Bit Error Rate Test
SMIQ
1125.5555.03
2.380
E-9
BLER TYPE
Displays the CRC type. Only the CRC_16_BIT type is supported at present.
IEC/IEEE-bus command
:BLER:SET:TYPE?
DATA POLARITY
Setting the data bit polarity.
NORM
Normal polarity
INV
Inverted polarity
IEC/IEEE-bus command
:BLER:SET:DATA[:POL] NORM
CLOCK SLOPE
Setting the clock edge polarity.
POS
Rising edge
NEG
Falling edge
IEC/IEEE-bus command
:BLER:SET:CLOC[:POL] RIS
INFORMATION DATA
ENABLE
Setting the polarity of the DUT's DATA ENABLE signal.
LOW
The bits received at low level of the data enable signal are
interpreted as information bits.
The bits received at high level of the data enable signal are
interpreted as checksum bits.
HIGH
The bits received at high level of the data enable signal are
interpreted as information bits.
The bits received at low level of the data enable signal are
interpreted as checksum bits.
IEC/IEEE-bus command
:BLER:SET:DEN LOW
UNIT
Setting the unit for BLOCK ERROR RATE display.
ENG
Display in exponential notation, exponent -3 or -6
SCI
Display in scientific notation, i.e. normalized to one character
ahead of the decimal point
%
Display of relative frequency in percent
ppm
Display of relative frequency in parts per million
IEC/IEEE-bus command
:BLER:UNIT ENG
2.23.2.2 CRC
Polynomial
CCITT CRC 16 : G(x) = x
16
+ x
12
+ x
5
+ x
1
is the only CRC polynomial currently supported.
At the beginning of information data (marked by the edge of the DATA ENABLE signal) the shift register
is initialized with 0. All information bits are then shifted through the shift register. The CRC component
is then read into a second register and compared bit by bit with the result of the calculation.
2.23.2.3 Measurement Result, Accuracy, Measurement Time
Range of values
The measurement results for the block error rate (i.e. the quotient of erroneous
blocks and total blocks) are normally between 10
-2
and 10
-4
. This means that a large
number of blocks may have to be tested before an erroneous block occurs.
Because of the large number of blocks involved the measurement time is usually
very long. Since 32-bit-wide counters are used for the total number of blocks and the
error bits, the maximum measurement time is 4.29 x 10
9
blocks.
Statistics
The BLER measurement measures statistical block errors, i.e. errors which do not
occur at regular intervals but at random. Although a single measurement
determines the exact number of errors in the measured interval, a statistically
