0

I'm trying to implement the UPLINK of a Ground Station controlling a small satellite. The idea is that the link should stay always active in between each transmitted telecommand. For this, I need to insert some DUMMY or IDLE sequence bytes such as 0xAA or similar.

I have found that some people already faced a similar issue and posted their questions here:

So far, the best I could achieve was to modify the EventStream Source block from https://github.com/osh/gr-eventstream in order to preload the vectors with my dummy sequence (i.e. 0xAA) instead of preloading them with zeroes. This is a general overview of the GNURadio graph I'm using:

GNURadio Flowgraph Picture

This solution however introduces a huge latency and the sent message does not appear at the output until a huge amount of time has expired (in the order of several seconds).

Is there a way of programming the USRP using GNURadio so that it constantly sends a fixed sequence which should only be interrupted when an incoming message is passed? I assume that the USRP has the ability of reading tagged streams in order to schedule transmissions. However, I'm not sure how to fit this in my specific application.

Thanks beforehand!

Joa

jcabeza
  • 11
  • 1

1 Answers1

0

I believe this could be done using a TCP or UDP source block.

Your control information could be sent to the socket using TCP/UDP. GNU Radio would then collect and transmit the packets. Your master control program would then have to handle the IDLE stuffing but solving the problem external to GNU Radio is easier.

Your master control program would basically do the following: 1. tx control data as needed 2. if no control data ready before next packet must be sent send an IDLE packet

Alex Colpitts
  • 11
  • 1
  • 3