An Experimental Study of Packet Loss and Forward Error Correction in Video Multicast over IEEE 802.11b Network
Video multicast over Wireless Local Area Networks (WLANs) faces many challenges due to varying channel conditions and limited bandwidth. A promising solution to this problem is the use of packet level Forward Error Correction (FEC) mechanisms. However, the adjustment of the FEC rate is not a trivial issue due to the dynamic wireless environment. This decision becomes more complicated if we consider the multi-rate capability of the existing wireless LAN technology that adjusts the transmission rates based on the channel conditions and the coverage range. In order to explore the above issues we conducted an experimental study of the packet loss behavior of the IEEE 802.11b protocol. In our experiments we considered different transmission rates under the broadcast mode in indoor and outdoor environments. We further explored the effectiveness of packet level FEC for video multicast over wireless networks with multi-rate capability. In order to evaluate the system quantitatively, we implemented a prototype using open source drivers and socket programming. Based on the experimental results, we provide guidelines on how to efficiently use FEC for wireless video multicast in order to improve the overall system performance.We show that the Packet Error Rate (PER) increases exponentially with distance and using a higher transmission rate together with stronger FEC is more efficient than using a lower transmission rate with weaker FEC for video multicast.