UTRA Physical Layer

1
UTRA Physical Layer
2
Contents (I)

• Introduction
• FDD Mode
• Physical Channel Concept
• Downlink Physical Channels
• Uplink Physical Channels
• Multiplexing, Coding, Spreading and Modulation
• Radio Transmission and Reception
• Procedures
• Summary

3
Contents (II)

• TDD Mode
• Frame Structures
• Physical Channels
• Burst Types
• Transport Channels
• Mapping of Transport Channels on Physical
  Channels
• Summary

4
Introduction
5
UMTS Terrestrial Radio Access (UTRA) Access Modes

• UTRA is able to operate on two access modes
• Frequency Division Duplex (FDD)
• Time Division Duplex (TDD)

6
Frequency Division Duplex (FDD) Time Division
Duplex (TDD)
Downlink (fd)
Base Station
Uplink (fu)
In the FDD mode fd fu In the TDD mode fd
fu
User Equipment
7
Implementation of FDD and TDD
FDD
TDD
Filter
Receiver
Transmitter
Filter
Duplexer
Receiver and Transmitter operate simultaneously
When the Receiver operates, the Transmitter
stops, and vice-versa
8
Frequency Division Duplex (FDD) Mode
9
PHYSICAL CHANNEL CONCEPT

• The basic Radio Resources are called Physical
  Channels.
• These channels are characterized by
• Spreading Code
• Carrier Frequency
• Phase (with reference to the un-modulated
  carrier 0 or p/2). This characteristic is only
  used in the Uplink.

10
PHYSICAL CHANNELS Classification

• Physical Channels are classified in
• Downlink
• Uplink

11
DOWNLINK PHYSICAL CHANNELS

12
UMTS Downlink Physical Channels (FDD)
13
Downlink Dedicated Physical Channel
14
Frame Structure
DPCCH
DPDCH
TPC
Pilot
TFCI
Data 1
Data 2
NTPC bits
N
bits
NTFCI bits
Ndata1 bits
Ndata2 bits
pilot
T
10 ms
f
Frame 1
Frame 2
Frame i
Frame 72
T
720 ms
super
15
Data Field Specifications

• Reference Parameter k
• k 0, 1, 2, 3, 4, 5, 6, 7
• Total Quantity of Bits 20 2k
• k is related to the spreading factor (SF) of the
  physical channel by means of the expression

16
Data and Control Fields
DPCCH
DPDCH
TPC
Pilot
TFCI
Data 1
Data 2
Npilot bits
NTPC bits
NTFCI bits
Ndata1 bits
Ndata2 bits
If no TFCI, then the TFCI field is blank.
17
Data Communication Efficiency
100
80
60
Efficiency ()
40
20
0
Data Rate (Kbps)
1024
2048
128
256
512
32
32
64
64
16
16

• Efficiency ranges from 20 to 97.5 as the data
  rate increases.

18
Pilot Patterns
DPCCH
DPDCH
TPC
Pilot
TFCI
Data 1
Data 2
Npilot bits
NTPC bits
NTFCI bits
Ndata1 bits
Ndata2 bits

• Yellow Bits may be used for Frame
  Synchronization.
• Transmission order is from left to right.
• Each two-bits pair represents an I/Q pair of QPSK
  modulation.

19
Transmit Power Control Field Patterns
DPCCH
DPDCH
TPC
Pilot
TFCI
Data 1
Data 2
Npilot bits
NTPC bits
NTFCI bits
Ndata1 bits
Ndata2 bits
20
Common Control Physical Channels
21
Primary Common Control Physical Channel (PCCPCH)

• Used to carry the Broadcast Control Channel (BCH)
• Fixed rate 32 Kbps
• Fixed Spreading Factor 256
• It is not transmitted during the first 256 chips
  of each Time Slot. This period is left to the
  Primary and Secondary Synchronization Channels.

22
Frame Structure
256 chips
DATA (Ndata bits)
Pilot 8 bits
Data 10 bits
(Tx OFF)
0.625 ms, 20 bits
Slot i
T
10 ms
f
Frame 1
Frame 2
Frame i
Frame 72
T
720 ms
super
23
Secondary Common Control Physical Channels
(SCCPCH)

• Applications
• To transport the Paging Channel (PCH).
• To transport the Forward Access Channel (FACH).
• Number of SCCPCHs depend of Cell traffic

24
Use of Transport-Format Channel Indicator (TFCI)

• There are two types of SCCPCH
• With TFCI
• Without TFCI
• It is the UTRAN that determines if the TFCI
  should be transmitted.
• It is mandatory for the User Equipment to be able
  to support the TFCI.
• Spreading factor SF 256 / 2k (k 06)
• Data rates between 32 and 2048 kbps.

