An Experimental Investigation of Parallel Multimedia Streams over IEEE 802.11e WLAN Networks using TXOP

In this paper we perform an experimental investigation of the IEEE 802.11 TXOP facility to enhance the transmission of parallel multimedia streaming sessions through efficient bandwidth reservation and explicitly consider both the audio and video streams. The delay constraints associated with the audio and video streams that comprise a multimedia session pose the greatest challenge since real-time multimedia is particularly sensitive to delay as the packets require a strict bounded end-to-end delay. We show how the TXOPlimit parameter can be efficiently dimensioned to reduce the tranmission delay for the video frames. Due to tis frame-based nature, video applications are considered to be bursty as each video frame is typically transmitted as a burst of packets. The size of the burst is related to the size of the video frame. The TXOP facility is particularly suited to efficiently deal with this burstiness since it can be used to reserve bandwidth for the duration of the packet burst. Through experimental investigation, we show that there is a significant performance improvement for the video streams by using the TXOPlimit parameter however there is no such improvement for the audio streams. We show that over-dimension the TXOPLimit parameter can cause the video stream to seize too much bandwidth which results in a deterioration in performance for the other competing traffic streams. This deterioration becomes more prominent as the number of parallel multimedia streams increases. We show that there is a performance improvement to all traffic streams by providing differentiated service to the constitutent I, P, and B video frame types in conjuction with the TXOP facility