2. AMPS
(Advanced
Mobile
Phone
Systems
North
American
Standard in
cellular band
(800 MHz)
TACS (Total
Access
Communic
ation
System)
UK originated
standards
based on
AMPS in 900
MHz band
NMT
(Nordic
Mobile
Telephony
System)
Scandinavian
standard in
450 MHz and
900 MHz
band
C-450
German
standard in
450 MHz
band
JTACS
(Japanese
Total
Access
Communic
ation
System)
Japanese
standard in
900 MHz
Band
1st Generation Standards
30 KHz
30 KHz
30 KHz
30 KHz
30 KHz
30 KHz
30 KHz
30 KHz
Frequency
FDMA — Frequency Division Multiple Access
3. IS-136 ( D-
AMPS )
PDC (Japan)
IS-95
CDMA
(cdmaOne)
GSM
1st Generation Standards
Frequency
Time
200 KHz
200 KHz
200 KHz
200 KHz
One timeslot = 0.577 ms One TDMA frame = 8 timeslots
Except IS-95 all
are TDMA based
4. 1990’s
• 1st system to use Digital modulation
• Variety of Multiple Access strategies
• Voice and low rate circuit switched data
• Same technology allows international roaming
• Secure air interface
The Second Generation
www.escsl.com
9. To PSTN
Core
Network
UTRAN
F
Gs
Gf
Iur
Lu-CS
GI
Gp
To IP Network
Other PLMN
AUC Authentication centre
EIR Equipment Identity Register
GGSN Gateway GPRS Support Node
HLR Home Location Register
MSC Mobile Switching Centre
PLMN Public Land Mobile Network
RNC Radio Network Controller
RNS Radio Network Subsystem
SGSN Service GPRS Support Node
UTRAN (UMTS Terrestrial Radio Access Network
VLR Visitor Location Register
RNS
RNS
Gn
UMTS Architecture [3]
11. Network Nodes
1. User Equipment
• Consist of ME and USIM
• The Mobile Equipment (ME) is the radio terminal used for
radio communication over the Uu interface
• The UMTS Subscriber Identity Module (USIM) is a smartcard
that holds:
– the subscriber identity,
– performs authentication algorithms,
– stores authentication and encryption keys
– subscription information that is needed at the terminal
12. Core Network [1]
1. Home Location Register – HLR
• is a database located in the user’s home system that stores
the master copy of the user’s service profile
• It is created when a new user subscribes to the system, and
remains stored as long as the subscription is active
2. Mobile Switching Centre/Visitor Location Register –
MSC/VLR
• It is the switch (MSC) and database (VLR) that serves the UE in
its current location for Circuit Switched (CS) services
• MSC switches the CS transactions
• VLR holds a copy of the visiting user’s service profile and more
precise information on the UE’s location within the serving
system
13. Core Network [2]
3. Gateway MSC – GMSC
• It is the switch at the point where UMTS PLMN is connected
to external CS networks
• All incoming and outgoing CS connections go through GMSC
4. Serving GPRS Support Node – SGSN
• Its functionality is similar to that of MSC/VLR but is typically
used for Packet Switched (PS) services
5. Gateway GSN – GGSN
• functionality is close to that of GMSC but is in relation to PS
services
14. Interfaces
1. Cu interface
• This is the electrical interface between the USIM smartcard
and the ME.
• The interface follows a standard format for smartcards.
2. Uu interface
• It is the WCDMA radio interface
• The UE accesses the fixed part of the system through this
interface
3. Iu interface
• It connects UTRAN to the CN
• the open Iu interface gives UMTS operators the possibility of
acquiring UTRAN and CN from different manufacturers
15. 4. Iur interface
• The open Iur interface allows soft handover between RNCs
5. Iub interface
• It connects a Node B and an RNC
• UMTS is the first commercial mobile telephony system where
the Controller–Base Station interface is standardised as a
fully open interface
Interfaces
17. Radio Access Network [1]
1. Radio Network Controller
• It is responsible for control of the radio resources in its area
• One RNC can control multiple Node Bs
• Its functionality is equivalent to BSC in GSM/GPRS
• RNCs can autonomously handles handovers without involving MSCs and SGSNs
Admission
Control
Radio Resource
Control (RRC)
Radio Bearer
Set-up /
Release
Code Allocation
(Outer Loop)
Power Control
Congestion
Control (Packet
Scheduling)
Handover
Control
(incl.
Combining /
Splitting)
S-RNS
Relocation (S-
RNC/D-RNC)
Ciphering and
Deciphering
Protocol
conversion (Iu
« Iub, Iur)
ATM switching
and
multiplexing
O&M tasks
18. Radio Resource Management
functions of RNC
PC
HC connection
based
functions
LC
AC network
based
functions
PS
RM
Packet Scheduler - PS
Resource Manager - RM
Admission Control - AC
Load Control - LC
Power Control - PC
Handover Control - HC
19. Radio Access Network [1]
1. Node B
• It is responsible for air interface L1 processing
• Also performs some RRM function such as inner loop power control
• It is equivalent to BTS in GSM/GPRS
• Node Bs are typically collocated with GSM BTSs
• The enigmatic term ‘Node B’ was initially adopted as a temporary term during the
standardization process, but then never changed
Spreading Scrambling Channel Coding Interleaving Modulation
Fast Power
Control
Measurement
reports to RNC
ATM
transmission
Micro-diversity
Combining (in
Softer HO)
20. 3GPP Rel-4 Network Architecture
MSC
Server
GMSC
Server
The 3GPP R4 introduces separation of connection, its control, and services for CN CS domain.
