aos

Overview ¶

Example: A high-rate downlink with AOS

The downlink guide uses TM frames, which carry packets and nothing else. AOS carries three different things, on three virtual channels, over one physical channel:

VC0  M_PDU  Space Packets, the same job TM does
VC1  B_PDU  a raw octet-aligned bitstream, with no packet structure
VC2  VCA    fixed-size opaque blocks, with no protocol header at all

It also adds two fields TM does not have:

Insert Zone  a fixed slot in every frame, for a synchronous stream
FHEC         Reed-Solomon over the frame header, so a corrupted header
             can be detected rather than mis-routed

That is what makes AOS the choice for a high-rate mission: an instrument producing a bitstream does not have to be dressed up as packets first.