Rethinking the Gain of Multicasting and Proactive Caching for VoD Service

Multicasting and proactive caching at wireless edge, as two promising techniques to accommodate the explosive Video-on-Demand (VoD) traffic in mobile networks, have received significant attention in recent years. Various advantages of the two techniques have been revealed in existing works, which however are mainly based on strong assumptions on the behaviors of users for VoD service. In particular, multicasting usually assumes adequate synchronous requests to the same videos while proactive caching mainly assumes perfect prediction of content popularity. In this article, we resort to a real dataset collected from a campus network to examine the impact of these assumptions, and rethink the gain of multicasting and proactive caching at base stations for VoD service. We first review the principles of the two techniques in reducing traffic load, and then evaluate and compare their performance based on the collected dataset. The results demonstrate the limited opportunity and performance gain of multicasting for synchronous VoD requests, and identify the potential of proactive caching under different qualities of content popularity prediction. Based on the results, some open research directions regarding the two techniques are outlined for future study.