1-Introduction to UMTS and WCDMA
-
Upload
vincent-massogue -
Category
Documents
-
view
69 -
download
6
description
Transcript of 1-Introduction to UMTS and WCDMA
Introduction to UMTS & WCDMA
April 2008
Oussama Akhdari
ROSI / INTPS / NAD / RASQ / International Radio support
2 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3G Generation General AspectsIntroduction to UMTSUMTS Radio Access Network QoS ArchitectureWCDMA Principles
Agenda
3 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
IMT 2000 Standards
IMT-2000 is a term used by the International Telecommunications Union (ITU) to refer to many third generation (3G) wireless technology, that provide higher data speed between mobile phones & base antennas. ITU activities on IMT-2000 comprise international standardization, including frequency spectrum & technical specifications for radio & network components, tariffs and billing, technical assistance & studies on regulatory and policy aspects.
IMT- DS
WCDMA/UTRA FDD
Direct Spread
IMT- MC
CDMA2000Multi-Carrier
IMT- TC
UTRA TDDTD - SCDMATime - Code
IMT- SC
UWC - 136Single-Carrier
IMT- FT
DECTFrequency Time
IMT2000 Terrestrial radio interfaces
IMT- OFDM
WiMaxOFDMA
CDMA CDMA - TDMA
Paired Spectrum Paired/Unpaired Spectrum
TDMA TDMA - FDMA
Unpaired Spectrum Paired Spectrum
OFDMA
4 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
IMT 2000 FrequenciesWorldwide frequency plans for IMT-2000 bands already identified
Assigning a non IMT2000 spectrum would result in higher handset prices for 3G systems complex circuitry to support international roaming across different frequency bands.
Europe
China
Japan Korea
North America
ITU Alloc.
5 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3rd Generation Projects
3GPP “3rd Generation Partnership Project” www.3gpp.org Present about 80% of the users within the World Technical specifications for the 3rd Generation Mobile System based on the evolved GSM core networks and UTRA. Include a Technical Specification Group (TSG) for the GSM EDGE Radio Access Network (GERAN). Responsible of GSM (2G) and UMTS (3G) including its evolution HSDPA/HSUPA (3.5G) Evolution of HSPA / SAE (System Architecture Evolution) / Long Term Evolution (LTE)
3GPP2 “3rd Generation Partnership Project 2” www.3gpp2.org Present about 20% of the Mobile users Working on AIE (Air Interface Evolution) / EV-DO Rev. C
IEEE 802.16 & WiMAX Forum Deployment very shy and limited to fixed WiMax (3.5 GHz)
6 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3GPP Specification Series www.3gpp.org
7 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3G Generation General AspectsIntroduction to UMTSUMTS Radio Access Network QoS ArchitectureWCDMA Principles
Agenda
8 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UMTS Terrestrial Radio Access - UTRAW-CDMA (UTRA FDD)
For the paired band Uplink and downlink are separated in frequency Chosen as the technology for UMTS publish, wide -area service
TD-CDMA (UTRA TDD) For the unpaired band Uplink and downlink are separated in time Flexible time duration for uplink & downlink for asymmetrical traffic Chosen for private, indoor services in the unpaired TDD
FDD Mode TDD Mode
1900 1920 1980FDD ULTDD
UL/DLTDD UL/DL
MSSUL
2010 2025MSSDL
2110 2170 2200
FDD DL
FUL
FDL
FUL/DL
FDD Mode TDD Mode
1900 1920 1980FDD ULTDD
UL/DLTDD UL/DL
MSSUL
2010 2025MSSDL
2110 2170 2200
FDD DL
1900 1920 1980FDD ULTDD
UL/DLTDD UL/DL
MSSUL
2010 20251900 1920 1980FDD ULTDD
UL/DLTDD UL/DL
MSSUL
2010 2025MSSDL
2110 2170 2200
FDD DL
FUL
FDL
FUL/DL
9 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UTRA FDD - Characteristics Wide band code division multiple access W-CDMA multiple access Frequency band Region 1 (Europe)
Uplink 1920 - 1980 MHz & Downlink 2110 - 2170 MHz GSM bands: 900 (including E-GSM band) & 1800 bands
ARCEP provided authorization to OFR & SFR to reuse 900 spectrum for UMTS
Mobistar to launch UMTS900 during 2008 New bands attributed to UMTS @ 2.6 GHz (new auctions?)
Carrier Bandwidth 2x5 MHz (theoretical occupied bandwidth = Chip rate 3,84 Mcps)
Services Both circuit and packet data & asymmetric bitrates AMR Multi Rate Wide Band AMR Multi service possible User Rate Up to 384 Kbits/s
FDD foreseen for Macro & Microcellular coverage for all Orange MCos.