• Media Gateway (MGW): an element for maintaining the connection and performing switching function when required.
• MSC server: an element controlling MGW.
21. UMTS - Hierarchy of Bearers
3GPP TS 23.107, QoS Concept and Architecture
TE MT UTRAN CN Iu
edge
node
CN
Gateway
TE
UMTS
End-to-End Service
TE/MT Local
Bearer Service
External Bearer
Service
UMTS Bearer Service
Radio Access Bearer Service CN Bearer
Service
Backbone
Bearer Service
Iu Bearer
Service
Radio Bearer
Service
UTRA
FDD/TDD
Service
Physical Bearer
Service
RAB
RABs
22. Multi-Access Radio Techniques
UMTS is designed to work in both TDD and FDD mode
But FDD option has been preferred by majority of 3G operators
23. Multiple Access Approaches
Frequency
Division
Multiple
Access
Each User has a unique
frequency
(1 voice channel per user)
All users transmit at the
same time
AMPS, NMT, TACS
User1
User2
User3
Frequency
Each Transmitter has a unique
spreading code
Each Data Channel has a unique
orthogonal code
Many users share the same
frequency and time
IS-95, cdma2000, WCDMA
Frequency
Code
Division
Multiple
Access
Spread
Spectrum
Multiple
Access
Multiple
Transmitters
and
Multiple Data
Channels
Each User has a unique
time slot
Each Data Channel has a unique
position within the time slot
Several users share the
same frequency
IS-136, GSM, PDC
Time
Division
Multiple
Access
User1
User2
User3
UserN
Time
26. Main Parameters [1]
• WCDMA is a wideband Direct-Sequence Code Division Multiple Access
(DS-CDMA) system
• user information bits are spread over a wide bandwidth by multiplying the
user data with quasi-random bits (called chips)
• to support very high bit rates (up to 2 Mbps), the use of a variable
spreading factor and multi-code connections is supported
• The chip rate of 3.84 Mcps leads to a carrier bandwidth of approximately
5 MHz
28. • Preparing the Data
and Signaling for
the UMTS Air
Interface
Overview of the UMTS Air Interface (Uu)
Channel Coding
TxRAKE
Signalling Data
Channels
Radio Framing
Spreading &
Channelisation
Scrambling
Modulation
Air interface
SMSSMS
define the UE actions
The user data is coded,
depending on the
applicationThe specifications
1 Different channels carry
different information
2
Data is coded, framed,
spread and channelised
The signal is now
scrambled
3
The signal is modulated
on a frequency to
represent binary values4
The UE uses a special
receiver to RAKE through
the air interface
5
29. Error Correction Code Parameter
Transport Channel
Type
Coding Scheme Coding Rate
BCH
Convolutional code
1/2
PCH
RACH
DCH,
FACH
1/3, 1/2
Turbo coding 1/3
30. • 1/2 and 1/3 rate convolutional channel coding and
turbo coding will be implemented.
• Rate matching is used to "fit" the data bit rate so that it
corresponds to the pre-defined fixed bit rates of the
air interface. Also puncturing can be used.
Channel coding, rate matching
Rate
Matching
- Convolutional coding
- Interleaving
Baseband data (n kb/s)
- 30 kb/s
- 60 kb/s
- 120 kb/s
- 240 kb/s
- 480 kb/s
- 960 kb/s
3.84 Mcps
1. 15 ksps
2. 30 ksps
3. 60 ksps
4. 120 ksps
5. 240 ksps
6. 480 ksps
7. 960 ksps
35. User 1
User 2
User 3
Narrow-band
data signals
Spread Spectrum
signals
1
2
3
Users transmit
their spread
spectrum signals
simultaneously
1&2&3
Output of user 2’s
receiver
2
1 &3
Spreading and Despreading [1]
36. Code Usage
In the Uplink (UE
BTS), the user's data
and signalling
information is
separated by
Channelisation Codes
data
signalling
In the Downlink
(BTSUE), cells are
seperated by
Scrambling Codes
In the Uplink
(UE BTS), terminals
are separated by
Scrambling Codes
In the Downlink (BTS
UE), user connections are
separated by
Channelisation Codes
Dedicated User
Channel
37. channelization Codes
CC1, CC2
CC3, CC4
CC5, CC6, CC7
CC1 , CC2, CC3
CC1, CC2
CC1, CC2, CC3, CC4
Uplink: Channelization Codes used to distinguish data (and control)
channels coming from each UE
Downlink: Channelization Codes used to distinguish data (and control)
channels coming from each cell
(Also called Walsh codes or spreading codes)
38. o o o o o o
SF = 1
Cch,1,0 =1
SF = 2
Cch,2,1 =10
Cch,2,0 =11
SF = 4
Cch,4,0 =1111
Cch,4,2 =1010
Cch,4,1 =1100
Cch,4,3 =1001
channelization Code tree
39. • Adapts user bit-rate to code length
• In reality, multipath, small timing errors diminish
the usable code space
Chip Rate = 3.840 Mcps
480 kb/s 480 kb/s 480 kb/s 480 kb/s 480 kb/s 480 kb/s 480 kb/s 480 kb/s
1
1-1 11
1-11-1 1-1-11 11-1-1 1111
1-11-11-11-
1
1-11-1-11-
11
1-1-111-1-
11
1-1-11-111-
1
11-1-111-1-
1
11-1-1-1-
111
1111-1-1-1-
1
11111111
Example: 8 users; one 8-bit code per user
channelization Codes
40. Scrambling Codes
SC3 SC4
SC5 SC6
SC1 SC1
Cell “1” transmits using SC1
SC2 SC2
Cell “2” transmits using SC2
Downlink: Scrambling Code used to distinguish each cell (assigned by
operator – SC planning)
Uplink: Scrambling Code used to distinguish each UE (assigned by
network)
41. Downlink Scrambling Codes
• Downlink Scrambling Codes
– Each Cell is assigned one and only one Primary Scrambling Code (of 512)
– Secondary Scrambling Codes may be used over part of a cell, or for other data
channels
Primary SC0
Secondary
Scrambling
Codes
(15)
Secondary
Scrambling
Codes
(15)
Secondary
Scrambling
Codes
(15)
Secondary
Scrambling
Codes
(15)
Code Group #1 Code Group #64
8192 Downlink Scrambling Codes
Each code is 38,400 chips of a 218 - 1 (262,143 chip) Gold Sequence
Primary SC7 Primary SC504 Primary SC511
43. 1
-1
-1
1
-1
1
8
-8
-8
8
-1
1
Desired Signal
Desired Spread Signal
Spreading code
Data after
Despreading
Data after Integration
Other user’s Data
Other Spread signal
Other signal after
despreading
Other signal after
Integration
Spreading and Despreading [3]
44. • In WCDMA, the terminal employs a RAKE receiver to handle Multipath
propagation. The RAKE consists of receivers), adjustable-by-system delay
functionality, code generator, and gain and phase tuning equipment. One
Multipath component that the RAKE recognizes is called a finger. Typically,
RAKE is able to handle several fingers. One of these fingers receives the
signal from the Uu interface and tries to open it with the code used for the
connection.
