Research On Interference Alignment Algorithms For D2D Communication Underlaying MIMO Cellular Networks

With the wide promotion of novel mobile services and the popularity of mobile intelligent terminals,the traditional cellular network based on the base station can't meet the requirements of high bandwidth and high data rate.Device to Device(D2D)communication technique has attracted much more attention due to its low delay,low power consumption and high transmission efficiency.Integrated D2 D technique into the cellular network,the interference in the system becomes more complicated.Therefore,interference alignment(IA)technique is used to solve the interference problem in the multiple input multiple output(MIMO)cellular network underlaying D2 D communication.To solve the interference problem which consists of inter-cell interference,intra-cell interference and the mutual interference between D2 D links and cellular links in the D2 DMIMO networks,a transmitting data streams allocation scheme based on the parity of the antennas number and the corresponding interference alignment algorithm are proposed in this thesis.Firstly,this algorithm minimizes the interference power from the base station to unexpected receivers,in order to design the pre-coding matrix of cellular link.And then Max-SINR(Signal to Interference plus Noise Ratio)criterion could be used to design the cellular link's interference suppression matrix.Finally,the linear interference alignment can eliminate intra-interference and the Max-DoF(Degrees of Freedom)of this scheme can be obtained.The theoretical analysis and simulation results verify that,comparing with other interference alignment algorithms,the proposed algorithm improves the scheme's degrees of freedom,spectrum efficiency and energy efficiency,and reduces the restriction for the number of antennas and enhances the flexibility.For the increasing overhead of cellular user when it participates in the process of interference alignment,an interference alignment algorithm for D2 D communication based on the cascaded pre-coding and the ESINR(Equivalent Signal to Interference plus Noise Ratio)criterion is proposed.First of all,in order not to increase the cellular user's overhead,the corresponding equivalent channel model is formed by the interference analysis between D2 D links and cellular link.Then the D2 D users' outer cascaded precoding matrices and outer cascaded interference suppression matrices are used to eliminate the interference between D2 D links and cellular link while ensuring the transmission of cellular user at the maximum rate.So the cellular link and the D2 D links are independent of each other.Furthermore,according to the ESINR criterion of D2 D transmitters and the MMSE(Minimum Mean Square Error)criterion of D2 D receivers,the D2 D users' inner cascaded pre-coding matrices and the inner cascaded interference suppression matrices are designed to eliminate the mutual interference between D2 D links.In addition,the QR decomposition is used to optimize the inner cascaded precoding matrices and the inner cascaded interference suppression matrices,and the convergence of this algorithm is analyzed.Finally,the simulation results verify that the proposed algorithm can effectively improve the performance of system capacity and average energy efficiency.