10 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3G vs. 2G Network services
A 3G networks has a very flexible air interface that can meet the demands of both packet services and circuit switched voice or data.
11 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Frequency resources within 3G MCo
The standard resources allocation is 3 carriers per MCo The resources allocation is country dependent (Local
Telecommunication authority strategy)
Uplink (MHz) Downlink (MHz) Total (MHz) Third carrier Available MHz Total (MHz)Mobistar 1964.9 - 1979.7 2154.9-2169.7 2 15 MHz Yes (1 carrier is used) 1910-1915 1 5 MHzOrange Spain 1935 - 1950 2125-2140 2 15 MHz Yes 1900-1905 1 5 MHzOrange France 1964.9 - 1979.7 2154.9-2169.7 2 15 MHz Yes (2 carriers are used) 1910.1-1915.1 1 5 MHzOrange Poland 1920.5 - 1935.3 2110.5 - 2125.3 2 15 MHz Yes 1915.1-1920.1 1 5 MHzOrange Romania 1950.1 - 1964.9 2140.1 - 2154.9 2 15 MHz Yes (2 carriers are used) 1904.9 - 1909.9 1 5 MHzOrange Slovekia 1920 - 1940 2110 - 2130 2 20 MHz Yes (2 carriers are used) 1900-1905 1 5 MHzOrange Switzerland 1950 - 1965 2140 - 2155 2 15 MHz Yes 1905-1910 1 5 MHz
Orange UK 1969.7 - 1979.7 2159.7 - 2169.7 2 10 MHz No (OUK granted only 2 carries, both used) 1904.9 - 1909.9 1 5 MHz
Mobinil (Granted) 1930 - 1935 2120 - 2125 2 5 MHzMobinil end 2010 1930 - 1940 2120 - 2130 2 10 MHzOrange Reunion 1940.2 - 1945.2 2130.2 - 2135.2 2 5 MHz 1 carrier is availableOrange Caraïbe 1940.2 - 1945.2 2130.2 - 2135.2 2 5 MHz 1 carrier is available
Not GrantedNot Granted
MCo UMTS FDD UMTS TDD
Not Granted1 carrier is available
12 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
FT Group Supplier
Mobistar Huawei ( ALU Swapped)Orange Spain E/// & NSNOrange France ALU & NSNOrange Poland NSN & HuaweiOrange Romania HuaweiOrange Slovekia ALUOrange Switzerland NSNOrange UK NSN Mobinil ( Egypt ) NSN & HuaweiOrange Reunion HuaweiOrange Caraïbe ALUOrange Moldova HuaweiCell Plus (Mauritius) Huawei
MCo Mco Suppliers
13 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3G Generation General AspectsIntroduction to UMTSUMTS Radio Access Network QoS ArchitectureWCDMA Principles
Agenda
14 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
WCDMA Access structure
15 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UMTS radio access networkNode B
Radio base station like the BTS in GSM RF Processing (Modulation, Coding, Interleaving, Spreading, de-spreading…)
RNC “Radio Network Controller” Controls radio resources of several Node Bs Manage the Radio Access Bearers for user data transport Control user mobility Supports the Iu interface to the core network
RNS “Radio Network Subsystem” Like BSS in GSM
UMTS Radio Access Network
Iu
Iur
UTRAN
Iub
RNS
RNSNodeB
NodeB
RNC
NodeB
NodeBRNC
16 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
RNC Roles: Serving, Drift, Controlling
RNC SRNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub IubIub Iub
UE
UTRANSRNSRNS
SRNC• Each connected mode UE is controlled by a Serving RNC (SRNC)• The SRNC terminates Iu towards the CN
DRNC SRNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub IubIub Iub
UE
UTRANSRNSDRNS
Macro DiversityCombining/splittingfunction
DRNC • Inter RNC soft handover requires a second RNC to be involved• Such an RNC lending resources to an SRNC for a specific UE acts as a Drift RNC (DRNC).
CRNC• Each RNC acts as Controlling RNC (CRNC) for the directly connected Node B’s and their cells• The CRNC controls the radio resources of its cells
CRNC CRNC
Core Network
Node B Node B Node B Node B
Iu Iu
Iur
Iub IubIub Iub
UTRANRNSRNS
17 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UTRAN interfaces
Iur interface logical interface between RNCs
Iur is a point-to-point interface between two RNCs
allows more independent radio resource management compared to GSM
RNC mobility (soft handover) Data from the serving RNC is transferred
to the drifting RNC through the Iur interface.
