Research On Interference Alignment In Multi-cell Multi-user MIMO Network

Interference alignment is an effective interference management technique,which can greatly improve system throughput by using limited spectrum.Multi-cell multi-user MIMO network has become an important scenario for studying interference alignment technology due to its complex interference relationship.The traditional interference alignment scheme in multicell multi-user MIMO network does not consider the difference and mobility of users.When there are large differences in transmit power and distance between users,the traditional scheme will leave large inter-cell interference;When the users are mobile,the traditional interference alignment scheme will directly fail because it cannot handle this change.Aiming at the differences in the transmit power and distance of users,this thesis considers the optimal selection of subspace and proposes an interference alignment scheme based on subspace differentiation;Aiming at the mobility of users,this thesis proposes the non-directional user signal to interference ratio.The calculation of this variable is used to dynamically select the optimal connection mode and an adaptive interference alignment scheme based on the dynamic selection of the desired transmitters is proposed.The main work and innovations of this thesis can be summarized as follows:1.Aiming at the problem of large inter-cell interference caused by the difference of users in the traditional scheme,an interference alignment scheme based on subspace differentiation is proposed.Considering the differences in power and distance of users in the multi-cell multiuser MIMO uplink,this thesis proposes the actual interference power(AIP)for the first time and calculates the AIP of each user.The users are reordered according to the AIP to optimize the choice of subspace.Aligning the signals of users with greater interference to the subspace composed of signals of users with less interference.Assigning multi-dimensional merge weight to each user through two objective weighting methods,so that the interference is aligned as much as possible to the dimension with smaller interference,thereby further reducing the intercell interference.2.Aiming at the problem that user mobility causes the failure of the traditional scheme,an adaptive interference alignment scheme based on the dynamic selection of the desired transmitters in the unmanned ship network is proposed.The proposed scheme selects the desired user set and connection mode through the calculation of the non-directional user signal to interference ratio.The iterative interference alignment algorithm is implemented for the nondirectional users,while the partial interference alignment algorithm is implemented for the directional users,and a proof of algorithm convergence is given.When the position of the unmanned ship changes,the desired user set and connection mode are dynamically updated and selected,and the corresponding interference alignment algorithm will also be updated adaptively.3.Based on MATLAB,the experimental environments of multi-cell multi-user MIMO uplink and unmanned ship networking scenario are built.The simulation experiments of the interference alignment scheme based on subspace differentiation and the adaptive interference alignment scheme based on the dynamic selection of the desired transmitters have been completed respectively.Experimental results show that the two schemes can effectively deal with the impact of user difference or mobility,and both can effectively eliminate interference and increase the total system rate at the same time.