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Delay Bound Rich Image Delivery over WLANs . Shira S. Krishnan Georgia Tech, ECE Multimedia Communications Laboratory. Introduction. Wireless LANs are being used extensively across homes, offices and campuses.

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Delay bound rich image delivery over wlans

Delay Bound Rich Image Delivery over WLANs

Shira S. Krishnan

Georgia Tech, ECE

Multimedia Communications Laboratory


Introduction
Introduction

  • Wireless LANs are being used extensively across homes, offices and campuses.

  • The 802.11b/g technology, popular today is used for low bandwidth requirements like voice, data and low density image applications.

  • For high density image and hi-def video transmission, next generation 802.11 technologies like 802.11n are being considered.

  • Compatibility of 802.11n with existing 802.11b/g or 802.11a installations is also of great interest.


Background
Background

A comparison of 802.11 technologies is listed in

the table below

  • Protocol


802 11n
802.11n

802.11n provides great advantages in terms of higher bandwidth and range

  • Reliability - Greater SNR

  • Predictable Coverage – Use of multiple spatial streams means fewer dead spots in a coverage area

  • Throughput – Higher data rates

    It achieves this through a variety of MAC enhancements like

  • Frame Aggregation – Mac Service Data Unit (MSDU) and Message Protocol Data Unit (MPDU) aggregation – single radio preamble for each transmission; Maximum frame size increased to 64 KB

  • MSDU – More efficient – Aggregation of Ethernet frames; MPDU – Aggregation of 802.11 frames

  • Block Acknowledgements – Ack for aggregated frames

  • Reduced Inter-frame Spacing – Lower overheads; can be used only in greenfield deployments


Traffic of interest
Traffic of Interest

  • Traffic of Interest is High Density Images that have a delay bound of 5 seconds.

  • Three different sizes of images are considered for analysis -- 10, 100 and 1000 Mb images

  • Analysis of these images is done in the raw format, Mathematically lossless compressed form of 2:1 and Diagnostically lossless compressed form of 10:1


Interactive time as a parameter
Interactive time as a parameter

  • For certain applications like image conferencing, reliable transmission is necessary over the network within specified time know as the interactive time

  • For such application TCP will have to be used to ensure reliability and high speed network used as a transmission medium to ensure satisfaction of delay bound requirements


Problem definition
Problem Definition

  • Identify a wireless system that is most suited for rich media delivery within a set interactive timeframe using a network designed to handle other forms of traffic.


Assumptions
Assumptions

  • Packet losses not considered

  • Wireless link failures not considered

  • 802.11n draft 2.0 specs used to model systems

  • Ns2 models modified suitably to reflect the scenario of interest


Results
Results

Size in Mb



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