[Paper Review] Radio Irregularity Model in OMNeT++

Behruz Khalilov, Anna Förster+1 more|arXiv (Cornell University)|Sep 7, 2017

Wireless Networks and Protocols2 references3 citations

TL;DR

This paper proposes the Radio Irregularity Model (RIM) in OMNeT++'s INET Framework to simulate directional path loss variations due to radio irregularity, using a Weibull-distributed coefficient of irregularity (DOI) that modifies free-space path loss. The model enhances simulation accuracy by capturing anisotropic propagation effects, with DOI as a configurable parameter to reflect real-world radio pattern deviations.

ABSTRACT

Radio irregularity is a non-negligible phenomenon that has an impact on protocol performances. For instance, irregularity in radio range leads to asymmetric links that cause the loss of packets in different directions. In order to investigate its effect, the Radio Irregularity Model (RIM) is proposed that takes into account the irregularity of a radio range and estimates path losses in an anisotropic environment. The purpose of this paper is to provide details of the RIM model developed in the INET Framework of the OMNeT++ simulator that can be used to investigate the impact of radio irregularity on protocol performance.

Motivation & Objective

• Address the lack of directional path loss modeling in existing wireless simulators, which assume spherical radio patterns.
• Investigate the impact of radio irregularity—caused by anisotropic propagation media and heterogeneous devices—on protocol performance.
• Develop a simulation model that captures directional path loss variance to improve the realism of wireless network simulations.
• Provide a configurable, open-source implementation within the INET Framework for reproducible and extensible research.
• Enable accurate evaluation of protocol performance under realistic radio irregularity conditions using OMNeT++

Proposed method

• Extend the FreeSpacePathLoss model in INET Framework to implement RIMFading, which introduces direction-dependent path loss adjustments.
• Generate a direction-specific coefficient of irregularity $K_i$ iteratively using a random walk with DOI as the step size limit.
• Use the Weibull distribution with configurable shape (b) and scale (a) parameters to model the statistical variation in received signal strength across directions.
• Compute the angle between transmitter and receiver in the xy-plane to determine the corresponding $K_i$ value for path loss adjustment.
• Apply the adjusted path loss as $DOI\text{AdjustedPathLoss} = \text{PathLoss} \times K_i$ to simulate directional radio irregularity.
• Ensure $|K_0 - K_{359}| \leq DOI$ to maintain consistency in the irregularity bounds across all 360 degrees.

Experimental results

Research questions

• RQ1 How does directional path loss variation due to radio irregularity affect the performance of wireless network protocols?
• RQ2 To what extent can the Degree of Irregularity (DOI) parameter capture real-world anisotropic propagation effects in simulation?
• RQ3 How well does the Weibull distribution model the empirical variation of received signal strength across different propagation directions?
• RQ4 What is the impact of using a directionally varying path loss model compared to spherical models in OMNeT++ simulations?
• RQ5 Can the RIM model be effectively integrated into the INET Framework to support realistic wireless network simulations?

Key findings

• The RIM model successfully captures directional path loss variations by introducing a DOI-dependent coefficient $K_i$ that varies per direction.
• The Weibull distribution with default parameters (a=1.5, b=1) effectively models the statistical variation of received signal strength across different angles.
• The model maintains consistency in irregularity bounds by enforcing $|K_0 - K_{359}| \leq DOI$, ensuring bounded directional deviation.
• The implementation is modular and extensible, allowing replacement of the Free Space Path Loss model with other path loss or fading models.
• The RIMFading model is released under the GPL license on GitHub, enabling open access and community extension for realistic wireless simulation research.
• The model provides a practical solution to simulate radio irregularity in OMNeT++ without requiring complex hardware deployments or field measurements.