Time Variant Scenarios

Consideration of moving Objects in dynamic Scenarios

 

Introduction

After the great success of wireless communications used in land mobile radio systems, wireless data exchange in time variant ad-hoc networks become interesting. The steadily increasing demand for mobile multimedia and safety applications requires looking for new concepts for the planning of wireless systems. Time variant scenarios can be found in several environments: Some examples are car-to-car communication scenarios used for driving assistance systems or Wi-Fi hotspots in railroad stations, airports or downtown areas. The main aspect in such applications is the time variance of these scenarios, as the locations of either transmitter, receiver or of obstacles in these scenarios change continuously. These effects influence the propagation situation and lead to time variant channel impulse responses.

Example: Car-to-car Communication

Application: Car-to-Car Communication

The development of ad-hoc networks, which are used for car-to-car communication, is based on extensive research activities. One import issue is the radio channel between the cars, because all the data is tranmitted by using this channel. Thus it is evident to have a reliable tranmission link between the cars.

 

More information about predictions in car-to-car scenarios are available on this separate website:

http://www.awe-com.de/Automotive

 

Computed propagation paths in a car-to-car scenario.

 

Application: Adaptive Cruise Control

The development of adaptive cruise control (ACC) is based on intensive research activities. The investigation of the radar channel is very important for the adaptation of the algorithms (for angle and distance estimation) to the hardware.

 

More information about predictions in car-to-car scenarios are available on this separate website:

http://www.awe-com.de/Automotive

 

Computed propagation paths in an ACC scenario.

 

Definition of Time Variant Scenarios

 

The database manager WallMan was adapted to the needs of time variant scenarios. The basis of the databases are either planar polygons for indoor scenarios or cylinders with polygonal ground plate for urban environments. Each element in the database can be either stationary (not moving) or non-stationary (dynamic). Translation and rotation vectors, as well as scalar values for the velocity or the acceleration are assigned to time variant objects for the definition of their behavior in the scenario, depending on the time. Predictions are then accomplished for arbitrary defined timestamps or with constant intervals for a period of time.

 

WallMan was also improved concerning the conversion and handling of large databases. Especially vehilce databases consist of thousands of polygons. Read here more about the vehicle databases.

Database manager Wallman displaying a dynamic scenario with several vehicles on a straight street.

 

Road Course Generator for Time Variant Vehicle Scenarios

The newly developed software package for time variant scenarios offers a tool for the simple and fast generation of road courses. This tool is evident when studying in car-2-car communication scenarios. As typical road courses are not linearly, it would be very complicated to enter a road course manually. Therefore the road course can be defined with different types of parts of streets, e.g. straight streets and curves. Straight streets are only defined by their length, whereas curves are defined by angle, radius and the direction (left or right). Out of these definitions the road course is created and guardrails and jambs are automatically added to the borders of the streets. Buildings, vegetation and other objects can also be included in time variant scenarios.

Example of an automatically generated road course, with guardrails and jambs.

 

New 3D Ray Tracing for Time Variant Scenarios

A new ray tracing algorithm was developed for prediction in time variant scenarios. Algorithms for the computation of diffractions and reflections are well known and are implemented in the new approach available for time variant scenarios. Even more, the consideration of the doppler shift is possible. Each time an interaction with a moving obstacle occurs, the doppler shift according to the following equation is determined:

 

The usage of polygonal car models is possible with the new ray tracing algorithm. However one problem is the complexity of the models: To obtain a realistic image of the reality very complex car models have to be used. This leads to much computation effort and extrem long prediction times. The other way is to use simplified models with only some polygons. But these models do not represent the reality, because only few reflections and diffractions occur on such models. WinProp offers a new approach to avoid all these problems: The usage of radar cross sections (RCS) is supported. Complex polygonal models can be substituted by several bistatic RCS, which can be measured or computed. The image on the right shows a polygonal model which was substituted by 20 RCS. The follwing equation is used to determine the scattered field:

 

The scattering matrix depends on the incident and scattered angles of the ray path on the scattering center.

Computed Doppler shift.

 

Substitution of polygonal model with radar cross sections.

 

Examples

The following images show some computation results of WinProp. Please click on the images to enlarge them:

 

Spatial channel impulse response (CIR).
Doppler shift for several snapshots. Click to enlarge.

 

 

Some computed propagation paths in a suburban Car-2-Car scenario.
Adaptive Cruise Control (ACC): Some computed propagation paths.

 

Wave propagation phenomena and propagation paths.

 

 

Download a presentation about time variant scenarios.

Read more on the separate WinProp Time Variant website.

Get more information about the database manager WallMan.

Read more about vehicle databases.

 

 

 

 

 

 

 

 

 

 

 

 

 
Brochure download:
Time Variant Scenarios

 

 


 

 

 

 

 

 

 

 

 

 

 

 
Brochure download:
Short range radio links