Research On Coded Caching Scheme For MISO BC Systems

With the development of 5G technology,multimedia content is mainly in the form of streaming media,resulting in an explosive growth of network traffic.The caching technology solves the problem that the communication systems are congested during peaktraffic times and underutilized during off-peak times.The main idea is during the off-peak times,the server allocates a part of the content to store in the users’ memories in advance,while during the peak-traffic times,these cached content will not be transmitted by server,to relieve the network traffic.In order to improve communication performance peak-traffic times,coded caching creates more coded gain or sum Degree-of-Freedom(sum-DoF)by utilizing the users’ local caches and coded signals to serve more users simultaneously.Although the coded caching technology for Multiple-Input-Single-Output Broadcast system model proposed by Naderializadeh et al.generated sum-DoF,the existing coded caching schemes incurred large subpacketization.To solve this problem,we apply the combinatorial design theory to design coded caching schemes for Multiple-Input-Single-Output Broadcast system,to achieve the optimal sum-DoF with low subpacketization.The main work is as follows:Based on the uncoded placement and one-shot linear delivery coded caching scheme in the Multiple-Input-Single-Output Broadcast system model,by combining zero-forcing with multicast coded caching gain in traditional coded caching schemes and using linear algebra,we propose a new combinatorial structure called Multiple-antenna Placement Delivery Array(MAPDA),which can characterize the multiple antennas coded caching scheme for Multiple-Input-Single-Output Broadcast system.Subsequently,by using the properties of MAPDA,we also provide an alternative version to prove the optimal sum-DoF for the coded caching scheme in this system model.Based on MAPDA,we propose two classes of coded caching scheme.The first scheme based on Latin Square achieves the optimal sum-DoF and the subpacketization is equal to the number of users under some constraints.Subsequently,for the second scheme,we propose a transformation approach to construct MAPDA from any g-regular PDA(a class of combinatorial structure which can characterize the coded caching scheme for Single-Input-Single-Output shared-link system proposed by Maddah-Ali and Niesen(MN)).When g-regular PDA corresponds to the MN PDA,the resulting MAPDA yields the optimal sum-DoF with reduced subpacketization compared to the existing schemes.Note that the second scheme can be extended to the multiple independent single-antenna transmitters(servers)corresponding to the cache-aided interference channel and the scenario of transmitters equipped with multiple antennas.Considering the actual situation,i.e.,users enter or leave the network at any time,the Multiple-Input-Single-Output Broadcast system is extended to the dynamic Multiple-Input-Single-Output Broadcast system.For the case of the dynamic Multiple-Input-Single-Output Broadcast network is the Multiple-Input-Single-Output Broadcast network,we directly adopt the coded caching scheme of Multiple-Input-Single-Output Broadcast system.For other cases of dynamic Multiple-Input-Single-Output Broadcast system,we take the grouping method to design coded caching schemes.Compared with coded caching scheme for the Multiple-Input-Single-Output Broadcast system,the subpacketization has been reduced at the expense of a small amount of sum-DoF.