spaper03_slides - Scene-Change Aware Dynamic Bandwidth...

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Scene-Change Aware Dynamic Bandwidth Allocation for Real-Time VBR Video Transmission Over IEEE 802.15.3 Wireless Home Networks - Yi-Hsien Tseng, Eric Hsiao-Kuang Wu , and Gen-Huey Chen Presented By : - Pranay Kothari - Nilu Nalini
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MOTIVATION Recent growth electronic devices and wireless networks smart phones, media servers, set-top boxes, flat-panel screens, and digital camcorders required “wire-like” performance
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IEEE 802.15.3 standard For high-rate wireless personal area networks (WPANs) Low cost Low power High data rates and Robust quality of service (QoS)
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WPAN - brief introduction Uses TDMA to allocate channel time among devices when B/W available Elementary topology unit: piconet Ad hoc wireless network Individual devices can exchange frames Master PNC and slave DEVs PNC : admission control and channel-time allocation Timing realized by superframe Beacon, contention access period (CAP), and channel time- allocation period (CTAP)
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WPAN…. Before transmitting data DEV has to send a request message to the PNC first PNC decides if request can be accepted according to the available channel time If accepted, PNC announces in next beacon
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Constant bit rate (CBR) encoding may reduce the picture quality , particularly at scene changes or intervals with significant detail or motion VBR encoding can offer higher picture quality and greater opportunity for statistical multiplexing gains MPEG-1 (used by VCD), MPEG-2 (DVD) and MPEG-4 are three instances of VBR
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CBR support for networks that do not support dynamic B/W allocation Require smoothing buffers coding kernels (which naturally generate bits at a varying rate) and the networks Luckily WPANs support dynamic B/W allocation hence smoothing buffers not needed less buffer delay and near perceptually constant picture quality
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Peak/mean ratio for VBR is usually high Requesting CBR for peak rate leads to low channel utilization Lower CBR may cause more delay, more buffer and more packet loss Real time VBR Next frame requirement not known Must predict channel time requirement for subsequent frames Only errors of prediction need to be buffered Higher channel utilization, less buffer, and less delay can be achieved as long as the prediction is accurate enough
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Existing Predictor LMS Predictors based on adaptive least mean square (LMS) algorithm are more suitable for a DEV simplicity and relatively good performance performance may degrade when a scene change occurs This paper modifies variable step-size LMS (VSSLMS) algorithm to relieve the prediction errors on scene changes Then using modified VSSLMS, authors proposed a dynamic bandwidth allocation scheme which is scene- change aware and can guarantee the delay bound of real-time VBR videos
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WPAN isochronous stream management Scenario: video conference DEV transmiting VBR video to a TV DEV has to send a channel time request to the PNC during a CAP DEV informed by beacon from the PNC of when it can start transmission
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Isochronous stream management in an IEEE 802.15.3 piconet
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spaper03_slides - Scene-Change Aware Dynamic Bandwidth...

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