Research On Interference Alignment Algorithms For Multi-Cell Full-Duplex Cellular Networks

Being a communication technology that can transmit data at the same time and in the same frequency,the full-duplex communication can theoretically double the communication capacity of the system.However,inter user interference both from the intra-cell and inter-cell in the full-duplex cellular network seriously degrades its full duplex gain.As an effective interference management method,interference alignment can overcome the shortcomings of traditional interference management methods and improve system capacity.In this thesis,interference alignment algorithm is applied to the interference management of multi-cell full-duplex cellular networks.The degrees of freedom(DoF)and full-duplex gain of multi-cell full duplex cellular networks are analyzed.To overcome the deficiency of the traditional interference alignment in multi-cell and multi-user scenarios,an interference graph based alignment algorithm for multi-cell full-duplex cellular networks is proposed,which not only can effectively improve the degree of freedom of the system,but also is not limited by network scale.The main work of the thesis is as follows: 1.A system model of single-cell full-duplex base station is established.The theoretical DoF of such system is analyzed,and an algorithm is designed and simulated to approximate the theoretical value.2.A multi-cell full-duplex cellular network model is established,and the theoretical DoF region of multi-cell full-duplex cellular network is derived and analyzed.By exploring the proper of the system and using the relationship between proper and feasibility,the degree of freedom of multi-cell full-duplex cellular networks can be treated as an optimization problem.By solving optimization,the DoF region and upper bound of two users(one uplink user and one downlink user)and multiple users(multiple uplink users and multiple downlink users)are obtained respectively.The DoF region of two users and multi-user is analyzed respectively,and the corresponding full-duplex gain is calculated and deduced.It is theoretically demonstrated that the traditional interference alignment methods give rise to limited full duplex gain in the interference management of multi-cell full-duplex cellular.3.To overcome the deficiency of interference alignment method in managing multi-cell full-duplex cellular networks,an alignment algorithm based on interference graph and incorporating multiple interference management methods is proposed.Firstly,successive interference cancellation is applied to eliminate the directional interference in the interference graph,turning the bidirectional interference between adjacent cells into unidirectional interference,then the base stations of some cells are closed and the remaining cells are clustered.The simulation results show that the DOF of each cell is 1.5 and the full-duplex gain is 1.5 when there are one uplink user and one downlink user,while the full-duplex gain of the traditional interference alignment method is about 1.1 under the same circumstance.Therefore,the proposed algorithm effectively improves the system capacity and full-duplex gain.