• The second finger receives the same signal from the Uu interface, and the
code used for this connection is inserted to the receiver after a short,
adjustable delay. When the signal is demodulated and regenerated, the
outcomes of the fingers can be summed together.
RAKE receiver
45. CDMA Rake Receiver
• Each RAKE finger tracks a different multipath component
– Sliding correlator used to obtain a correlation peak for each multipath
component
– Also used to track other cells during soft handover
• Searcher finger is used to measure other cells (for handover)
Finger #1
Finger #2
Finger #3
Finger #N
Buffer/delay
Correlators
Channel
C
O
M
B
I
N
E
R
Power measurements
of neighbouring BS
Sum of individual multipath
components:
- maximum ratio
- strongest select
- equal gain
Searcher Finger
50. Definition of Channels
The MAC sub-layer is responsible for
mapping logical channels onto transport channels.
The physical layer is responsible for
mapping transport channels onto physical channels.
51. Logical Channels in UL and DL
Abbr. Channel’s Name
1 BCCH Broadcast Control Channel
2 PCCH Paging Control Channel
3 CCCH Common Control Channel
4 DCCH Dedicated Control Channel
5 DTCH Dedicated Traffic Channel
6 CTCH Common Traffic Channel
Abbr. Channel’s Name
1 CCCH Common Control Channel
2 DCCH Dedicated Control Channel
3 DTCH Dedicated Traffic Channel
DL UL
52. Mapping of Transport Channels onto Phy. Channels
Transport
Channels
PRACH
RACH
DPCCH
DPDCH
DCH
Physical
channels
P-CCPCH
S-CCPCHPhysical
channels
AICH PICHP-SCH
DPDCHCPICH
Transport
Channels
BCH FACH PCH DCH
S-SCH
53. Dedicated Transport Channel
1. DCH – Dedicated Channel
• Downlink/uplink Transport channel
• A point-to-point channel allocated to a specific user
• Carries information intended for the given user including data
and higher layer control information
• Characterised by features such as
– fast power control
– fast data rate change on a frame-by-frame basis
– possibility of transmission to a certain part of the cell
Transport Channels [2]
54. Common Transport Channels
1. BCH – Broadcast Channel
• It is a downlink channel
• Used to broadcast system and cell-specific information over the
entire cell
• The terminal cannot register to the cell without the possibility
of decoding the broadcast channel
– transmit with relatively high power
– low and fixed data rate
Transport Channels [3]
55. 2. FACH – Forward Access Channel
• It is a downlink channel
• Used to carry control information to a mobile station when
the system knows the location cell of the mobile station
• May also carry short user packets
3. PCH - Paging Channel
• It is a downlink channel
• Used to carry control information to a mobile station when
the system does not know the location cell of the mobile
station
• It is used to inform the mobile station of incoming calls
Transport Channels [4]
56. 4. RACH – Random Access Channel
• It is an uplink channel
• Used to carry control information
• It is used for initiating a call (initial access to the serving BS)
• It may also carry short user packets
• must be heard from the whole desired cell coverage area
Transport Channels [5]
57. Uplink Physical channels
Dedicated Physical Data
Channels
(Uplink DPDCH)
Dedicated Physical Control
Channel
(Uplink DPCCH))
Physical Random Access
Channel
(PRACH)
Common Physical ChannelsDedicated Physical Channels
Uplink Physical Channels [1]
58. 1. PRACH - Physical Random Access Channel
• It is used to carry RACH
• Its transmission is based on Slotted ALOHA approach with
fast acquisition indication
• A UE can start the transmission at a number of well-defined
time-slots called access slots
• Consist of one or several preambles of length 4096 chips and
a message of length 10 or 20 ms
Common Uplink Physical Channel [1]
PRACH
59. Radio frame: 10ms Radio frame: 10ms
5120 Chips
Random Access TransmissionAccess Slot #0
Random Access TransmissionAccess Slot #1
Random Access TransmissionAccess Slot #7
Random Access TransmissionAccess Slot #8
Access Slot #14
#0 #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14
RACH access slot numbers and their spacing
Common Uplink Physical Channel [2]
PRACH
60. Access Preamble
Control Part
Data Part
Message Part
0P 1P
jP
1,2)(Nmsec10*N 4096 chips
Structure of the random access transmission
Common Uplink Physical Channel [3]
PRACH
61. Uplink Physical Channels [2]
Dedicated Uplink Physical Channel
1. DPDCH - Dedicated Physical Data Channel
• Used to carry dedicated data i.e. the dedicated transport channel (DCH)
• There may be zero, one, or several uplink DPDCHs
