The document discusses synchronization in 3G networks. It describes that synchronization is used for the cell search procedure where the UE searches for and locks onto an appropriate cell. The cell search procedure involves 3 steps - slot synchronization, frame synchronization and code group identification, and scrambling code identification. This is done using the synchronization channel (SCH), which consists of the primary synchronization channel (P-SCH) and secondary synchronization channel (S-SCH). The SCH enables slot synchronization using primary synchronization codes and frame synchronization and code group identification using secondary synchronization codes. Finally, scrambling code identification determines the exact scrambling code of the cell.

3. NEED OF SYNCHONIZATION
• Synchronization in 3G is basically used for Cell search
procedure.
• In this procedure, the UE(User Equipment) searches for an
appropriate cell and latches on to it.

4. Cell Search Procedure is carried out in 3 steps:
1. Slot synchronization
2. Frame synchronization & code group identification
3. Scrambling Code Identification
For these purposes, we use the Synchronization Channel (SCH).

5. SYNCHRONIZATION
CHANNEL(SCH)
• SCH is a downlink physical channel.
• It is used in the cell search procedure.
• SCH consists of 2 channels:
1. Primary Synchronization Channel(P-SCH)
2. Secondary Synchronization Channel(S-SCH)
• The Primary and Secondary SCH are sent in
parallel

6. • Every cell transmits information in the form of frames
• 1 frame has 15 slots
• 1 slot has length = 2560 chips
• Frame duration = 10 milliseconds
• Slot Duration = 667 microseconds
• Chip duration=260 nanoseconds
• Chip rate=3.84 Mcps

8. PRIMARY SYNCHRONIZATION
CHANNEL
Uses a 256 chip spreading sequence known as Primary
Synchronization Code (PSC).
PSC consists of first 256 chips of every slot.
It is identical for every cell.
Used for slot synchronization
Used to determine the beginning of a slot

9. SECONDARY SYNCHRONIZATION CHANNEL
It also consists of 256 chip length known as Secondary
Synchronization Code (SSC)
SSC also consists of first 256 chips of every slot
There are 15 different SSC’s & they can form 64 unique
secondary SCH sequences (code groups).
It is used in numbering of slots.

10. FRAME SYNCHRONIZATION
It is used to determine:
1. slot number
2. the radio frame boundary
3. code group of the cell
Frame Synchronization is done by correlating the received signal
with all possible SSC sequences, and identifying the maximum
correlation value.
Since the cyclic shifts of the sequences are unique the code group
as well as the frame synchronization is determined.

11. SCRAMBLING CODE
IDENTIFICATION
In this step, the UE determines the exact primary scrambling code
used by the found cell.
Each code group identifies 8 possible primary scrambling codes, &
the correct one is found by correlating each one in turn over the
CPICH of that cell.
Then the correct primary scrambling code can be used to decode
BCH information from the primary common control physical
channel (P-CCPCH)

12. Difference between Primary Scrambling
code & Primary synchronization codes

14. INTRODUCTION
WCDMA defines two dedicated physical channels -
(a)DPDCH(Dedicated Physical Data Channel):
Carries dedicated data generated at layer 2 and above .
(b)DPCCH(Dedicated Physical Control Channel):
Carries layer 1 control information.
• Each connection is allocated one DPCCH and zero , one or
several DPDCHs.
• It is used for combining physical channels.

15. SPREADING TECHNIQUE(an
overview)
• Spreading is applied to the mentioned dedicated
channels. It basically consists of two operations:-
(A)CHANNELIZATION OPERATION:------
Transforms each data symbols into chips thus increasing
the bandwidth of the signal.
It makes use of orthogonal codes(OVSF codes-orthogonal
variable spreading factor codes).

16. (B)SCRAMBLING OPERATION:-------
Used on top of spreading , scrambling code (PN
sequence code) is added to the spread signal.
It is used for cell separation in DL and user
separation in UL, this implies it does not change signal
BW but only makes signal from different sources
separable to each other.

17. RELATIONSHIP BETWEEN
SPREADING AND SCRAMBLING
As the chip rate is already achieved in spreading by the
channelization code, the symbol rate is not affected by the
scrambling.

18. POWER WEIGHTING IN
UPLINK
In UL, data modulation of both DPDCH and DPCCH is
BPSK.
The modulated DPCCH will be sent in Q plane, while first
DPDCH will be sent in I plane and then subsequently
added DPDCHs are mapped alternatively to I/Q plane.
Now spreading modulation used in UL is dual channel
QPSK which is used after data modulation. Spreading
modulation comprises of spreading and scrambling
operation as mentioned.

19. PROCEDURE
One DPCCH and up to six parallel DPDCHs can be
transmitted simultaneously.
The data on the I and Q branches are multiplied by
different channelization codes.
After channelization, the real valued spread signal are
weighted by gain factors which are different for data and
control channels , however all data channels should
have an equal factor.

20. The weights designate the amount of power with which each
of the data and control channels are to be transmitted.
The gain factors βd and β are used to set different QOS
c
(Quality of Service) requirements for different channels
(channels with higher QOS requirement can be sent with high
power levels).
Gain factors may vary frame to frame based on CTF(current
transport format) combination.
After transforming signal from real to complex, it is then
scrambled by a complex valued scrambling code which can be
long or short.

21. Simplified diagram depicting power weight assignments in uplink

22. Power weighting in uplink

23. POWER WEIGHTING IN
DOWNLINK (PROCEDURE)
QPSK is used for data modulation in DL.
Each pair of two bits are serial to parallel converted and
mapped to the I and Q branches respectively. Mapping is
done in a way that odd and even numbered symbols are
mapped to I and Q branch respectively.
The data in the I and Q branches in downlink are spread to
the chip rate by the same channelization code as used in
uplink.
The signal which is spread is subsequently scrambled by a
cell specific scrambling code.

24. SIMPLIFIED DIAGRAM OF POWER
WEIGHTING IN DOWNLINK

26. DIFFERENCES IN POWER WEIGHT
MECHANISM IN UPLINK AND
DOWNLINK
UPLINK DOWNLINK
(1)Data modulation here is (1)Data modulation here is
done by BPSK done by QPSK
(2)Data rates used in I and Q (2)Data rates used in I and Q
planes are different planes are same
(3)Scrambling code is mobile (3)Scrambling code is cell
station specific in uplink specific in downlink

27. •THANK
YOU!!!!!!!