Improving IEEE 802.11 WLAN: QoS and Throughput Perspective

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Improving IEEE 802.11 WLAN: QoS and Throughput Perspective. Sunghyun Choi, Ph.D. Assistant Professor School of Electrical Engineering Seoul National University E-mail: schoi@snu.ac.kr URL: http://ee.snu.ac.kr/~schoi. Introduction to My Group in SNU. - PowerPoint PPT Presentation

Text of Improving IEEE 802.11 WLAN: QoS and Throughput Perspective

  • Improving IEEE 802.11 WLAN: QoS and Throughput PerspectiveSunghyun Choi, Ph.D.Assistant ProfessorSchool of Electrical EngineeringSeoul National UniversityE-mail: schoi@snu.ac.krURL: http://ee.snu.ac.kr/~schoi

  • Introduction to My Group in SNUMultimedia & Wireless Networking Lab. (MWNL) Within School of Electrical Engineering, Seoul National UniversityStarted September 2003One of the youngest groups in SoEE, SNU1 (+2) Ph.D. & 3 masters students

  • Introduction to My Group in SNU (Contd)Working on WLAN MAC and aroundResource management power, rate, QoS & mobilityTCP/UDP over WLAN4G wireless network Cross-layer design(Sensor networks)

  • ContentsIntroductionQoS provisioningThroughput enhancementConclusion

  • Introduction to IEEE 802.11 WLANWireless Ethernet with comparable speed Supports up to 11 and/or 54 Mbps within >100 m rangeEnable (indoor) wireless and mobile high-speed networkingRuns at unlicensed bands at 2.4GHz and 5GHzConnectionless MAC and multiple PHYs

  • Limitations of Current 802.11Lack of QoS supportBest-effort service with contention-based MACLow throughput due to large overhead< 5 Mbps throughput at 11 Mbps 802.11b link

    My group is currently working on improving both aspectsWill show only preliminary results here

  • QoS Improvement

  • Emerging IEEE 802.11e MACNew draft standard for QoS provisioningExpected to be finalized by early next yearDefining a new MAC backward compatible with the legacy MACLegacy 802.11 MAC DCF (+ PCF) 802.11e MAC HCF with two access mechanismsControlled channel access Contention-based channel access (EDCA)

  • 802.11 Distributed Coordination Function (DCF)Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

    Busy Medium

    SIFS

    PIFS

    DIFS

    Backoff Window

    Slot Time

    Defer Access

    Select Slot and decrement backoff as long as medium stays idle

    DIFS

    Contention Window

    Immediate access when medium is idle >= DIFS

    Next Frame

  • 802.11e Access Category (AC)Access category (AC) as a virtual DCF4 ACs implemented within a QSTA to support 8 prioritiesMultiple ACs contend independentlyThe winning AC transmits a frame

    Backoff AIFS[0] BO[0]

    AC0

    AC1

    AC2

    AC3

    Backoff AIFS[1] BO[1]

    Backoff AIFS[2] BO[2]

    Backoff AIFS[3] BO[3]

    Virtual Collision Handler

    Transmission Attempt

  • Differentiated Channel Access of 802.11e EDCAEach AC contentds with AIFS[AC] (instead of DIFS) and CWmin[AC] / CWmax[AC] (instead of CWmin / CWmax)

    Busy Medium

    SIFS

    PIFS

    AIFS[AC]

    Backoff Window

    SlotTime

    Defer Access

    Select Slot and decrement backoff as long as medium stays idle

    AIFS[AC]+SlotTime

    Contention Window from [1,1+CWmin[AC]]

    Immediate access when medium is idle >= AIFS[AC]+SlotTime

    Next Frame

  • Simulation Results - DCF vs. EDCADelay comparison2 video (1.5 Mbps CBR), 4 voice (36.8 kbps CBR), 4 data (1 Mbps Poisson)

