because they have a high speed compared to fft
Orthogonal frequency-division multiplexing
hi.... for DIT fft algorithm, refer to this link, it has c-code for that. http://cnx.org/content/m12016/latest/
Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital. Pilot signals and training symbols (preambles) may also be used for time.
2.4GHz is used & OFDM
SISO-OFDM is an OFDM system with one transmit and one receive antenna.
because they have a high speed compared to fft
FFT reduces the computation since no. of complex multiplications required in FFT are N/2(log2N). FFT is used to compute discrete Fourier transform.
plot(abs(fft(vectorname)))the FFT function returns a complex vector thus when you plot it, you get a complex graph. If you plot the absolute value of the FFT array, you will get the magnitude of the FFT.
FT is needed for spectrum analysis, FFT is fast FT meaning it is used to obtain spectrum of a signal quickly, the FFT algorithm inherently is fast algorithm than the conventional FT algorithm
There's no need for it.
OFDM uses 48 subchannels for data and 4 are used as Pilot Carriers.
Orthogonal frequency-division multiplexing
In OFDM, sub-carrier spacing is maintained in such a way that the maximum of one sub-carrier occurs at the minimum of the successive sub-carrier, a loss of orthogonality results if this pattern is not achieved in the sub-carriers of OFDM transmission. Loss of orthogonality is due to ISI, ICS, Frequency offset amongst the sub-carriers of OFDM.
Inter symbol interference (ISI) in OFDM systems can be minimized by using a cyclic prefix. This involves adding a copy of the end of each OFDM symbol to the beginning before transmission. The cyclic prefix helps to mitigate the effects of multipath fading and reduces ISI by allowing the receiver to separate the OFDM symbols with a guard interval.
FFT is faster than DFT because no. of complex multiplication in DFT is N^2 while in FFT no. of complex multiplications are N/2(log2N). for example if N=8 no. of complex multiplications required in DFT are 64. while no. of complex multiplications required in FFT are 12 thus reduces computation time.
OFDM