Remcom Inc. 315 S. Allen St., Suite 416  State College, PA  USA Tel:  Fax:   © 2011 Remcom Inc. All rights reserved. Urban Propagation Models

Hybrid SBR/UTD Propagation Model Input building and terrain vector data and positions of Tx/Rx points, and perform pre-processing operations Find geometrical ray paths by using a fast and robust ray tracing procedure based on the Shooting and Bouncing Ray (SBR) method Store geometrical paths obtained from SBR ray-tracing procedure Construct the geometrical optics and the edge-diffracted paths from the geometrical path database Evaluate E-fields using the Uniform Theory of Diffraction (UTD) and material-dependent-reflection and -transmission coefficients Combine E-fields with antenna patterns to find path loss, delay, delay spread, angle of arrival, coverage areas, interference, etc.

Application of SBR to Ray Tracing for GTD Method An inherently robust approach applicable to complex geometries Apply ray tracing acceleration techniques to reduce run time Shoot and bounce rays from Tx/Rx points and building edges Find rays which intersect Tx/Rx collection surfaces Sort rays to eliminate duplicate paths Construct full or partial paths –Tx/Rx –Edge – Rx/Tx –Edge – Edge Save partial paths in RAM and/or on hard disk for reuse

Line-Of-Sight Rays from Source

Rays Shot From Diffraction Point

Ray Tracing Locating Diffraction Points

Ray Tracing Acceleration Reuse Diffracted Paths for Different Tx Sites

Ray Tracing Acceleration Rx Point Bounding Boxes It is usually best to leave collection surface radius and bounding box parameters to default values. Values can be reset in the Advanced Receiver Properties window.

Urban Canyon 2D Model Fast and robust ray-tracing algorithms for complex urban environments Ray paths stored to allow fast recalculation for different frequencies, antennas, transmitters, or building wall types Assumes tall buildings and low antenna heights Semi-automated building pre-processor has been developed to reduce unnecessary building complexity Assumes a fairly flat ground Vertical plane components, including ground effects, are added analytically Reflection and diffraction points must lie on the surface of the building

Summary of Urban Canyon Model Maximum reflections: 30 Maximum transmissions: N/A Maximum diffractions: 3 Environments: Urban Terrain: Flat or slightly hilly, maximum of 50 faces Foliage: Direct rays, no lateral wave Indoor: N/A Objects: N/A Range: Usually < 3 km, but can depend on application

Summary of Urban Canyon Model (2) Antenna heights: Lower than most buildings Antenna types: All Ray tracing: SBR for horizontal plane, image method for ground reflection Minimum frequency: About 100 MHz Maximum frequency: Depends on application

Limitations of the Urban Canyon Model Advantage: greatly reduces computation time by executing a 2D ray trace using only the street level “footprints” of buildings Drawbacks: –Only accurate in a fully high-rise environment with a flat ground –Antennas must be lower than all building roofs –Omits terrain effects –Omits paths over buildings

Full 3D UTD Model The most general propagation model Primarily intended for urban and indoor environments Can also be applied to propagation over irregular terrain Allows for reflections, transmissions and diffractions This model accounts for all polarization changes due to interactions with the features SBR and Eigenray ray-tracing methods –The Eigenray method is a generalization of the multiple image method

Summary of Full 3-D Urban Model Maximum reflections: 30 (SBR), 3 (Eigenray) Maximum transmissions: 30 (R + T ≤ 30) Maximum diffractions: 4 (SBR), 3 (Eigenray) Environments: Urban, indoor, rural Terrain: All Foliage: Attenuation of direct rays, no lateral wave Indoor: All Objects: All Range: Usually < 10 km, but can depend on application

Summary of Full 3-D Urban Model (2) Antenna heights: All Antenna types: All Transmitters: Point sources (antennas) and plane waves (in v2.4) Ray tracing: SBR or Eigenray method Minimum frequency: Depends on application, about 100 MHz for urban areas Maximum frequency: Depends on application API to Full 3-D included

Full 3D Example: Directional Tx on a Building Rooftop Vertically polarized directional antenna mounted on one of the taller buildings with a 6° downtilt, frequency = 1.9 GHz Antenna has roughly 45° H- plane and E-plane half-power beamwidths, 14 dBi maximum gain Calculate received power 2 meters above the ground Uses full 3D model with 10 reflections, 2 diffractions, no transmissions

Full 3D Example: Directional Tx on a Building Rooftop(2) Received Power for 0 dBm transmitted power

Full 3D Example: Ray Paths to Rx Point in the Main Beam Receiver

Full 3D Example: Ray Paths to Rx Point Outside Main Beam Receiver

Full 3D Example: Ray Paths to Rx Point Behind Main Beam Receiver

Vertical Plane (UTD) and MWFDTD for Over Rooftop Propagation The vertical plane UTD model and the MWFDTD model are primarily intended for predicting propagation over irregular terrain, but they can also be used for propagation over building rooftops

X3D Ray Model The X3D Ray Model is a 3D ray-tracing model with acceleration to take advantage of multi-core systems and graphics processing units (GPU). Uses Shooting and Bouncing Ray (SBR) technique Exact path calculations use image theory to correct paths for improved accuracy Includes absorption losses due to water vapor and oxygen Ray paths evaluated with Uniform Theory of Diffraction (UTD) GPU ray tracing acceleration provides substantial performance improvement –Requires a CUDA-capable GPU Multi-threading takes advantage of multi-core CPUs X3D places no restriction on object shape, includes transmissions through surfaces, and supports indoor propagation.

X3D Ray Model Ray tracing: SBR, with exact path corrections Maximum reflections: 30 Maximum transmissions: 8 Maximum diffractions: 3 Environments: all Foliage: currently no support for foliage Range: depends on application Antenna heights: all Antenna types: all Minimum frequency: 100 MHz Maximum frequency: depends on application

Exact Path Correction It is unlikely an SBR ray will exactly hit a receiver To compensate, a collection radius is constructed around the receiver Rays intersecting the collection radius are considered to reach the receiver Exact path corrects SBR errors, resulting paths with the accuracy of image method In the diagram, the intersecting blue ray will be adjusted to the black ray Method provides more accurate geometric paths, power, time of arrival, phase, etc. Transmitter Ray misses Rx Intersecting Ray

Atmospheric Absorption X3D received power & path loss include absorption from oxygen and water vapor Temperature, pressure, & relative humidity are set in the study area properties window.

X3D Limitations The following is a list of limitations of the new X3D model. Upcoming versions of InSite will add these capabilities: Requires a GPU Ray tracing is not restricted to the study area boundary Sinusoid waveforms only No foliage modeling Outputs –Animated field output –Efield vs time, Efield vs frequency, power delay profile No output generated for co-located receiver points