S-SCH and P-SCH

[splendidm]

Hi
I WCDMA system - P-SCH and S-SCH are transmitted in
syncronous/Multiplexed manner.

I don't understand how this is done exactly??

Mahesh

[app]

Well, almost nobody understand 3GPP UMTS standards TS 25.212 and TS
25.213, which define it ;-)

[wirelessman]

Checkout the TS 25.213 Document from 3gpp, It has well described

[app]

>From TS 25.213
(http://www.3gpp.org/ftp/Specs/archive/25_series/25.213/25213-440.zip)
, can someone explain me this, after Table 1 in chapter 4.2.1:

"The binary DPCCH and DPDCHs to be spread are represented by
real-valued sequences, i.e. the binary value "0" is mapped to the real
value +1, the binary value "1" is mapped to the real value -1. One
DPCCH and up to six parallel DPDCHs can be transmitted simultaneously.

After the process of channelisation, the real-valued spread signals are
weighted by gain factors. After weighting, the stream of real-valued
chips on the I- and Q-branches are then summed and treated as a
complex-valued stream of chips."

So, what does that mean: "the stream of real-valued chips on the I- and
Q-branches are then summed and treated as a complex-valued stream of
chips"? How are real numbers converted to complex here? If the sums of
the sigma boxes incoming to I and Q of Figure 1 are like, lets's say, 6
and -7, what is the complex value then? Is it 6I+(-7)Q? How do you
scramble this? How do you convert it to a 4-valued stream on possible
QPSK symbols? (Further divided into 8 OQPSK phase shifts?)

[venkat-iitm]

hai all,
Let me try to answer the query.

After summing the I and Q individually, the final sum is treated as I +
jQ, note that this is a complex value and the scrambling code is aslo a
complex value (+/- 1 +/- j1).

When we multilply the I + jQ with the scrambling code this causes a
shift in the constalation of the original signal before signal. If u
see the signal after the scrambling operation it will be either real,
either imaginary or a complex value ( if I and Q are unbalanced), so,
it can be treated as 8 OQPSK.

Note that there is nothing like 4 valued, it can be either purely real
or purely imaginary or complex, but, we need not care that. we just
modulate the real with sin(2*pi*Fc*t) and imaginary with
cos(2*pi*Fc*t).

Please correct if any corrections,

Regards,
Venkat

[wirelessman]

good one .. venkat