RF Signal in the Real World

• Co-Channel Interference
  • 解決方法加強Power提升SNR

• Neighboring Channel Interference

• Non-802.11 Interference

• Free Space Path Loss
  • FSPL (dB) = 20log(d) + 20log(f) + 32.44
  • Frequency or distance 愈大, Loss愈大
  • 解決方法: 加強signal或receiver放近d
• DRS (802.11device智能轉換modulation)

• Reflection
  • Multipath (不利於SISO, 有利於MIMO:多個copy)

• Absorption
  • Water/human body
• Scattering
• Refraction
• Diffraction
• Fresnel Zone
  • Narrow line-of-sight wireless transmission
  • Fresnel Zone 都不應有野擋