25
Frame Structure
TFCI
Pilot Npilot bits
DATA (Ndata bits)
N
bits
TFCI
k
0.625 ms, 202
bits (k 06)
T
10 ms
f
Frame 1
Frame 2
Frame i
Frame 72
T
720 ms
super
26
Secondary Common Control Channel Fields
TFCI
Pilot Npilot bits
DATA (Ndata bits)
N
bits
TFCI
27
Differences between Primary and Secondary Common
Control Physical Channels

• PCCCH has a fixed rate (32 Kbps).
• SCCCHs can support variable rate, based on the
  value of the associated Transport-Format Channel
  Indicator (TFCI) .
• SCCCHs are only transmitted when there is data to
  send.
• PCCCH is transmitted over the whole cell.
• SCCCHs may be transmitted on narrow lobes pointed
  to the target UE channel (only valid for a
  Secondary CCPCH carrying the FACH).

28
Synchronization Channel (SCH)
29
Synchronization Channel(SCH)

• It is used for Cell Search.
• It consists of two sub-channels
• Primary Synchronization Channel
• Secondary Synchronization Channel

30
Characteristics of the Primary Synchronization
Channel

• Transmitted once per Time Slot.
• Contents is the same in each Time Slot.
• Aligned in time with the BCCH.
• Un-modulated.
• Spreading Factor 256

31
Characteristics of the Secondary Synchronization
Channel(SSCH)

• It consists of repeatedly transmitting a length
  16 sequence of un-modulated codes of length 256
  chips.
• Each Secondary Synchronization code is chosen
  from a set of 17 different codes of length 256.
• The Secondary SCH sequence indicates which of the
  32 different code the cell's downlink scrambling
  code belongs.
• 32 sequences are used to encode the 32 different
  code groups each containing 16 scrambling codes.

32
Synchronization Channel Time Structure
1 Time Frame 16 Time Slots
Primary Synchronization Channel (PSCH)
Secondary Synchronization Channel (SSCH)

• The same code is used for all bursts of the PSCH
• SSCH is a sequence of 16 different codes.
• The SSCH sequence identifies the Cell Group

33
Interleaving of Synchronization Channel and
Primary Common Control Channel
Primary Common Control Physical Channel (PSCH)
Data
Pilot
Data
Pilot
Primary Synchronization Channel (PSCH)
256 chips
256 chips
256 chips
Secondary Synchronization Channel (SSCH)
2560 chips
2560 chips
34
Multiplexing of Synchronization Channels
Lower position during
256 chips per slot
0
S
1
c
SCH
p
0
d
i
c
s
S
To IQ modulator
c
DPDCH/DPCCH
ch,1
CCPCH
c
scramb
c
ch,N
35
Physical Downlink Shared Channel (PDSCH)
36
Physical Downlink Shared Channel (PDSCH)

• It is the physical channel that supports the
  Downlink Shared Channel.
• It is shared by several UE by means of Code
  Multiplexing.
• It is always associated with another physical
  channel.

37
Physical Shared Channel Control Channel (PSCCCH)
38
Physical Shared Channel Control Channel (PSCCCH)

• Contains information shared by several UE.
• Its Control Information field includes TPC to be
  applied by the UE pool.
• Detailed structure is still under development.

39
Physical Shared Channel Control Channel
(PSCCCH)Frame Structure
40
Acquisition Indication Channel (AICH)Page
Indication Channel (PICH)
41
Acquisition Indication Channel (AICH)

• It is a physical channel used to carry
  Acquisition Indicators (AI) corresponding to the
  signature of the Random Access Channel Preamble.

16 symbols (1 ms)
4 symbols (0.25 ms)
AI
empty
AS 2
AS i
AS 8
AS 1
One frame (10 ms)
AS Access slot
42
Page Indication Channel (PICH)

• PICH provides Page Indicators (PI) to the User
  Equipment.
• One PICH frame has 10 ms length.
• Each frame comprises 8 access slots.
• 5, 10 or 20 Page Indicators may be included in an
  Access Slot.

