Hi bastian,
To solve the following issue (as you predicted):
*"Consider what happens if one branch receives frames while the other
one doesn't,Consider what happens if one branch receives frames while
the other one doesn't."
*I combine the LLR of the SIGNAL fields from two branches and use that
to decode the SIGNAL filed. The decision is used to decode both the
branches. As of now it works, I mean doesn't crash at all! *
*Could you comment on this configuration.
Regards
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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