
131
Many users can be accommodated by allocating each a unique
spreading code. It is common to use a pseudo-noise (PN) generator to
multiply the bit rate and then to modulate the carrier with either FSK
or PSK.
Although spread spectrum is a digital system, in quality of signal
there are similarities with analogue:
Analogue Digital
Signal/noise ratio Energy per bit, E
b
/N
o
Intelligibility, signal/
noise + distortion
Bit error rate
References
Belcher, R. et al. (1989). Newnes Mobile Radio Servicing Handbook. Butter-
worth-Heinemann, Oxford.
Kennedy, G. (1977). Electronic Communications Systems, McGraw-Hill Koga-
shuka, Tokyo.
Winder, S.W. (2001). Newnes Telecommunications ...