Scalable delivery of correlated video content over cache-aided broadcast networks

The increasingly dynamic, unpredictable, and personalized nature of the content that users consume challenges the efficiency of existing caching-based solutions in which only exact content reuse is explored. This calls for novel content delivery schemes that account for the additional gains that can be obtained from the joint compression of correlated content distributed throughout the network, such as updated versions of dynamic data. This chapter reviews state-of- the- art studies on the fundamental limits of cache-aided communication systems for the delivery of correlated content. Two scenarios are considered: (i) a static setting, in which the same correlated content library is used during both the caching and delivery phases and (ii) a dynamic setting, in which an updated version of the content library may become available during the delivery phase. For the static setting, a class of achievable schemes based on a two-step source coding approach is described. The content library is first jointly compressed, with resulting files cached and delivered using a combination of correlation-unaware cache-aided delivery schemes. For the dynamic setting, a second class of achievable schemes is described, in which, during the caching phase, content pieces are stored based on their correlation with the rest of the library, and during delivery, the requested content is jointly compressed while using cached information as references. With accompanying performance analyses and numerical results, this chapter illustrates that as we move towards real-time and/ or personalized media dominated services, where exact cache hits are almost nonexistent (challenging the efficiency of traditional caching schemes), the high correlation present among increasingly dynamic content still enables exploiting network cached information as references for network compression.