  • Our Software-Based Approach for RT Traffic SupportIEEE 802.11e is not available yetEven if it becomes available, many existing legacy 802.11 APs will be thereEspecially, for WISP with many deployed APs, replacing existing APs costs a lot of money Software (or firmware) upgrade-based approach is very desirable at least in the short term

  • System Architecture

  • Measurement ConfigurationLinux + HostAP driver for Intersil chipsetsone RTP (1.448 Mbps CBR) + one FTPImplement dual queue

  • One-Way Delay of RTP Traffic OriginalModified

  • Percentage Gain in Performance Parameters

    Chart2

    -0.0384315762

    0

    -0.1034482759

    -0.25

    0

    -0.342019544

    -0.28125

    -0.4

    -0.3333333333

    Percentage

    Percentage Gain in Performance Parameters

    Sheet2

    Test 2one sever-one clientPercentage

    origianaltwo queueGain

    ThroughputTCP3.7363.8162.14%

    RTP1.4481.447-0.07%

    JitterAvg.2.72.0-25.93%

    Max.4.03.0-25.00%

    min.1.01.00.00%

    One-way delayAvg.30.114.1-53.16%

    Max.34.029.0-14.71%

    min.27.010.0-62.96%

    Max delay variation25.012.0-52.00%

    -233.751%

    Test 1one sever-one clientPercentage

    origianaltwo queueGain

    ThroughputTCP3.8513.703-3.84%

    RTP1.4481.4480.00%

    JitterAvg.2.92.6-10.34%

    Max.4.03.0-25.00%

    min.2.02.00.00%

    One-way delayAvg.30.720.2-34.20%

    Max.32.023.0-28.13%

    min.30.018.0-40.00%

    Max delay variation27.018.0-33.33%

    Sheet1

    test4one sever-one clientPercentage Gaintest4one sever-one clientPercentage

    origianalone queuetwo queuetwo - oritwo - oneorigianaltwo queueGain

    ThroughputTCP3.8512.9953.703-3.843%23.639%ThroughputTCP3.8513.703-3.843%

    RTP1.4481.4471.4480.000%0.069%RTP1.4481.4480.000%

    JitterAvg.2.9003.3082.600-10.345%-21.403%JitterAvg.2.9002.600-10.345%

    Max.4.0005.0003.000-25.000%-40.000%Max.4.0003.000-25.000%

    min.2.0002.0002.0000.000%0.000%min.2.0002.0000.000%

    One-way delayAvg.30.70018.00020.200-34.202%12.222%One-way delayAvg.30.70020.200-34.202%

    Max.32.00015.00023.000-28.125%53.333%Max.32.00023.000-28.125%

    min.30.00020.00018.000-40.000%-10.000%min.30.00018.000-40.000%

    Max delay variation27.00044.00018.000-33.333%-59.091%Max delay variation27.00018.000-33.333%

