Re: [Discuss-gnuradio] Google Summer of Code 2014 applicant : Optimization with VOLK

[Abhishek Bhowmick]

Hi,

So, according to some suggestions,  I looked into how I can potentially use better signal processing for the OFDM receiver. I was thinking of a LS estimator with higher order interpolation or an MMSE estimator for the channel estimator part. Also, a MMSE-DFE or Viterbi equalizer. These will need matrix operations and other computations, which can potentially be developed into new volk kernels.
1. Are the computational complexities involved feasible in the current framework ?
2. Though they can give better BER in adverse channel conditions, can they do deliver more in terms of throughput/performance?

3. Is it a good idea to include such implementations alongside doing new volk kernels in the same proposal ?

Abhishek

On Wed, Mar 12, 2014 at 3:38 AM, Florian Kaltenberger <address@hidden> wrote:

Hi Nathan and Abhishek,

On 10/03/2014 23:22, West, Nathan wrote:

Ah! So there was a slight miscommunication. Yes, porting the OpenAirInterfaces
SIMD code to VOLK is a good option as well. The turbo channel coder/decoder
is part of that. I've *briefly* looked at the code to see what is
currently there, and
it's my understanding that the work involved will be to write generic
C implementations
of vectorized code where the generic version does not exist. Beyond
that porting to
newer/different ISAs (AVX or NEON depending on your preference and hardware
availability). I think Florian is on the gr-discuss mailing list, but
I've CCed him to
hopefully provide more details as he's more familiar with the original
code base.

I only joined this mailing list recently, so I probably missed a part of the discussion. Let me summarize briefly what OpenAirInterface can provide. We have optimized SIMD (SSE4) implementations of the LTE turbo encoder and decoder as well as the LTE tail-biting Viterbi encoder and decoder. We also have the 802.11 Viterbi encoder and decoder. The only functions for which we have generic non-vectorized functional equivalents is the LTE turbo decoder.
I am not sure I understand why it is necessary to write generic versions for the already optimized SIMD code. My idea was to port the optimized SIMD code from OpenAirInterface to VOLK, such that is can be used by GR applications. I am not familiar with VOLK (yet) but this might just be as easy as writing a wrapper function.
As Nathan suggested, the more interesting part is probably to upgrade the code to AVX2 or similar. 

Cheers,
Florian.

--
Regards;
Abhishek Bhowmick,

Senior Undergraduate,

Department of Electrical Engineering,

IIT Bombay.