User's Manual

5.8GHz PDH User’s Manual
24
Pseudo-Random Bit Sequence (PRBS):
Random noise was first regarded as an element that damages the quality and quantity
of communicative signals in communication technology. The random noise in signal
channels often distorts the simulated signal produced or bit error to appear upon the
demodulation of digital signals. At the same time, it is also one of the elements that limit the
channel capacity. Consequently, human’s early attempt was to remove or lessen all the
pseudo noise in the communication system. Nonetheless, some of them decided to obtain
all these pseudo noise. For example, communicative equipments or systems testing in
laboratory require an addition of certain noise. So it is necessary to produce/obtain noise
here.
In the late 1940s, along with the communication theory, Claude Shannon pointed out
that under certain conditions, for the most effective communications, must adopt signals
containing the statistical property of white noise. Besides, in order to achieve
communications of high reliability and privacy, we must use random noise. However, the
biggest difficulty faced in using random noise is that it is not easy to repeatedly produced
and processed. Until the 60’s, the pseudo random noise came about and solve all these
problems.
Pseudo random noise poses statistical property similar to random noise. At the same
time, it can be repeatedly produced and processed easily. It has increasingly been
extensively use practically because it poses the advantages of random noise and none of
its disadvantages. In today’s world, it has been extensively used in digital circuit produced
periodic series (after filtering). In the future, this shall be called the periodic series or the
random series.
Pseudo random sequences are generated using a binary shift register with taps that
are modulo-2 added together and fed back to the register's input. The name commonly