Correct Answer - Option 4 : OFDM
OFDM:
Orthogonal frequency division multiplexing (OFDM) is a modulation technique is used within 4G LTE.
Using multiple carriers, each carrying a low data rate, OFDM is ideal for high-speed data transmission because it provides resilience against narrow band fading that occurs as a result of reflections.
1. MSK (minimum shift keying) is used in 2G but due to increased transmission bandwidth later GMSK (Gaussian Minimum Shift Keying) used in 2G.
2. FSK is used in low-frequency radio transmission. Eg - telemetry, weather balloon radiosondes, caller ID, garage door openers.
3. BPSK is used in OFDM and OFDMA to modulate the pilot subcarriers used for channel estimation and equalization.
