Design Of Interference Management Methods Based On Interference Alignment And Steering

As mobile communications enters the 5G era,the number of devices connecting the network has been growing exponentially,yielding higher requirements for data rate of communication networks.In order to improve the performance of communication networks,5G employs high-density deployment of base stations so as to achieve a higher degree of spectrum resource reuse,incurring co-channel interference(CCI)to edge users in a cell,and hence managing CCI in 5G communication systems becomes an increasingly important issue.Therefore,designing effective interference management(IM)schemes and improving the spectral efficiency(SE)of the communication system are the focus of this thesis.Firstly,this thesis proposes interference alignment steering(IAS)and interference steering alignment(ISA)based on interference alignment(IA)and interference steering(IS).IAS implements IA at the interfering transmitter(Tx),so that one interference is aligned into an one-dimensional subspace orthogonal to the interfered desired transmission at the interfered receiver(Rx).Then IS is realized at the interfered Tx so that the remaining interferences are steered into the one-dimensional subspace determined by the previously aligned interference.IAS includes two implementations,IAS with partial adjustment at the interfering Tx(IAS-PAIT),and IAS with full adjustment at the interfering Tx(IAS-FAIT).IAS-PAIT only performs IA on one transmission from the interfering Tx,so the orthogonality among the multiple desired signals received by the interfering Rx cannot be guaranteed.As a comparison,IAS-FAIT adjusts all the transmissions from the interfering Tx other than the one adjusted previously so as to ensure the orthogonality of multiple desired transmissions observed by the interfering Rx.ISA implements IS at the interfered Tx to steer multiple interferences to an one-dimensional subspace orthogonal to the interfered desired transmission at the interfered Rx.Then the interfering Tx applies IA to the remaining one interfering component,i.e.,aligns the interference into the one-dimensional subspace determined by IS.ISA can minimize the power overhead of IS at the interfered Tx,hence can ensure the transmission performance of the interfered communication pair.Both IAS and ISA are implemented corporately by the interfering and interfered communication pairs in realizing interference management,and both communication pairs pay for the overhead of IM,thereby they can effectively managing interference.IAS and ISA consumes additional power at the interfered Tx while realizing the IM.By taking the interactions among multiple interferences into account,this thesis proposes cooperative interference alignment with space-power adjustment(CIA-SPA)and cooperative interference alignment with power adjustment(CIA-PA).Both schemes are implemented by the interfering Tx.CIA-SPA adjusts the equivalent interference obtaining from multiple interfering components to an one-dimensional subspace orthogonal to the direction of the interfered desired transmission by adjusting the spatial characteristics of one interference and the strength of all interferences.CIA-PA adjusts the intensity of all interfering components by multiplying a complex coefficient with each interference,so that the equivalent interference of multiple disturbances is adjusted to an one-dimensional subspace orthogonal to the desired transmission.Compared to CIA-SPA,CIA-PA can guarantee the orthogonality of all desired signal components(acting as interferences with respect to the interfered Rx)at the interfering Rx associated with the interfering Tx,yielding no CCI to the interfering communication pair.Simulation results have shown that both CIA-SPA and CIA-PA can effectively manage interferences and improve system SE.Finally,the thesis summarizes the research work and gives some possible research directions.