Research On Incentive Mechanism For Cooperative Scalable Video Coding (SVC) Multicast Based On Contract Theory

According to classical video multicast technique,data are encoded into fixed format with single code rate.It is difficult for users under bad channel conditions to decode highquality encoded videos,due to the heterogeneity among the channel conditions between users and the base station(BS).Therefore,users' QoEs(quality of experience)are limited by those under bad channel conditions.Scalable video coding(SVC)is proposed in the H.264 and H.265 standards to stream layered videos.Users under different channel conditions decode different amounts of layers and obtain different video qualities.Difference between users' QoEs accounts for the indispensability of stimulating user cooperation in relaying video layers,so that video qualities,QoEs and fairness in the system get boosted.To overcome the two key challenges in inventive of user cooperation in SVC multicast,i.e.,asymmetric information between users and delay stringency in video streaming,a contract-based incentive mechanism with fast convergence is proposed in this paper.The main research contents and contributions are summarized as follows:1.The problem of relay selection in SVC multicast is formulated as a market with multiple principals and multiple agents,where principals make rules based on the contract theory,agents provide video layers and receive reward.Different from traditional application of the contract theory in asymmetric information problem,we apply it to multito-multi scenario with corresponding resource schedule scheme.2.A three-stepped scheduling scheme is proposed to make video layer streaming pair.To begin with,principals design contracts with several items consisting of service and reward.Subsequently,agents preselect an item in each contract and report to the BS.Finally,the BS matches users based on KM(Kuhn-Munkras)algorithm to maximize social welfare.3.As an improvement of former contract parameter determination strategy,the Matching-Aware strategy is proposed to make it free of the probability distribution of relay types and more competitive in matching process.Numerical results corroborate that the proposed Matching-Aware strategy conforms to the basic constrains of the contract theory and achieves higher average video qualities and social welfare.