B. P. Lathi, Zhi Ding - Modern Digital and Analog Communication Systems-Oxford University Press (2009)

324 SAMPLING AND ANALOG-TO-DIGITAL CONVERSION
data are now transmitted to the monitoring station (Fig. P6.2-5). The ECG signal bandwidth
is 100 Hz. The maximum acceptable error in sample amplitudes is 0.25% of the peak signal
amplitude. The sampling rate must be at least twice the Nyquist rate. Determine the minimum
cable bandwidth needed to transmit these data.
Figure P.6.2-5
Monitoring
station
Processing
center
Cable
Receiver
e
e
e
6.2-6 A message signal m(t) is transmitted by binary PCM without compression. If the SQNR is required
to be at least 47 dB, determine the minimum value of L = 2 n required, assuming that m(t) is
sinusoidal. Determine the actual SQNR obtained with this minimum L.
6.2-7 Repeat Prob. 6.2-6 for m(t) shown in Fig. P6.2-7.
Hint: The power of a periodic signal is its energy averaged over one cycle. In this case, however,
because the signal amplitude takes on the same values every quarter cycle, the power can also be
found by averaging the signal energy over a quarter cycle.
Figure P.6.2·7
6.2-8 For a PCM signal, determine L if the compression parameter µ = I 00 and the minimum SNR
required is 45 dB. Determine the output SQNR with this value of L. Remember that L must be a
power of 2, that is, L = 2 n for a binary PCM.
6.2-9 A signal band-limited to 1 MHz is sampled at a rate 50% higher than the Nyquist rate and quantized
into 256 levels by using a µ-law quantizer with µ = 255.
(a) Determine the signal-to-quantization-noise ratio.
(b) The SQNR (the received signal quality) found in part (a) was unsatisfactory. It must be
increased at least by 10 dB. Would you be able to obtain the desired SQNR without increasing