part 6 3g systems 1
TRANSCRIPT
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Part 6. 3G Mobile Communication Systems
―WCDMA and cdma2000
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Introduction― Objectives to develop 3G
Achieving significantly higher transmission speed capability, encompassing
circuit- and packet-switched networks as well as support of multimedia services.
Higher spectral efficiency and overall cost improvement by utilizing advanced
technologies.
Maximizing the commonality by radio interfaces for multiple operating
environments.
Compatibility of services within IMT-2000 and fixed networks.
2G: voice
3G: voice, image, video
Data Networks
2G: low rate 2G: low rate
3G: high rate3G: high rate
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Introduction― Key Properties Emphasized in 3G
Improved performance over 2G, including:
– Improved capacity;
– Improved coverage, enabling migration from a 2G deployment.
A high degree of service flexibility, including:
– Support of a wide range of services with maximum bit rates above 2 Mb/s and the
possibility for multiple parallel services on one connection;
– A fast and efficient packet-access scheme.
A high degree of operator flexibility, including:
– Support of asynchronous inter-base-station operation;
– Efficient support of different deployment scenarios, including hierarchical cellstructure and hot-spot scenarios;
– Support of evolutionary technologies such as adaptive antenna arrays and multi-user
detection.
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Introduction― Differences Between 2G and 3G Systems
Flexible offer of mobile multimedia services
– Voice/fax/data
– Wideband data services (high speed Internet/high quality images)
Slow bit pipe provided by 2G
Faster bit pipe by 3G
<64kbps
(25-64kHz)Voice
Low rate data
2Mbps
(5MHz)Internet
Voice
ImagesMulti-media
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Introduction― Spectrum allocation of 3G (1)
1992, ITU, World Administrative Radio Conference
– the frequencies around 2GHz were available for use by 3G mobile systems
– called International Mobile Telephony 2000 (IMT-2000)
– defined several different air interfaces based on CDMA or TDMA– target: a single common global IMT-2000 air interface for 3G
Target: a single common global IMT-2000 air interface for 3G
– Europe and Asia: same air interface WCDMA, frequencies around 2GHz– North America: spectrum around 2GHz has been auctioned for 2G and no new
spectrum is available for IMT-2000, 3G must be implemented within the
existing bands by replacing part of the spectrum with 2G
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Introduction― Spectrum allocation of 3G (2)
WRC-2000 IMT-2000 Frequencies source:
http://www.umtsworld.com/
technology/frequencies.htm
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The nature of communications has been changing …
– People to People→ People to Things→ Things to Things
Family of ITU standards consisting of two main systems
– Direct Spread Option (Wideband CDMA) with chip rate of 3.84
Mcps and BW of 5 MHz.
– Multi-Carrier Option (Cdma2000).
Key 3G Requirements:
– High Speed Packet Data: 144 kbps -- Vehicular; 384 kbps --Pedestrian, 2 Mbps -- Indoor
– Global Roaming
Introduction― 3G Standards
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Introduction― Standardization Efforts (1)
SDO working for radio interfaces standardization
source: Willie W. Lu,"Broadband wireless mobile"
Universal Wireless Consortium (UWC)
Standard
Development
Organization
Partnership
Project
Radio
Interfaces
Japan
China
North America
Korea
Japan
Europe
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Introduction― Standardization Efforts (2)
3GPP (3G Partnership Project)– Spearheaded by ETSI (European Telecommunication Standards Institute)
– Memberships as in December 1998: ARIB (Japan), ETSI (Europe), T1 (USA), TTA
(Korea) and TTC (Japan); May 1999: CWTS (China)
– Aim: to prepare, approve, and maintain globally applicable technical specificationsand technical reports for a 3G mobile system (called Universal Mobile
Telecommunication System UMTS) based on the evolved GSM core network and
Universal Terrestrial Radio Access (UTRA) (UTRA TDD+FDD=> WCDMA)
3GPP2– Spearheaded by ANSI (American National Standards Institute)
– Memberships as in January 1999: ARIB, TIA (USA), TTA and TTC.
