  The explosion of mobile video traffic imposes tremendous challenges on
present cellular networks. To alleviate the pressure on backhaul links and to
enhance the quality of experience (QoE) of video streaming service, small cell
base stations (SBS) with caching ability are introduced to assist the content
delivery. In this paper, we present the first study on the optimal caching
strategy of scalable video coding (SVC) streaming in small cell networks with
the consideration of channel diversity and video scalability. We formulate an
integer programming problem to maximize the average SVC QoE under the
constraint of cache size at each SBS. By establishing connections between QoE
and caching state of each video, we simplify the proactive caching of SVC as a
multiple-choice knapsack problem (MCKP), and propose a low-complexity algorithm
using dynamic programming. Our proactive caching strategy reveals the
structural properties of cache allocation to each video based on their
popularity profiles. Simulation results manifest that the SBSs with caching
ability can greatly improve the average QoE of SVC streaming service, and that
our proposed caching strategy acquires significant performance gain compared
with other conventional caching policies.
