A Research On Techniques Of Asymmetric Coded Caching

With the development of wireless communication technology and the gradual enrichment of Internet content services,the traffic load in network communication systems has grown rapidly.As a result,network resources have become extremely scarce,which makes the research of resource-efficient network especially significant.The traffic load in content delivery networks shows strong temporal variability,where the network resources are extremely destitute during peak hours and abundance during the off-peak hours.The caching technology that relies on idle network resources and storage resources of terminal nodes to alleviate traffic load during peak hours has been widely used in the Internet.In a traditional caching system,users only cache some popular contents locally during off-peak hours when the network sources are underutilized.When the user requests resources at the peak time,the contents are partially available in a local or close-by cache memory and the remaining parts need to be delivered using simple orthogonal unicast transmissions.The new code caching technology creates multicasting opportunities in the content transmission phase by jointly designing the content placement and delivery,and better exploit the cache memories available at user devices to relieve the traffic burden at peak times.Due to the difficulty of the problem,most of the literature follows the symmetric setting of,in which all the users are equipped with the same cache size,and the link between the server and the users is a single shared link.However,in practice,owing to the heterogeneous nature of devices,the equal cache assumption is often not met.Furthermore,the delivery channel quality may be different for different users.Therefore,although the asymmetry model makes the coded caching problem more complex,the construction of the coded caching scheme under the asymmetry model has become an important research direction in the field of coding caching.For heterogeneous-cache-size coded caching problem of K = 2 users with one common and two private links,we find the optimal cache and delivery strategy with coded prefetching and using the private links to transmit part of the requested files uncoded.For heterogeneous-cache-size coded caching problem of K ? 3 users,we find an optimal coded cache placement scheme for some special heterogeneous-cache-size points,where L users out of the total K users have no cache and the other K-L users have equal cache of size N-L.And by performing memory-sharing between these special heterogeneous-cache-size points and existing equal/unequal-cache-size memory-rate points,we obtain a new coded cache placement and delivery scheme for the heterogeneous-cache-size coded caching problem.