MAC-Layer Support for Real-Time Video over IEEE 802.11 DCF Networks

Jong-Ok KIM
Hideki TODE

IEICE TRANSACTIONS on Communications   Vol.E89-B    No.4    pp.1382-1391
Publication Date: 2006/04/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e89-b.4.1382
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Multimedia Systems for Communications
video streaming,  IEEE 802.11 DCF,  packet bursting,  channel access,  

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IEEE 802.11 DCF is a contention-based channel access protocol, and medium access delay greatly increases as the number of contending stations in a service area increases. This severely affects on delay-sensitive video applications. In this paper, we focus on MAC-layer solutions for realizing high quality video transmission in 802.11 DCF networks. A new channel access protocol based on the timestamp (TS) of video packets is proposed for real-time video. The TS information is carried by RTP header from the video application to 802.11 MAC. For video packets with the same RTP TS, they are simultaneously transmitted in a single channel access. Additional contention and back-off processes can be avoided because the whole packets of a video frame are completely delivered. The proposed TS-based access protocol can be easily implemented by the DCF with packet bursting. In addition, it is backward compatible to the legacy DCF. Extensive simulations show that the TS-based channel access achieves lower cumulative distributions of application-level video frame delay when compared to the DCF protocol.