Question

Which of the following modulation techniques requires the highest Eb/No (energy per bit to noise power spectral density ratio) to maintain a specified BER (Bit Error Rate)?

Select one:

a. QPSK

b. 16-PSK

c. 8-PSK

d. BPSK

Answer 1

• 16 PSK has more BER with respect to Eb/No ratio but gives more spectral width and can carry more traffic. So, it would require higher Eb/No to maintain a specific BER.

• Consider the following evidences in support of given answer:

• Although the spectral width of QPSK is more then BPSK and that of 8-PSK is more than QPSK, it incurs more Eb/No ratio.
• Similarly, 16-PSK has more spectral width as compared to both 8-PSK and QPSK and thus it can carry more traffic, but it is again at the expense of Eb/No ratio.
• When we consider the BER, 8 PSK is better than 16 PSK as the BER values with respect to the Eb/No in case of 8 PSK are lower than the values obtained in the case of 16 PSK.
• Again, 4 PSK is better than both 8 PSK and 16 PSK because the BER values with respect to the Eb/No in case of 4 PSK are lower than the values obtained in the case of 8 PSK and 16 PSK.