Channelisation codes , Scrambling codes , code tree

[chillin4ever]

Are scrambling codes and channelisation codes derived from same code tree in WCDMA downlink?

Second question is in WCDMA downlink :

In the downlink the DCH spreading factor is constant,as well as with the common channels.The only exception is the DSCH,which also has a varying spreading factor.

So why is SF constant in downlink ???????????

 

[Shivanand.kadwadkar]

Are scrambling codes and channelisation codes derived from same code tree in WCDMA downlink?
--> As far i know Both channelisation and Scrambling code are totally different channelisation codes i derived from tree but we have fixed scrambling code the code we use is called PN codes
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In the downlink the DCH spreading factor is constant,as well as with the common channels.The only exception is the DSCH,which also has a varying spreading factor.
May be because DSCH is shared channel and we vary spreading factor to accommodate more user the reason is by changing SF we can change speed of data transfer