Abstract
In the case of broadband wireless communication systems with high carrier frequencies, high-speed wireless communication is feasible, but if high-capacity backhaul is not supplied to all base stations, a backhaul bottleneck may occur. To solve this backhaul bottleneck problem, one can use wireless caching or device-to-device (D2D) caching technology that installs a cache on a mobile end device, use the cache to store video content, and then supply the video content when requested by other end devices. Prior to peak traffic hours, video content can be stored on mobile end devices according to the content preferences, but it is difficult to solve cell overload problems that occur during peak traffic hours. This is because peak traffic hours can persist for a long time, and thus device positions, content preferences, and cell loads are liable to change during peak traffic hours. Providing broadband radio and high-capacity backhaul to all cells can create cost issues, but if there are some cells with broadband wireless resources and high-capacity backhaul, these cells may often support sufficient data even during peak traffic hours. If a mobile end device can intermittently enter a cell with sufficient data supply, it can update its cache using some short-term information. In this paper, we compare wireless caching schemes that update the caches of mobile end devices during peak traffic hours with the goal of reducing overload data. If high-capacity base stations are installed within a certain distance interval from each other to reduce the content update period, then good performance can be obtained by frequently updating the caches while considering the short-term content preferences of nearby overload cells. In addition, if a mobile device can predict its movement path, performance can be further improved by considering only the overload cells in the predicted path.
Highlights
The amount of data demanded by users in wireless networks is rapidly increasing
This paper discusses the differences between proactive caching schemes including off-peak-hour caching, peak-hour caching, and content prefetching. (b) Most caching systems aim to increase the hit ratio, but this paper shows that if not all cells are overloaded, there may be a difference between increasing the hit ratio and reducing the overload data. (c) This paper considers short-term content preferences that are predicted based on currently viewed content as well as long-term content preferences considering content popularity, user characteristics, and user location. (d) This paper shows that it is difficult for peak-hour caching to achieve good performance only by reducing the content update period
To keep explanation as clear as possible, this paper considers the case where the base station is used as a relay, and we assume that when a mobile helper is in a cell, the content in the cache can be delivered to any user equipment (UE) in the cell upon request
Summary
The amount of data demanded by users in wireless networks is rapidly increasing. In order to satisfy these data demands, it is necessary to increase the wireless capacity per unit area. (e) This paper shows that performance can be improved by reducing the number of cells considered by a mobile helper, and this would be achieved by predicting the helper’s movement path, estimating the overload information of cells, and reducing the content update period. In peak-hour caching, a mobile helper can update the cache during peak hours while in an underload cell, that may have broadband wireless resources and high-capacity backhaul. It is assumed that a mobile helper can predict its movement path and high-capacity cells are installed within a certain distance interval from each other, in a way that the content update period falls within the validity period of the content prediction information. Content prefetching requires a helper to be able to predict its movement path and requires the content update period to be less than the validity period of the content prediction
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