Electronic Communication Systems 2nd Edition by Roy Blake

Exercise 20

A direct-sequence spread-spectrum system uses FSK with a chipping rate of 20 to 1. The signal-to-noise ratio for the spread signal is - 5 dB (that is, the signal is 5 dB weaker than the noise in the same bandwidth). If the data is transmitted at 50 kb/s, calculate:
(a) the chipping rate
(b) the bandwidth occupied by the spread signal if the modulation scheme used allows 1.5 bits/s/Hz
(c) the signal-to-noise ratio for the despread signal at the receiver