Question

For Networks -> Help me find out:

1.)   Television channels are 6 MHz wide. How many bits/sec can be sent if four-level digital signals are used? Assume a noiseless channel.

2.)   A modem constellation diagram similar to Fig. 2-23 has data points at the following coordinates: (1, 1), (1, −1), (−1, 1), and (−1, −1). How many bps can av modem with these parameters achieve at 1200 symbols/second?

Answer 1

Answer 1

Television Bandwidth (B) = 6 MHz

Digital signals level (V) = 4

Using Nyquist theorem, max sample can be = 2 B log₂V bits per second = 2*6*10⁶*log₂4 = 24 million bits per second

It means sample data rate = 24 Mbps

Answer 2

This is QPSK encoding. QPSK transmits 2 bits per symbol which means total bits transferred per second = 2*1200 = 2400 bps.