Reduced Transmission in Multi-Server Coded Caching

Coded caching has been widely used in the wireless network for shifting the some transmissions during the peak traffic times to the off-peak traffic times. Multi-server coded caching, which can share responsibility for the total amount of transmission in the wireless network during the peak traffic times by means of the collaboration among these servers, can be seen everywhere in our life. The three servers setting (two data servers and one parity check server) is used in practice, e.g. redundant array of independent disks-4. In this scenario, there are total $N$ files which are equally stored in two data servers respectively and $K$ users each of which has the memory size of $M$ files. Each server connects to users by an independently channel. During the off-peak traffic times, two data servers place some parts of each files in each user's cache. In that time, servers do not know users' requests in future. During the peak traffic times each user just requests one file from $N$ files. Luo et al. in 2016 proposed the first coded caching scheme for this setting. In this paper, we proposed some method that further reduces the amount of transmission in each channel when $\frac{KM}{N}$ is odd. This method also improves the transmission rate for systems with general multiply servers.