2. DPCCH – Dedicated Physical Control Channel
• Used to carry control information consists of:
– pilot bits to support channel estimation
– transmit power-control (TPC) commands
– feedback information (FBI)
– an optional transport-format combination indicator (TFCI)
• One DPCCH and up to six parallel DPDCHs can be transmitted
simultaneously ONE
DPDCH
&
DPCCH
62. Uplink Physical Channels [3]
K determines the number of bits per uplink DPDCH/DPCCH slot
spreading factor SF:
SF = 256/2k
DPDCH spreading factor may thus range from 256 down to 4
Slot #0 Slot #1 Slot # i Slot #14
1 Radio Frame: Tf= 10ms
DPDCH
&
DPCCH
65. Spreading for uplink DPCCH and DPDCH
I+jQ
Slong, n or Sshort,n
Q
j
DPDCH
DPCCH
DPDCH– Cch,SF,k (k = SF/4)
DPCCH – Cch,256,0
I
66. Dedicated Physical Channel (Downlink DPCH)
A time multiplex of a downlink DPDCH and a downlink DPCCH
Primary Common Control
Physical Channel
(P-CCPCH)
Secondary Common Control
Physical Channel
(S-CCPCH)
Synchronisation
Channel
(P-SCH & S-SCH )
Acquisition Indication
Channel
(AICH)
Page Indication
Channel
(PICH)
Common Pilot Channel
(CPICH)
Common Physical Channels
Downlink Physical Channels [1]
67. Downlink Physical Channels [2]
Dedicated Downlink Physical Channels
1. DPCH - Dedicated Physical Channel
• Time multiplexing of the DPDCH and DPCCH is used in the downlink.
• spreading factor SF:
SF = 512/2k
• In the downlink the spreading factors range from 4 to 512, with some
restrictions on the use of spreading factor 512 in the case of soft
handover.
• The downlink DPDCH consists of QPSK symbols. Each symbol consists of
two bits while in the case of uplink the DPDCH consists of BPSK symbol
(one symbol corresponds to one bit).
68. Slot #0 Slot #1 Slot #i Slot #14
1 Radio Frame Tf= 10ms
Frame structure for downlink DPCH
Data
Ndata1 bits
Pilot
Npilot bits
TFCI
NTFCI bits
TPC
NTpc bits
Data 2
Ndata 2 bits
DPCCH DPDCH DPCCH DPDCH DPCCH
Downlink Physical Channels [3]
70. 1. CPICH - Common Pilot Channel
• It is a fixed rate channel carries a pre-defined bit/symbol sequence
• Aids in channel estimation to the terminal
Slot # 0 Slot #14Slot# iSlot # 1
Pre-defined symbol sequence
Tslot = 2560 chips, 20 bits = 10 symbols
1 radio frame : Tf = 10 ms
Common Downlink Physical Channels [1]
Primary CPICH
Same channelization code always used
Scrambled using primary scrambling code
One per cell
Broadcast over entire cell
71. 2. P-CCPCH - Primary Common Control Physical Channel
• Used to carry BCH
• SF=256
• P-CCPCH is not transmitted during first 256 chips
Frame structure for Primary Common Control Physical Channel
(Tx OFF)
Slot # 0 Slot #14Slot# iSlot # 1
Tslot = 2560 chips, 20 bits
256 chips
Data 18 Bits
1 radio frame : Tf = 10 ms
Common Downlink Physical Channels [3]
72. 3. S-CCPCH - Secondary Common Control Physical Channel
• Used to carry FACH and PCH
• SF = 256/2K
• FACH and PCH can be mapped to same secondary CCPCH
• Primary CCPCH has fixed pre-defined rate while secondary CCPCH has
variable rate
• Primary CCPCH is continuously transmitted over entire cell while
secondary CCPCH is only transmitted only when there is data available
4. P-SCH Primary Synchronisation Channel
– Carries a unique code (Primary Synchronization Code PSC) which is used in all
UMTS cells around the world.
5. S-SCH Secondary Synchronization Channel
– Carries a “sequence of 15 secondary synchronization codes which depends on the
Scrambling Code Group of the cell.
Common Downlink Physical Channels [4]
73. 6. AICH – Acquisition Indicator Channel
• Used to carry Acquisition Indicators (AI) in response to PRACH Preamble
7. PICH – Page Indicator Channel
• Used to carry Page Indicator (PI)
• PICH is always associated with a S-CCPCH to which PCH is mapped
Common Downlink Physical Channels [6]
74. Cell Search and Initial Access
The initial Cell Search is carried out in three steps:
Step 1: Slot synchronisation - using the primary synchronisation channel.
Step 2: Frame synchronisation and code-group identification using the
secondary synchronisation channel.
Step 3: Scrambling-code identification-identified through symbol-by-
symbol correlation over the primary CCPCH with all the scrambling
codes within the code group.
75. Structure of Primary and Secondary
Synchronisation Channels (SCH)
cp Primary Synchronisation Code ( It is the same for every cell in the system)
cs
i,k Secondary Synchronisation Codes ( Where i=0,1….63 is the number of the scrambling
code group, and k= 0,1,…14 is the slot number. Each code is chosen from a set of
16 different codes of length 256).
