it shows how errors are measured in tranmission

1. By Anchal Arora
13MCA0157

2.  The bit error rate (BER) is the number
of bit errors per unit time. Thebit error ratio
(also BER) is the number of bit errors divided
by the total number of transferred bits during a
studied time interval.
 BER is a unitless performance measure, often
expressed as a percentage.

3.  The bit error probability pe is the expectation
value of the bit error ratio. The bit error ratio
can be considered as an approximate estimate
of the bit error probability. This estimate is
accurate for a long time interval and a high
number of bit errors.

5.  The packet error ratio (PER) is the number of
incorrectly received data packets divided by
the total number of received packets. A packet
is declared incorrect if at least one bit is
erroneous. The expectation value of the PER is
denoted packet error probability pp, which for
a data packet length of N bits can be expressed
as:

6.  In telecommunication transmission, the bit
error rate (BER) is the percentage of bits that
have errors relative to the total number of bits
received in a transmission, usually expressed
as ten to a negative power.
 For example, a transmission might have a BER
of 10 to the minus 6, meaning that, out of
1,000,000 bits transmitted, one bit was in error.

7.  The BER is an indication of how often
a packetor other data unit has to be
retransmitted.
 Too high a BER may indicate that a slower
data rate would actually improve overall
transmission time for a given amount of
transmitted data since the BER might be
reduced, lowering the number of packets that
had to be resent because of an error.

8.  A BERT (bit error rate test or tester) is a
procedure or device that measures the BER for
a given transmission.
 A bit error rate tester (BERT), also known as
a bit error ratio tester.

9. The main building blocks of a BERT are:
 Pattern generator, which transmits a defined test
pattern to the test system
 Error detector connected to the test system, to
count the errors generated by or test system
 Clock signal generator to synchronize the pattern
generator and the error detector
 Digital communication analyser is optional to
display the transmitted or received signal.
 Electrical-optical converter and optical-electrical
converter for testing optical communication
signals.