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Gold Codes

A Gold sequence, is a type of binary sequence, which is constructed by XOR-ing two m-sequences of the same length with each other. A Gold code sequences set has $2^{n}-1$ sequences and each sequence of the set has a period of $2^{(n-1)}$.

The cross-correlations of a set of Gold codes are low and it helps with the multiple broadcasting devices which uses the same frequency range.

Gold Code generation

•Two maximum length sequences of the same length $2^{n}-1$ are picked. Their absolute cross-correlation must be less than or equal to $2^{(n+2)/2}$. (n is the size of the LFSR)

•By XOR-ing these two sequences in various phases $2^{n}-1$ times a set of Gold codes with the highest absolute cross-correlation $2^{(n+2)/2}+1$ for even n and $2^{(n+1)/2}+1$ for odd n can be obtained.

•To obtain another Gold Code in some other phase, two Gold codes from the same set can be XORed.

The number of ones and zeros within a set of Gold codes differ by one.

Gold sequences have better cross-correlation properties than m-sequences, if the LSFRs are chosen appropriately.

Also with using a preferred-pair of m-sequences a set of gold codes can be constructed.Any solution of preferred-pairs of m-sequences does not exist for m=0 (mod 4).