The strong interference suffered by users can be a severe problem in cache-enabled networks (CENs) due to the content-centric user association mechanism. To tackle this issue, multi-antenna technology may be employed for interference management. In this paper, we consider a user-centric interference nulling (IN) scheme in two-tier multi-user multi-antenna CEN, with a hybrid most-popular and random caching policy at macro base stations (MBSs) and small base stations (SBSs) to provide file diversity. All the interfering SBSs within the IN range of a user are requested to suppress the interference at this user using zero-forcing beamforming. Using stochastic geometry analysis techniques, we derive a tractable expression for the area spectral efficiency (ASE). A lower bound on the ASE is also obtained, with which we then consider ASE maximization, by optimizing the caching policy and IN coefficient. To solve the resultant mixed integer programming problem, we design an alternating optimization algorithm to minimize the lower bound of the ASE. Our numerical results demonstrate that the proposed caching policy yields performance that is close to the optimum, and it outperforms several existing baselines.
翻译:由于内容中心用户关联机制,用户受到的强烈干扰可能是缓存网络中一个严重问题。为了解决这一问题,可以使用多防网技术进行干扰管理。在本文中,我们考虑在双层多用户多用多防网中,在双层多用户多防网CEN中采用以用户为中心的干扰(IN)计划,在宏观基地站和小型基地站采用混合最流行和随机的缓冲政策以提供文件多样性。在用户的内层中,所有干扰的 SBS 都被要求使用零推进波形仪来抑制该用户的干扰。我们使用随机几何几何测地分析技术,为区域光谱效率(ASE)找到一种可移动的表达方式。还获得了对ASE的较低约束,然后我们考虑通过优化缓存政策和IN系数来实现ASE最大化。为了解决由此产生的混合组合编程问题,我们设计了一种交替的优化算法,以尽量减少ASE的下限。我们的数字结果显示,拟议的缓冲政策使业绩接近于现有基准和基准。