On the Fundamental Limits of Fog-RAN Cache-Aided Networks With Downlink and Sidelink Communications
On the Fundamental Limits of Fog-RAN Cache-Aided Networks With Downlink and Sidelink Communications
复制标题
DOI：
10.1109/tit.2021.3054518
复制
发表时间：
2018-11
影响因子：
2.5
通讯作者：
Kai Wan;Daniela Tuninetti;Mingyue Ji;G. Caire
中科院分区：
文献类型：
--
作者：
Kai Wan;Daniela Tuninetti;Mingyue Ji;G. Caire
Maddah-Ali和Niesen(MAN)在2014年表明，单瓶颈链路广播网络中的编码缓存允许为任意数量的配备缓存的用户提供服务，其总链路负载(每单位时间的比特)不随用户数量而扩展。从那时起，从信息论和(网络)编码理论的角度，以及从应用的角度，编码缓存这一一般性话题引起了极大的兴趣。在此基础上，本文考虑了一种特殊的网络拓扑结构，称为缓存辅助雾无线接入网(Fog-RAN)，它包括一个与内容服务器位于同一位置的宏蜂窝基站(MBS)，多个装有缓存的小小区基站(SBSS)，以及许多没有缓存的用户。一些用户直接由MBS广播下行链路服务，而另一些用户由SBSS服务。SBSS还可以通过侧通道(称为“侧链路”)通过多轮直接通信来交换数据。对于这种新颖的Fog-RAN模型，在标准的最坏情况需求场景下，研究了(A)SBSS处的高速缓冲存储器的数量、(B)下行链路(从MB到直接服务的用户和SBSS)上的负载和(C)侧链路上的总负载之间的基本权衡。我们提出了一个逆界，它的主要新奇之处在于联合限定了下行负载和旁路负载。在可实现性方面，利用网络拓扑结构，提出了两类内存负载点，分别为SBS侧链路负载最小和MBS下行链路负载最小。通过在这两类内存负载点之间共享内存，得到了一些精确的或有序的最优性结果。几个现有模型(例如，设备到设备编码高速缓存、具有共享高速缓存的单瓶颈链路编码高速缓存、具有无高速缓存用户的单瓶颈链路编码高速缓存)被恢复为该网络模型的特例，并且给出了独立感兴趣的副产品结果。最后，讨论了拓扑感知缓存与拓扑不可知缓存的作用。
Maddah-Ali and Niesen (MAN) in 2014 showed that coded caching in single bottleneck-link broadcast networks allows serving an arbitrarily large number of cache-equipped users with a total link load (bits per unit time) that does not scale with the number of users. Since then, the general topic of coded caching has generated enormous interest both from the information theoretic and (network) coding theoretic viewpoint, and from the viewpoint of applications. Building on the MAN work, this paper considers a particular network topology referred to as cache-aided Fog Radio Access Network (Fog-RAN), that includes a Macro-cell Base Station (MBS) co-located with the content server, several cache-equipped Small-cell Base Stations (SBSs), and many users without caches. Some users are served directly by the MBS broadcast downlink, while other users are served by the SBSs. The SBSs can also exchange data via rounds of direct communication via a side channel, referred to as “sidelink”. For this novel Fog-RAN model, the fundamental tradeoff among (a) the amount of cache memory at the SBSs, (b) the load on the downlink (from MBS to directly served users and SBSs), and (c) the aggregate load on the sidelink is studied, under the standard worst-case demand scenario. We propose a converse bound whose key novelty is to jointly bound the downlink load an the sidelink load. For the achievability, by leveraging the network topology, we propose two classes of memory-loads point, where the SBS sidelink load is minimum and the MBS downlink load is minimum, respectively. By memory-sharing between these two classes of memory-loads points, some exact or order optimality results are obtained. Several existing models (e.g., Device-to-Device coded caching, single bottleneck-link coded caching with shared caches, single bottleneck-link caching coded caching with cache-less users) are recovered as special cases of this network model and by-product results of independent interest are given. Finally, the role of topology-aware versus topology-agnostic caching is discussed.