Iub interface Interface between RNC and Node B Allows the RNC & BTS to negotiate about radio resources Transports uplink & downlink transport frames & O&M data Manage Data & signaling Traffic 2 E1 required @ least when HSPA is introduced High Traffic Areas may need a higher IuB capacity
UMTS Radio Access Network
Iu
Iur
UTRAN
Iub
RNS
RNSNodeB
NodeB
RNC
NodeB
NodeBRNC
18 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Core network - circuit switched
Iu - CS for circuit switched services
MSC-Mobile Services switching Center
switch for circuit switched (CS) services
VLR-Visitor Location Register register database for visitors of the radio network
GMSC - Gateway MSC switch from mobile network to external networks for circuit switched services
Core NetworkCN
Iu-CS
GGSNSGSN
MSC/VLR GMSC
HLR
19 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Core network - packet switched
HLR - Home Location Register permanent database of subscriber data
Iu - PSfor packet switched services
SGSN - Serving GPRS Support Node
switch for packet switched (PS) services
GGSN - Gateway GPRS Support Node
switch from mobile network to external networks for packet switched services
Core NetworkCNIu-PS
GGSNSGSN
MSC/VLR GMSC
HLR
20 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Iu interface main Function Establishing, maintaining, and releasing radio access bearers Performing intra-system & inter-system handovers as well as SRNC relocations Transferring NAS signaling messages between UE & CN (direct transfer) Location services - transfers requests from CN to RAN, and location information from RAN to CN. Simultaneous access to CS & PS core network domains for single UE Paging the user, provides the CN with the capability to page user equipment Controlling the security by sending the security keys to RAN and by Setting the operation mode for security functions Reporting data volume Controlling the tracing of the user equipment activity
21 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3G Generation General AspectsIntroduction to UMTSUMTS Radio Access Network QoS ArchitectureWCDMA Principles
Agenda
22 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UMTS QoS Architecture
UMTS QoS is provided by the UMTS bearer service, which consists of two parts:
Radio access bearer (RAB) service Provides the confidential transport of user data between the UE and
CN with a QoS that is adequate for the negotiated UMTS bearer Consists of a radio bearer (RB) service & a Iu bearer service
“The RB service is realized in the radio link control (RLC) layer between the SRNC & the UE, using UTRA FDD/TDD, while the Iu bearer service provides transport between the UTRAN & CN”
CN bearer service connects the UMTS CN with CN gateway to the external network
23 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
CN = Core networkTE = Terminal EquipmentMT = Mobile Termination
UMTS QoS Architecture
TE MT UTRAN CN IuEDGENODE
CNGateway
UMTS
“End-to-End Service”
TE/MT LocalBearer Service
UMTS Bearer Service External BearerServiceUMTS Bearer Service
Radio Access Bearer Service(RAB)
CN BearerService
BackboneBearer Service
Iu BearerService
Radio BearerService (RB)
UTRA FDD/TDD Service
(Radio Physical Bearer Service)
PhysicalBearer Service
TETE MT UTRAN CN IuEDGENODE
CNGateway
UMTS
“End-to-End Service”
TE/MT LocalBearer Service
UMTS Bearer Service External BearerServiceUMTS Bearer Service
Radio Access Bearer Service(RAB)
CN BearerService
BackboneBearer Service
Iu BearerService
Radio BearerService (RB)
UTRA FDD/TDD Service
(Radio Physical Bearer Service)
PhysicalBearer Service
TE
24 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UMTS QoS Architecture The RAB is the service that the access stratum provides through its service access points (SAP) to the non-access stratum (NAS) for transfer of user data between the user equipment (UE) and the core network (CN)
The RAB provides transport of user data with the quality of service (QoS) adequate to the UMTS bearer service negotiated on the non-access stratum. This service is based on the characteristics of the radio interface and is maintained for a moving user equipment
A bearer service includes all aspects to enable the provision of a contracted QoS. These aspects are the control signaling, user plane transport, and QoS management functionality
The UMTS operator offers the UMTS bearer service, which provides the UMTS QoS.
25 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
QoS Classes
There are four different QoS classes (or traffic classes) for UMTSbearer service and radio access bearer service:
conversational streaming interactive background
The main distinguishing factor between these classes is how delay sensitive the traffic is.
Conversational class is meant for traffic that is very delay sensitive, while background class is the most delay insensitive traffic class.
RNC manages the QoS requirements.
