Time-Variant

Wireless communication 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:
• Vehicle-to-vehicle or vehicle-to-infrastructure communication used for driving assistance systems
• Driver assistance systems such as adaptive cruise control (ACC)
• 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

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/or obstacles are time-variant. These effects influence the propagation and lead to time-variant channel impulse responses.

The workflow for time-variant simulations with moving geometrical objects is different from the workflow in which transmitters or receivers move in time but all geometrical objects in the database remain stationary. In the first case, the movement of objects has to be specified in WallMan. In the other case, antenna patterns can be specified to move along trajectories in ProMan without the need to specify any time-dependent behavior in WallMan. Table 1 provides an overview.

Table 1. Workflows involving time variance.
Intended Scenario in ProMan Preparation in WallMan Key step in ProMan
Indoor Convert external indoor database or create/edit indoor database Specify that a transmitting antenna will move along a trajectory and/or specify that a prediction point will move along a trajectory.
Urban Convert external urban database or create/edit urban database
Rural/suburban Optionally, convert external topography database
Tunnel Optionally add objects to a .idb file created in TuMan
Time-variant with moving objects

Convert external indoor database or create/edit indoor database.

Specify movement of groups of objects.

Specify that a transmitting antenna will move with a moving object group, and/or specify that a prediction point will move with a moving object group.
Time-variant with moving objects defined via external control software Convert external indoor database or create/edit indoor database. Define groups of objects. (*)
Note: (*) To define the time-variant movement of a group of objects via external control software, the .nip file can be edited.
Lines like the following example can be inserted at the end of the Database block in the .nip file.
***** Dynamic postion [object number, time,x,y,z,az,tilt,roll,velocity,direction] per time step ******
GROUP_POSITION_TIME_VARIANT 1 0.000000, 0.000000, 0.000000, 0.000000, 0.00, 0.00, 0.00, 2.000, 1.000000, 0.000000, 0.000000
GROUP_POSITION_TIME_VARIANT 1 1.000000, 2.000000, 0.000000, 0.000000, 0.00, 0.00, 0.00, 2.000, 1.000000, 0.000000, 0.000000
GROUP_POSITION_TIME_VARIANT 1 2.000000, 4.000000, 0.000000, 0.000000, 0.00, 0.00, 0.00, 2.000, 1.000000, 0.000000, 0.000000
GROUP_POSITION_TIME_VARIANT 1 3.000000, 6.000000, 0.000000, 0.000000, 0.00, 0.00, 0.00, 2.000, 1.000000, 0.000000, 0.000000
GROUP_POSITION_TIME_VARIANT 1 4.000000, 8.000000, 0.000000, 0.000000, 0.00, 0.00, 0.00, 2.000, 1.000000, 0.000000, 0.000000
GROUP_POSITION_TIME_VARIANT 1 5.000000, 10.000000, 0.000000, 0.000000, 0.00, 0.00, 0.00, 2.000, 1.000000, 0.000000, 0.000000