An Experimental Investigation of the Effects of Contention on Video Streaming Applications over IEEE 802.11b WLAN Networks (original) (raw)
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Study of the Behaviour of Video Streaming over IEEE 802.11b WLAN Networks
IEEE International Conference on Wireless and Mobile Computing, Networking and Communications, 2006. (WiMob'2006), 2006
The performance of video streaming over WLAN networks is not only influenced by the state of the network but also by the encoding configuration parameters of the video stream, such as the video content being streamed, how the video is encoded and how it is transmitted. In this paper, we analyse the unique delay characteristic of video streaming applications in a WLAN environment. We show that the "burstiness" of video is due to the frame-based nature of encoded video. We show how each video frame is transmitted as a burst of packets that is queued at the Access Point causing the delay to exhibit a sawtooth-like characteristic over time that is related to the frame rate and frame structure of the encoded video. To our knowledge, this sawtooth-like characteristic of video streaming over WLAN has not been previously reported on. In this paper, not only do we consider the end-to-end delay, but more importantly we consider the total delay required to transmit the entire video frame. We present experimental results for VBR and CBR video streams and calculate the upper bounds on video encoding parameters for streaming realtime interactive video over a WLAN.
2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio Communications, 2006
The bursty nature of video streaming applications is due to the frame-based structure of video and this has an important impact on the resource requirements of the WLAN, affecting its ability to provide Quality of Service (QoS) particularly under heavily loaded conditions. In this paper we analyse this bursty behaviour in depth. We show how each video frame is queued at the AP causing the packet delay to vary in a sawtooth manner that is related to the frame rate, the number of packets per video frame, and the packet size. We infer the maximum background traffic load that can be supported so that it does not negatively impact on the video streaming application. We demonstrate that there is a critical threshold load value above which the AP can no longer reliably support the video stream and compare it to the threshold load values calculated through analysis. Using this knowledge, the AP can employ resource allocation mechanisms to regulate the incoming traffic to the AP transmission queue so that QoS can be provided for streaming applications.
2006
Real-time multimedia streaming applications require a strict bounded end-to-end delay and are considered to be bursty as each video frame is typically transmitted as a burst of packets. In this paper we show how the distribution of video frame sizes can be used to efficiently dimension the IEEE 802.11e TXOP limit parameter to efficiently deal with this burstiness in order to enhance the transmission of real-time video streaming services. Through experimental investigation, we show that by using the mean video frame size to dimension the TXOP limit parameter, the transmission delay for the video frame is reduced by 67% under heavily loaded conditions. Other techniques investigated in this paper include applying the TXOP facility separately to each of the constituent I, P, and B video frame types.
2007
Multimedia streaming applications have a large impact on the resource requirements of the WLAN. There are many variables involved in video streaming, such as the video content being streamed, how the video is encoded and how it is sent. This makes the role of radio resource management and the provision of QoS guarantees extremely difficult. For video streaming applications, packet loss and packets dropped due to excessive delay are the primary factors that affect the received video quality. In this paper, we experimentally analyse the effects of contention on the performance of video streaming applications with a given delay constraint over IEEE 802.11 WLANs. We show that as contention levels increase, the frame transmission delay increases significantly despite the total offered load in the network remaining constant. We provide an analysis that demonstrates the combined effects of contention and the playout delay constraint have on the video frame transmission delay.
Performance Analysis of Video Transmission Over IEEE 802.11a/e WLANs
IEEE Transactions on Vehicular Technology, 2007
This paper presents efficient mechanisms for delaysensitive transmission of video over IEEE 802.11a/e Wireless Local Area Networks (WLANs). Transmitting video over WLANs in real time is very challenging due to the time-varying wireless channel and video content characteristics. This paper provides a comprehensive view of how to adapt the quality of service signaling, IEEE 802.11e parameters and cross-layer design to optimize the video quality at the receiver. We propose an integrated system view of admission control and scheduling for both contention and poll-based access of IEEE 802.11e Medium Access Control (MAC) protocol and outline the merits of each approach for video transmission. We also show the benefits of using a cross-layer optimization by sharing the Application, MAC, and Physical layer parameters of the Open Systems Interconnection stack to enhance the video quality. We will show through analysis and simulation that controlling the contention-based access in IEEE 802.11e is simple to realize in real products and how different cross-layer strategies used in poll-based access lead to a larger number of stations being simultaneously admitted and/or a higher video quality for the admitted stations. Finally, we introduce a new concept called time fairness, which is critical in enhancing the video performance when different transmitter-receiver pairs deploy different cross-layer strategies.
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2003
Live video streaming service, which is common nowadays in the Internet, is supposed to be very challenging and demanding service in next-generation wireless networks. However, both limited quality of service (QoS) support and unstable quality of the air interface can restrain its wide deployment. In this paper we consider live video streaming over IEEE 802.11b wireless local area network (WLAN), which is claimed to be used as a part of layered infrastructure of next-generation mobile systems to provide coverage in highly populated areas . We performed our experiments under different signal-to-noise ratios (SNRs) and different competing TCP and UDP traffic volumes. The main conclusion of our paper is that despite a common belief live streaming multimedia services are not ready for wide implementation in hot-spot areas where both high traffic volume and relatively weak signal strength (less than 30 dB) may deny the service easily.
Implementation Issues for a Video Streaming Server in Ieee 802.11 e Wlans
Recent years have seen a proliferation of real-time multimedia traffic over a more and more heterogeneous Internet. Video streaming at high, consistent quality over wireless links proves to be a difficult task. Several optimization techniques have been proposed and studied, mostly through theoretical analysis and simulation. This article describes the implementation of a cross-layer H.264 video streaming server and the evaluation of its performance in IEEE 802.11e WLANs. Measurements present the benefits of employing several key cross-layer mechanisms which aim to improve the video transmission quality over wireless links. A cross-layer signaling solution is implemented, which addresses important QoS issues between user-space and the kernel traffic control and device driver components. Network support for efficient multiqueue transmission is enabled in the Linux network driver. In addition, the paper discusses the implementation of an enhanced scheduling scheme for the receive-side, in order to provide prioritization of video streams over elastic traffic, and also for better control of latency and improved throughput for multimedia flows.