Data Integrity sensitive
+
Delay sensitive
-
+ -
Data Integrity sensitive
+
Data Integrity sensitive
+
Delay sensitive
-
+
Delay sensitive
-
+
Data Integrity sensitive
+
Data Integrity sensitive
+
Delay sensitive
-
+
Delay sensitive
-
+ --
Data Integrity sensitive
+
Data Integrity sensitive
+
Delay sensitive
-
+
Delay sensitive
-
+
26 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
QoS Classes
Traffic classes provide the means for the network to differentiate between end-to-end user applications according to their required traffic characteristics.
The purpose is to offer good quality connections for both real time & non-real time traffic between MS and the background data networks.
The radio interface is the main capacity limiting factor & must be planned & controlled to achieve the required system performance
Error correction and delay is managed and prioritized to ensure goodquality connections.
27 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Application Groups
Traffic class Conversational Class Streaming class Interactive class Background class
Fundamentalcharacteristics
Conversational RT. Preserve timerelation (variation)between informationentities of the stream. Conversational pattern (stringent & low delay)
. Streaming RT
. Preserve timerelation (variation)between informationentities of the stream
. Interactive best effort. Request response pattern. Preserve payload content
. Background best effort. Destination is not expecting the data within a certain time. Preserve payload content
Example of theapplication Voice Streaming video Web browsing Background
download of emails
Service classes and priorities are one of the main differences between 2G and 3G. Priorities are obtained from CN.
WCDMA RAN uses the QoS parameters obtained from CN to optimize the use of radio resources. In GSM BSS, packet-switched traffic is always lower priority traffic, using only whatever resources are available.
28 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
3G Generation General AspectsIntroduction to UMTSUMTS Radio Access Network QoS ArchitectureWCDMA Principles
Agenda
29 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
WCDMA Transmitter The WCDMA transmitter looks similar to the TDMA transmitter, with the synchronization, control/signaling and multiple user data channels. In a WCDMA transmitter, neither time nor frequency is used to separate different users, but codes in an operation known as spreading.
30 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Multiple Access TechniquesFDMA Frequency Division Multiple Access
uses band pass for carrier signal which are non-overlapping in the frequency domain
TDMA Time Division Multiple Accesscarrier signals are non overlapping in the time domain
CDMA Code Division Multiple Accessspreads the signal over the entire available bandwidth by using codes with good correlation properties
FFrreeqquueennccyy
TTiimmee
PPoowweerr
OOnnee UUsseerr
FFrreeqquueennccyy
TTiimmee
PPoowweerr
UUsseerr
Power
Time
FrequencyOne User
Carrier 1 Carrier 2
31 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
W-CDMA No Frequency reuse
W-CDMA = Wideband Code Division Multiple Access Users are separated with code sequences: spreading / despreading technique
All users are transmitting simultaneously on the same frequency In FDD mode, different frequencies are used on uplink and downlink
Frequency Planning No Frequency Planning
All cells are assigned the same frequency
All cells within a given cluster are
assigned different set of frequencies
32 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spread spectrum technique
The user bits are coded with a unique sequence (code). The bits of the code are called chips and the chip rate is higher than the user bit rate
TimeDomain
Bandwidth = 3.84 Mhz for UMTS
Code Ci(t)
Resulting spread signalDi (t) = Si (t) x Ci(t)
Bit1 Bit2
Source signal Si (t)before spreading
Frequency
Domain Narrowband signal
Bit Rate =Rb
Chip Rate =Rc = 3.84 Mcps in UMTS
Chip Rate =RcSpreading Factor
SF =Rc/Rb
33 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Channelization coding
34 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading Example
Spreading with a spreading factor of 4 is shown in the Figure below.
35 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading / Despreading
In the receiving path, despreading is achieved by auto-correlation with the same code Due to low cross-correlation properties with other codes, the received signal energy is increased compared to noise and other signal interference The gain due to despreading is called processing gainExample for PS 128 Kbps:
dBkbpskcps
RateBitUserRateChipPG 77.1430
1283840
36 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading / Despreading
The figure shows the properties of the Channelization (Orthogonal) codes.
