Spreading and Scrambling in UMTS (WCDMA) --> DESPREADING
I am attempting to simulate a WCDMA system from the 3GPP standards and
I am aware that the OVSF channelisation codes provide the spreading
operation and the scrambling codes (terminal specific) are applied on
a chip by chip basis multiplication to the sum of the channelised
That is, simply for demonstrations sake, I have 2 data streams, 2
channelisation codes and 1 scrambling code.. I will proceed as
r[n] = (x1[k]*c1[n] + x2[k]*c2[n]) * s[n], where x1[k], x2[k] is the
baseband data, c1[n], c2[n] are the orthogonal channelisation codes at
the chip rate, and s[n] is the scrambling code also at the chip rate.
So, in order to despread the signal at the receiver by means of a
correlator receiver, let us say I wish to recover signal x1[k] (let us
assume the system is perfectly synchronous, no multiipath etc..
Would I multiply the incoming signal by c1[n]s[n] and then proceed to
integrate/summate? I am doing this and I am getting large cross
correlations with the other present data, that is c2[n]s[n].
Am I supposed to expect cross correlations similar to that of the
original spreading Gold-code?
Any further information on the correlator receive specific to the
combined effect of scrambling and spreading would be very helpful.