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opensand:emulated_satcom_features:physical:spots:index

Spots

OpenSAND is capable of emulating multiple spots, each representing a different beams of the satellite. Satellite terminals are associated to only one spot, which can be used to represent different geographical zones. On the other hand, any gateway can handle more than one spot, and two different gateways can serve the same spot (although different carriers).

Each spot has its own dedicated carriers, so STs associated to different spots never share the same bandwidth.

OpenSAND Exploitation

ST assignment to each spot can be configured using the OpenSAND Manager.

The configuration is available by clicking the Satellite Terminals Assignment button in the Run tab. This will open a window, as displayed in the picture at the left.

In this window, all the ST are listed, and their associated Spot and GW can be selected using the corresponding combo boxes. Spots are identified by a numeric ID. New spots can be created by clicking in the Add spot button. When the configuration is finished, Save must be clicked to apply the changes.

Each spot can have different configurations (for one particular gateway): each spot has its own carriers configuration, and hence, its own scheduling as well (with its associated configuration).

Although two spots with the same ID and associated to different gateways can have the same carrier configuration, they are separate carriers, and are not shared.

OpenSAND Software Design

Spots are a central part of the Block Dvb, especially on the gateway side (BlockDvbNcc), since a gateway can serve more than one spot. This implies a different DVB scheduling for each spot (on the forward band), and a different return access mechanism and resource management on the return band. On each GW, and for each spot, two objects, SpotDownward and SpotUpward, are created: one for the forward band, and another for the return band, respectively. SpotDownward and SpotUpward also vary depending if a transparent or regenerative satellite is used, and both extend the DvbChannel, each implementing the specific methods for the forward and return band.

On the terminal (BlockDvbTal) instead, only one configuration is used: the one corresponding to the associated spot/gateway, used by each DvbChannel of said block.

Spots configuration is also used in the Satellite Carrier Block: there is a satellite_carrier_channel_set (more information in emulated satellite carriers) for each Spot on the gateways, since each gateway can serve more than one spot. The satellite handles the traffic to/from all spots, and has a satellite_carrier_channel_set for each pair spot/gateway. The terminal, since it is associated to only one spot/gw, has only one satellite_carrier_channel_set.