37 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading example
De-spreading applied to another user with a different
spreading code
Increase the data rate by 8 corresponds to a widening of the occupied spectrum of the
spread user data signal
38 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Channelization codes
Orthogonal Variable Spreading Factor (OVSF) are used for channelization for spreading
The codes are mutually orthogonal, if they are synchronized in the time domain Codes are taken from the OVSF code tree
The code tree corresponds to different discrete Spreading Factor (SF) levels, SF=1, 2, 4, 8…(n2) SF: 4 - 512 is allowed in the WCDMA DL SF: 4 - 256 is allowed in the WCDMA UL
Following codes are not allowed to be used: Codes between a used code and the code tree root Codes following a used code
39 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading codes: OVSF code tree
1c4,1=
c4,2=
c4,3=
c4,4=
c2,1=
c2,2=
c1,1= 1
1 1
1 -1
11
1 1
1 -1
1 -1
reverse
copy 1 1copy
reverse-1 -1
1 -1
-1 1reverse
SF=4SF=1 SF=2
1 1 1 1 1 1 1
1 1 1 1 -1-1-1
-1-1-1
-1-1-1
-1-1-11 1 1 1-1
-1-1
-1-1-1
-1-1-1
-1-1-11 1 1 1-1
-1-1
-1-1-1
-1-1-1
-1-1-11 1-1
-1-1
-1-1-1
1 1-1-1-1
-1-1-11 1-1
-1-1
-1-1-1
1 1-1-1-1
-1-1-11 -1
-1-1
-1-1-1
1 1 -1-1-1
-1-1-1
1
1 -1-1-1
-1-1-1
1 -1-1-1
1 -1-1-1
1
SF = 1 SF = 2 SF = 4 SF = 8
Up to SF = 256
…
1c4,1=
c4,2=
c4,3=
c4,4=
c2,1=
c2,2=
c1,1= 1
1 1
1 -1
11
1 1
1 -1
1 -1
reverse
copy 1 1copy
reverse-1 -1
1 -1
-1 1reverse
SF=4SF=1 SF=2
1 1 1 1 1 1 1
1 1 1 1 -1-1-1
-1-1-1
-1-1-1
-1-1-11 1 1 1-1
-1-1
-1-1-1
-1-1-1
-1-1-11 1 1 1-1
-1-1
-1-1-1
-1-1-1
-1-1-11 1-1
-1-1
-1-1-1
1 1-1-1-1
-1-1-11 1-1
-1-1
-1-1-1
1 1-1-1-1
-1-1-11 -1
-1-1
-1-1-1
1 1 -1-1-1
-1-1-1
1
1 -1-1-1
-1-1-1
1 -1-1-1
1 -1-1-1
1
SF = 1 SF = 2 SF = 4 SF = 8
Up to SF = 256
…
40 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
OVSF : Orthogonality property
1c4,1=
c4,2=
c4,3=
c4,4=
c2,1=
c2,2=
c1,1= 1
1 1
1 -1
11
1 1
1 -1
1 -1
1 1
-1 -1
1 -1
-1 1
1 1 1 1 1 1 1
1 1 1 1 -1-1-1
-1-1-1
-1-1-1
-1-1-11 1 1 1-1
-1-1
-1-1-1
-1-1-1
-1-1-11 1 1 1-1
-1-1
-1-1-1
-1-1-1
-1-1-11 1-1
-1-1
-1-1-1
1 1-1-1-1
-1-1-11 1-1
-1-1
-1-1-1
1 1-1-1-1
-1-1-11 -1
-1-1
-1-1-1
1 1 -1-1-1
-1-1-1
1
1 -1-1
-1-1
1 -1-1
1 -1-1
1Codes freeCodes used
41 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Uplink and Downlink Channelization Code Usage
Downlink: Channelization Codes used to distinguish data channels coming from each cell
Uplink: Channelization Codes used to distinguish data channels coming from each User Equipment, UE
42 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading and scrambling codes Spreading codes (channelization codes)
used to differentiate mobiles and services different lengths (spreading factor) according to service in UMTS Orthogonal Variable Spreading Factor (OVSF) in UMTS
Scrambling codes To distinguish between User Equipments in uplink To distinguish between cells in downlink
DLUL
Node B
SpreadingOVSF
(Service/ user identifier)
ScramblingPN
(Cell identifier)
DescramblingDespreading
UE
Descrambling Despreading
SpreadingOVSF
(Service identifier)
ScramblingPN
(User identifier)
43 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
The CDMA Cocktail Party
What do YOU hear…
A) If you only speak Japanese?
B) If you only speak English?
C) If you only speak Italian?
D) If you only speak Japanese, but the Japanese-speaking person is all the way across the room?
E) If you only speak Japanese, but the Spanish-speaking person is talking very loudly?
