We develop the optimal economical caching schemes in cache-enabled heterogeneous networks, while delivering multimedia video services with personalized viewing qualities to mobile users. By applying scalable video coding (SVC), each video file to be requested is divided into one base layer (BL) and several enhancement layers (ELs). In order to assign different transmission tasks, the serving small-cell base stations (SBSs) are grouped into K clusters. The SBSs are able to cache and cooperatively transmit BL and EL contents to the user. We analytically derive the expressions for successful transmission probability and ergodic service rate, and then the closed form of EConomical Efficiency (ECE) is obtained. In order to enhance the ECE performance, we formulate the ECE optimization problems for two cases. In the first case, with equal cache size equipped at each SBS, the layer caching indicator is determined. Since this problem is NP-hard, after the l0-norm approximation, the discrete optimization variables are relaxed to be continuous, and this relaxed problem is convex. Next, based on the optimal solution derived from the relaxed problem, we devise a greedystrategy based heuristic algorithm to achieve the near-optimal layer caching indicators. In the second case, the cache size for each SBS, the layer size and the layer caching indicator are jointly optimized. This problem is a mixed integer programming problem, which is more challenging. To effectively solve this problem, the original ECE maximization problem is divided into two subproblems. These two subproblems are iteratively solved until the original optimization problem is convergent. Numerical results verify the correctness of theoretical derivations. Additionally, compared to the most popular layer placement strategy, the performance superiority of the proposed SVC-based caching schemes is testified.
翻译:我们开发了缓存式混混网络中的最佳经济缓冲计划,同时向移动用户提供带有个性化浏览品质的多媒体视频服务。我们通过应用可缩放视频编码(SVC),将要求的每个视频文件分为一个基层(BL)和几个增强层(ELs)。为了分配不同的传输任务,将正在使用的小型基站(SBS)分组为K组。SBS能够缓存并合作向用户传输 BL和EL内容。我们通过分析获取成功传输概率和ergodi服务率的表达方式,然后获得封闭形式的ECononomicPapple(ECE) 。为了提高欧洲经委会的性能,我们为两个案例制定了欧洲经委会的优化问题。第一个案例是,每个小细胞基站的缓冲大小相等。由于这个问题很硬,在以 l0 调控调后, 离散式优化变现变量会持续下来,而这种淡化的问题是 convexxx。 下一步,根据最优化的Ormalalalalalality 递归为最接近的Scadeal deal 。我们根据的是, rodeal deal deal deal deal deal deal deal deal deal deal deal deal deal deal deal sal deal deal deal disal deal disal deal deal deal deal deal disal deal deal disal dism pre pre 。