What is the significance of the DFT in SC-FDMA systems? [closed]

1. What is the purpose of using SC-FDMA?
2. What is the main reason of implementing SC-FDMA in uplink LTE?
3. How does SC-FDMA differ from FDM?
4. Why LTE uses OFDMA for DL and SC-FDMA for UL?

What is the purpose of using SC-FDMA?

SC-FDMA (aka DFT-precoded/spread OFDMA) is the multiuser version of single carrier modulation with frequency do- main equalization (SC/FDE). The main objective of SC-FDMA is to introduce transmission with lower PAPR than OFDMA.

What is the main reason of implementing SC-FDMA in uplink LTE?

SC-FDMA is preferred for LTE uplink mainly due to its advantage of having low peak-to-average power ratio (PAPR) during signal transmission. The performance of SC-FDMA depends on modulation scheme used for it.

How does SC-FDMA differ from FDM?

It uses multiple RF carrier signals at different frequencies which sends some of the bits on each of the assigned channels. This seems to be similar to FDM but in case of OFDM, total subcarriers are divided into subchannels and these subchannels are mapped to one single data/traffic source.

Why LTE uses OFDMA for DL and SC-FDMA for UL?

LTE uses a pre-coded version of OFDM called Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink. This is to compensate for a drawback with normal OFDM, which has a very high Peak to Average Power Ratio (PAPR).