion only set a fixed offset for each Pico eNB, which is irrational. This thesis designs a specific offset value for each Pico eNB. Its calculation takes the environment into consideration and includes two parts:the interference condition and user densities.The proposed offset can achieve better load balancing with only small loss in average spectral efficiency. The feasibility of its practical deployment is also discussed.Finally, a comparative analysis of Distributed Antenna and Picocell Systems is made. Based on the existing evaluation methodology of heterogeneous networks, a set of assessment methods are proposed. Practical schemes are designed to approach the system capacity. The results show that in such an interference-limited model, the Distributed Antenna Systems has benefited from the cooperation of antenna ports within a region, thus its performance is superior to Picocell Systems.The Distributed Antenna and Picocell Systems is the important part in heterogeneous networks, representing the trend of the development and evolution of existing cellular network infrastructure, which also target on the the next-generation cellular mobile communication systems. This thesis carried out research from both theoretical analysis and performance evaluation on the characteristics of both systems. The proposed joint precoding and joint resource allocation strategies for Distributed Antenna Systems, and deployment algorithm and cell selection strategies for Picocell Systems will provide a reference for practical deployment, in order to make them more widely used in the next generation mobile communication system.