A Research On Techniques Of Interference Alignment In Mobile Communication Networks

With the rapid development of wireless communication services,future wireless network is facing a dilemma of limited spectrum resources and complex propagation environment to meet the raising demands of better coverage,higher throughput and lower transmission power that has resulted in a huge development of a vast variety of techniques to improve spectrum utilization,In this development process,new network architecture and transmission mechanisms have been proposed,such as self-organizing networks,heterogeneous networks,relay coordinated transmission.The introduction of these new network architectures and transmission mechanisms essentially constitutes a new jamming network and inevitably brings new interference issues.In recent decades,research on interference alignment has attracted a great deal of attention because it can suppress the interference and maintain a reasonable degree of freedom,which is regarded by the academic community as an innovative wireless transmission strategy that can effectively suppress interference,has made a major theoretical breakthrough in network capacity analysis.In recent years,many interference channel models and corresponding interference techniques have been proposed one after another,and the interference properties are examined from different perspectives.This paper also proposes three kinds of channel models to solve the interference and provides corresponding interference alignment transmission strategy.Firstly,we consider the two-hop Gaussian broadcast channel with confidential messages that consists of an orthogonal broadcast channel from a source to two relays and a interference part from the two relays to two destinations that treat each other as a eavesdropper.We establish the exact secure degrees of freedom of the model by combining real interference alignment and cooperative jamming technology that the desired signal can be divided at its target destination,undesired signal and cooperative jamming signal can also aligned perfectly at this destination.And the maximum of this degree of freedom is obviously improved compared with the traditional one-hop or unsupported Gaussian broadcast channel model.Secondly,this paper also studies an important mode in wireless communication —instantaneous relayassisted channel,which has a wide range of applications in wireless communications.We study the secure degrees of freedom(d.o.f.)of instantaneous relay-assisted wireless networks by considering three fundamental wireless network structures: 1)instantaneous relay-assisted Gaussian broadcast channel with confidential messages and an external eavesdropper;2)instantaneous relay-assisted Gaussian wiretap channel;3)instantaneous relay-assisted Gaussian multiple access wiretap channel,and based on this,it extends to the K-user Gaussian multiple-access eavesdropping channel.In those models,there are direct links between sources and destinations and a trust instantaneous relay that adopts amplify and forward mode and sends a jamming signal at the same time to help the destination.We study the achievable secure rate and secure d.o.f.of those models by combining real interference alignment and cooperative jamming technology.We give the corresponding reachability proofs,and by comparing them with the inverse propositions,the results show that their degrees of freedom are all optimal.Finally,based on the previous work,this paper introduces a new minimum distance calculation method for multidimensional constellation point sets,which extends the real interference alignment from a single antenna system to a multi-antenna system model.This real-interference alignment method for MIMO systems results in a simpler interference management scheme,which also allows us to avoid the complexity and high SNR requirements of asymptotically aligned schemes in MIMO systems.Based on this scheme,this section introduces a MIMO broadcast channel with confidential signals and achieves achievable security degrees of freedom.