Which spreading technique multiplies the data with a pseudo-random noise sequence to spread the spectrum?

Which spreading technique multiplies the data with a pseudo-random noise sequence to spread the spectrum?

• A. Direct-Sequence Spread Spectrum (DSSS)
• B. MIMO-OFDM
• C. FHSS
• D. 802.11g

Answer: (A)

Spreading the spectrum by multiplying the data with a pseudo-random noise sequence is the essence of direct-sequence spread spectrum. In this approach, the data is converted into a stream of chips and then multiplied by a PN sequence, producing a signal whose bandwidth is many times the original data rate. This spreading adds processing gain, making the signal more resistant to interference and easier to separate from others using the same spectrum. At the receiver, the same PN sequence is used to despread the signal, recovering the original data and providing a form of code division multiple access. The other options don’t describe this particular spreading method. MIMO-OFDM is about using multiple antennas and splitting data across many subcarriers rather than spreading a signal with a PN sequence. FHSS spreads by hopping across frequencies according to a sequence rather than multiplying the data by a PN code. 802.11g is a wireless standard that uses OFDM, not the direct-sequence spreading technique (though some older standards like 802.11b used DSSS).

Spreading the spectrum by multiplying the data with a pseudo-random noise sequence is the essence of direct-sequence spread spectrum. In this approach, the data is converted into a stream of chips and then multiplied by a PN sequence, producing a signal whose bandwidth is many times the original data rate. This spreading adds processing gain, making the signal more resistant to interference and easier to separate from others using the same spectrum. At the receiver, the same PN sequence is used to despread the signal, recovering the original data and providing a form of code division multiple access.

The other options don’t describe this particular spreading method. MIMO-OFDM is about using multiple antennas and splitting data across many subcarriers rather than spreading a signal with a PN sequence. FHSS spreads by hopping across frequencies according to a sequence rather than multiplying the data by a PN code. 802.11g is a wireless standard that uses OFDM, not the direct-sequence spreading technique (though some older standards like 802.11b used DSSS).