Documentation

This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English verison of the page.

Note: This page has been translated by MathWorks. Please click here
To view all translated materals including this page, select Japan from the country navigator on the bottom of this page.

Descrambler

Descramble input signal

  • Library:
  • Communications System Toolbox / Sequence Operations

Description

The Descrambler block descrambles a scalar or column vector input signal. The Descrambler block is the inverse of the Scrambler block. If you use the Scrambler block in a transmitter, then you use the Descrambler block in the related receiver.

This schematic shows the descrambler operation. The adders and subtracter operate modulo N, where N is the value specified by the Calculation base parameter.

At each time step, the input causes the contents of the registers to shift sequentially. Using the Scramble polynomial parameter, you specify the on or off state for each switch in the descrambler. To make the Descrambler block reverse the operation of the Scrambler block, use the same parameter settings in both blocks. If there is no signal delay between the scrambler and the descrambler, then the Initial states in the two blocks must be the same.

To achieve repeatable initial descrambler conditions, you can use one of these optional input ports:

This block can accept input sequences that vary in length during simulation. For more information about sequences that vary in length, see Variable-Size Signal Basics (Simulink).

Ports

Input

expand all

Input data signal, specified as an NS-by-1 vector. NS represents the number of samples in the input signal. The input values must be integers from 0 to Calculation base1.

Data Types: double

Reset scrambler, specified as a scalar. The scrambler is reset if a nonzero input is applied to the port.

Dependencies

To enable this port, set Initial states source to Dialog Parameter and select Reset on nonzero input via port.

Initial states of the descrambler registers when the simulation starts, specified as a nonnegative integer vector. The length of ISt must equal the order of the Scramble polynomial parameter. The vector element values must be integers from 0 to Calculation base1.

Dependencies

To enable this port, set Initial states source to Input port.

Output

expand all

Output descrambled data, returned as an NS-by-1 vector. NS equals the number of samples in the input signal.

Data Types: double

Parameters

expand all

Calculation base used in the descrambler for modulo operations, specified as a nonnegative integer. The input and output of this block are integers from 0 to Calculation base1.

Polynomial that defines the connections in the descrambler, specified as a character vector, integer vector, or binary vector. The Scramble polynomial parameter defines if each switch in the descrambler is on or off. Specify the polynomial as:

  • A character vector, such as '1 + z^-6 + z^-8'. For more details on specifying polynomials in this way, see Character Representation of Polynomials.

  • An integer vector, such as [0 -6 -8], listing the descrambler coefficients in order of descending powers of z-1, where p(z-1) = 1 + p1z-1 + p2z-2 + ...

  • A binary vector, such as [1 0 0 0 0 0 1 0 1], listing the powers of z that appear in the polynomial that has a coefficient of 1. In this case, the order of the descramble polynomial is one less than the binary vector length.

Example: '1 + z^-6 + z^-8', [0 -6 -8], and [1 0 0 0 0 0 1 0 1] all represent this polynomial:

p(z-1) = 1 + z-6 + z-8

  • Dialog Parameter – Specify descrambler initial states by using the Initial states parameter.

  • Input port – Specify descrambler initial states by using the ISt port.

Initial states of descrambler registers when the simulation starts, specified as a nonnegative integer vector. The length of Initial states must equal the order of the Scramble polynomial parameter. The vector element values must be integers from 0 to Calculation base1.

Dependencies

This parameter is available when Initial states source is set to Dialog Parameter.

Select this parameter to reset the Descrambler block via input port Rst.

Dependencies

This parameter is available when Initial states source is set to Dialog Parameter.

See Also

Blocks

System Objects

Introduced before R2006a

Was this topic helpful?