Ah, so, by the way, 10bit-out-of-20bit-set generator attached.
On 15.07.2016 04:54, Henry Barton wrote:
> I’m designing a CDMA system with a spreading factor of 20. I recently
> wrote an app to go through all the binary permutations up to 2^20 and
> report which ones have an equal number of 0’s and 1’s, or at least
> differ by only one. It came up with so many “hits” that I have to
> wonder if they're really orthogonal. Does anyone know offhand how many
> good spreading codes I can realistically expect from 1048576 possible
> entries?
>
>
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#include <stdint.h>
#include <stdio.h>
int main(){
/* Get all 20 bit values with 10 bit set;
* based on
https://graphics.stanford.edu/~seander/bithacks.html#NextBitPermutation
*/
uint32_t first = 0x3FF; // 10 binary ones
uint32_t v = first;
while(v < (first << 10)){
printf("0x%05X, ", v);
uint32_t t = (v | (v - 1)) + 1;
v = t | ((((t & -t) / (v & -v)) >> 1) - 1);
}
}
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