44 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Scrambling Coding
45 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
SC: Scrambling Code
Downlink Scrambling Code
SC#2
SC#0
SC#1
SC#116
SC#114
SC#115
RNC
SC#2
SC#0
SC#1
SC#2
SC#0
SC#1
SC#2
SC#0
SC#1
SC#116
SC#114
SC#115
SC#116
SC#114
SC#115
SC#116
SC#114
SC#115
RNC
Downlink scrambling code The number of codes used in the downlink is restricted to 8192 in Total to speed up the process for the UE to find the correct scrambling code. 512 of these are primary codes (the rest are secondary codes, 15 codes per primary). The primary codes are divided into 64 code groups each group containing 8 different codes.One code per cell (sector/carrier) : Configurable by operatorOnly the primary scrambling code is used for all Common Channels
46 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Modulation
Graphical representation of an QPSK modulated signal
1 Modulation Symbol represents 2 data bits Modulation efficiency = 2 bits/symbol
47 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Filtering
Filtering allows the transmitted bandwidth to be significantly reduced without losing the content of the digital data improves the spectral efficiency Raised-Cosine Data Filter
occupied bandwidth = symbol rate x (1+ α)
48 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
“Near-Far-Problem”
Illustration Example: Up to around 80 dB attenuation between UE1 and UE2
If UE1 and UE2 transmitted with the same power, UE1 would jam UE2 : so-called “near-far” effect
Solution : power control Need for an efficient power control able to fight against slow AND fast fading!
UE 1
UE 2
Before despreading After despreading
49 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Power control
In UMTS FDD, all users are sharing the same frequency band
W-CDMA requires power control to minimize the level of interference (interference-limited system)
Power control is applied on both uplink and downlink
Power control minimizes the transmission power to match the quality target for each radio access bearer service
No one should get more power than necessary to reach the required QoS Avoids near-far problem on uplink Minimizes waste of common power resource on downlink
50 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Interference limiting system
Thanks to spreading / despreading Desired signal is raised Interference signals are kept low
The level of interference must be controlled to allow the decoding of the received signal
spreadingspreading DespreadingDespreading
BB
ChannelChannel
WW
Thermal NoiseThermal Noise
BBProcessing
gainspreadingspreadingspreadingspreading DespreadingDespreadingDespreadingDespreading
BB
ChannelChannel
WW
Thermal NoiseThermal NoiseThermal NoiseThermal Noise
BBProcessing
gain
BBProcessing
gain
51 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Interference limited
0
2
4
6
8
10
12
14
16
18
20
0 10 20 30 40 50 60 70
Number of simultaneous users per sector
Inte
rfere
nce
leve
l rel
ativ
e to
Noi
se le
vel
(dB
)
52 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Cell breathing
Considering the limitation of maximal transmit power, the increase of required received power due to high traffic will lead to decrease the cell range
The cell coverage decreases when the traffic increases : so-called “cell breathing” phenomenon
Coverage and capacity are linked in CDMA systems
53 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Tr affic den s it y
in cr e ase s
Deployed intersite distance
Load control
In order to avoid power control instability and coverage holes due to high traffic level the level of interference received by a base station should be controlled by means of admission and load control algorithms
54 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Other W-CDMA particularities
No frequency reuse pattern
Scrambling code planning required 512 scrambling codes in W-CDMA
Soft-handover capability
RAKE receiver
SC#116
SC#114
SC#115
SC#2
SC#0
SC#1
55 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Mobile connected to more than one base station during handover procedure Called “softer” handover for sector cells of the same site Soft Handover for Dedicated Channels (circuit and packet data) Hard Handover
HS-DSCH Inter-frequency handovers Inter-RAT Handovers
Soft Handover i
Macrodiversity
Received PilotSignal
Node-B 2
3 dB
Node-B 1
Same carrier
RNC
56 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Soft Handover ii
Advantages Avoids link failure during handover, “make before break” handover Reduces the interference level by decreasing the required UE transmit power Increases downlink quality thanks to macro-diversity at the UE receiver level
Drawbacks Increases the required number of traffic channels Can create too much downlink interference : trade-off on the percentage area of soft-handover
57 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
RAKE receiver
Reflections, diffractions, attenuations caused by obstacles will lead to multipath
RAKE receiver is a spread-spectrum receiver that is able to track and demodulate resolvable multipath components : takes benefit of multipath diversity
In W-CDMA, with 3.84 Mcps, a RAKE receiver will be able to discriminate multipath having delays higher than one chip duration (0.26 µs)
58 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
The RAKE Receiver
CDMA Mobile Station RAKE Receiver ArchitectureEach finger tracks a single multipath reflection
• Also be used to track other base station’s signal during soft handover
One finger used as a “Searcher” to identify other base stations
Finger #1
Finger #2
Finger #N
Searcher Finger
Combiner
Sum ofindividual multipath components
Power measurement of Neighboring Base Stations
59 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
0 50 100 150 200 250 300 350 400-2
0
2
4
6
8
10
12
14
16
18
0 50 100 150 200 250 300 350 400-2
0
2
4
6
8
10
12
14
16
18
0 50 100 150 200 250 300 350 400-2
02468
10
121416
18
The RAKE Receiver
1/2-chip delay
To Viterbi Decoder
Composite Received Signal
PN, Walsh Codes
1/2-chip delay
1/2-chip delay
Ai
Ai
Ai
Correlator
Correlator
Correlator
Equal Combining, ML Combining,
or Select Strongest
time
0 50 100 150 200 250 300 350 400-2
0
2
4
6
8
10
12
14
16
18
1
23
1
23
1
23
1
23 1
2
3 + Interference
+ Interference
+ Interference
60 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
RAKE receiver ii
It combines the delayed replicas of the transmitted signal to improve reception quality : time-diversity technique
Identify the delay positions on which significant energy arrives and allocate correlation receivers (RAKE fingers) to those peaks
Within each correlation receiver, track the changing phase and amplitude values and correct them (thanks to pilot symbol estimation)
Combine the demodulated and phase-adjusted symbols across all active fingers and present them to the decoder for further processing (maximal ratio combining)
61 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading Spectrum Advantages
The wideband transmission has the advantage of being less sensitive to frequency selective interference and fading.
