| 1. |
- Forsgren, Daniel, et al.
(författare)
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Objective End-to-End QoS Gain from Packet Prioritization and Layering in MPEG-2 Streaming
- 2002
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Ingår i: International Packetvideo workshop 2002.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Layered video coding as well as prioritized packet scheduling are two well-known methods that may improve the quality of service level in real-time applications with high bandwidth requirements, and are used over packet switched networks. However, it is often difficult to get an idea of, and to quantify, the actual gains that may be achievable, especially from an end-to-end perspective.In this paper, we present some experimental results from using temporally layered MPEG-2 video combined with basic per-layer IP packet prioritization. The goal has been to find out if a basic scheme is useful at all in combination with this particular source coding method, and if so, how much the objective video quality can be increased during bandwidth-constrained periods. The quality is measured in terms of PSNR and the results are compared to the case of equal packet priority. Also, different packet sizes as well as packet queuing disciplines are used. We conclude that using even a relatively simple temporal layering strategy in combination with packet prioritization can quite significantly improve the end-to-end quality of MPEG-2 video, especially in moderately bandwidth constrained situations. Furthermore, packet size and queuing discipline is found to have an impact.
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| 2. |
- Khatib, Iyad Al, et al.
(författare)
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Wireless LAN Access Points as Queuing Systems : Performance Analysis and Service Time
- 2003
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Ingår i: Mobile Computing and Communications Review. - : Association for Computing Machinery (ACM). - 1559-1662 .- 1931-1222. ; 7:1, s. 28-30
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Tidskriftsartikel (refereegranskat)abstract
- Since the approval of the IEEE 802.11b by the IEEE in 1999, the demand for WLAN equipment and networks has been growing quickly. We present a queuing model of wireless LAN (WLAN) access points (APs) for IEEE 802.11b. We use experimentation to obtain the characteristic parameters of our analytic model. The model can be used to compare the performance of different WLAN APs as well as the QoS of different applications in the presence of an AP. We focus on the delay introduced by an AP. The major observations are that the delay to serve a packet going from the WLAN medium to the wired medium (on the uplink) is less than the delay to serve a packet, with identical payload, but travelling from the wired medium to the WLAN medium (on the downlink). A key result is an analytic solution showing that the average service time of a packet is a strictly increasing function of payload.
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| 3. |
- Österberg, Patrik, et al.
(författare)
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Receiver-controlled dynamic forward error correction for video streaming
- 2003
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The proportion of real-time traffic, being transported over IP networks, appears to be ever increasing. Real-time traffic may, for example, consist of video and audio data, which have real-time constraints in terms of metrics such as maximum delay, delay jitter and packet loss. Bounds on such metrics can be hard to satisfy by the network, hence there is an incentive to make multicast streaming of video more packet-loss resilient. Receiver-driven layered multicast has been proposed for dealing with band limitations, and environments with heterogeneous terminals. We have extended these ideas to handle packet loss, by adding receiver-driven forward error control (FEC). The aim of this paper is to further improve the performance, by optimizing the distribution of the error protection between the layers.
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| 4. |
- Österberg, Patrik, et al.
(författare)
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Receiver-Controlled Joint Source/Channel Coding on the Application Level, for Video Streaming over WLANs
- 2003
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Ingår i: The 57th IEEE Semiannual Vehicular Technology Conference, 2003. VTC 2003-Spring.. - 0780377583 ; , s. 1558-1561, s. 1558-1561
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Konferensbidrag (refereegranskat)abstract
- The proportion of real-time traffic, being transported over internet protocol (IP) networks, appears to be ever increasing. Real-time traffic may, for example, be video and audio, which have real-time constraints such as maximum delay and delay jitter. Such requirements can be hard to satisfy in a wired infrastructure, and are even more so in a wireless network. Therefore there is a need to make transmission over wireless local area networks (WLANs) more reliable. The aim of this paper is to outline a proposal of such a scheme, which enables efficient transmission of MPEG-4 video over an IEEE 802.11b WLAN, and to experimentally verify its efficiency. Receiver-driven layered multicast has been proposed before, for dealing with band limitations and environments with heterogeneous terminals. We extend these ideas to handle packet loss, by adding receiver-driven unequal error protection (UEP). The proposal can be viewed as receiver-controlled joint source/channel (JSC) coding on the application level.
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