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Unformatted text preview: IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 10, NO. 8, DECEMBER 2008 1465 Video Capacity of WLANs With a Multiuser Perceptual Quality Constraint Jing Hu, Sayantan Choudhury , Member, IEEE , and Jerry D. Gibson , Fellow, IEEE Abstract As wireless local area networks (WLANs) become a part of our network infrastructure, it is critical that we understand both the performance provided to the end users and the capacity of these WLANs in terms of the number of supported flows (calls). Since it is clear that video traffic, as well as voice and data, will be carried by these networks, it is particularly important that we investigate these issues for packetized video. In this paper, we in- vestigate the video user capacity of wireless networks subject to a multiuser perceptual quality constraint. As a particular example, we study the transmission of AVC/H.264 coded video streams over an IEEE 802.11a WLAN subject to a constraint on the quality of the delivered video experienced by r% (75%, for example) of the users of the WLAN. This work appears to be the first such effort to address this difficult but important problem. Furthermore, the methodology employed is perfectly general and can be used for different networks, video codecs, transmission channels, protocols, and perceptual quality measures. Index Terms Multiple users, perceptuial video quality, video capacity, WLAN. I. INTRODUCTION A. Motivation R ECENTLY there has been broad interest in using packe- tized video over wireless networks such as IEEE 802.11 wireless local area networks (WLANs). As a result, there have been numerous studies related to video over WLANs [1]. In particular, research has been performed on cross-layer designs for video over WLANs, including a) designing the network matched to the special characteristics of video [2][4], b) compressing and transporting video adaptively with respect to the lower layers in the OSI stack of the network [5][12], and c) solving the cross-layer design problem as an optimization problem with the objective of selecting a joint strategy across multiple OSI layers [13][15]. However, the video capacity of a WLAN in terms of the maximum number of video users the WLAN can support, a fundamental limit in video communica- tions over WLANs, has received relatively little attention. The reasons are as follows. First, videos can be compressed to essentially any desired bit rate, resulting in different reconstructed video quality, and Manuscript received November 01, 2007; revised July 16, 2006. Current ver- sion published December 10, 2008. This work was supported by the California Micro Program, Applied Signal Technology, Cisco, Dolby Labs, Inc., Sony-Er- icsson, and Qualcomm, Inc., and by NSF Grants CCF-0429884, CNS-0435527, and CCF-0728646. The associate editor coordinaitng the review of this manu- script and approving it for publication was Prof. Deepa Kundur....
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This note was uploaded on 11/30/2011 for the course CIS 6930 taught by Professor Staff during the Fall '08 term at University of Florida.

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