Metageek: Introduction to Eye PA

Notes:
  • Ethernet is full-duplex (traffic in both directions simultaneousy
  • Wi-Fi is half-duplex (can’t talk at same time) 
  • Similar to human conversation
Notes:
  • If data never makes it (i.e. interference) the device needs to retransmit, over and over until ACK is received
Notes:
  • Only one device can speak at a time on any given channel
  • The more devices, less opportunity to speak 
  • Similar to dinner conversation around dinner table
  • More people, more difficult to get a word in
Notes:
  • Distance matters as well - competing for time to talk
  • Further devices go to slower, more reliable data rate (
  • Data rates affect half-duplex nature of Wi-Fi
  • Only get about 60% of data rate due to management overhead
  • Slower devices ‘hold up’ conversation
  • Similar to ‘slow kid in back of calssroom'
  • Typical of Co-Channel interference
  • Want devices to get on, and get off quickly
Co-Channel
  • Retransmission 
  • Distance from AP
  • Interference from devices on same channel
Adjacent
  • Devices yell and scream over each other
  • Similar to adjacent diner table
Notes:
  • ‘Packet’ (layer 3) are actually frames (layer 2)
Notes:
  • Spectrum analysis is comparable to checking the ethernet cable - raw radio frequency