Path Loss Models(Rec. P.1411)

• line-of-sight path

  • basic transmission loss (UHF)
  • free-space (mm wavelengths)

• non line-of-sight paths

  • diffraction, reflection, scatter
  • multi-screen diffraction model or method of Rec. P.526
    • building heights, density, street width, orientation
    • crossing streets, corner angle

• multipath

  • delay spread e.g. r.m.s. 0.8 - 3 ms (urban - suburban)

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• LOS path: treatment dependent on frequency:
  • at UHF, power law with change of slope at breakpoint
  • at mm wavelengths, breakpoint is outside range of cell and so free-space is assumed.

• NLOS, over rooftop paths - diffraction considered dominant mechanism
  • multi-screen diffraction model if rooftop heights are approximately the same, otherwise method of Rec. P.526 (in which highest edge must be identified)

• NLOS, street canyon paths - model given for diffraction and reflection at corners of street crossings.

• All methods use the geometric parameters shown in previous slides.

• Multipath also contributes as a propagation mechanism; if delays are too large, BER can be unacceptably large due to intersymbol interference.