The fundamental tradeoff in a WLAN with multiple video users is between the number of video users the WLAN can support and the perceptual quality each user experiences. Our previous work has investigated the delivered AVC/H.264 video quality over 802.11a WLANs with multipath fading. In this paper we study two extreme scenarios to formulate the upper and lower boundaries for video user capacity of an 802.11a WLAN operated under the contention based distributed coordination function (DCF): the worst scenario is when all users happen to be sending/receiving their intra-coded (I) frames at the same time and the best scenario is when all users happen to be coordinated in I frame refreshing. To calculate the video user capacity boundaries we study the dependence of coded video data rate on the properties of individual videos as well as the major video coding parameters: group of picture size (GOPS), quantization (QP) and video packet payload size (PS). Two heuristic formulas are proposed to calculate approximately the I frame and inter-coded (P) frame sizes respectively. The video user capacity boundaries are further explored in the context of the delivered video quality constraints investigated in our previous work.
['Jing Hu', 'Sayantan Choudhury', 'Jerry D. Gibson']
Perceptual quality constrained video user capacity of 802.11a WLANs with multipath fading