Optimal bandwidth adaptation for layered video multicasting in IEEE 802.11 WLANs

With widespread adoption of wireless local area networks (WLANs), video dissemination over wireless links such as video telephony, video gaming, and mobile TV broadcasting have become fast growing applications. Since wireless channel is error-prone, the receiving data rate of mobile stations (MSs) needs to be selected properly to avoid high packet loss rate and serious service quality degradation. In addition, to enhance reliability of video multicasting, application-layer forward error correction (AL-FEC) is a promising approach against packet losses. However, at the WLAN access point (AP), how to adaptively select a proper combination of transmission rate and AL-FEC code rate to multicast layered videos in WLANs becomes an important issue. In this paper, we propose a reward-based bandwidth adaptation mechanism to dynamically determine the best combination of transmission rate and AL-FEC code rate to multicast layered video in IEEE 802.11 WLANs. Our goal is to maximize the system reward which represents the video quality experienced on all users, under a given resource budget. A reward-based policy iteration algorithm is proposed as a heuristic approach to solve the optimization problem and its performance is compared with that of two baseline algorithms: exhaustive search and genetic algorithm. We demonstrate the performance of our approach via simulations. The simulation results show our approach can provide better service quality even through system resource is sparse.