20 symbols (1.25 ms)
AS 2
AS i
AS 8
AS 1
One frame (10 ms)
AS Access slot
43
UPLINK PHYSICAL CHANNELS

44
UMTS Uplink Physical Channels
Uplink Physical Channels
Common
Dedicated
Physical Random Access Channel
Uplink Dedicated Physical Data Channels
(PRACH)
(DPDCH)
Fast Uplink Signalling Channel
(FAUSCH)
Physical Common Packet Channel
(PCPCH)
45
Uplink Dedicated Physical Data Channels
Uplink Physical Channels
Common
Dedicated
Physical Random Access Channel
Uplink Dedicated Physical Data Channels
(PRACH)
(DPDCH)
Fast Uplink Signalling Channel
(FAUSCH)
Physical Common Packet Channel
(PCPCH)
46
Frame Structure
DATA Ndata bits
DPDCH
TPC NTPC bits
FBI NFBI bits
Pilot Npilot bits
TFCI NTFCI bits
DPCCH
k
0.625 ms, 102
bits (k 0..6)
T
10 ms
f
Frame 1
Frame 2
Frame i
Frame 72
T
720 ms
super
47
Data Field
DATA Ndata bits
DPDCH
48
Distribution of Bits in the Control Fields
TPC NTPC bits
FBI NFBI bits
Pilot Npilot bits
TFCI NTFCI bits
DPCCH
49
Pilot Patterns
TPC NTPC bits
FBI NFBI bits
Pilot Npilot bits
TFCI NTFCI bits
DPCCH
Patterns for 5 Bits per Time Slot

• Patterns are defined for 5, 6, 7 and 8 Pilot Bits
  per Time Slot.
• Shadowed bits may be used for Frame
  Synchronization.

50
Transport-Combination Format Indicator (TFCI)
Field Pattern
TPC NTPC bits
FBI NFBI bits
Pilot Npilot bits
TFCI NTFCI bits
DPCCH

• This field is optional UTRAN may request its
  presence to the User Equipment.
• If it is present, it is represented by a 32-bits
  word transmitted in each Frame.
• The TFCI value may be negotiated between UTRAN
  and UE on a frame-to-frame basis.
• Actual values of TFCI are not yet defined.

51
Feedback Information Pattern
TPC NTPC bits
FBI NFBI bits
Pilot Npilot bits
TFCI NTFCI bits
DPCCH

• The contents of this field is still under
  development.

52
Transmit Power Control Field Patterns
TPC NTPC bits
FBI NFBI bits
Pilot Npilot bits
TFCI NTFCI bits
DPCCH
53
Physical Random Access Channel
Uplink Physical Channels
Common
Dedicated
Physical Random Access Channel
Uplink Dedicated Physical Data Channels
(PRACH)
(DPDCH)
Fast Uplink Signalling Channel
(FAUSCH)
Physical Common Packet Channel
(PCPCH)
54
General Characteristics

• Provides the UE the capability to access the
  Fixed Network.
• Access Method is based on the Slotted Aloha
  principle.
• Access Time Slots have 1.25 ms offset.
• Access Time Slots boundaries are referred to the
  Broadcast Common Control Channel (BCCH) time
  reference.

55
Access Slots Timing
56
Random Access Burst Structure
57
Preamble Structure

• Based on 16 Complex Symbols (Signature)
• Each Symbol is spread by means of a 256 chips
  real orthogonal Gold code
• There are a total of 16 possible Signatures

58
Message Structure
Data
Data
N
bits
data
TFCI
Pilot
Control
N
bits
N
bits
TFCI
pilot
k
T
0.625 ms, 102
bits (k0..3)
slot
Slot 1
Slot 2
Slot i
Slot 16
Random-access messageT
10 ms
RACH
59
Data and Control Fields Contents
Data
Data
N
bits
data
TFCI
Pilot
Control
N
bits
N
bits
TFCI
pilot
Data Field
Control Fields
60
Fast Uplink Signalling Channel (FAUSCH)Physical
Common Packet Channel (PCPCH)
Uplink Physical Channels
Common
Dedicated
Physical Random Access Channel
Uplink Dedicated Physical Data Channels
(PRACH)
(DPDCH)
Fast Uplink Signalling Channel
(FAUSCH)
Physical Common Packet Channel
(PCPCH)
FAUSCH and PCPCH will be included in the Release
2000
61
Multiplexing, Coding, Spreading and Modulation