– Aim: to cooperate in the preparation of globally applicable technical specifications
for a 3G mobile system based on the evolved ANSI/TIA/EIA-41 core networks andcdma2000.
OHG (Operators’ Harmonization Group)
– To prevent a multiple standard problem.
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Introduction― Standardization Efforts (3)
Radio interfaces defined for IMT-2000
source: Willie W. Lu,
"Broadband wireless mobile"
IMT-Direct Spread
IMT-Multi Carrier
IMT-Time Code
IMT-Single Carrier
IMT-Frequency Time
IMT Radio
Technologies
Access
Technologies
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Introduction─ IMT2000 Capability (1)
Indoor
2Mbps
Indoor
2Mbps Pedestrian
384kbps
Pedestrian
384kbps
Vehicular
144kbps
Vehicular144kbps
IMT2000
Network
Planned to deploy in May 2001
Frequency band:2GHz band
Information rates: up to 2Mbps
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Introduction― IMT2000 Capacity (2)
Variable bit rates to offer bandwidth on demand
Multiplexing of services with different quality requirements on a single
connection, e.g., speech video and packet data
Delay requirements from delay-sensitive real-time traffic to flexible best-effortpacket data
Quality requirements from 10% frame error rate to 10-6 bit error rate
Coexistence of second and third generation systems and inter-system handovers
for coverage enhancements and load balancing Support of asymmetric uplink and downlink traffic, e.g., web browsing causes
more loading to downlink than to uplink
High spectrum efficiency
Coexistence of FDD and TDD modes
source: H. Holma and A. Toskala,
"WCDMA for UMTS"
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Introduction― Commercial 3G Services (1)
Start with crazy spectrum auctions in Europe
– Huge success of 2G
– Telecommunication companies in Europe spent more than 120 billion$ on
3G licenses
– Great Britain: 34 billion$
– Germany: 46 billion$
– Vodafone: 9.4 billion$ for one license in Great Britain
“We spent €10 billion
too much”
Sir Peter Bonfield, CEO, BT
Sunday Times, London,
18th February 2001
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Introduction― Commercial 3G Services (2)
Voice
E-m ai l i n g
W
e b b r o w
s i n g
TransactionsBankingReservations for flights
and accommodations Stock trading, etc
Daily informationWeatherNews Stock prices, etc.
Data baseRestaurant guideTown pageDictionaryTrain transfer info.Cooking recipes, etc.
EntertainmentKaraoke
Network gameMovie listingsFortune-telling etc.
A successful example of 3G– The world first 3G network was launched by NTT DoCoMo, Japan, in 2001
– Big success of its 3G services “i-mode”: internet services are added to voice
communications
– Creation of mobile multimedia era
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Introduction― Commercial 3G Services (3)
Jan. 2004
Hutchison
Dec. 2004
Smartone
H.K. CSL
Jun. 2005
Sunday
Jul. 2006
3G
subscribers:
1million
3G in Hong Kong
– Mainland China: no 3G services
– Hong Kong: only WCDMA is employed
Jun. 2008
3G
subscribers:
2.38million
all mobile
subscribers:
10.98million
Oct. 2001
Spectrum
Auction
four 3G
licenses; valid
for 15 years;each with a
spectrum of
2x14.8MHz
+1x5MHz
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Introduction― Commercial 3G Services (4)
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Introduction― Commercial 3G Services (5)
CDMA20001x
WCDMA
CDMA20001xEV-DO
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Summary: What Is 3G?
Why necessary?
– Explosive expansion of markets
– Mobile multimedia communications
– Global standard terminals
– Big business chances
– Lower cost due to mass markets
Which services?
– Unknown, but services indicated by the success of “i-mode”
– Point-to-point, point-multi points, broadcasting services
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WCDMA
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Introduction (1)
Wideband CDMA– a predominant wireless access technology for the 3G systems
– designed to offer wideband services
wireless internet services: download information from the Web, video transmission,...
