Convert mask vector to shift for shift register configuration
shift = mask2shift(prpoly,mask)
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 polynomial prpoly
.
The prpoly
input can have one of these formats:
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
The mask
input is a binary vector whose length
is the degree of the primitive polynomial.
Note:
To save time, |
For more information about how masks and shifts are related
to pseudonoise sequence generators, see shift2mask
.
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 vector mask
as
a polynomial, treat mask
as a list of coefficients
in order of descending powers.
The first command below converts 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.
The second command shows that a mask of 1 is equivalent to a shift
of 0. In both cases, notice that the length of the mask
vector
is one less than the length of the prpoly
vector.
s = mask2shift([1 1 0 0 1],[1 0 0 1]) s2 = mask2shift([1 1 0 0 1],[0 0 0 1])
The output is below.
s = 4 s2 = 0
[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.
isprimitive
| log
| primpoly
| shift2mask