62
Multiplexing of Physical Channels
TC
TC
TC
TC
Channel coding
Coding
Coding
optional TC multiplex
interleaving
interleaving
Static rate matching
Rate
Rate
matching
matching
Inner interleaving
Interleaving
Interleaving
(inter-frame)
(optional)
(optional)
Transport-channel
multiplexing
Multiplex
Dynamic rate matching
Rate
(uplink only)
matching
Inner interleaving
(intra-frame)
Interleaving
63
UTRA/FDD Transport Channels Coding
Convolutional
coding
Turbo
coding
Service-specific
coding
64
Downlink Spreading and Modulation (I)
I
p(t)
DPDCH/DPCCH

S
P
c
c
sin(
t)
w
ch
scramb
Q
p(t)
c
channelization code
ch
c
scrambling code
scramb
p(t) pulse-shaping filter (root raised cosine,
roll-off 0.22)
65
Downlink Spreading and Modulation (II)

• Data and Control streams are de-interleaved by a
  serial-to-parallel conversion. Each output stream
  is applied to the I and Q paths.
• I and Q paths are spreaded by a channel-specific
  code (Channelization Code).
• I and Q paths are subsequently spreaded by a
  Cell-specific code (Scrambling Code).
• Pulse Shaping is applied to reduce spectrum
  occupancy and Inter-Symbol Interference (ISI)

66
Uplink Spreading and Modulation (I)
Channelization
codes (OVSF)
c
cos(
t)
w
D
c

scramb
I
Real
(optional)
p(t)
DPDCH
c
scramb
IjQ
c
sin(
t)
w
C
Q
Imag
p(t)
DPCCH
j

c
,c
channelization codes
D
C
c
primary scrambling code
scramb
c
secondary scrambling code (optional)
scramb
p(t) pulse-shaping filter (root raised cosine,
roll-off 0.22)
67
Uplink Spreading and Modulation (II)

• Data information (DPDCH) uses the I-path.
• Control information (DPCCH) uses the Q-path.
• Independent spreading codes (Channelization
  Codes) are used for the I and Q paths.
• A UE-specific spreading code (Scrambling Code) is
  subsequently applied.

68
Radio Transmission and Reception Characteristics

69
Basic CharacteristicsValid for Region 1 (Europe)
and 3 (Asia)

• Frequency Bands
• 1920 to 1980 MHz (Uplink)
• 2110 to 2170 MHz (Downlink)
• RF Carrier Spacing
• 5 MHz
• RF Channel Raster
• 200 KHz
• Power Control Rate
• 1600 Cycles per Second

Region 2 (Americas) is not yet defined.
70
User EquipmentTransmitter Characteristics
71
User EquipmentReceiver Characteristics
A Bit Error Rate (BER) equal or less than 0.001
must be achieved under the following situations
PCCPCH Primary Common Control Physical
Channel DPCH Dedicated Physical Channel PN
Pseudo Noise
72
Procedures

