The correct answer is: A. IEEE 802.11a
CCK-OFDM (Complementary Code Keying-Orthogonal Frequency Division Multiplexing) is a modulation scheme used in the IEEE 802.11a wireless networking standard. It is a combination of two modulation schemes: CCK and OFDM. CCK is a modulation scheme that is used to improve the performance of wireless networks in noisy environments. OFDM is a modulation scheme that is used to improve the performance of wireless networks in high-speed data transfer.
CCK-OFDM is a more complex modulation scheme than CCK or OFDM alone, but it offers better performance in both noisy and high-speed data transfer environments. It is the modulation scheme used in the IEEE 802.11a wireless networking standard, which operates in the 5 GHz band.
The other options are incorrect because they do not use CCK-OFDM.
- IEEE 802.11b uses DSSS (Direct Sequence Spread Spectrum) modulation.
- IEEE 802.15.4 uses BPSK (Binary Phase Shift Keying) modulation.
- IEEE 802.11g uses OFDM modulation.