MMC05-1: An Adaptive FEC Scheme to Reduce Bursty Losses in a 802.11 Network

One of the challenges that video transmission over wireless networks (such as IEEE 802.11) must face is the packet loss that can heavily decrease the received video quality. What makes the challenge more difficult is the bursty nature of wireless losses. Many video decoders can mask the effects of small amounts of random packet loss, however, most are unable to successfully hide the effects of burst losses (periods with high loss data rate). Forward error correction (FEC) is a technique extensively adopted to increase error resilience. In unicast transmission, the FEC redundancy is usually added adaptively on the basis of a loss pattern feedback. In many cases the loss pattern is represented through a very simple statistics: the average packet error rate (PER). This paper proposes a technique to adaptively introduce FEC redundancy that exploits a feedback scheme based on a 4-state Markov model to describe the loss pattern. The model allows us to obtain a description of the loss pattern in terms of burst and gap length and density. The feedback is based on the RTCP extended Report - IP Video Metrics Report Blocks that includes statistics on error patterns, such as the average PER, burst length and density. Our simulation results show that the proposed method smoothes out the burst losses and outperforms solutions based on the average PER.