locked
Question on TTS11sSrc block RRS feed

  • Question

  • Hello!!

    I play with SoraSDK2.0 to implement some idea based on 802.11a code. In the 802.11a transmission chain in brick model, I do not know preamble generation code in TTS11sSrc break.

    1) What is the meaning of (rep<48>::vmemcpy ((vcs*)(lut+32 * size of Complex 16), (vcs *) lut). Comment of this is "this is an explicit overflow". My guess on this line is to make 10 identical symbols in STS. But, I am not sure whether my guess is right.

    2) What is the meaning of Windowing and why is it necessary? My guess on this line is to make delimiter on STS and LTS. But, I am not sure whether my guess is right.

    // Windowing

       lut[0].re >>= 1; lut[0].im >>= 1;
       lut[1].re >>= 1; lut[1].im >>= 1;

       lut[318].re >>= 1; lut[318].im >>= 1;
       lut[319].re >>= 1; lut[319].im >>= 1;

    3) In IFFTx block in CreateModGraph11a, this block uses IFFT<128> (in, out) function. However, TTS11sSrc break does not use this function. But, instead, this brick uses procedure that consists of three step.

    IFFTSSEEx<128>((vcs*)temp);
       rep<32>::vshift_right ((vcs*)temp, 4);

       for (i = 0; i < 128; i++) {
       lut[i] = temp[FFTLUTMapTable<128>(i)];
       }

    But, I think that these two are equivalent. Why do you define IFFT operation in different way? Is there any reason or any difference between them?

    Could anyone explain these three parts in preamble generation?

    Thank you.




    • Edited by Jaeims Sunday, February 16, 2014 7:05 AM
    Saturday, February 15, 2014 4:03 AM