mask2shift

Convert mask vector to shift for shift register configuration

Syntax

shift = mask2shift(prpoly,mask)

Description

shift = mask2shift(prpoly,mask)returns the shift that is equivalent to a mask, for a linear feedback shift register whose connections are specified by the primitive polynomialprpoly. Theprpolyinput can have one of these formats:

Apolynomial character vector
A binary vector that lists the coefficients of the primitive polynomial in order of descending powers
An integer scalar whose binary representation gives the coefficients of the primitive polynomial, where the least significant bit is the constant term

Themaskinput is a binary vector whose length is the degree of the primitive polynomial.

Note

To save time,mask2shiftdoes not check thatprpolyis primitive. If it is not primitive, the output is not meaningful. To find primitive polynomials, useprimpolyor see[2].

For more information about how masks and shifts are related to pseudonoise sequence generators, seeshift2mask.

Definition of Equivalent Shift

If A is a root of the primitive polynomial and m(A) is the mask polynomial evaluated at A, the equivalent shift s solves the equation A^s= m(A). To interpret the vectormaskas a polynomial, treatmaskas a list of coefficients in order of descending powers.

Examples

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Convert Mask to Shift

Open Live Script

Convert masks into shifts for a linear feedback shift register.

Convert a mask of $x^{3} + 1$ into an equivalent shift for the linear feedback shift register whose connections are specified by the primitive polynomial $x^{4} + x^{3} + 1$ .

s1 = mask2shift([1 1 0 0 1],[1 0 0 1])

s1 = 4

Convert a mask of1to a shift. The mask is equivalent to a shift of0.

s2 = mask2shift([1 1 0 0 1],[0 0 0 1])

s2 = 0

Convert a mask of $x^{2}$ into an equivalent shift for the primitive polynomial $x^{3} + x + 1$ .

s3 = mask2shift('x3+x+1','x2')

s3 = 2

References

[1] Lee, J. S., and L. E. Miller,CDMA Systems Engineering Handbook, Boston, Artech House, 1998.

[2] Simon, Marvin K., Jim K. Omura, et al.,Spread Spectrum Communications Handbook, New York, McGraw-Hill, 1994.

Version History

Introduced before R2006a