Question

Suppose a full-scale voice signal with bandwidth 10 kHz is sampled at the Nyquist rate and quantized by using a b-bit uniform quantizer. The bit stream is then transmitted using binary PAM over an AWGN channel that is capable of passing frequencies in the range of [0, 200kHz].

1. Suppose that the signal is transmitted at the maximum bit rate and the two-sided spectral density of noise at the receiver is 10-6 W/Hz. What is the required signal power to guarantee a BER less than or equal to 10-5?

2. Now suppose that the passing frequency range of the channel becomes [0, 100kHz]. To keep the same bit rate, what kind of digital modulation scheme should be adopted? Determine the corresponding BER and the probability of symbol error (SER) if the signal power remains the same as that in Q2.2.  

Answer 1