OFDM can be used a multiple access scheme allowing simultaneous frequency separated transmissions to and from multiple mobile terminals
In OFDM as well as SC-FDMA, equalization is achieved on the receiver side after the FFT calculation, by multiplying each Fourier coefficient by a complex number. Thus, frequency-selective fading and phase distortion can be easily combated. The advantage is that FFT and frequency domain equalization requires less computation power than the conventional time-domain equalization.
A related concept is the combination of a single carrier transmission with the single-carrier frequency-domain-equalization (SC-FDE) scheme. [9] The single carrier transmission, unlike SC-FDMA and OFDM employ no IFFT or FFT at transmitter, but introduce the cyclic prefix to transform the linear channel convolution into a circular one. After removing the cyclic prefix at receiver, an FFT is applied to arrive in the frequency domain, where a simple single-carrier frequency-domain-equalization (SC-FDE) scheme can be employed, followed by the IFFT operation.
đang được dịch, vui lòng đợi..