Wednesday 22 January 2014

Chapter 1 - 802.11 Overview

    • Data link layer - 2 sub-layers
      • upper : LLC 802.2 logical link layer
      • lower portion: MAC sub-layer (Media Access Control)
        • interface between lower PHY layer & LLC
    • MSDU
      • Network layer sends data to data link layer (LLC), becomes known as MAC Service Data Unit
        • MSDU is IP packet + LLC data
      • 3 frame types: mgt, control, data
        • only data frames carry payload
        • max MSDU size 2,304 bytes (+ encryption overhead)
    • MPDU
      • MAC Protocol Data Unit
      • 802.11 frame
      • MAC header + MSDU + 32 bit CRC (FCS)
      • MPDU passed to physical layer for transmission
      • Image(22)
    • Physical layer - 2 sub-layers
      • upper portion: Physical layer convergence procedure (PLCP)
        • takes MPDU & prepares for transmission (PPDU)
      • lower portion: Physical Media Dependant (PMD)
        • modulates PPDU and transmits as bits
    • PSDU:
      • PLCP service data unit
      • Just MPDU in physical layer
    • PPDU:
      • PLCP sub-layer takes PSDU & adds preamble & PHY header to form PPDU
      • Image(23)

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