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SCFDMA using FFT Coprocessor of TCI6638K2K

Sravya Keerthana R
Prodigy 170 points

Other Parts Discussed in Thread: TCI6638K2K

Hi,

Can SCFDMA be done using FFT Coprocessor of TCI6638K2K. If yes, what is the configuration required for FFTc?

regards,

Sravya Keerthana 

  • 0
    Guru 13202 points

    Hello!

    Producing SC-FDMA requires two Fourier stages, DFT followed by IDFT. Device's FFTC can do LTE DFT sizes, as well as forward and inverse transforms. Moreover, FFTC may apply or remove 7.5 kHz frequency shift. So I believe one can produce uplink signal, though I have no practice doing that. As one may noticed, TI does not support for these cellular targeted devices any more. Please refer https://www.ti.com/lit/ug/sprugs2c/sprugs2c.pdf.

  • 0 in reply to Victor Kazmirenko
    Prodigy 170 points

    Hi,

    In SCFDMA, 7.5 kHz frequency shift is to be done at the output side(i.e, on time domain samples), but the 7.5 kHz frequency shift for FFTc is being done at the input side using the below mentioned formula. Can the same  frequency shift be done for the output samples? 

     H(n) = e± j2*pi*(n+4*n o )a/M

  • 0 in reply to Sravya Keerthana R
    Guru 13202 points

    Hi,

    I believe your observation is correct, and FFTC design suits best for receiving of LTE uplink. Still, frequency shift is rather cheap operation comparing to DFT calculation. So one may consider additional step and process FFTC output data on DSP performing that complex multiplication. Also, if you have some FPGA on your output path, CORDIC in vector rotating mode with phase accumulator would do the job. This latter solution I have tried myself. 

    Probably, my first answer was misleading in the sense that complete uplink signal processing can be done with use of FFTC alone. I would refrain claiming that.