Research On Interference Alignment Algorithm With Limited Feedback For Multi-user MIMO Systems

With the development of wireless communication systems,the sideffect of interference on spectral efficiency is increasely serious.Interference management has become an important research direction in the field of wireless communication.Interference Alignment(IA)as a breakthrough interference management strategy,it can not only effectively suppress interference,but also bring the system capacity gain.In the interference-limited system,IA technology attracts tremendous attention.The core idea of IA technology is to alignment the interference signal vector at the receiver in a specific low-dimensional subspace,and let the desired signal transmissed in its orthogonal subspace,which leads to the receiver to decode its desired signal without any interference.However,the implementation of IA requires the transmitter shall fully know the channel state information(CSI),which not only will bring a heavy feedback overhead to the systems,but also is difficult to achieve in the actual communication systems.Therefore the research of IA algorithm under the limited feedback condition is of great significance to promote the practical development of IA technology.The application of IA technology to MIMO system can effectively play the technical advantages of both and improve the overall performance of wireless communication systems.In view of this,the thesis focuses on the research of interference alignment algorithm with limited feedback in multiuser MIMO systems.The contents of this paper are outlined as follows.A limited feedback IA algorithm combined with linear dispersion space-time code is presented in multiuser MIMO systems.The algorithm combines pre-coding and linear dispersion space-time coding.The complete elimination of the interference is achieved in proposed algorithm by rationally designing the precoding matrix,the linear dispersion space-time block and receiving matrix of the receiver under the condition that only a single user CSI is fed back.The simulation results show that compared with the existing research,the new IA algorithm can greatly reduce the system CSI feedback overhead when the interference is completely eliminated.Aiming to implement IA and to reduce the feedback overhead of IA limited feedback,an IA algorithm combined with space-time-frequency resources is presented in multiuser MIMO interference systems.Firstly,based on expansion of the channel intime domain and combined the space and time resource,an IA scheme named ST-IA is proposed.The ST-IA algorithm obtains the closed solution of the interference-aligned precoding matrix and the receive filter matrix that can fully eliminate the interference.At the same time,it reduces the computational complexity of the IA and relaxes the restrictions of the number of transmit and receive antennas so as to eliminate interference completely.Then,based on ST-IA,the STF-IA algorithm is proposed and focuses on the optimal design of feedback overhead.By introducing the frequency dimension,the transmitter can reconstruct the required CSI with only a small amount of feedback information by constructing the CSI matrix used.Thus a win-win goal can be obtained by not only completely eliminateing the interference,but reduceing the feedback overhead.