# Recovering DSSS signal from below noise Floor

I want to understand what actually happens in the direct sequence spread spectrum demodulator ? Why is it said that the signal is recovered from below the noise floor ? Can someone please explain the physical / intuitive interpretation of demodulation in DSSS. ?

That means that if there was signal energy of $e$ in each single sample, and the sequence is $N$ samples long, then the energy of each symbol is $eN$ at the receiver. Noise, which also gets summed up, however, doesn't grow linear with the length $N$ of the sum (unlike the actual TX signal, it isn't correlated with the spreading sequence).
The fact that signal energy grows linear with $N$, but noise doesn't, means that you get an SNR improvement, which can lift the signal, whose power is below the noise power level, above the noise floor.