Learn more about Communications Blockset

Scrambler - Scramble input signal

Library

Sequence Operations

Description

The Scrambler block scrambles the input signal, which must be a scalar or a frame-based column vector. If the Calculation base parameter is N, then the input values must be integers between 0 and N-1.

One purpose of scrambling is to reduce the length of strings of 0s or 1s in a transmitted signal, since a long string of 0s or 1s may cause transmission synchronization problems. Below is a schematic of the scrambler. All adders perform addition modulo N.

At each time step, the input causes the contents of the registers to shift sequentially. Each switch in the scrambler is on or off as defined by the Scramble polynomial parameter. You can specify the polynomial by listing its coefficients in order of ascending powers of z^-1, where p(z^-1) = 1 + p₁z^-1 + p₂z^-2+..., or by listing the powers of z that appear in the polynomial with a coefficient of 1. For example p = [1 0 0 0 0 0 1 0 1] and p = [0 -6 -8] both represent the polynomial p(z^-1) = 1 + z^-6 + z^-8.

The Initial states parameter lists the states of the scrambler's registers when the simulation starts. The elements of this vector must be integers between 0 and N-1. The vector length of this parameter must equal the order of the scramble polynomial. (If the Scramble polynomial parameter is a vector that lists the coefficients in order, then the order of the scramble polynomial is one less than the vector length.)

Dialog Box

Calculation base: The calculation base N. The input and output of this block are integers in the range [0, N-1].
Scramble polynomial: A polynomial that defines the connections in the scrambler.
Initial states: The states of the scrambler's registers when the simulation starts.

Pair Block

Descrambler

Scrambler - Scramble input signal

Library

Description

Dialog Box

Pair Block

See Also

Related Products & Applications