Joint power and subcarrier allocation for layered multicast streaming with proportional rate ratio constraint in OFDMA wireless networks

This paper addresses the optimal multicast resource allocation problem in orthogonal frequency division multiple access (OFDMA) system, where the fine granularity scalability (FGS) video coding is exploited to perform source coding. With FGS, the multicast information is coded into base layer data and enhancement layer data, and there is a predefined proportional rate ratio between the transmission rate of the base layer and the enhancement layer so that an approximate playing progress can be maintained at the receiver. The multicast resource allocation problem is formulated as a mixed binary integer programming problem with the objective of maximizing the network total throughput while maintaining the required proportional rate ratio under a total transmit power constraint for the base station. The problem is solved by using Lagrangian dual decomposition method, resulting in an optimal joint subcarrier and power allocation algorithm with computational complexity being linear with the number of subcarriers. Numerical simulations are conducted to evaluate the performance of the proposed algorithm in terms of convergence and throughput. Simulation results show that the proposed optimal algorithm converges very fast and significantly outperforms the available suboptimal schemes.