The power density of the spectrum is decreased several times and the transfer of information is still possible even below background noise.
CDMA is very spectrum efficient due to the possibility of reusing each carrier in each cell.
High Capacity in comparison with GSM
Soft handover is required in WCDMA.
62 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Spreading Spectrum Drawbacks
The power levels of all UE’s transmissions received at the BS must be equal if the bit rates are equal and therefore fast power control is necessary
As UEs in soft handover mode require resources of more than one cell, the system capacity may be reduced.
63 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
an exchange!
based on discussions!
… share our experiences
any questions?let’s discuss!
64 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Back UP
65 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Logical channels i
PCCH - Paging control Channel (DL) DL Paging information
BCCH - Broadcast Control Channel (DL) DL System control information e.g. Cell identity, UL interference level
CCCH - Common control Channel (UL/DL) For transmitting control information between the network and UEs The CCCH is commonly used by UEs having no RRC connection and after cell reselection e.g. initial access (RRC connection request, cell update)
66 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Logical channels ii
CTCH - Common Traffic Channel (DL) channel to transfer dedicated user information to all or a group of UEs e.g. SMS Cell broadcast
DCCH - Dedicated Control Channel (UL/DL) transmits dedicated control information between UE and UTRAN e.g. measurement reports, radio bearer setup
DTCH - Dedicated Traffic Channel (UL/DL) The DTCH carries user data e.g. speech, Fax, video, web, ...
67 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
DL Transport Channels i
BCH - Broadcast Channel For broadcasting of system information over entire cell no power control, fix bit rate
PCH - Paging Channel association with Page Indicator Channel PICH, to support efficient sleep mode procedures must be broadcast over entire cell
FACH - Forward Access Channel Common DL channel used for transmission of
control information small amount of packet data
open loop power control
68 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
DL Transport Channels ii
DCH - Dedicated Channel DCH is the only Dedicated Transport Channel Channel dedicated to one UE Supports
Fast Power Control, variable bit rate, SHO, transmit diversity, beam forming
DSCH - Downlink Shared Channel Similar to the FACH Carries dedicated user data and/or control information Always associated with a downlink DCH (with SF of 256) DSCH supports
sharing between different users no SFH, but Fast PC due to associated DCH
69 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UL Transport Channels
RACH - Random Access Channel carries control information or small amounts of packet data
e.g. for initial access or non-real-time dedicated control or traffic data transmitted over entire cell supported by open loop power control
CPCH - Common Packet Channel
Similar to DSCH in DL, used for transmission of bursty data traffic possibility to
transmit over part of the cell (beam forming) change rate fast fast power control
initial risk of collision, but collision detection (CD/CA-ICH) is shared by the UEs in a cell -> common resource
DCH - Dedicated Channel (same as for UL)
70 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Physical Channels
Channels without connection to transport channels are called Stand-alone channels
All Stand-alone channels exist in DL only
Stand alone channels are CPICH Common Pilot Channel SCH Synchronization Channel (Primary & Secondary) AICH Acquisition Indication Channel PICH Paging Indicator Channel CSICH CPCH Status Indicator Channel CD/CAICH Collision Detection / Channel Assignment
Indicator Channel
71 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
DL Physical Channels - CPICH
CPICH - Common Pilot Channel Primary CPICH (PCPICH)
• SF=256, predefined bit/symbol sequence, fixed channelization code• Scrambled with the primary scrambling code• Only one PCPICH per cell• Used for level measurements & channel estimation• The PCPICH is the phase reference for all DL physical channels• Transmitted over the entire cell
