802.11g & 802.11e

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802.11g & 802.11e Presenter : Milk

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802.11g & 802.11e. Presenter : Milk. Outline. 802.11g Overview of 802.11g 802.11g & 802.11b co-exist QoS Limitations of 802.11 802.11e Overview of 802.11e EDCA HCCA DLP Block Acknowledgement Admission Control Power Management. 802.11g. 802.11g Overview of 802.11g - PowerPoint PPT Presentation

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  • 802.11g & 802.11ePresenter : Milk

  • Outline802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock AcknowledgementAdmission ControlPower Management

  • 802.11g802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • Overview of 802.11gProvide high data ratesBackward compatibility with legacy 802.11 and 802.11b devicesThe new features of 802.11gThe provision of four different physical layers Protection Mechanisms

  • 802.11g PHY layersCCK - Complementary code keyingOFDM - Orthogonal frequency division multiplexing PBCC - Packet Binary Convolutional Code

  • Different WLAN system characteristics

  • 802.11g802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • 802.11g & 802.11b co-existMany legacy 802.11b devices cannot detect the ERP-OFDM signals and it can result in collisions between 802.11b and 802.11g stations.The 802.11g suggests a solution, which is based on the channel reservation for the ERP-OFDM transmissions.Use RTS/CTS to protect ERP-OFDMUse CTS-to-Self to protect ERP-OFDM

  • Protection MechanismssenderreceiverNon-ERPCTSERP-OFDMdatasenderreceiverNon-ERPRTSNon-ERPCTSERP-OFDMdataRTS/CTSCTS to SelfERP-OFDMACKERP-OFDMACKRTS NAVCTS NAVCTS NAV

  • QoS Limitations of 802.11802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • QoS Limitations of 802.11DCF (Distributed Coordination Function)Only support best-effort servicesNo guarantee in bandwidth, packet delay and jitter

    PCF (Point Coordination Function)Unpredictable beacon frame delay due to incompatible cooperation between CP and CFP modesTransmission time of the polled stations is unknownPoint Coordinator(PC) does not know the QoS requirement of traffic

  • Beacon delay exampleTBTTTBTTTBTT - target beacon transmission time

  • 802.11e802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • Overview of 802.11eSupport QoS in WLANBackwardly compatible with the DCF and PCFHybrid Coordination Function (HCF) access method is added, includingContention-Based channel accessEnhanced Distributed Channel Access (EDCA)Controlled channel access HCF Controlled Channel Access (HCCA)

  • Major Enhancements in 802.11e

    Basic elements for QoSTraffic DifferentiationConcept of Transmission Opportunity (TXOP)New Contention-based channel accessEnhanced Distributed Channel Access (EDCA) New Contention-free channel accessHCF Controlled Channel Access (HCCA) Other new mechanisms for higher throughputBlock Acknowledgement (Block Ack)Direct Link Protocol (DLP)

  • Traffic Differentiation

  • 802.11e802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • EDCADifference from original DCFContention between ACs (Not STAs)New Inter-frame Space (IFS) for each AC: Arbitration Inter frame Space (AIFS)Transmission Opportunity (TXOP)

  • Access Category (AC)In EDCA, media access is based on the AC of MSDU4 ACs are definedAC_BK (background)AC_BE (best-effort)AC_VI (Video)AC_VO (Voice)In EDCA, the size of Contention-Window (CW) and Inter-frame space (IFS) is dependent on AC

  • Arbitration Interframe Space (AIFS)QSTA use AIFS to defer the contention window or transmission for each ACAIF[AC] = AIFSN[AC]x aSlotTime+ aSIFSTimeAIFSN for each AC is broadcast via beacon frame containing EDCA Parameter Set elementDIFS = 2 x aSlotTime+ aSIFSTime

  • Transmission Opportunity (TXOP)TXOP: the duration of a QSTA to transmit frame(s)When will a QSTA get a TXOP ?Win a contention in EDCA during CPReceive a CF-poll (polled TXOP) from HC

  • Transmission Opportunity (TXOP) (cont.)In TXOP, frames exchange sequences are separated by SIFS

  • Multiple backoff of MSDU streams withdifferent priorities

  • 802.11e802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • HCF Controlled Channel Access (HCCA)The procedure is similar to PCFHybrid Coordinator (HC)Operate at QAPControl the iteration of CFP and CPBy using beacon and CF-End frame and NAV Mechanism (Same as PCF)Use polling Scheme to assign TXOP to QSTAIssue CF-poll frame to poll QSTAPolling can be issued in both CFP & CP

  • 802.11e Superframe

  • 802.11e802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • Direct Link Protocol (DLP)Direct LinkDirectly send frames from one QSTA to another in QBSS

  • The handshake procedureNotes:1.DLS Request and DLS Response are both Action management frame2.The direct link will become inactive if no frames have been exchanged for DLPTimeoutValue duration.3.Recipient shall not go into power save for DLPTimeoutValue duration.4.After timeout, the frames are transmitted via AP again.

  • 802.11e802.11gOverview of 802.11g802.11g & 802.11b co-existQoS Limitations of 802.11802.11eOverview of 802.11eEDCAHCCADLPBlock Acknowledgement

  • Brief of Block Ack(Optional function in implementation)Improve channel efficiencyBy aggregating several acks into one frameTwo typesImmediate Block AckSuitable for High-bandwidth, low latency trafficDelayed Block AckSuitable for applications tolerating moderate latency

  • Procedure of Block Ack

  • Immediate Block Ack

  • Delayed Block Ack

    2.4GHz802.11802.11g802.11b(BSS)

    802.11gERP-OFDM802.11a802.11aSIFS=16us802.11gERP-OFDM802.11b802.11bSIFS=10usOFDM6us

    802.11b802.11gOFDM

    CTS-to-self CTS(RA)MACCTS CTS

    RTS/CTS802.11gRTSCTSCCKACKOFDM 4AIFSBACKOFF8PRIORITY MAPPING4AC