73
Power Control Procedures
74
Uplink Power ControlOpen Loop Procedure
75
Uplink Power ControlOuter Loop Procedure
76
Uplink Power ControlClosed Loop Procedure
BASE STATION PROCEDURE
MOBILE STATION PROCEDURE
ESTIMATE RECEIVED DPCCH
DECREASE POWER DTPC dB
DOWN
TPC ?
ESTIMATE TOTAL UPLINK RECEIVED INTERFERENCE
UP
INCREASE POWER DTPC dB
TPC DOWN
Yes
No
SIRESTgtSIRTARGET
TPC UP
77
Downlink Power ControlOuter Loop Procedure
78
Downlink Power ControlClosed Loop Procedure
BASE STATION PROCEDURE
ESTIMATE RECEIVED DPCCH
DECREASE POWER DTPC dB
DOWN
TPC ?
UP
ESTIMATE TOTAL UPLINK RECEIVED INTERFERENCE
INCREASE POWER DTPC dB
TPC DOWN
Yes
No
SIRESTgtSIRTARGET
TPC UP
79
Cell Search Procedures (I)Initial Cell Search
(Attachment)
CELL SEARCH PROCEDURE
ACQUIRE Frame Synchronization Timing
RECEIVE Primary Synchronization Channel
ACQUIRE Base Station Scrambling Code
SELECT Strongest Base Station
DETECT Primary Common Control Channel
RECEIVE Secondary Synchronization Channel
ACQUIRE Super Frame Synchronization
IDENTIFY Base Station Code Group
READ Broadcast Control Channel
80
Cell Search Procedures (I)Idle and Active Modes
Cell Search
CELL SEARCH PROCEDURE
READ Base Stations Priority List
SEARCH Base Station
See details in next slide
No
Base Station Acquired ?
Yes
END Search
81
Cell Search Procedures (II)Idle and Active Modes
Cell Search
SEARCH Base Station
ACQUIRE Frame Synchronization Timing
READ Broadcast Control Channel
RETURN
DETECT Primary Common Control Channel
ACQUIRE Super Frame Synchronization
82
Random Access Procedure
RANDOM ACCESS PROCEDURE
SELECT Spreading Factor for Message Part
WAIT
ESTIMATE Downlink Path Loss
ACQUIRE Base Station Synchronization
Yes
Time-out ?
CALCULATE Uplink Transmit Power
READ Broadcast Common Control Channel Information
No
No
Received BS ACK ?
SELECT (randomly) an Access Slot
SELECT Preamble Spreading Code
Yes
END
TRANSMIT Random Access Burst
SELECT Message Spreading Code
83
Handover Procedures
84
Soft Handover (I)

• During Soft Handover, two or more Base Stations
  are used to simultaneously communicate with the
  same Mobile Station.
• These Base Stations form the Active Set.
• All Active Set Base Stations use the same RF
  Carrier Frequency.
• Each Active Set Base Station maintains its own
  Scrambling Code.

85
Soft Handover (II) Active Set Update
86
Softer Handover

• It is the special case of Soft Handover in which
  Active Set Base Stations are part of the same
  physical site.
• Softer Handover allows more efficient combining
  implementations than Soft Handover (e.g. to use
  Maximal Ratio Combining instead of Selection
  Combining).

87
Inter-frequency Handover (I)

• In Inter-frequency Handover, the RF carrier
  frequency changes.
• It is used in the following situations
• Handover between cells using different RF carrier
  frequencies.
• Handover between overlapping cells.
• Handover between different Operators and/or
  Systems (e.g. UMTS/GSM).

88
Inter-frequency Handover (II)Hierarchical Cell
Structures

• Hierarchical Cell Structures (HCS) are set of
  cells geographically co-located, but using
  different RF carriers.
• Inter-frequency Handover is required in HCS.

89
Inter-frequency Handover (III)Mobile
Implementation

• Slotted Mode

• Two strategies are suggested
• Slotted Mode (see right)
• Dual Receivers.

90
Physical Layer Description (FDD)Summary (I)

• UMTS-FDD is a Code Division Multiple Access
  (CDMA) system.
• The Spreading Factor associated to each channel
  may be independently selected.
• Cells are characterized by a specific spreading
  code (Scrambling Code).
• Communication Sessions are also characterized by
  a specific spreading code (Channelization Code).
• Pilot Symbols are used to allow coherent
  detection of QPSK signals and spreading codes.

91
Physical Layer Description (FDD)Summary (II)

• In the downlink, two synchronization channels
  (primary and secondary) are regularly transmitted
  to allow attachment of the mobile stations.
• Moreover, a broadcast channel (BCCCH) is
  regularly transmitted in order to provide to the
  mobile stations, information about specific
  parameters from the Cell.
• In order to avoid the Near-Far Effect, UMTS
  incorporates 3 Power Control mechanisms Open,
  Outer and Closed Loops.
• Soft Handover is used when a mobile station
  migrates between Cells operating at the same
  carrier frequency.

