We consider the optimal design of a scheduling policy for adaptive videostreaming in a wireless network formed by several users and helpers. A featureof such networks is that any user is typically in the range of multiplehelpers. Hence, in order to cope with user-helper association, load balancingand inter-cell interference, an efficient streaming policy should allow theusers to dynamically select the helper node to download from, and determineadaptively the video quality level of the download. In order to obtain atractable formulation, we follow a "divide and conquer" approach: i) Assumingthat each video packet (chunk) is delivered within its playback delay ("smoothstreaming regime"), the problem is formulated as a network utility maximization(NUM), subject to queue stability, where the network utility function is aconcave and componentwise non-decreasing function of the users' video qualitymeasure. ii) We solve the NUM problem by using a Lyapunov Drift Plus Penaltyapproach, obtaining a scheme that naturally decomposes into two sub-policiesreferred to as "congestion control" (adaptive video quality and helper stationselection) and "transmission scheduling" (dynamic allocation of the helper-userphysical layer transmission rates).Our solution is provably optimal withrespect to the proposed NUM problem, in a strong per-sample path sense. iii)Finally, we propose a method to adaptively estimate the maximum queuing delays,such that each user can calculate its pre-buffering and re-buffering time inorder to cope with the fluctuations of the queuing delays. Through simulations,we evaluate the performance of the proposed algorithm under realisticassumptions of a network with densely deployed helper nodes, and demonstratethe per-sample path optimality of the proposed solution by considering anon-stationary non-ergodic scenario with user mobility, VBR video coding.
展开▼
