【作者】 张鹏；

【导师】 刘志新；

【作者基本信息】 燕山大学 ， 控制理论与控制工程， 2017， 硕士

【摘要】 无线异构网络作为5G网络的基础,具有提高网络覆盖面积,减小移动网络覆盖盲区,尤其是室内区域;增大网络传输容量,提高网络可靠性,提高频谱资源利用率,节约能量等优点。异构网络的典型代表为Femtocell网络,然而由于Femtceoll网络的引入,给移动网络带来了新的问题与挑战。由于Femtocell网络与宏蜂窝网络共享频谱资源,势必会造成严重的信号干扰,导致双层异构网络中不仅存在层内干扰,还存在跨层干扰。由于实际通信环境具有复杂性与动态性,尤其是随着未来移动网络大规模、超密集部署,使得双层异构网络中的瞬时信道增益变化更加复杂与多变。此外,随着未来异构网络接入方式更加灵活、开放,使得移动网络中的信息安全传输问题成为目前亟待解决的问题之一。因此,本文针对双层异构网络中存在的不确定因素,设计鲁棒干扰管理方案以及安全传输方案。首先,针对在慢衰落通信环境中双层异构网络上行链路干扰管理问题,同时考虑信号链路与干扰链路的信道增益不确定性,分别建模为椭球集不确定性和高斯不确定性两种信道增益模型。针对这两种慢衰落信道模型,分别提出了两种鲁棒干扰管理方案,来保证用户的服务质量。其次,在快衰落通信环境下,针对信道增益变化迅速时难以解决的干扰管理问题,提出了两种鲁棒干扰管理方案。第一种干扰管理方案基于信道增益的统计特征,将概率约束问题转化为确定型约束;第二种则基于信道增益的样本值,提高了干扰管理方案在实际系统中的实用性。最后,针对双层异构网络中的下行链路安全传输问题,为了提高安全传输性能,本文提出了一个基于子信道分配与功率控制的联合优化安全传输方案。该方案利用异构网络中普遍存在的干扰抑制监听者的信噪比,在不消耗额外功率的前提下,提高信息安全传输速率。此外,针对异构网络中的不同需求,提出了一个切换效用函数框架。更多还原

【Abstract】 As the foundation of 5G,wireless heterogeneous networks has the advantages of enhancing coverage area,reducing blind area(especially indoor area),increasing network transmission capacity,enhancing the reliability of networks,improving the utilization of spectrum resources,energy saving and so on.Femtocell networks are the typical example of two-layer heterogeneous networks.However,the introduction of femtocell networks brings a lot of new problems and challenges for mobile networks.Since femtocell networks share spectrum resources with macrocell networks,it definitely results in co-channel interferences,including inner-tier interference and cross-tier interferences.Due to the complexity and dynamics of real mobile networks,especially with the larger and denser deployment for the networks in the future,the instantaneous channel gains in two-tier heterogeneous networks become more complicated and changeable.Moreover,the access mode of heterogeneous networks becomes more flexible and open in the future,which leads to serious information transmission security.Therefore,Considering the uncertainties of channel gains in the two-tier heterogeneous networks,robust interference management scheme and secure transmission scheme are designed.First,considering the uplink interference management problem under flat fading environment,we simultaneously investigate the uncertainties in both signal links and interference links.The uncertainties are,respectively,modeled as ellipsoid uncertainty and Gaussian uncertainty.Under the present of the both flat fading channels,two robust interference management scheme are proposed for the wireless heterogeneous networks.Then,considering fast fading environment with channel gains change quickly,the interference management problem is usually hard to solve due to the fast changing of channel gains.Aiming at dealing with the problem,we propose two interference management schemes for the heterogeneous networks.The first scheme based on statistical characteristics converts probability constraint into deterministic constraints.The other utilizes the channel gains samples to guarantee the QoS of users,which largely enhance its applicability in practical systems.Finally,a joint subchannel and power allocation secure transmission scheme is proposed for the downlink transmission security problem in the two-tier heterogeneous networks to enhance the secure performance.In the scheme,ubiquitous interferences in the heterogeneous networks are exploited to degrade the eavesdropper’s performance and then the secure transmission performance is improved without consuming extra energy.Moreover,a switch-function-based frame is established to model the different requirements in the secure transmission problem.更多还原