Time Variant Scenarios

Consideration of moving objects in time-variant scenarios

 

Introduction


Wireless communications in time variant ad-hoc networks is very challenging. The increasing demand for mobile multimedia and safety applications in time-variant environments requires new concepts for the development of such wireless systems.


Time variant scenarios can be found in several environments:

  • car-to-car (or car-to-infrastructure) communication scenarios used for driving assistance systems
  • MESH and sensor networks in time-variant scenarios
  • Wi-Fi hotspots in railroad stations, airports or city centers

  • Stations and underground stations with moving trains

  • Airports with moving airplanes

  • Elevators inside buildings


Car-to-car communications
The main difference in such applications compared to the classical network planning is the time variance of these scenarios. The locations of transmitters, receivers, and obstacles are time-variant (i.e. moving). These effects influence the propagation and lead to time variant channel impulse responses. Doppler shifts and the directional channel impulse response are mandatory results when simulating such time-variant scenarios.

Definition of Time Variant Scenarios

The tool  WallMan of the WinProp suite can be used to define the movement of the objects in the time variant scenarios.
Time variant behavior can be assigned individually to each element in the vector database or to groups of objects.
Further information about the definition of the time-variant hehavior is available on the database page.


WallMan can be used to define time
variant scenarios with several vehicles
on a straight street.

Propagation Model for Time Variant Scenarios


For the time-variant scenarios all propagation models of the indoor scenarios can be used.
Besiudes the indoor propagation models also a new ray-optical model is available to predict additionally the Dooplershift for each propagation path (see figure).


Computation result of the
Ray Tracing model

Prediction Results


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

 

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

 

 

Presentation about time variant scenarios

Read more about the definiton of time variant scenarios
Read more about the Propagation Models
Publications related to time variant scenarios

Read more about vehicle databases

 

 

 

 

 

 
Brochure:
Time Variant Scenarios

 

 

 

 

 

 

 
Brochure :
Short Range Radio Links

 

 


 

 

Application: Car-to-Car Scenario

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

The development of ad-hoc networks used for car-to-car and car-to-infrastructure communications requires an analysis of the radio channel between the cars. Thus it is evident to understand this radio link and to model it with accurate propagation models.

Application: Adaptive Cruise Control

Computed propagation paths in an ACC scenario

The development of adaptive cruise control (ACC) relies on a deep understanding of the radar channel between the car and its environment. Simulations of this radio channel help to improve the algorithms for angle and distance estimation.

Application: Railway Station
Click to enlarge
Main station with trains
(Click to enlarge)


The planning of radio coverage in areas with significant time-variance is more reliable if the time-variance is included in the simulations. So drop-outs can be seen and analyzed easily.
Especially for train stations (also underground statons) and airports the models for the time variant scenarios are important.