| Compared with the traditional wireless network,the fifth-generation mobile communication network(5G)has significant improvement in system capacity,number of access devices,transmission rate,delay time,spectrum efficiency,energy cost and many other aspects.As 5G network is developing towards the direction of network diversification,broadband,integration and intelligence,its wireless communication network will be a super dense heterogeneous network connected with various types of systems.Such a complex network topology will also introduce complex and serious interference problems,resulting in the decline of network performance and system efficiency.In order to reduce the interference and improve the network capacity,this paper studies the problem of interference alignment in the downlink of multi-input and multi-output cellular cell in the double-layer heterogeneous network.First of all,this paper extends the grouping-based interference alignment algorithm in the single layer network to the user location-based interference alignment(ULIA).It aligns the cross-layer interference of Macro station to a specific subspace,and designs the first stage beamforming matrices of Macro stations.Then,the distributed method is used to eliminate the same layer interference between macro users.Secondly,in order to get closer to the real complex network structure in reality,this paper also proposes a regional centralized interference alignment(RCIA)algorithm based on the double-layer heterogeneous multi-cell multi-user scenario.The algorithm improves the idea of double-layer single cell grouping,and flexibly combines the closed and distributed interference alignment technology,reasonably eliminating four different types of interference that can not be ignored caused by multiple macro cellular cells.The simulation results by MATLAB show that both the two algorithms can effectively improve the system capacity,spectrum efficiency,and reduce the computational complexity. |
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