2560 chips
One 10 ms SCH radio frame
acs
i,1
acp
Slot #0 Slot #1 Slot #14
acp
acs
i,14
Primary
SCH
acp
acs
i,0Secondary
SCH 256 Chips
76. Fast Cell
Search
Downlink primary scrambling codes
Scrambling Code
Group 0
•SC 0
•----
•SC7
Scrambling Code
Group 1
•SC 8
•----
•SC 15
---------------
•-----
•----
•----
Scrambling Code
Group 63
•SC 504
•----
•SC 511
Find the Exact SC of cell
Only 8 Possibilities Using P-CPICH
Find Out the SC group #
Only 64 possibilities Using S-SCH
79. Power Control [1]
3. Open loop power control
The open loop power control is used to adjusts the transmit
power of the Physical Random Access Channel.
80. Power Control [2]
Downlink Power control
1. Inner loop power control
The downlink inner loop power control adjusts the base station
transmit power in order to keep the received downlink SIR at a
given SIR target.
2. Outer loop
The outer loop adjusts the SIR target used by the inner loop
power control. The SIR target is independently adjusted for each
connection based on the estimated quality of the connection.
Typically a combination of estimated bit error rate and frame
error rate is used for the quality estimate.
81. UE2
UE1
Power Control [3]
Uplink Power control
1. Inner loop power control
The uplink inner loop power control adjusts the MS transmit
in order to keep the received uplink SIR at a given SIR target.
Power Control
Commands to the
mobiles
P1
P2
Keep Received Power
Level P1 and P2 Equal
RNC
83. UE
Power Control [5]
2. Outer loop
The outer loop adjusts the SIR target used by the inner loop power
control. The SIR target is independently adjusted for each connection
based on the estimated quality of the connection.
Outer Loop Power
Control
If quality<target.
Increase SIR Target
Frame
Reliability info
SIR Target
Adjustments
Commands
BS Fast Power Control
If SIR < SIR Target. Send *Power
Up* Command
RNC
Mobile
stand still
SIR target
Time
86. Handover Types
Soft Handover
• In DCH mode, MS has concurrent traffic connections with two BS’s
Softer Handover
• Similar to Soft Handover, but between two sectors of the same cell
Inter-Radio Access Technology (IRAT) Handover
• CS Handover from a WCDMA system to another system
• Traffic and Control Channels are Disconnected and must be Reconnected (hard handover)
Inter-frequency Handover (IFHO)
• When the MS must change WCDMA carrier frequency during the Handover
• Traffic and Control Channels are Disconnected and must be Reconnected (hard handover)
Inter-RAT Cell Change
• Manages PS UE mobility between cells using WCDMA RAN and cells using GSM/GPRS
Cell Reselection
• Manages UE mobility between WCDMA cells with same frequency, different frequency and between WCDMA cells
and GSM/GPRS cells, when the UE is in idle mode or CELL_FACH state
87. WCDMA Handover Scenarios
RNS
RNC
RNS
RNC
Node B Node B Node B Node B
Iu Iu
Iur
Iub IubIub Iub
Inter-Node
(Soft)
Intra-Node
(Softer)
Inter-RNS
(Soft with Iur;
Hard with no Iur)
UTRAN
Core Network
88. Soft Handover Key Points
• When fast power control is used, soft handover is
essential
– Allows MS to operate in most conservative power
control mode
• Soft handover provides performance benefits
– “Seamless” coverage at cell fringes
– Handover may be less noticeable to the user
• Soft handover also degrades system capacity
– Uses redundant physical layer resources from adjacent
or overlapping cells
Handover
89. WCDMA With and Without SHO
time
Trouble zone: Prior to Hard Handover,
the MS causes excessive interference to BS2
BS2 Receive Power Target
UE responding to BS1
power control bits
UE responding to BS2
power control bits
time
BS1 Receive Power Target
Handover
91. Measurement Reporting
1. Measure
2. Filter
3. Apply quality offsets to cells individualOffset
4. Compare with measurement criterion
5. Send measurement report with EVENT (if occurred)
f1 f1
f2
Handover
92. WCDMA Soft Handover Process
• One finger of the RAKE receiver is constantly scanning
neighboring Pilot Channels.
• When a neighboring Pilot Channel reaches the t_add
threshold, the new BS is added to the active set
• When the original Base Station reaches the t_drop
threshold, originating Base Station is dropped from the
active set
Monitor Neighbor BS Pilots Add Destination BS Drop Originating BS
Handover
94. Event 1a, Primary CPICH enters Reporting Range
Event cause:
Radio Link addition /
replacement due to
measurements related to best
cell in Active Set
Event 1a and 1b
reportingRange1a
hysteresis1a
timeToTrigger1a
UE sends Measurement Report message for EVENT 1a and the cell is added to AS. If AS is full
maxActiveSet, the cell will replace the worst cell in the current AS, provided the reported cell
has better quality
Handover
95. Event 1b, Primary CPICH leaves Reporting Range
Event cause:
Radio Link removal from due to
measurements related to best cell
in Active Set
Event 1a and 1b
reportingRange1b
hysteresis1b
timeToTrigger1b
UE sends Measurement Report message for EVENT 1b and the cell is removed from the AS
(one cell is always kept in AS to maintain connection).
Handover
96. Event 1c, non-active Primary CPICH becomes better
than active Primary CPICH
Event cause:
Radio Link substitution due to
measurements related to least
good cell in AS while the AS is full
hysteresis1c
timeToTrigger1c
UE sends Measurement Report message for EVENT 1c and the cell replaces the least good cell
in the AS.
