Could you please tell me how the UE can use 2x SF2 in HSUPA?

[lihanbok]

Hi All,
Could you please tell me about UE uplink OVSF code tree. I don't understand why UE can use 2xSF2 + 2xSF4. Because in the downlink if you use 2xSF2, we can not use any SF4. I have already search many times in the Internet, but I didn't find the document about how the UE can use 2x SF2. Please share document about SF of UE uplink in HSUPA. Thank you so much!
Best Regards,
Lihanbok.

[wolverine]

The answer lies in the use of I and Q modulation. Essentially you have two copies of the SF tree, and as they are orthogonal they don't interfer with each other. So when you read about 2xSFX, this is possible as one SF is taken from the I path and the other from the Q path. Looking at the diagram below E-DPDCH #1 and E-DPDCH #2 can use the same spreading factor (4,1 in this example).

WCDMA UL.JPG