Алгоритмы канального уровня

  • Published on
    18-Mar-2016

  • View
    62

  • Download
    3

Embed Size (px)

DESCRIPTION

. : http://www.sumkino.com/wsn/course. axel@wl.unn.ru http://www.wl.unn.ru. . - PowerPoint PPT Presentation

Transcript

  • axel@wl.unn.ruhttp://www.wl.unn.ru

    :http://www.sumkino.com/wsn/course

  • WSN

  • ( , Ethernet ..) , .

    (MAC) .

  • CordlessheadsetBluetoothAccessPoint 802.11Zigbee/802.15.4

  • MAC MAC FDMATDMACSMA

  • MAC

    : ALOHA (Pure and Slotted), CSMA

    : FDMA, TDMA, CDMA

  • MAC MAC

    . MAC .

    MAC .

    .

  • MAC .

    . Goodput.

    .

    , .

  • MAC . :

    .

    , .

    Overhearing .

    Control Packet Overhead goodput.

  • .

    (overhearing)

    (Voice).

    QoS

  • Time Division Multiply Access: TDMA .

  • Time Division Multiply Access: TDMA TDMA , .

    :

    . - (FDMA, CDMA).

    .

    .

  • Bluetooth (piconets).

    master 7 slave .

    Master (poll) .

    Scatternet

  • ALOHA :packet radio networkssend when ready18-35% channel utilization

    CSMA (Carrier Sense Multiple Access):listen before talk50-80% channel utilization

  • CSMA - .CBADCBAD

  • MACA MACA (Ethernet) .

    RTS-CTS-DATA .

    CTS, . RTS, CTS.

  • MACAW (Wireless) .

    RTS-CTS-DATA-ACK .

    ACK, .

  • 802.11CFABEDRTSRTS = Request-to-Send

  • 802.11CFABEDRTSRTS = Request-to-SendNAV = 10NAV =

  • 802.11CFABEDCTSCTS = Clear-to-Send

  • 802.11CFABEDCTSCTS = Clear-to-SendNAV = 8

  • 802.11CFABEDDATA DATA CTS. ACK.

  • 802.11CFABEDACK

  • CSMA/CA .

    CSMA/CA: . : , . : RTS CTS . , .

  • CSMA/CA .

    NAV (Network Allocation Vector )

    NAV (overhead) RTS/CTS/DATA/ACK.

    (/)

    Backoff .

  • Backoff Interval , backoff [0,MaxBackoff]. MaxBackoff- , .

    backoff () . , .

    backoff 0 RTS .

  • Backoff Interval: MaxBackoff=31B1-backoff 1B2-backoff 2

  • Backoff Interval Backoff MAC . MaxBackoff . MaxBackoff .

    backoff . IEEE 802.11 DCF: backoff MaxBackoff .

  • Backoff Interval

    CTS RTS, MaxBackoffMaxBackoff ( )

    , MaxBackoff .

    MaxBackoff .

  • WSN

  • CSMA vs TDMA

  • CSMA vs TDMA

  • MAC WSNMAC WSN

    2000 2004 16

    .

  • MAC WSN

  • MAC WSN

  • MAC WSN .

    ? (Control Packet Overhead) (Overhearing unnecessary traffic)

    .

  • MAC MAC

    . , .

    } WSN

  • S-MAC: Co-ordinated Adaptive Sleeping

    Ye, Heidemann (USC), Estrin (UCLA)

  • S-MAC: Co-ordinated Adaptive Sleeping (TDMA) (CSMA).

    . , ,

    . , CSMA/CA.

  • S-MAC: Co-ordinated Adaptive Sleeping : / .

    S-MAC : . RTS/CTSOverhearing , .

  • : .

    : .

    duty cycle ~10%

  • .

    : . , . (SYNCHRONIZER) , . (FOLOWER) .

  • .

    (SYNC) .

    , , .

  • :

  • : multi-hop .

    : .4123listen .

  • S-MAC

    IEEE 802.11 ad hoc mode

    backoff

    RTS/CTS

    RTS/CTS/DATA/ACK

  • : .

    : , .

    ?

    ?

  • S-MAC: Mica Motes (UC Berkeley) 8-bit CPU at 4MHz,128KB flash, 4KB RAM20Kbps radio at 433MHzTinyOS S-MAC duty cycle duty cycle ( )

  • S-MAC: 11 , . S-MAC .

    .* Wei Ye, John Heidemann Medium Access Control in WSN

  • S-MAC: , .Latency under highest traffic loadNumber of hopsAverage message latency (S)10% duty cycle withoutadaptive listen 10% duty cycle with adaptive listen No sleep cycles Latency under lowest traffic loadNumber of hopsAverage message latency (S)10% duty cycle withoutadaptive listen 10% duty cycle withadaptive listen No sleep cycles * Wei Ye, John Heidemann Medium Access Control in WSN

  • S-MAC: .Effective data throughput under highest traffic loadNumber of hopsEffective data throughput (Byte/S)No sleep cycles 10% duty cycle with adaptive listen 10% duty cycle without adaptive listen .* Wei Ye, John Heidemann Medium Access Control in WSN

  • S-MAC: CSMA/CA .

    () , RTS/CTS MAC , .

  • B-MAC: Versatile Low-power medium access for sensor networks

    Joe Polastre, Jason Hill, David Culler(U.C. Berkeley)

  • B-MAC , .

    (Unscheduled sleep)

    . , .

    (Unscheduled wakeup)

    CSMA/CA app-specific .

  • B-MACBMACsetMode (Listening/Transmit)setPreambleLengthsetCheckIntervalRTS/CTS MACTree-optimizedMACEvent-responseoptimizedMACBMAC (link-layer reliability) RTS/CTS ( )

  • B-MACLong PreambleData transmissionSenderReceiverReceive dataCarrier sense , carrier sense .

    RTS/CTS .

  • B-MACLong PreambleData transmissionSenderReceiverReceive dataCheck intervalCarrier sense CheckInterval , .

    carrier sense , .

  • B-MAC

  • B-MAC

  • B-MAC

  • WSN

  • Medium Access Control in Wireless Sensor Networks Wei Ye and John Heidemann

    Energy-Efficient Medium Access Control Koen Langendoen and Gertjan Halkes

    An Adaptive Energy-Efficient MAC Protocol for Wireless Sensor Networks Tijs van Dam,Koen Langendoen, Sensys 2003

    Medium Access Control with Co-ordinated Adaptive Sleeping for Wireless Sensor Networks W. Ye, J. Heidemann, D. Estrin, IEEE/ACM Transactions on Networking, 2004.

  • The End

  • Design Discussion: MAC layer for event detectionGiven:1 High-powered camera sensorMany (20) low-power camera sensorsRequirement:Low-power cameras are periodically sensingTrigger high-power camera when low-power ones detect motion within time Delta.Discuss appropriate choice of MAC layer (TDMA/FDMA/CDMA/CSMA) forSingle hop vs multihopLarge vs Small DeltaScheduled vs unscheduled sleep