Event 1c
Handover
97. Event 1d, Change of Best Cell
Event cause:
ANY cell (AS or monitored)
becomes better than the current
best cell in the AS.
hysteresis1d
timeToTrigger1d
UE sends Measurement Report message for EVENT 1d. If the cell already belongs to AS, no
action is taken by RNC. Else, the cell will be added to the AS, and if the AS is full, the least
good cell will be replaced.
Event 1d
Handover
98. SRNC
” Measurement Control”
” Measurement Report”
(BCCH/DCCH)
(DCCH)
RNC
Evaluation
Perform
Measurement
UE Evaluation
Execution
Radio Link
Add/Removal/Replace
”Active Set Update” (DCCH)
Radio Link
Add/Removal/Replace
”Active Set Update Complete” (DCCH)
Radio Link
Add/Removal/Replace
RNC
Evaluation
”Measurement Control” (DCCH)
Signaling Flow in SHO
Handover
99. Compressed Mode
• The physical channel is reconfigured to create transmission and
reception gaps.
• UE then tunes to other frequencies (GSM) to conduct measurements
• Signaling required to prepare for the measurements
– Additional UE and network processing load
• Recommendation:
– Minimise time in compressed mode
– Avoid going in and out of compressed mode
Handover
Decreasing the
Spreading Factor by
2:1
• Increases Data Rate
so bits get through
twice as fast!
Puncturing bits
• weakens FEC coding
Higher layer
scheduling
• Reduces available
timeslots for user
traffic
Data compression can be accomplished by:
101. Compressed Mode
• Using slotted downlink transmission mode, a single-receiver
mobile station can carry out measurements on other
frequencies without affecting its normal data flow.
• The information normally transmitted during a 10ms frame is
compressed in time, either by code puncturing or by reducing
the spreading factor by a factor of 2.
• As a result, an idle time period of 5ms is created within each
frame. During this time, the MS receiver is idle and can be
used for inter-frequency measurements.
102. HO Triggering Thresholds set in RNC
Event Triggered HO
reasons fulfilled in RNC
RNC commands selected UE(s) to start
IF/IS measurements
Measurements are done in
Compressed Mode (CM)
UE reports best GSM cells (RSSI) to RNC
RNC makes HO decision and
commands UE to target cellv
BSIC verification for GSM cells
UE reports best UMTS cells
(Ec/Io; RSCP) to RNC
Compressed Mode (for IFHO and ISHO)
Steps during
Inter Frequency Handover
and
Inter-system Handovers
Only in ISHO
Both IFHO and ISHO
104. Introduction
• In order to meet the increasing demand for high data-rate
multimedia services, the 3rd Generation Partnership Project
(3GPP) has released a new high-speed data transfer feature
named High-Speed Downlink Packet Access (HSDPA).
• It offers peak data rates of up to 14 Mbps, resulting in a better
end-user experience for downlink data applications, with
shorter connection and response times.
• HSDPA improves the use of streaming applications and Web
browsing applications.
105. Key Features
Short physical
layer frames
Adaptive
Modulation and
Coding (AMC)
Fast Hybrid-ARQ Fast scheduling Fixed SF =16
HSDPA can be seen as an extension of the
DSCH with new features such as:
107. New Channel Structure
1. HS-DSCH – High Speed Downlink Shared Channel
• It is the primary radio bearer
• HS-DSCH can be shared between users in the time domain
• Transmission Time Interval consists of three time slots (2ms)
to shorten round trip delays
• Constant spreading factor of 16
• Maximum of 15 parallel codes allocated
108. 2. HS-SCCH – High Speed Shared Control Channel
• Carry download signaling information in the downlink direction
• Transmitted before each scheduled TTI
• Has a duration of 3 time slots
• Multiple HS-SCCH can be configured to support parallel HS-DSCH
transmissions
• A UE can be allocated a maximum of 4 HS-SCCH
UE-ID (H-RNTI)
Channelization
Code Set
Modulation
Scheme
TB Size
Redundancy
Version
HARQ Process
Indicator
109. Figure : HS-SCCH and HS-DSCH timing relationship
Part 1 Part 2
Downlink DCH (DPCCH/DPDCH)
1 Slot
1 Slot
Codes
to receive
HS-SCCH
HS-DSCH
110. 3. HS-DPCCH – High Speed Dedicated Physical Control
Channel
• Carry ACK/NACK information and link quality information in
the uplink direction
• This information is used by Node B scheduler to determine
the destination terminal and transmission data rates to be
used
• Consist of two parts:
• Part I: ACK/NACK transmission
• Part II: Downlink Channel Quality Indicator (CQI) to indicate;
– estimated transport block size
– modulation type
– number of parallel codes
CQI (N) ACK
111. Figure: HSDPA Channel operation
HS-DPCCH: CQI
HS-SCCH: DL Transfer Information
HS-DSCH: Data Transfer
HS-DPCCH: ACK / NACK
UE
Summary of HSDPA Channels
112. Adaptive Modulation and Coding
• Continuously optimizing
