Links

Link objects are used in Visualyse to:

  • Connect Stations together
  • Define parameters related to the propagation of radio waves
  • Set the criteria by which interference levels are judged

The Link is where Stations, Carriers, frequencies, propagation models, interference criteria and interference statistics gathering are combined to define a communications path.

The Links Dialog can be invoked in the normal ways, i.e.

  • Via the toolbar icons
  • Via the Model menu
  • By right mouse click in the Model View

There are four types of Link that you can create, depending on what you want to do.

A Fixed Link has explicitly defined start and end Stations, which do not change during the simulation, but which are not necessarily fixed Stations. Many modelling scenarios call for the use of fixed links.

A Receive Link has an explicitly defined end Station, but no defined start Station. This type of Link could be used for earth observation satellites for example, or in any case where a fixed receive signal is known.

A Transmit Link has an explicitly defined start Station (or Group of Stations) but no defined end Station. This type of Link would be used for a broadcast system being considered only as an interferer. Receive Stations are not relevant to the scenario and can therefore be omitted.

The ‘source’ of a transmit Link multiple Stations, multiple beams and multiple Antennas. So, for example, if you have a Group of two Stations each with two Antennas which themselves have two beams there are various ways of specifying a transmit Link:

  • Both Stations transmitting through both their Antennas using all beams, or:
  • One Station transmitting through both Antennas using both beams, or:
  • One Station transmitting through one Antenna using both beams, or:
  • One Station transmitting through one Antenna using one beam.

In a Dynamic Link the start and/or end Station, are selected from a group according to one of several criteria that may vary through the simulation. For example, in the case of a nonGSO satellite constellation, the feeder Link Earth Stations will experience handover from satellite to satellite that will be dependent on elevation angle. This would be modelled as a Dynamic Link in Visualyse.

Fixed and Dynamic Links contain two Link Paths, one for the forward communication direction and one for the return direction. Forward and return directions are defined in relation to the start and end Stations, the forward path always running from the start Station to the end Station. Each direction can have separately defined powers and criteria.

A Receive Link has a single Link Path into the receive while a transmit Link has no Link Paths at all.

All Link dialogs have an option to change how Links are shown on the map and 3D views. This is done via a combination of the ‘Display’ button in the Link dialog and the Link display method in the configure option of the view menu.

The Link dialog also defines the powers, propagation characteristics and the interference criteria levels for the Links.

The dialog is in the form of tabbed sheets. Each tab is described in detail below. Tabs that are common to more than one Link type are described first.