    -171.005%-64.938%-171.005%

    test4one sever-one clientPercentage

    origianaltwo queueGain

    TCP throughput3.8513.703-3.843%

    RTP troughput1.4481.4480.000%

    Jitter Avg.2.9002.600-10.345%

    Jitter Max.4.0003.000-25.000%

    Jitter Min2.0002.0000.000%

    One-way delay Avg.30.70020.200-34.202%

    One-way delay Max.32.00023.000-28.125%

    One-way delay Min.30.00018.000-40.000%

    Max delay variation27.00018.000-33.333%

    -171.005%

    test4one sever-one clientPercentage

    origianaltwo queueGain

    TCP throughput3.7363.8162.14%

    RTP troughput1.4481.447-0.07%

    Jitter Avg.2.72.0-25.93%

    Jitter Max.4.03.0-25.00%

    Jitter Min1.01.00.00%

    One-way delay Avg.30.114.1-53.16%

    One-way delay Max.34.029.0-14.71%

    One-way delay Min.27.010.0-62.96%

    Max delay variation25.012.0-52.00%

    Sheet1

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Percentage

    Percentage Gain in Performance Parameters

    day1

    0

    0

    0

    0

    0

    0

    0

    0

    0

    Percentage Gain

    Percentage Gain in Performance Parameters

    Atest1one sever-one clienttwo server-one clientPercentage Gain

    origianaltwo queueorigianaltwo queueone servertwo server

    TCP throughput3.7683.8043.7363.8160.955%2.141%

    RTP troughput1.4491.4481.4481.447-0.069%-0.069%

    Jitter Avg.3.0002.1502.7002.000-28.333%-25.926%

    Jitter Max.4.0003.0004.0003.000-25.000%-25.000%

    Jitter Min2.0001.0001.0001.000-50.000%0.000%

    One-way delay Avg.7.00022.55030.10014.100222.143%-53.156%

    One-way delay Max.9.00025.00034.00029.000177.778%-14.706%

    One-way delay Min.5.00019.00027.00010.000280.000%-62.963%

    Max delay variation27.00016.00025.00012.000-40.741%-52.000%

    535.847%-233.751%

    othertest2one sever-one clienttwo server-one clientPercentage Gain

    origianaltwo queueorigianaltwo queueone servertwo server

    TCP throughput3.6633.8013.6933.7843.767%2.464%

    RTP troughput1.4491.4491.4471.4470.000%0.000%

    Jitter Avg.2.8572.0502.8572.100-28.246%-26.496%

    Jitter Max.4.0003.0004.0003.000-25.000%-25.000%

    Jitter Min2.0001.0002.0001.000-50.000%-50.000%

    One-way delay Avg.18.47625.85020.04825.50039.911%27.195%

    One-way delay Max.21.00028.00022.00029.00033.333%31.818%

    One-way delay Min.16.00023.00017.00023.00043.750%35.294%

    Max delay variation35.00016.00023.00015.000-54.286%-34.783%

    -40.538%-41.972%

    Btest3one sever-one clienttwo server-one clientPercentage Gain

    origianaltwo queueorigianaltwo queueone servertwo server

    TCP throughput3.3263.3113.3603.314-0.451%-1.369%

    RTP troughput2.0412.0422.0442.0440.049%0.000%

    Jitter Avg.2.3002.0502.2502.050-10.870%-8.889%

    Jitter Max.3.0003.0004.0003.0000.000%-25.000%

    Jitter Min2.0001.0001.0002.000-50.000%100.000%

    One-way delay Avg.14.40031.50035.80026.700118.750%-25.419%

    One-way delay Max.18.00034.00038.00030.00088.889%-21.053%

    One-way delay Min.10.00029.00032.00024.000190.000%-25.000%

    Max delay variation25.00011.00028.00012.000-56.000%-57.143%

    280.769%-62.503%

    oldtest4one sever-one clientPercentage Gain

    origianalone queuetwo queuetwo - oritwo - one

    TCP throughput3.8512.9953.703-3.843%23.639%

    RTP troughput1.4481.4471.4480.000%0.069%

    Jitter Avg.2.9003.3082.600-10.345%-21.403%

    Jitter Max.4.0005.0003.000-25.000%-40.000%

    Jitter Min2.0002.0002.0000.000%0.000%

    One-way delay Avg.30.70018.00020.200-34.202%12.222%

    One-way delay Max.32.00015.00023.000-28.125%53.333%

    One-way delay Min.30.00020.00018.000-40.000%-10.000%

    Max delay variation27.00044.00018.000-33.333%-59.091%

    -171.005%-64.938%

  • Limitations and Future WorkLimitations of the current approachRunning on top of legacy MAC with a single FIFO queueAP cannot prevent/control contention from stationsDownlink RT transmission could be severely delayed due to the uplink contentionsHow to handle this situation is an on-going effort

  • Throughput Improvement

  • IEEE 802.11n InitiativeA new standardization effort to achieve over 100 Mbps throughput over WLANVia both PHY and MAC enhancement

    We are considering the MAC improvement for throughput enhancement

  • Frame Size Affects Throughput802.11 MAC/PHY have big