Hello, people!
I am trying to build a working graph gor 16QAM transmission, but have an issue I don't know how to deal with.
Receiving part seems to me ok(I added screenshot of constellations I get), but decoding is not.
Result is depending on loop bandwidth of constellation receiver block.
If it is set to something big (around 0.1), then I receive a bunch of good bits and and then a bunch of garbage, then again, a bunch of good bits and a bunch of garbage. And a bunch means several kilobits, so it is quite a lot. If loop bandwidth of constellation receiver is set to a small value (like 0.001), then the result is stable in time, but it can be either good bits or garbage. Like from 10 runs 2 or 3 times there is a good stable decoding of good bits and others are complete garbage.
I suspect that constellation receiver may lock into different states and one of them is correct and others are not.
So, my questions are:
- Am I right, that receiving part is ok, and constellation looking normal for decoding?
- Is there something I could do in this graph to fix it, or completely different approach required?
Thank you in advance!
Gennady Kazachek
qam16_flowgraph.grc
const.png