Also, the use of ???masks??? allows us to obtain a desired shift without changing the loaded values.
This is accomplished by combining certain outputs of the shift registers.
Earlier, we have shown the EPM??™s role is to find valid multipaths. Sometimes, in searching for
multipath candidates, there is a need to test the present time hypothesis against phase offsets of the
q(x) xn # p(x1)
q(x) 1 C1x C2x2 c Cn1xn1 xn
PN sequence. Also, some CDMA systems separate users by phase shifts provided to the MS by the
higher layers. It is for this reason that we focus our next discussion on shifting PN sequences. We will
discuss two ways to shift a PN output chip sequence [11].
Method Tool
Initial loading Polynomial a0 a1x a2x2
Masks Polynomial m0 m1x m2x2
Both of these methods are possible with the help of Fig. 7.26. The initial contents of the PN generator
are shown in the shift registers. The mask is shown as multiplier coefficients for the PN states.
3G WIDEBAND CDMA 361
TABLE 7.1 GF(2) Primitive Polynomials
Degree Primitive polynomials
2 x2 x 1
3 x3 x 1
4 x4 x 1
5 x5 x 1
6 x6 x 1
7 x7 x3 1
8 x8 x4 x3 x2 1
9 x9 x4 1
10 x10 x3 1
11 x11 x2 1
12 x12 x6 x4 x 1
13 x13 x4 x3 x 1
14 x14 x10 x6 x 1
15 x15 x 1
16 x16 x12 x3 x 1
17 x17 x3 1
18 x 18 x7 1
19 x19 x5 x2 x 1
20 x20 x3 1
21 x21 x2 1
22 x22 x 1
23 x23 x5 1
24 x24 x7 x2 x 1
25 x25 x3 1
26 x26 x6 x2 x 1
27 x27 x5 x2 x 1
28 x28 x3 1
29 x29 x2 1
30 x30 x23 x2 x 1
FIGURE 7.
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