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

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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>> Discuss-gnuradio@gnu.org
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>
>


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