The effects of packet reordering in a wireless multimedia environment

Packet reordering has been shown to be an ever-increasing phenomenon on the Internet and must be taken into account when considering performance analysis of both fixed, wireless and mixed media networks. Previous work (J. Bennet et al., 1999) has demonstrated that TCP suffers degraded performance in situations of high packet reordering. This paper will consider why video traffic over UDP also performs badly in situations of high packet reordering, due to the temporal inter-packet dependencies introduced by the MPEG video encoding structure. Wireless networks are especially prone to problems due to the higher levels of link layer retransmissions found in noisy wireless environments. An experimental investigation into the effects of video packet reordering using the Windows Media streaming system is presented. A method for invoking packet reordering is introduced, and a tool for client-side measurements of video quality is presented. Typical measurements of video performance undergoing reordering are shown, with a study of buffering occupancy at the client, and the potential impact this could have on video packet reordering demonstrated.