dvb rcs2

DVB-RS2

Table of content

• DVB-RS2
  • OpenSAND Exploitation
    • Encapsulation
    • DVB burst Scheduling
      • Probes
    • Multiple access and MODCOD
  • OpenSAND Design

OpenSAND implements a protocol based on the DVB-RCS2 standard for the return link.

This protocol fragments and encapsulates network packets into DVB bursts which are sent through dedicated carriers, which are then rebuilt into network packets at their reception.

The DVB bursts scheduling is based on a Strict Priority algorithm. Priorities are assigned to each QoS FIFOs.

To optimize the performance in various conditions, the DVB-RCS2 protocol allows the use of different MODCODs by terminal assigned to the same carrier.

The DVB-RCS2 protocol allows different types of multiple access: DAMA or SCPC.

OpenSAND Exploitation

The DVB-RCS2 protocol provides the following features.

Encapsulation

The encapsulation protocol used for DVB-RCS2 is RLE.

For more information about encapsulation, please consult the encapsulation page.

DVB burst Scheduling

Every terminal has a specific DVB-RCS2 scheduler. Its Strict Priority algorithm associates a priority to each QoS FIFOs. Thus, the packets with the highest priority are sent on the first place, continuing by the following lower priority, etc.

For more information, please consult the QoS page.

Probes

The probes related to the DVB-RCS2 scheduling available on OpenSAND are detailed below (other probes are detailed on their specific feature pages, for example DAMA, MODCOD, etc.):

• SOF interval: Available on terminals under the Perf section, it shows the time (in milliseconds) passed between two Start of Frame.
• Queue size probes: Available on the terminals. They display the size of the FIFO queues at each scheduling loop. One probe exists for each queue (AF, BE, EF, NM, SIG). The size is displayed in kbits and in number of packets (packets used in the Encapsulation layer, e.g. RLE) inside the packets section.
• Queue loss probes: Available on the terminals. They display the data lost in the FIFO queues at each scheduling loop when the FIFO surpasses the maximum length. One probe exists for each queue (AF, BE, EF, NM, SIG). The loss is displayed in kbits and in number of packets (packets used in the Encapsulation layer, e.g. RLE) inside the packets section.
• Throughput probes: Available on the gateways, on the terminals and on the satellite.
  • On the gateway, the probe L2_from_SAT (in the Throughputs section for each spot) displays the throughput of the layer 2 on the return link (DVB bursts).
  • On the terminal, the throughput probes are located in the Throughputs section. They are divided in two sections:
    • L2_to_SAT_after_sched: contains probes displaying the throughput at the output of each FIFO queue (and one for the total) during one scheduling loop.
    • L2_to_SAT_before_sched: contains probes displaying the throughput at the input of each FIFO queue (and one for the total) during one scheduling loop.
  • On the satellite, the throughput probes are located in the Throughputs section of each spot and each gateway. The probes corresponding to DVB-RCS2 are those on the return link (L2_from_ST and L2_to_GW) for transparent mode, or in the uplink (L2_from_ST and L2_from_GW) for regenerative. The throughput considered is that of the DVB bursts.

Multiple access and MODCOD

Depending on the used multiple access method (DAMA or SCPC), different MODCODs can be enabled.

This list of enabled MODCODs is defined for each return link carrier on a star topology (or downlink carrier on a mesh topology).

In case the multiple access SCPC is selected, the protocol used is DVB-S2 and the available MODCODs are its own.

The list of all DVB-RCS2 MODCODs is defined on a unique file.

For more information about MODCOD, please consult the MODCOD page.

OpenSAND Design

The DVB-RCS2 scheduling is implemented on the block DVB in each DamaAgent object of the Terminal in a star topology, or in each SpotDownwardRegen object of the Satellite in a mesh topology.

The encapsulation protocol, multiple access method, and MODCOD restrictions for the DVB-RCS2 protocol are implemented by the OpenSAND Manager and the configuration.