– the code rate
– modulation scheme
– number of codes employed
– transmit power
• QPSK and 16 QAM
• Code rates: ¼ to ¾
• Based on channel quality reported on CQI
• Users experiencing favorable channel conditions will be allocated higher
data rates
• A single user can receive up to 10.8 Mbps peak data rates
• Maximum data rate specified in HSDPA is 14.4 Mbps
QPSK16 QAM
Adaptive
Modulation and
Coding (AMC)
113. Adaptive Modulation and Coding
Adaptive
Modulation and
Coding (AMC)
Modulation coding
rate
Data rate
(1 code)
Data rate
(5 codes)
Data rate
(15 codes)
QPSK 1/4 120kbps 600kbps 1.8Mbps
QPSK 1/2 240kbps 1.2Mbps 3.6Mbps
QPSK 3/4 360kbps 1.8Mbps 5.4Mbps
16QAM 1/2 480kbps 2.4Mbps 7.2Mbps
16QAM 3/4 720kbps 3.6Mbps 10.8Mbps
114. Hybrid ARQ Fast Hybrid-ARQ
Advantage: improve transferring reliability
Disadvantage: lower utilization in bad
channel state
Advantage: good performance in
lower Bit Error Rate (BER)
Disadvantage: bad performance in
high BER
F
E
C
A
R
Q
H
A
R
Q
Combine FEC and ARQ, each
sending packet includes error
detection bit and error correction bit
Error packet A
Packet A
Packet A
Error packet A
Packet A
Packet A
missing data
Packet A
missing
data
HARQ phase I
（Resending is in RNC，R99）
HARQ phase II, III
（Resending is in Node B, HSDPA）
Packet A
Discard Reserve
Resend
whole packet Resend data
Soft
combination
Packet BPacket B
Send SendReceive Receive
Lower efficiency
Longer time delay
Higher efficiency
Shorter time delay
115. Hybrid ARQ
• Hybrid Automatic Repeat request
• Stop and Wait (SAW) protocol
• HARQ allows the UE to request retransmission
• HARQ is implemented at MAC-hs (Media Access Control high
speed) terminated at Node B
• With HARQ UE does not discard the erroneous energy
• UE stores it and later combines with retransmission (Soft
Combining)
Fast Hybrid-ARQ
Chase Combining
• Retransmitting same
information
Incremental Redundancy
• Different redundancy
information can be send during
re-transmission
116. Fast Packet Scheduling (1)
• the scheduler is located at the Node B as opposed to the RNC
• this enables the scheduler to quickly track the UE channel condition and
adapt the data rate allocation accordingly
• Several algorithms can be used for the scheduler such as:
1. Round Robin (RR)
• a first-in first-out approach
• provides a high degree of fairness
• users can be served even when they are experiencing weak signal
lowering the overall system throughput
Fast scheduling
117. 2. Maximum Carrier to Interference (C/I)
• schedules users with the highest C/I during the current TTI
• highest system throughput
• no effort to maintain any kind of fairness
3. Proportional Fair
• Good trade-off between RR and maximum C/I
• schedules users according to the ratio between their
instantaneous achievable data rate and their average served
data rate
Fast Packet Scheduling (2) Fast scheduling
118. Physical Layer Procedures
STEP I: Scheduler at Node B evaluates for different users:
– the channel conditions
– Pending data in buffer
– Time elapsed since last served
– Pending retransmissions
STEP II: Once a terminal is selected, Node B checks for:
– The available codes
– Type of modulation can be used
– Terminal capability limitations
STEP III: Node B starts to transmit HS-SCCH two slots before HS-DSCH TTI
STEP IV: MS monitors HS-SCCH and decodes Part I and Part II of HS-SCCH
STEP V: MS then use this buffered information to decode HS-DSCH
STEP VI: Upon detecting this combined data, MS send ACK/NACK in the
uplink direction depending on the CRC results
119. Figure: Terminal timing with respect to one HARQ process
HS-SCCH
HS-DSCH
HS-SCCH
N Slots
7.5 slots (approx)
Downlink transmission
Uplink transmission
HS-DPCCH (ACK / NACK + Feedback )
CRC result
124. Mobility
• UTRAN determines the serving HS-DSCH cell for an HSDPA-capable
UE
• A new measurement event is defined
• measurement basically reports the best serving HS-DSCH cell to the
serving RNC based on a measurement of the P-CPICH Ec/I0
• serving RNC sends a synchronised radio link reconfiguration prepare
message to the Node B
• At a specified time index, the source cell stops transmitting to the
user
• MAC-hs packet scheduler in the target cell is thereafter allowed to
control transmission to the user
• PDUs for the user are moved from the MAC-hs in the source cell to
the MAC-hs in the target cell during the HS-DSCH handover
126. Key Features
• Fast HARQ terminated at Node B
• Fast Node B based uplink scheduling
• Higher order modulation
127. UE
Fast Hybrid ARQ
• Fast HARQ is to allow the Node B to ask for the UE to retransmit the uplink packet if it
was not received correctly
• One Node B received a packet correctly but other didn’t.
