step
System object: comm.PreambleDetector
Package: comm
Detect preamble in data
Syntax
idx = step(prbdet,x)
[idx,detmet] = step(prbdet,x)
idx = prbdet(x)
[idx,detmet] = prbdet(x)
Description
Note
Starting in R2016b, instead of using the step
method
to perform the operation defined by the System object™, you can
call the object with arguments, as if it were a function. For example, y
= step(obj,x)
and y = obj(x)
perform
equivalent operations.
idx = step(prbdet,x)
returns the location
of the end of the preamble in data sequence x
,
using preamble detector prbdet
. The index is of
data type double
.
[idx,detmet] = step(prbdet,x)
also returns
the detection metric, detmet
. This syntax is available
when the Input
property is 'Symbol'
. detmet
has
the same dimensions and data type as x
.
The output, detmet
, is determined by one
of these algorithms:
If either the preamble or input data is complex, the detection metric is the absolute value of the cross-correlation of the preamble and the input signal.
If both the preamble and input data are real, the detection metric is the cross-correlation of the preamble and the input signal.
idx = prbdet(x)
is equivalent to the first
syntax.
[idx,detmet] = prbdet(x)
is equivalent
to the second syntax.
Note
prbdet
specifies the System object on
which to run this step
method.
The object performs an initialization the first time the step
method
is executed. This initialization locks nontunable
properties and input specifications, such as dimensions, complexity,
and data type of the input data. If you change a nontunable property
or an input specification, the System object issues an error.
To change nontunable properties or inputs, you must first call the release
method
to unlock the object.