Re: [Discuss-gnuradio] Issue while adding streaming data : Integrating MRC in gr-ieee 80211

Not sure what this video shows, but I guess that's the same thing. If
one queue of the add block is full (and the other is empty) then, I
guess, the flow graph is stuck and the USRP will stop receiving.

On 04/27/2018 11:00 AM, 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.
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Discuss-gnuradio mailing list
>>> Discuss-gnuradio@gnu.org
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>
>>
>

--
Dipl.-Inform. Bastian Bloessl
Researcher @ CONNECT Center
Trinity College Dublin

GitHub/Twitter: @bastibl
https://www.bastibl.net/

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