• Due to limited UE power the UE may not be able to transmit at the same data rate
incase of retransmission
RNC
Node B
UE
Packet
RLC ACK/NACK
Retransmission
Rel ‘99 Uplink DCH
RNC
Node B
Packet
Retransmission
L1 ACK/NACK
Uplink E-DCH
Correctly Received
Packet
Combining of Packets
128. Fast Packet Scheduling
• The uplink scheduling is Node B based
• Node B gives UE a set of data rates based on uplink load measurements
RNC
Node B
Traffic volume
measurement
TFC
Control
Data
transmission
Rel ‘99 Uplink DCH
RNC
Node B
UE
Scheduling info
Data
transmission
Scheduling
Assignment
Uplink E-DCH
UE
130. Physical Channels
1. E-DPDCH – Enhanced Dedicated Physical Data Channel
• used to carry the E-DCH user data
• There may be zero, 1, 2 or 4 E-DPDCH on each radio link
• SF = 256 , 128, 64 , 32 , 16 , 8 , 4, 2
2. E-DPCCH – Enhanced Dedicated Physical Control Channel
• used to transmit control information associated with the E-
DCH
• There is at most one E-DPCCH on each radio link
• E-DPDCH and E-DPCCH are always transmitted
simultaneously
131. Slot #0 Slot #1 Slot # i Slot #14
E-DPDCH Frame Structure
Data Slot #2
1 Sub frame = 2 ms
Message part Radio Frame TRACH Tf = 10ms
Control
Data Ndata bits
10 Bits
E-DPDCH
E-DPCCH
Tslot = 2560 chips, Ndata = 10*2k bits (k = 0...7)
Tslot = 2560 chips
132. 3. E-RGCH – E-DCH Relative Grant Channel
• It is a fixed rate (SF=128) dedicated downlink physical channel
• Indicates to the UE whether to increase, decrease or keep unchanged the
transmit power level of the E-DCH
• UP , DOWN or HOLD commands
4. E-HICH - E-DCH Hybrid ARQ Indicator Channel
• It is a fixed rate (SF=128) dedicated downlink physical channel
• carry the uplink E-DCH hybrid ARQ acknowledgement indicator
5. E-AGCH - E–DCH Absolute Grant Channel
• It is a fixed rate (30 kbps, SF=256) downlink physical channel
• Provides an absolute power level above the level for the DPDCH
(associated with a DCH) that the UE should adopt
133. Figure: New physical channels introduced by HSUPA
E-HICH
E-RGCH, E-AGCH
E-DPCCH
E-DPDCH
HARQ
Uplink Scheduling
C-Plane
U-PlaneUE
135. Comparing HSDPA and HSUPA
Feature HSDPA HSUPA
Peak Data Rate 14.4 Mbps 5.6 Mbps
Modulation Scheme (s) QPSK, 16QAM QPSK
TTI 2ms 2ms (optional) / 10ms
Transport Channel Type Shared Dedicated
Adaptive Modulation and Coding
(AMC)
Yes No
HARQ HARQ with incremental
redundancy; Feedback in HS-
DPCCH
HARQ with incremental
redundancy; Feedback in dedicated
physical channel
( E-HICH)
Packet Scheduling Downlink Scheduling
(for capacity allocation)
Uplink Scheduling
(for power control )
Soft Handover Support ( U-Plane) No
(in the Downlink
Yes
Editor's Notes
21
23
The inherently wide carrier bandwidth of WCDMA supports high user data rates and also has certain performance benefits
the network operator can deploy multiple 5 MHz carriers to increase capacity
WCDMA supports highly variable user data rates, The user data rate is kept constant during each 10 ms frame; the data capacity among the users can change from frame to frame
Supports the operation of asynchronous base stations employs coherent detection on uplink and downlink based on the use of pilot symbols or common pilot
WCDMA is designed to be deployed in conjunction with GSM. Therefore, handovers between GSM and WCDMA are supported
39
41
A common channel is a channel (resource) used by all users or a group of users in a cell. In the downlink a common channel is a point-to-multipoint channel and in the uplink the channel is contended by users.
A dedicated channel is a point-to-point channel allocated to a specific user.
BCCH is a downlink channel used to broadcast system and cell-specific information over the entire cell.
FACH is a downlink channel used to carry control information to a mobile station when the system knows the location cell of the mobile station. FACH may also carry short user packets.
PCH is a downlink channel used to carry control information to a mobile station when the system does not know the location cell of the mobile station. It is used to inform the mobile station of incoming calls.
RACH is a uplink channel used to carry control information. It is used for initiating a call (initial access to the serving BS). RACH may also carry short user packets.
CPCH is a uplink channel used to carry infrequent medium sized packets.
DSCH is a downlink channel used to carry infrequent medium and large sized packets and can be shared in time between several users.
The MS receives from the BCH the available sub-channels (Access slots), scrambling codes and signatures.
The MS selects randomly one of the RACH sub-channels from the group its access class allows it to use. It also selects a signature randomly from the available signatures.
A 1 ms access preamble is transmitted using the selected signature.
The MS monitors the Acquisition Indication Channel (AICH) to see whether the BS has received the preamble.
If no AICH is detected, the MS increases the access preamble transmission power by a fixed amount given by the BS and transmits it again in the next available access slot.
When an AICH is detected, the MS transmits the 10 ms or 20 ms massage part of the RACH.
The DPDCH and DPCCH are spread to a fixed chip rate of 3.84 Mchips/s by the channelization codes, Cd and Cc, respectively.
The DPDCH uses Cch,SF,k code where SF is the spreading factor (256 to 4) and k is the branch no. of the code tree for the same SF (k = 0, …, SF-1). The value of k = SF/4 is used for the DPDCH.
The DPCCH uses Cch,256,0 i.e., the top branch of the code tree for SF = 256.
Bd and Bc are gain factors used to adjust the relative transmitted power of the DPDCH and DPCCH.
Slong, n or Sshort, n is the scrambling code for nth mobile station. The mobile station is identified by its scrambling code.
One DPCCH and up to six parallel DPDCHs can be transmitted simultaneously.
The synchronisation channel consists of two channels, the primary and secondary synchronisation channels.
The primary SCH uses a code of 256 chips transmitted over every slot.
The primary SCH code is the same for every cell in the system.
The primary SCH is used for slot synchronisation.
The secondary SCH consists of 64 sequences, each sequence has a 15 code of length 256 chips. Each BS transmits a specific sequence in every frame (one code per time slot), repeatedly.
Each code sequence is associated to one downlink scrambling code group.
The secondary SCH is used for frame synchronisation.
