Research On Interference Management Techniques In Wireless Communication Networks

With the development of technology, the demand of people for information in all directions becomes higher and higher. Wireless communication technology is the most effective measure to meet the need. Wireless communication has the characteristics of the low deployment cost, networking flexibility, supporting mobility, good coverage and scalability, etc. It has been widely used in many communication networks such as indoor access, short range communication, satellite communication, mobile communication and sensor networks, etc. With the emerging of multiple types of wireless communication systems, wireless networks shows heterogeneous and hierarchical features. Various types of interference existing in such networks become the key factor restricting the improvement of network performance. Therefore, how to design effective interference management mechanism so as to improve spectrum efficiency becomes the critical issue to the field of wireless communications. In this paper, communications algorithms based on interference management are designed in coordinated multi-point(Co MP) transmission and cognitive radio systems, respectively.First, in communication scenario of downlink coordinated multi-point transmission, a signal processing algorithm based on interference alignment(IA) and interference neutralization(IN) is proposed. With base station(BS) side cooperation, transmit precoder and receive filter are jointly designed, and then concurrent transmission of multiple data streams is implemented. In the design of preprocessing, IN is applied to the interferences carrying same data so as to align the interfering signals to opposite directions in a subspace. On the other hand, for interferences carrying different information, IA is employed to align them to the same direction in a subspace, thus reducing the signal dimension observed at the receiver side. Based on different precoding schemes at the transmitter’s end, receivers adopt orthogonal projection based filtering(OPF) so as to recover the desired data. The proposed scheme could achieve effective interference cancellation and suppression by exploiting limited collaboration only at the BS side. Moreover, it fully exploits the spatial multiplexing capability brought by multi-antenna systems. Simulation results show that IAN-Co MP can effectively suppress the inter-cell interference and significantly improve the spectral efficiency for cell-edge users.Then, in the communications scenario with cognitive radio(CR) multi-input multi-output(MIMO) uplink users, the dynamic spectrum sharing and user scheduling algorithm based on interference alignment is designed. The precoding vectoris are designed based on interference alignment(IA) and singular value decomposition(SVD), such that the cognitive and authorized signal can coexit with no interference. Moreover, the difference of spatial transmission performance originating from various channel matrices is exploited to implement appropriate user scheduling. Simulation results show that the proposed method can effectively improve the spectral efficiency and significantly improve the average throughput of the system.