– data rate: indoor: 2Mbps, pedestrian: 384kbps, vehicular: 144kbps
– wide bandwidth (5MHz) is needed for high data rate
physical limitations and impairments on radio
channels presents a fundamental technical challenge
to reliable high data rate communications
Two Modes: FDD and TDD
– Frequency division duplex: optimized for wide-
area coverage, i.e., public macro and micro cells
– Time division duplex: optimized for public micro
and pico cells and unlicensed cordless applications
uplink
downlink
BS
BS
MS
MS
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Introduction (2)
Freq.Uplink Downlink
190MHz
5MHz 5MHzFDD: paired
spectrum; ideal
for symmetric
services (voice);
inefficient forasymmetric
services (e.g. mp3
downloading)
Freq.Uplink
Downlink
5MHz
TDD: no need for
paired spectrum;
flexible, efficientfor asymmetric
services
TimeUplink Downlink
TimeUplink
Downlink
Downlink Downlink
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Introduction (3)
Main features of WCDMA Asynchronous inter-base-station operation
– no requirement on any external system such as GPS
– new challenges like cell acquisition and soft handoff
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Introduction (4)
Main features of WCDMA Variable rate transmission
– to provide multimedia services
– multi-code transmission is employed in downlink to achieve higher bit rates
Adaptive antenna array– null out interference and maximize the signal to interference ratio
– particularly useful for multimedia communications
a small number of high rate users give
significant interference to low rate users.
Without adaptive antenna array, the link
capacity would be significantly reduced.
– dedicated pilot symbols in both up- and
down-link facilitate user-unique antenna
patterns
Turbo coding
– large coding gain
Desired
user
with
low rate
services with high
rate
serviceslike online
game
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System Architecture (1)
source:
http://www.mobileguru.co.uk/Mo
bile_Technology_globe.html
New protocols for WCDMA
UMTS R99 Architecture
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System Architecture (2)
UTRA Terminologies UE: User Equipment
– interfaces the user and the radio interface
– consists of Mobile Equipment (ME) and UMTS Subscriber Identity Module (USIM)
UTRAN: UMTS Terrestrial Radio Access Network
– handles all radio related functionality
– consists of Node B (Base Station) and Radio Network Controller (RNC)
Core Network
– evolved GSM core network
– switching and touting calls and data connection to external networks
– consists of Home Location Register (HLR), Mobile Services Switching Center
(MSC), Visitor Location Register (VLR), Gateway MSC, Service GPRS Support
Node (SGSN), Gateway GPRS Support Node (GGSN)
External Network
– consists of Circuit Switching (CS) network and Packet Switching (PS) network
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System Architecture (3)
Note: the
functionality
of each pair is
not necessary
the same
Compare GSM and UMTS Terminologies
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Radio Interface - Channel Concepts
Three separate channel concepts in UTRA: logical channel, transport channel andphysical channel
Logical channels define what type of data is transferred
Transport channels define how and with which type of characteristics the data is
transferred by the physical layer Physical channels define the exact physical characteristics of the radio channel
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Radio Interface - Transport Channels (1)
Transport Channels: Data generated at higher layers is carried over the air withtransport channels, which are mapped in the physical layer to different physical
channels
HigherLayers
Physical
Layer
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Radio Interface - Transport Channels (2)
CCTrCh (Coded Composite Transport Channel): a technology in the UMTSphysical layer, is the connection between Transport Channel and Physical Channel
which results a data stream from encoding and multiplexing of one or several
transport channels
One physical control channel + one or more physical data channel => one CCTrCh
Two types of Transport Channels
– dedicated channel (DCH): identified by a certain code on a certain frequency,reserved for a single user only; carries all the information intended for the given user
from layers above the physical layer, including data for the actual services and
higher layer control information
Features: fast power control, fast data rate change on a frame-by-frame basis,support adaptive antenna, support soft handover (illustrated in later sections)
