Re: [Discuss-gnuradio] Constellation Blocks

[Tom Rondeau]

On Sun, Oct 2, 2016 at 12:10 PM, Sebastian Müller <address@hidden> wrote:

Hi list,

I’m a bit confused about the constellation blocks that are going to replace the deprecated specific modulation blocks.

In previous examples, we used 

[Signal]->[Packet Encoder]->[Mod Block]->[Channel]->[Demod Block]->[Packet Decoder]->[Sink]. 

Now, I’ve tried to replace this chain with non-deprecated blocks. First, I’m wondering why I can choose differential encoding in the „Constellation Object“ block as well as in the „Constellation Modulator“ block. What happens if I only select it in one of them? Also, there is no way to select differential encoding in the „Constellation Decoder“, but AFAIK the receiver must know if differential encoding is used. How is this correctly intended?

Second, I’m wondering what is going to replace the deprecated „Packet Encoder“. Theoretically, we need an encoding to transfer the infinite input alphabet (float) to a finite output alphabet (int8). I’ve not found a block that handles this task. Any ideas on how to replace the signal chain above is appreciated!

Best,

Sebastian

Sebastian,

Good questions. The differential issue should be looked into and addressed. It's possible that the definition of the constellations could be simplified or cleaned up quite a bit to make it easier to use.

As for the packet encoder, that's a very static way of defining a packet. Take a look at this page to see the new concepts using the packet formatter and parser concept:

http://gnuradio.org/doc/doxygen/page_packet_comms.html

Tom