Re: [Discuss-gnuradio] Dynamic OFDM carrier allocation

[Johnathan Corgan]

On Mon, Nov 28, 2016 at 3:42 AM, <address@hidden> wrote:

 

    1. I want the block to transmit the range of unallocated carriers to another part of the flowgraph. I've read about the Probe blocks and message passing, but they look overly complicated for the task. Could I directly access a GRC variable from my python code and set its value to the new range? Or should I use messages / probes?

​Message passing is a straightforward way for the work (or another message handling) function of one block to pass arbitrary metadata to another block anywhere in the flowgraph.

Unfortunately, GRC variables are an abstraction that turns ​into a set of function calls in the generated flowgraph, so there is nothing to "access". So you need to create message-based configuration ports in the blocks that need updating, then connect those to a message output port on the block that calculates the average and outputs the message.

    2. It depends on the first question, but if I wanted to first average the obtained unallocated carriers and then transmit the value, how would a block that transmits 1 value every 5 inputs work in this situation? I guess messages would make more sense, as I could send the message once I am sure of the carrier allocation, and only update the variable with meaningful values.

​You can keep track and average in the message receiver or transmitter.​

    3. As for the Carrier Allocation block, I've read in https://lists.gnu.org/archive/html/discuss-gnuradio/2014-02/msg00416.html that it is not possible to update the allocated carriers during execution. When implementing a new block capable of doing that, would the constant change of the allocation cause problems with the tagged stream of constant length that comes before it?

​If the upstream tagged stream assumes a fixed number of allocated carriers, then you'd need to change that so the tagged stream length tracks the changing number of allocated tones.

This is sort of a lot to tackle all at once; I'd focus on getting one thing at a time right.

--

Johnathan Corgan
Corgan Labs - SDR Training and Development Services

http://corganlabs.com