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Introduction to Simulating radio propagation models and COOJA ARM

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One radio…

REFRACTION

REFLECTION

DIFFRACTION

- … receiving a radio signal
- Typically 4 different categories
- Problem:
- What happens to the radio signal?
- (And how is sound quality affected?)

SCATTERING

WSN radio model types

- Unit Disk Graph
- COOJA’s Standard Radio Medium
- Bit Error Ratio (BER)
- Collected statistical data (or empirical models)
- Ray tracing

COOJA ARM

- Advanced Radio Medium
- “Advanced” when compared to “Standard” :)
- Radio propagation models introduction
- How ARM works

Wiki’s definitions

- Radio Propagation

“... is a term used to explain how radio waves behave when they are transmitted, or are propagated from one point on the Earth to another.”

- Radio Propagation Model

“... characterization of radio wave propagation as a function of frequency, distance and other conditions.”

Empirical models

- Lots of different models exist
- Outdoor
- City, Terrain, Rain, Earth curvature
- Okumura model built using data collected in Tokyo
- Indoor
- ITU Model for indoor Attenuation
- Log Distance Path Loss Model
- Typical parameters: frequency, distance, number of floors, coefficients tuned to different environments etc.
- Above models based on empirical data

Analytical approach

- Based on ray tracing
- Calculates multi-path effects
- Used in COOJA ARM

Small-scale vs. Large-scale

- Small-scale effects
- Sum of many received signal from different directions
- Often Gaussian random
- Scattering
- Large-scale effects
- Shadowing
- Reflections

Free Space Propagation Model

- (FSPL)
- Predicts signal strength for LOS paths

Antenna gains

Wavelength

Transmitted vs. received power

Distance

Ray tracing in ARM

- 2D positions
- Supports attenuating obstacles
- Only rectangles
- Refractions
- Reflections
- Diffractions
- Potential support:
- Scatterings

Using ARM

- Registers two plugins
- Changing formula parameters
- Visualizing radio coverage
- Listens to all radios in the simulation
- Transmitted power
- Antenna gains
- Packet lengths
- SNR threshold
- (Channel)

FSPL mentioned earlier

Fixed “penalty” constants

FUTURE:Should be replaced by angle dependent formulas

Maximum values used by ray tracer

May become very time-consuming =)

Formula ViewerArea Viewer

- Shows radios, obstacles and channel propagation

Area Viewer

- Obstacles are set by analyzing the background image

Area Viewer

- User may track ray paths from a transmitter to a point
- Uses the current formula settings

Area Viewer

- Show surroundings of transmitter:
- Signal strength
- SNR ratio
- Probability of reception
- Delay spread

Area Viewer

Received signal strength vs. Probability of reception

Future work

- Validate models
- Parameter estimation / Model calibration
- From actual measurements

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