并行传输编码缓存问题研究

Study on coded caching with parallel transmission

基于提高网络传输的效率并得到更好的低延迟效果的目的,缓存技术应运而生。不同于传统缓存技术,编码缓存技术通过巧妙创造多播机会,使得服务器的一次广播传输能够同时满足多个用户的不同需求,从而得到全局缓存增益。考虑一个并行传输的编码缓存网络,其中服务器可以向所有用户广播消息,同时,用户之间也可以互发信息。提出了一种非编码预存储的编码缓存方案,该方案可分为三个阶段:预缓存阶段、分配阶段和交付阶段,通过向服务器和用户网络预先分配不同的工作量来获得最佳的传输延迟。仿真结果表明,所提并行传输缓存交付方案相比于单独进行服务器多播传输或单独进行D2D网络节点之间的传输,具备更好的实现效果。同时,所提方案在考虑两种不同信道的传输能力差距后,得到了比忽略信道传输能力时更好的实现效果。最后,证明了在非编码预存储的情况下,所提出的并行传输缓存交付方案在服务器广播信道与D2D网络传输信道的信道容量相同且用户缓存资源充足时的最优性。

In order to improve the efficiency of network transmission and obtain a better low-latency performance,caching technology appeared.Unlike traditional caching technology,coded caching enables a single broadcast transmission from the server to simultaneously satisfy different demands of users by creating multicast opportunities with a global caching gain obtained.A coded caching network with parallel transmission is considered in which the server can broadcast messages to all users and users can also send messages to each other.An uncoded prefetching coded caching scheme is proposed which is composed of three phases:the pre-caching phase,the allocation phase and the delivery phase,where the optimal delivery time is obtained by pre-allocating different workloads to the server and users.It is shown that the proposed scheme with parallel transmission has a better performance compared with either server-multicast transmission alone or transmission within a D2D network alone.Also,after considering the channel capability gap between the two different channels,the proposed scheme obtains a better performance than when channel transmission capability is ignored.Finally,the proposed cache and delivery scheme with parallel transmission in the case of uncoded prefetching is proved to be optimal when the users’cache resources are sufficient and the server broadcast channel and the D2D network transmission channel have the same channel capacity.