# Spreading sequence and processing gain

The following has been mentioned regarding spreading using a 32 chip sequence

32x spreading contributes a theoretical 15 dB gain to the link budget,

I have no clue, why so? Are we referring to the processing gain?

I thought spreading was performed to mitigate narrow band noise and ISI.

• The "15 dB" number comes from the fact that $15 \approx 10 \log_{10}(32)$. Processing gain in the context of direct-sequence spread spectrum signals comes during the despreading process; the bandwidth of the despread signal is 32 times smaller than the spread signal, hence the gain. – Jason R Jun 17 '15 at 17:36
• Isnt the processing gain $G$ due to the fact, we suppressed the interference by $G$? – Henry Jun 17 '15 at 18:04
• That's one way to look at it. The despreading process also spreads any narrowband interference, pushing a lot of its energy out of the band of the despread signal. – Jason R Jun 17 '15 at 18:12