Research On Interference Alignment Algorithm In Co-frequency Co-time Full Duplex Communications

With the continuous development of mobile communication and the limitation of spectrum resources, how to improve the system capacity, and save spectrum resources has become an important issue of the academic research. Compared with the existing time division duplex(TDD) and frequency division duplex(FDD) technology, the co-time co-frequency full duplex(CCFD) technology can double the utilization rate of wireless resource in theory, and has become the research hotspots of current wireless mobile communications areas. However,full duplex technology also has serious interference problems, although there exist some interference cancellation schemes in the full duplex communication, the effect is not ideal. Interference alignment(IA) technology can not only be used to eliminate the interference, but also improve the system capacity. Therefore, this thesis discusses the problem of eliminating complex interference in multiuser full duplex network by using interference alignment technology. The main work of this thesis is as follows:For the multiuser full duplex interference channel, this thesis eliminates the self-interference and mutual interference by using the interference alignment technology at the same time. First, considering both the self-interference and mutual interference, this thesis transforms the multiuser full-duplex system into a one-way channel model based on its characteristic, then, the corresponding relationship between the equivalent model and the original model is given. Second, based on this thoughtfulness, the iterative interference alignment and the maximum signal to interference plus noise ratio algorithm are presented to eliminate both self-interference and mutual interference in multiuser full duplex communications. Last, the simulation results show that the interference alignment scheme in this thesis can improve the system capacity and the average energy efficiency.For the multi-user full-duplex relay interference channel, the self-interference cancellation and interference alignment schemes based on maximum global mutual information are presented. First, based on the singular value decomposition of the channel matrix, the self-interference cancellation scheme is designed, and the specific algorithm of self-interference cancellation matrix is given. Second, in order to save the resources of relay, the precoding technology is used to align the transmitter signal, and the feasibility conditions of the signal alignment are given. Furthermore, based on the maximum global mutual information, the receiver interference suppression algorithm is presented, and the system degrees of freedom is analyzed. Last, theoretical analysis and simulation results show that, compared with the existing typical full duplex relaying scheme, the self-interference cancellation and interference alignment schemes in this thesis can effectively improve the system mutual information and the degrees of freedom. In addition, the relay only needs to do simple power constraints, and it is not necessary to do complex signal processing which reduces the complexity of signal processing for the whole system.