92
Time Division Duplex (TDD) Mode
93
TDD Frame Structure
frequency
10 ms
4.096
Mchip/s
625 µs
time

• 16 Time Slots (TS)
• 1 Time Slot 2560 chips
• Each TS may be used in Uplink or Downlink
• At least one TS must be used in Uplink
• At least one TS must be used in Downlink

94
Single Switching Point Frames
10 ms
Symmetric DL/UL Allocation
10 ms
Asymmetric DL/UL Allocation
95
Multiple Switching Point Frames
10 ms
Symmetric DL/UL Allocation
10 ms
Asymmetric DL/UL Allocation
96
Use of CDMA in the TDD Mode (TD-CDMA Concept)
1 Time Frame 10 ms
code 8
.
.
.
.
code 1
1 TS 625 µs

• TDD mode traffic capacity is increased by means
  of superimposing several signals in the same Time
  Slot.
• Each Signal differs from the other in the use of
  a separate Spreading Code.
• In general, up to 8 signals may be
  code-multiplexed.

97
Concepts of Transport Channels and Physical
Channels
Layer 2
Layer 2
Transport Channel
Transport Channel
Layer 1
Physical Channel
User Equipment
UTRAN
98
TDD Transport Channels
Transport Channels
Common
Dedicated
Broadcast Channel
(BCH)
Paging Channel
(PCH)
Forward Access Channel
(FACH)
Synchronization Channel
(SCH)
Downlink Only
Random Access Channel
Uplink Only
(RACH)
Uplink / Downlink
ODMA Random Access Channel
(ORACH)
99
TDD Physical Channels
Physical Channels
Common
Dedicated
Common Control Physical Channel
(CCPCH)
Physical Synchronization Channel
(PSCH)
Physical Random Access Channel
(PRACH)
Downlink Only
Uplink Only
Uplink / Downlink
100
TDD Burst Types
Burst Type 1
Burst Type 2
101
Dedicated Physical Channels Burst Types
Application

• Burst Type 1 has a longer Midamble. Therefore it
  allows a more accurate multi-user detection, as
  is required in the Uplink.
• Burst Type 2 has a shorter Midamble, and
  therefore, higher User Data throughput. It is
  more suitable for the Downlink, which will
  require more capacity in, e.g. Wireless Internet
  applications.

102
Common Control Physical Channels

• Used to transport the BCH, PCH and FACH.
• Burst type is the same as for the Dedicated
  Physical Channels (DPCHs)

103
Physical Random Access Channels

• These channels support the bursts send by UEs in
  order to signal their presence to the Base
  Station of the cell where they intend to camp on.
• As bursts are randomly sent, a certain risk of
  collision in the same Time Slot exists.
• As each access burst has its own Spreading Code
  (8 different options), the risk of collision is
  significantly reduced.

104
Physical Random Access ChannelsAccess Bursts

• Two types of Random Access Bursts are specified.
• Each Burst uses only 1/2 Time Slot.
• The UE may send both bursts in a single Time
  Slot, thereby increasing the probability of
  reaching the Base Station without collision.

105
Physical Synchronization Channel (PSCH)

• It has a similar structure as in the FDD mode.
  Two code sequences are periodically broadcasted
• Primary Synchronization Code (Cp)
• Secondary Synchronization Code (Cs)
• In each Frame, two Time Slots are allocated for
  the Primary Synchronization Channel TS0 and TS7.

106
Physical Synchronization Channel (PSCH)Internal
Burst Structure
107
Mapping of Transport Channels on Physical
Channels
108
Mapping of BCH, PCH and FACH on CCPCHs
Layer 2
Layer 2
Radio Interface
User Equipment
UTRAN
109
Mapping of DCHs and ODCHs on DPCHs
Layer 2
Layer 2
Radio Interface
DCH
DCH
PCH
ODCH
ODCH
ODCH
User Equipment
UTRAN
110
Mapping of RACH on PRACH
Layer 2
Layer 2
Radio Interface
User Equipment
UTRAN
111
Mapping of ORACH on PRACH
Layer 2
Layer 2
Radio Interface
User Equipment
Relay Station
112
Mapping of SCH on PSCH
Layer 2
Layer 2
Radio Interface
User Equipment
UTRAN
113
Physical Layer Description (TDD)Summary

• In the TDD mode, the same carrier frequency is
  used in the uplink and downlink.
• This mode allows asymmetric communication by
  allocating different number of Time Slots in the
  uplink and downlink.
• Each Time Frame contains 16 Time Slots.
• Each Time Slot may allocate 8 users, that may be
  distinguished by different Spreading Codes.

114
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UTRA Data Communication Protocols Description