Forums

Spreading Codes

Started by EJulius 3 weeks ago2 replieslatest reply 3 weeks ago96 views

I’m working with spreading codes (CDMA and DSSS) and was wondering if the codes always need to be +1 and -1?

At first, I thought that this was not necessary and I could use some random complex numbers as my spreading codes. However, I’m noticing that using random complex values is difficult when there is noise involved because dividing by small numbers (when removing the code) can amplify my noise. And I see that this wouldn’t happen with +1 and -1.

Is this correct? Or should I be able to use any arbitrary spreading code made up of random complex values?

thanks

[ - ]
Reply by fharrisJuly 14, 2021

You want to look at complementary code keying (CCK) and in particular non binary cck codes.

The cck codes replaced the Barker spreading sequences in 802.11.

the CCK codes are also used by Richard Van Nee in two papers called Magic Wand (see Prasad and Van Nee) to obtain amazing reductions of PAPR in OFDM modulators

see two papers below

SDR-04.ppt

sdr_2004_paper_2.pdf

Best regards,

fred h

[ - ]
Reply by jimelectrJuly 16, 2021

Hi, fred and Julius.  That's 802.11, I'm sure, the IEEE standard for wireless LAN. I will check out those CCK codes, another interest of mine for comms and radar.  Thanks.  Jim