Secondary CPICH (SCPICH)• SF=256, arbitrary channelization code• Zero, one or several SCPICH per cell• Not necessarily transmitted over entire cell
72 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
DL Physical Channels - SCH
SCH - Synchronization Channel Time multiplexed with PCCPCH
• first 256 chips of slot SCH, rest PCCPCH Primary SCH
• Consists of a a fixed 256 chips code Primary Synchronization Code (PSC)
• The PSC is the same for every cell in the system• The PSC is repeated in each slot
Secondary SCH• Transmitted in parallel to the Primary SCH• In each of the 15 slots a different Secondary Synchronization Code
SSC is transmitted• The SSC sequence indicates the used downlink scrambling code set
(8 codes) out of 64 scrambling code groups
73 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
DL Physical Channels - Other Stand-Alone
AICH - Acquisition Indication Channel• SF256, Frame length 20ms 5120 chips/slot• Used to confirm reception of (P)RACH
PICH - Paging Indicator Channel• SF=256, carries the paging indicators• associated with an SCCPCH to which a PCH transport channel is
mapped• Once a PI message has been detected on the PICH, the UE decodes
the next PCH frame transmitted on the SCCPCH whether there is a paging message intended for it.
CSICH - CPCH Status Indication Channel CD/CA-ICH - CPCH Collision Detection/Channel Assignment Indicator Channel
• All CPCH related physical channels support the operation of the UL CPCH transport channel
74 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
DL Physical Channels
DL Channels associated with a transport channel PCCPCH - Primary Common Control Physical Channel
Used to carry the BCH Time multiplexed with SCH Fixed transmit power / fixed data rate
SCCPCH - Secondary Common Control Physical Channel Used to carry the FACH or PCH / no fast power control
PDSCH - Physical Downlink Shared Channel Carries DSCH Not yet included in 3GR1.1
DPCCH - Dedicated Physical Control Channel Pilot field, TFCI field, TPC field
DPDCH - Dedicated Physical Data Channel carries “real” user data + Layer 3 signaling on DCCH
75 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
UL DPCH
UL Physical Channels
UL Channels associated with a transport channel PRACH - Physical Random Access Channel
• Carries RACH• open loop power control / collision risk
PCPCH - Physical Common Packet Channel• Carries CPCH• Fast power control on the message part / open loop for pre-ample
DPCCH - Dedicated Physical Control Channel• Pilot field, TFCI field, FBI field, TPC field
DPDCH - Dedicated Physical Data Channel• Carries “real” user data + Layer 3 signaling on DCCH
76 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Valid for all Dedicated Physical Channels
Existing in uplink or downlink Possibility to use beam forming Possibility to change rate fast on a frame basis (10 ms) Fast power control (Closed Loop Power Control)
77 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
One radio frame, Tf = 10 ms
TPC NTPC bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10*2k bits (k=0..7)
Data2Ndata2 bits
DPDCH
TFCI NTFCI bits
Pilot Npilot bits
Data1Ndata1 bits
DPDCH DPCCH DPCCH
DL Physical Channel Example
Example of physical channel structure: DL - DPDCH
Signaling information (DPCCH) is time multiplexed with DPDCH
78 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Pilot Npilot bits
TPC NTPC bits
DataNdata bits
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips, 10 bits
1 radio frame: Tf = 10 ms
DPDCH
DPCCHFBI
NFBI bitsTFCI
NTFCI bits
Tslot = 2560 chips, Ndata = 10*2k bits (k=0..6)
UL Physical Channel Example
Example of physical channel structure: UL - DPDCH/DPCCH
DPCCH and DPDCH are in UL NOT time multiplexed, they are I/Q multiplexed.
79 Groupe France Télécom Introduction to UMTS & WCDMA / April 2008 /confidential/Oussama Akhdari
Use of DPCCH
On the DPCCH channel the following information is transmitted Pilot field
Bit sequence known in the receiver and and used for radio channel estimation
Optimal adaptation of RAKE receiver TFCI field
Transport Format Combination Indicator FBI field (UL DPCCH only)
Feed Back Information given by the UE to the Node B for optimizing closed loop transmit diversity mode (phase &
amplitude) site selection diversity transmission (SSDT)
TPC field Transmit Power Control This field is used to transmit the power control commands to the
Node B (UL) or the the UE (DL).