Question: why ofdm is not used in uplink?
Answer: SC-FDMA. It is not possible to use OFDMA on the uplink since, as told before, it presents a high Peak-to-average Power Ratio. ... On SC-FDMA before applying the IFFT the symbols are pre coded by a DFT (Discrete Fourier Transform). This way each subcarrier after de IFFT will contain part of each symbol.