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The 1-Byte Wireless QoS Solution: Scheduling Algorithms for QoS Wireless Channels

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The 1-Byte Wireless QoSSolution: Scheduling Algorithmsfor QoS over Wireless ChannelsRahulMangharam2002Advisor: Prof. RajkumarThesis filed as partial requirement for Masters of Science, August 2002The 1-Byte Wireless QoS SolutionMasters ThesisRahul MangharamDept. of Electrical and Computer EngineeringCarnegie Mellon University([email protected])Advisor: Professor Ragunathan RajkumarDept. of Electrical and Computer EngineeringCarnegie Mellon University(raj @ ece.cmu.edu)The 1-Byte Wireless QoS SolutionAbstractFor bursty traffic with a large peak-to-average ratio and a stochastic channel, is itpossible to minimize the response time of every frame while maximizing the effectivechannel utilization and maintain fairness? This is the question fee resolve in this paper.In wireless networks with a single shared channel, channel access is a core issue forflows with throughput and timeliness requirements on the uplink. This paper presents adetailed MPEG-4 packet-level simulation comparing two Medium Access Control(MAC) architectures and four scheduling strategies that cover a range of classes:Dynamic-TDMA, Proportional Share Algorithms, Real-Time Scheduling Algorithms,and Size-based Scheduling Algorithms.Our results demonstrate that only a single byte is necessary for Quality of Service (QoS)support in infrastructure-based wireless networks. Our adaptation of the ShortestRemaining Processing Time (SRPT) algorithm, Fair-SRPT, is a superior schedulingalgorithm and outperforms other algorithms in terms of QoS performance, channelutilization efficiency and response time under all utilization levels and error rates. Inaddition, a MAC protocol based on dynamic superframes and group polling scales wellwith higher data rates and under all error rates. An attractive feature of the proposedapproach is that it can be implemented with no modifications to the IEEE 802.11estandard. We have extended the ns-2 network simulator to model centralized wirelessMAC protocols (e.g. IEEE 802.11e and high-rate 802.15.3), and a modular frameworkto plug-in scheduling algorithms.Keywords: Scheduling algorithms, wireless MAC, QoS, link layer protocols, MPEG-4.Rahul Mangharam2The l-Byte Wireless QoS SolutionContents4.14.24.2.14.2.24.2.34.2.455.15.25.366.16.288.18.28.38.48.58.5.18.5.28.5.38.5.48.699.19.1.19.29.2.19.39.49.4.19.5Introduction ............................................................................... 4Problem Statement ........................................................................ 6Solution Approach ........................................................................ 8Background ................................................................................. 9The Medium Access Control LayerTraffic Types and NotationReal-Time TrafficMultimedia MPEG-4 TrafficNon-Real Time TrafficTraffic NotationShared Resource Scheduling ..................: ........................................ 11Real-Time SchedulingProportional Share Resource AllocationSize-based SchedulingMedium Access Control Protocols ...................................................... 15Per-packet and per-flow polling - IEEE 802.11/eGroup Polling - IEEE 802.15.3Overview of MPEG-4 Digital Video ...................................................16Performance Analysis ........................... ......................................... 17Selecting Criterion for Comparable Scheduling AlgorithmsSimulation EnvironmentMAC functions supportedAssumptionsPerformance MetricsJob Failure RateMean Response TimeMean Response Time as a function of average datarateIdle Capacity UsageMethodologyGroup Polling Simulation Results and Analysis ....................................22Job Failure Rate Vs Channel utilizationWhy F-SRPT outperforms other scheduling algorithms?Job Failure Rate Vs Packet Error RateWhy F-SRPT outperforms other scheduling algorithms?Mean Response Time Vs Channel UtilizationFairness of F-SRPTComparison of Fair-SRPT and SRPTEffect of Dynamic SuperframesRahul Mangharam 3The l-Byte Wireless QoS Solution10 Observations .............................................................................3410.1 The 1-Byte Solution10.2 Scalability of MAC10.3 Deadline Awareness12 Conclusion ....................................................................................3413 Acknowledgements ..........................................................................3514 References ....................................................................................36Appendix A: Per-Flow Polling Simulation Results ..........................................38Rahul Mangharam 4The l-Byte Wireless QoS Solution1. IntroductionThe wireless link is considered a bottlenecked resource due to the relative low dataratecapability and difficulty in effectively allocating the shared resource to provide serviceguarantees [1]. In networks with a shared channel, link access is a core issue for flowswith QoS (throughput and timeliness) requirements on the uplink. Whether the wirelesslink is at the edge of the network or between multiple hops in an ad hoc network, thecommon resource allocation challenges are due to the stochastic nature of the channel,the network being interference dominated and the bursty nature of multimedia traffic.QoS is defined as the ability of the system to maintain timeliness guarantees for framesdelivered over a shared link.The goal of this paper is to outline and evaluate a simple and efficient scheme to delivertimeliness guarantees for MPEG-4 multimedia traffic in a wireless network with acentralized medium access controller (MAC)° The centralized controller or access point(AP) enjoys privileged access to the channel and is responsible for allocating mediumaccess opportunities to every associated node. The scheduling algorithm within the AParbitrates which node accesses the medium when, for how long and on whichlogical/physical channels. We aim to maximize the user perceived quality of service byminimizing the response time for delivering frames across a wireless link. The focus ison the particular cases of frames sent from a node to its associated AP and from onenode directly to another and not via the commonly


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