5G technology works on the principle of:

Concept

A radio air interface is built on a waveform / multiplexing scheme that decides how bits are mapped onto the radio signal. Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier technique: the high-rate data stream is divided across a large number of narrow, mutually orthogonal subcarriers sent in parallel. Because the subcarriers are orthogonal, they can overlap in frequency without interfering, which yields high spectral efficiency and robustness against multipath fading.

Why OFDM for 5G

5G New Radio (NR) defines its downlink and uplink waveform on OFDM (CP-OFDM, with an optional DFT-spread variant for the uplink). Splitting the wideband channel into many narrowband subcarriers turns a difficult wideband, frequency-selective channel into many easy flat sub-channels, enabling the very high data rates and reliable broadband transmission that 5G targets. Hence the governing principle is OFDM.

Contrast with the other choices

• Amplitude Modulation — an analog, single-carrier scheme for legacy broadcast; far too low-rate for a broadband cellular link.

• Time Division Multiple Access — a multiple-access method (users share a carrier in time slots), not the underlying signal waveform.

• Frequency Division Duplexing — a duplexing method that separates uplink and downlink onto different bands, not a modulation/multiplexing waveform.