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WCDMA PhysicalLa er
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Outline
Physical Layer Functions
3GPP WCDMA Parameters
Modulation
Channelization
Scrambling
Initial Synchronization
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Downlink Channel Transmission
C R C a t t a c h m e n t
R a t e m a t c h i n gR a t e
m a t c h i n g
1s t
i n s e r t i o n o f D T X
i n d i c a t i o n
T r B k c o n c a t e n a t i o n /
C o d e b l o c k s e g m e n t a t i o n
C h a n n e l c o d i n g
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T r C H M u l t i p l e x i n g
1s t
i n t e r l e a v i n g
R a d i o f r a m e s e g m e n t a t i o n
2n d
i n s e r t i o n o f D T X
i n d i c a t i o n
2n d
i n t e r l e a v i n g
P h y s i c a l c h a n n e l
s e g m e n t a t i o n
P h y s i c a l c h a n n e l m a p p i n g
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Physical Layer Functions
Encoding/decoding of transport channels
Error detection on transport channels and indication to higher layers
Rate matching/Rate de-matching
Interleaving
Multiplexing/De-multiplexing of coded composite transport channels
Mapping of coded composite transport channels onto physicalchannels
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Physical Layer Functions
Modulation and spreading / De-spreading and Demodulation ofphysical channels
Synchronization Soft handover execution
Power control
RF Processing, Radio characteristics measurements
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3GPP WCDMA Parameters
Carrier spacing = 5MHz
Chip rate = 3.84Mcps
Frame Length = 10ms, 15 slots/frame, 2560 chips/slot
Uplink SF = 4 to 256
Downlink SF = 4 to 512
Uplink Modulation QPSK, 16QAM
Downlink Modulation QPSK, 16QAM, 64QAM
Channelization codes are OVSF codes, Scrambling codes are
complex PRN
Soft handover with up to 6 base-stations is permitted.
Fast power control commands: 1500Hz.
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FDD Operating Bands
Band Uplink Downlink
I 1920 1980 MHz 2110 2170 MHz
II 1850 1910 MHz 1930 1990 MHz
III 1710-1785 MHz 1805-1880 MHz
IV 1710-1755 MHz 2110-2155 MHz
V 824 849 MHz 869-894 MHz
VI 830-840 MHz 875-885 MHz
VII 2500-2570 MHz 2620-2690 MHz
VIII 880 915 MHz 925 960 MHz
IX 1749.9-1784.9 MHz 1844.9-1879.9 MHz
X 1710-1770MHz 2110-2170 MHz
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Modulation
QPSK, 16QAM, 64QAM modulations are supported.
Based on modulation type used bits are grouped into 2(QPSK),
4(16QAM), 6 (64QAM) to form a symbol For each symbol I,Q values to be transmitted are mapped as per
3GPP specs
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Channelization
Channelization codes are used to separate different transmissionsor channels from the same device
Each physical channel from a UE or cell uses differentchannelization code
Channelization codes do spreading, i.e. increase the signal BW
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Different UE can use same channelization codes for ULtransmission
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Channelization
Orthogonal codes, based on OVSF (orthogonal variable spreadingfactor) technique are used
Channelization codes are picked from a code tree Once a code is picked, no other codes from its sub-tree can be
picked
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Scrambling
Scrambling codes are used to separate different transmittingdevices
Each UE, Cell uses a unique scrambling code Scrambling codes do not spread the signal, BW remains
unchanged @ chip rate
cram ng co es are comp ex pseu o ran om num er sequence
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I
S
P
Cch,SF,m
j
Sdl,n
Q
I+jQ
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Downlink Channelization, Scrambling and
Modulation
I
S
P
Cch,SF,m
Sdl,n
Q
I+jQ
G1
cos(t)
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G2
GP
GS
S-SCH
P-SCH Im{S}
Re{S}
-sin(t)
Splitreal &imag.parts
Pulse-
shaping
Pulse-shaping
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Uplink Channelization, Scrambling and
Modulation
I
cd,1 d
S long,n or S short,n
I+jQ
D P D C H 1
cd,3 d
D P D C H 3
cd,5 d
D P D C H 5
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j
Q
cd,2 d
D P D C H 2
cd,4 d
D P D C H 4
cd,6 d
D P D C H 6
c c c
D P C C H
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Initial Synchronization
Three step process to identify
Slot timing of the cell
Frame timing of the cell Scrambling code of the cell
UE is capable of receiving DL transmission once the above 3 are
available SCH (primary and secondary) and CPICH channels are used for
this purpose
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PrimarySCH
Secondary
SCH
256 chips
2560 chips
acs,
acp
acs,
acp
acs,
acp
Slot #0 Slot #1 Slot #14
Physical Channel - SCH
One 10 ms SCH radio frame
primary - SCH, same for every cell, no channelization/scramblingused
Number of scrambling codes for DL = 512, divided into 64 code
groups Secondary - SCH, indicates which of the 64 code groups
scrambling code of that cell belongs to, nochannelization/scrambling used
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Physical Channel - CPICHPre-defined symbol sequence
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits = 10 symbols
1 radio frame: Tf= 10 ms
A A A A A A A A A A A A A A A A A A A A A A A AAntenna 1
Uses Fixed channelization code and the scrambling code of the cell Broadcast over entire cell
Used for channel estimation and initial synchronization
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slot #1
Frame#i+1Frame#i
slot #14
-A -A A A -A -A A A -A A -A -A A A -A -A A A -A -A A A -A -AAntenna 2
slot #0
Frame Boundary
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Initial Synchronization
Slot Timing
Correlate the incoming chips with PSC word over a slot
Correlation peak indicates the location of PSC word and hencethe start of the slot
Scrambling code group
16 SSC words are defined by 3GPP 64 code words (each containing 15 SSC words from above) are
defined by 3GPP
Receive the SSC words being transmitted at start of slot for 15consecutive slots (1 frame)
Identify which of the 64 code words is being transmitted to findscrambling code group
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Initial Synchronization
Frame timing
Identify the phase of the code word to find frame start timing of
the cell Scrambling code
Receive known sequence of pilots using all 8 scrambling codes
rom t e scram ng co e group The scrambling code that gives best results is the scrambling
code of the cell
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Physical Channel - PCCPCH
Data
18 bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits
(Tx OFF)
256 chips
Broadcast over entire cell, with OVSF code #1
The Tx-off space is taken up by the SCH channel
Contains the BCH transport data - System information
Fixed spreading factor (=256)
This is the only channel with fixed channel coding scheme.
