ttp

TTP

Table of content

• TTP
  • OpenSAND Exploitation
  • OpenSAND Software Design

TTP (Timeslot Time Plan) messages, inspired from DVB-RCS/RCS2 TBTP (Terminal Burst Time Plan) messages, are control messages implemented in OpenSAND to allow the gateways inform the satellite terminals about the resource allocations (number of slots per frame) for the return link.

TTP messages are sent periodically, one for each frame from the gateways to the terminals. One TTP is generated by each gateway for each spot. The procedure has two steps:

• The GW sends the TTP message towards the SAT using a dedicated carrier for control messages.
• The SAT broadcasts the TTP message on a dedicated control carrier to the corresponding GW/Spot.

When sending a TTP, the GW includes the capacities allocated (the slots dedicated per frame) to each terminal located in the spot, calculated by the DAMA Controller entity in the gateway.

In OpenSAND TTP messages are not affected by attenuation, so they are never lost. They carry, however, C/N information used by the ACM loop.

OpenSAND Exploitation

These features are transparent to the user, and no configuration is needed.

No probes exist associated to signaling messages, although some logs are emitted when a certain type of signaling message has been received/emitted.

OpenSAND Software Design

TTP messages are implemented as specializations of the DvbFrameTpl (which means that each type of message has different header fields).

The specific header fields to this type of message are:

Header fields:

• group_id: the terminal group ID.
• superframe_count: the superframe to which the time plan applies to.
• frame_loop_count: the frame number of frames in the superframe.
• frames: the frames in the superframe (described below)

The emulated time plans for each frame are composed of the following elements:

• tal_id: the termianl ID.
• offset: the offset inside in the superframe.
• assignment_count: the number of timeslots assigned.
• fmt_id: the fmt_id (MODCOD) to use.
• priority: the traffic priority.

The class Ttp implements methods for initializing and working with DvbFrames of this type.

TTP messages are created by the BlockDdvNcc(actually by SpotDownward) periodically, and filled out by the DamaCtrl class located on that gateway.