The Advantages of Grouping Method for Repeated Requests in Coded Caching

Recently, coded caching has been widely studied due to its ability of significantly reducing the amount of transmissions (i.e., rate) during peak-traffic time. While to achieve this rate, each file is divided into a number of packets, which is even exponentially increasing with users. In practice, we prefer to design a coded caching scheme to achieve smaller rate with lower packet number. In order to reduce the packet number, the well known grouping method has been proposed by Shanmugam et al. in [1] and generated by Cheng et al. in [2]. However, the rate of the scheme obtained by grouping method is very large since there is no multicasting gain generated between different user groups. Thus, many other schemes have been investigated from other perspective. In this paper, we will show that when some files are requested more than once, the scheme obtained by grouping method has a smaller rate and smaller packet numbers than that of some other improved schemes.