WAAS information from the Stanford GPS Lab

Galileo (GIOVE-B) E5 (E5a + E5b) Code Generators

Grace Gao, Dennis Akos, Per Enge

The GIOVE-B and proposed GALILEO E5 signal is composed to two signals modulated using AltBOC. These are the E5a and E5b code. Examined individually, the codes look like BPSK signals. We will examine whether a secondary code exists on the signal. Given the similarities to GIOVE-A, the secondary codes are likely the same.

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•Results:

–The code is a linear code (28th order polynomial)
–Factorize obtained code generator polynomials
–The code sequence can be generated by modulo 2 addition of maximal length sequences of the factor polynomials
–The code generator polynomials are the same as those on GIOVE-A E5. The initial states are different

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E5a-A code: 10230 bits, 1ms, Gold code

Polynomial A1: X¹⁴+X⁸+X⁶+X¹+1

Polynomial A2: X¹⁴+X¹²+X⁸+X⁷+X⁵+X⁴+1

Initial state A1: [1 1 1 1 1 1 1 1 1 1 1 1 1 1]

Initial state A2: [1 0 0 1 1 0 0 1 0 0 0 0 0 0]

Secondary code:

E5a-B code: 10230 bits, 1ms, Gold code

Polynomial B1: X¹⁴+X⁸+X⁶+X¹+1

Polynomial B2: X¹⁴+X¹²+X⁸+X⁷+X⁵+X⁴+1

Initial state B1: [1 1 1 1 1 1 1 1 1 1 1 1 1 1]

Initial state B2: [1 0 0 0 1 1 1 0 1 0 1 1 0 0]

Secondary code:

E5b-A code: 10230 bits, 1ms, Gold code,

Polynomial A1: X¹⁴+X¹³+X¹¹+X⁴+1

Polynomial A2: X¹⁴+X¹²+X⁹+X⁸+X⁵+X²+1

Initial state A1: [1 1 1 1 1 1 1 1 1 1 1 1 1 1]

Initial state A2: [0 0 0 0 1 0 1 0 1 1 0 0 1 0]

Secondary code:

E5b-B code: 10230 bits, 1ms, Gold code, 100 bit secondary code

Polynomial B1: X¹⁴+X¹³+X¹¹+X⁴+1

Polynomial B2: X¹⁴+X¹²+X⁹+X⁸+X⁵+X²+1

Initial state B1: [1 1 1 1 1 1 1 1 1 1 1 1 1 1]

Initial state B2: [0 1 0 1 0 0 0 0 0 1 0 1 1 1]

Secondary code:

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