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1 radio frame: Tf= 10 ms
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FDD Physical Channels
Common Pilot Channel (P-CPICH)
Synchronization Channel (SCH)
P-CCPCH
S-CCPCH
Paging Indication Channel (PICH)
Ph sical Random Access Channel PRACH
Acknowledge Indication Channel (AICH) Dedicated Channel (DPCH): contains DPCCH (L1 ctrl) and
DPDCH(data) fields.
HSDPA channels HS-SCCH, HS-DSCH and HS-DPCCH (rel5)
E-DCH channels E-DPCCH, E-DPDCH, E-AGCH, E-RGCH andE-HICH (rel6)
F-DCH (rel6)
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Transport Channels
BCH - carries system wide information
FACH - downlink common signaling channel
RACH - uplink common signaling channel PCH - paging channel
DCH - dedicated channel
E-DCH HSUPA dedicated channel
HS-DSCH HSDPA dedicated channel
MTCH, MCCH MBMS transport channels
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Transport to Physical Channel Mapping
Dedicated Physical Data Channel (DPDCH)
Dedicated Physical Control Channel (DPCCH)
Fractional Dedicated Physical Channel (F-DPCH)
E-DCH Dedicated Physical Data Channel (E-DPDCH)
E-DCH Dedicated Physical Control Channel (E-DPCCH)
E-DCH Absolute Grant Channel (E-AGCH)
E-DCH Relative Grant Channel (E-RGCH)
E-DCH Hybrid ARQ Indicator Channel (E-HICH)
Physical Random Access Channel (PRACH)
Common Pilot Channel (CPICH)
Transport Channels
DCH
RACH
Physical Channels
E-DCH
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Primary Common Control Physical Channel (P-CCPCH)
Secondary Common Control Physical Channel (S-CCPCH)
Synchronisation Channel (SCH)
Acquisition Indicator Channel (AICH)
Paging Indicator Channel (PICH)
MBMS Notification Indicator Channel (MICH)
High Speed Physical Downlink Shared Channel (HS-PDSCH)
HS-DSCH-related Shared Control Channel (HS-SCCH)
Dedicated Physical Control Channel (uplink) for HS-DSCH (HS-DPCCH)
BCH
FACH
PCH
HS-DSCH
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THANKS
Q & A ?DISCUSSION.FORUM.NOKIA.CO
M/VTUEDUSAT
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Register / Login
Go To discussion.forum.nokia.com
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BACKUP
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HSDPA
Circuit switched Vs Packet switched calls Uses 3 physical channels (2 on the DL, 1 on the UL) HS-PDSCH
Shared data channel, SF = 16.
HS-PDSCH can use multiple codes Higher order modulation 16-QAM, 64QAM To achieve greater peak data rate
are c anne a ows ynam c a oca on o resources amongusers (e.g. guided by channel quality indicator from UE)
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HSDPA
HS-SCCH
Channelization-code-set information
Modulation scheme information
Transport-block size information
Hybrid-ARQ process information
Redundancy and constellation version
New data indicator UE identity
HS-DPCCH - UL
ACK/NACK
CQI
No soft handover, UTRAN can command serving cell change New concept of hybrid ARQ (HARQ)
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HARQ Hybrid Automatic Repeat Request
Channel coding (forward error correction) relies on transmittingredundant bits so that the receiver can perform error correction
Idea with hybrid ARQ is that if the UE does not receive a blockcorrectly (i.e. CRC pass), it still contains useful information
Some additional information can be transmitted and added to whathas been received until the message is decoded successfully
Chase combining (CC): The SAME bits are transmitted again and
Incremental redundancy: Some NEW parity bits are transmittedwhich can be concatenated with the already received bits to helpdecode the message
Constellation remapping : The SAME bits are transmitted butmapped onto the IQ constellation in a different way (16 QAM only)
Redundancy version bits on the HS-SCCH indicate which of thesepossibilities is being performed
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HARQ Hybrid Automatic Repeat Request
New data indicator on the HS-SCCH indicates that this is a newtransmission, rather than an retransmission -> indicates that allreceived data is flushed and start decoding from scratch
Up to 8 multiple HARQ processes run in parallel With HARQ retransmission is desirable because it means that just
the right amount of resources (power etc) has been used to get themessage through to the UE
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