Ok I understand now. Could you point me how to approach for such
synchronization between the two branches. Or if there are any existing
open source example if you know.
For this implementation, I was following one of your recently
co-authored paper "Low-Complexity Soft-Bit Diversity Combining for
Ultra-Low Power Wildlife Monitoring". However it seems that the source
code is not open yet.
Sumit
On 27/04/2018 11:00, Sumit Kumar wrote:
Yes indeed, this could also happen! I note this in my to-do list.
But as of now there are no warnings of overruns etc. I recorded it.
What is making USRP to stop receiving.
https://www.youtube.com/watch?v=SPXLJ3iEWg8&feature=youtu.be
Sumit
On 27/04/2018 10:41, Bastian Bloessl wrote:
Hi,
I'm not sure if I get it, but don't you need some synchronization
logic between the branches. Consider what happens if one branch
receives frames while the other one doesn't, then data queues up in
the add block, which will sooner or later lead to overruns,
independent from the buffer size.
Best,
Bastian
On 04/27/2018 09:54 AM, Sumit Kumar wrote:
Hi,
I am working on soft bit maximal ratio combiner (SBMRC). It's
basically a MRC but instead of combining the actual signals
according to their SNR, we combine the LLRs from separate branches
and send them to Soft Decision Viterbi Decoder (SDVD). For this, I
have modified gr-ieee 80211 which generates soft bits and integrated
a SDVD with it. It works good when I use either single branch or
both branch separately.
In order to implement SBMRC, for every OFDM symbol decoded, a vector
of LLR (size 48 X 1) is generated from both the receiver branches.
These two vectors of LLR are further added and sent to SDVD. I
configured the ADD block to take 48 floats as input.
First I made a simulator for SBMRC, but even after increasing the
output buffer size to 500000, warnings of buffer over flow kept coming.
Then I used USRP, it simply refuses to work. I am using NI 2901
Tx/Rx A and Tx/Rx B ports as my receive branches. The LEDs go green
for a second then stop. No error no warning.
Looks like the *ADD *block is the cause. I have never seen this, so
I am clueless where to debug. Am I missing something fundamental here ?
The attached picture *usrp_sbmrc* says details of my schematic and
the results when I use USRP.
The attached picture *sbmrc_sim* says details of my schematic and
the results when I use simulations.
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