On Interference Management And Power Transfer In Cooperative Wireless Networks

Due to the rapid growth of the mobile web, the wireless communication technology has been challenged by both the demand of transferring massive amounts of information, and the energy consumption by the mobile terminals. The bandwidth of the mobile data access, and the active time of the terminals have already become two of the major concerns of the subscribers. The inferference management techniques are able to mitigate the interference in the cellular networks which are limited by the co-channel interference, therefore to enhance the data transfer rate of the mobile access. Meanwhile the wilreless power transfer techniques can provide energy to the mobile terminals which are limited by the source of energy, thus can improve the terminals' capability of staying online.Cooperative wireless communication technology initially emerges as an effective approach to uplift the transfer rate of subscribers who are located at the edge of the cells, and has drawn extensive attention. By sharing system information within itself, and coordinatively utilizing both the time/frequency/space domain and the power resource, the cooperative wireless network can effectively improve the data transfer rate and power transfer efficiency. In the cooperative wireless network, both the spectrum efficiency and system throughput capacity can be enhanced by deploying coordinated the inter cell scheduling and the interference management,while the terminals' active time as well as the utilization of the renewable energy can be amended by using cooperative power transfer to charge the wireless terminals.The research in this thesis is sponsored by both the open projects from National Key Laboratory of Wireless Mobile Communication(Innovation Technological Centre of Wireless Mobile), named as "The signal processing and resource scheduling of distributed joint processing systems",and the Beijing Natural Science Foundation Project "Energy efficiency network technologies research for heterogeneous cellular networks with coordinated small cells". This dissertation conducts studies on the interference management techniques and wireless energy transfer techniques based on cooperative wireless networks. The detailed research and contributions are issued as follows:1. This thesis provides an overview of the current research of the interference management and wireless energy transfer based on cooperative wireless networks. First, both the information and the energy transfer systems in the cooperative wilress networks are summized. Then the research on the interference management and the wireless power transfer techniques in the cooperative wireless networks, and the challenges posed are analayed. Finally, the CoMP (Coordinated Multipoint) based interference management and RF signal based wireless energy transfer are summarized intensively, as the research basis of this thesis.2. Multicell interference coordination in CoMP system via cell clustering is studied. CoMP controls the interference within the system by coordinating transmission between cells, however the coordination can only be applied to a set of a small number of cells, called cluster, because of the practical limitations. The clustering decides both the intra and inter cluster interference, and thus the performance of the coordination. This thesis proposed two clustering algorithms respectively based on the regular cell model and irregular cell model. The algorithm based on the regular cell model takes both the user distribution and the state of interference channel into account, and let the base stations choose their own partners by predicting the coordination gain. At the meantime, the algorithm based on the irregular cell model constructs a bipartite graph according to the interference condition between the users and the cells,and clustering the nodes with help of the bipartite graph in order to facilitate coordinating the interference. The simulation results indicate that both algorithms are able to effectively promote the edge users'throughput as well as to maintain the fairness in the system.3. Single cell downlink wireless energy transfer scheme is studied.In single cell wireless powered communication system, energy and information signal duplex can be realized on time domain. Although the energy signal precoding and the duplex time should be jointly optimized,the iterative search is prohibitively complex. An energy efficient and low complexity energy precoding is proposed in this thesis to guarantee the information QoS. First, a convex function is established to estimate the lower bound the energy transfer power with respect to the duplex time, to obtain the time which minimizes the lower bound estimation. Then with the given duplex time, the semidefinite relaxation method is used to minimize the energy transfer power under the constraints of QoS requirments. Simulation results demonstrates that proposed scheme provides similar energy efficiency compared to the optimal solution,while avoiding the iterative search.4. Furthermore, the cooperative multicell wireless energy transfer is studied. The cells are assumed to operate on renewable energy harvesting,together with access to the smart grid. First, an energy precoding algorithm using Lowner-John ellipsoid approximation is proposed to reduce energy transfer power while guarantee the information QoS. Then,twe energy cooperation schemes between cells via the smart grid are proposed depending on both renewable energy harvesting and QoS requirments: if the renewable energy is sufficient, the cooperative energy transfer is optimized to maximize the sum of information rate; if the renewable energy is insufficient, then the transfer is optimized to minimize the purschased amount of electricity to ensure the information QoS. The simulation results first demonstrate the proposed energy precoding provides better energy efficiency, then it shows that proposed energy cooperation schemes improves the sum of information rate when harvested energy is sufficient, while the purchased electricity energy is saved to guarantee the QoS when the harvested energy is insufficient.