– common channel: a resource divided between all or a group of users in a cell
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Radio Interface - Transport Channels (3)
Six types of Common Transport Channels– Broadcast Channel (BCH): downlink, transmit network information, e.g., available
random access codes and access slots, important for register
– Forward Access Channel (FACH): downlink, carry control information or packet
data– Paging Channel (PCH): downlink, carry data relevant to the paging process when the
network wants to initiate communication with the terminal
– Random Access Channel (RACH): uplink, carry control information from the
terminal, e.g., requests to set up a connection, or packet data
– Uplink Common Packet Channel (CPCH): uplink, carry packet-based user data
– Downlink Shared Channel (DSCH): downlink, carry dedicated user data and/or
control information, shared by several users, associated with a downlink DCH
Basic network operation needs BCH, RACH, FACH and PCH; DSCH and CPCH isoptional
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Radio Interface - Transport Channels (4)
Mapping of Transport Channels onto the physical channels
Transport Channels Physical Channels
DCH
BCH
FACH
DSCH
RACH
PCH
CPCH
Dedicated Physical Data Channel (DPDCH)
Dedicated Physical Control Channel (DPCCH)
Primary Common Control Physical Channel (PCCPCH)Secondary Common Control Physical Channel (SCCPCH)
Physical Random Access Channel (PRACH)
Physical Downlink Shared Channel (PDSCH)Physical Common Packet Channel (PCPCH)
Synchronization Channel (SCH)
Common Pilot Channel (CPICH)
Acquisition Indication Channel (AICH)
Paging Indication Channel (PICH)
CPCH Status Indication Channel (CSICH)
Collision Detection/ Channel Assignment Indicator
Channel (CD/CA-ICH)
Not directly visible to
higher layers, carry onlyinformation relevant to
physical layer procedures
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Physical Layer (FDD)
Multiple access method: DS-CDMA System bandwidth 5M
– allocated spectrum: 1920-1980MHz and 2110-2170MHz
– chip rate: 3.84Mcps
Radio frame structure
– 10ms/frame, 15slots, 2560chips/slot
Slot #0 Slot #1 Slot #i Slot #14
One radio frame: Tf =10ms
Tslot=2560 chips
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Uplink - Introduction
Spreading factors: 4- 256
modulation scheme: BPSK
Two type of uplink dedicated physical channels
– uplink dedicated physical data channel (uplink DPDCH)carry the DCH transport channel
can be zero, one, or several DPDCH on each radio link
– uplink dedicated physical control (or pilot) channel (uplink DPCCH)
carry control information: known pilot bits to support channel estimation forcoherent detection, transmit power control (TPC) commands, feedback information
(FBI), and an optional transport-format combination indicator (TFCI)
one and only one uplink DPCCH on each radio link
– DPDCH and DPCCH are I/Q code multiplexed within each radio frame Variable data rate: change the spreading factor on DPDCH on a frame-by-frame
basis
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Uplink - Frame Structure
Source: Jiangzhou Wang, BroadbandWireless Communications, 3G, 4G
and Wireless LAN
Frame structure for uplink DPDCH/DPCCH
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Uplink - Spreading
Spreading for uplink DPCCH and DPDCHs
Source: Jiangzhou Wang,Broadband Wireless
Communications, 3G, 4G and
Wireless LAN
Complex Scrambling
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Uplink - Design Criteria (1)
Two terminal oriented design criteria– maximize the terminal amplifier efficiency
– minimize the audible interference from the terminal transmission
Uplink DPDCH and DPCCH: Why I/Q code multiplexed (Dual channel QPSKmodulation)?
– Time multiplexed: audible interference due to discontinuous transmission
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Uplink - Design Criteria (2)
uplink DPDCH and DPCCH: Why I/Q code multiplexed? (Con't)– Pure code multiplexed: multicode transmission, increases transmitted signal
envelope variations => Higher PAPR (Peak-to-Average Power Ratio)
– I/Q code multiplexed: DPCCH is maintained on a separate continuous channel, no
pulse transmission, minimize audible interference
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Uplink - Design Criteria (3)
uplink DPDCH and DPCCH: Why complex scrambled?– power levels of the DPDCH and DPCCH are typically different; lead to extreme
cases to BPSK-type transmission if transmitting the branches independently
– the I and Q branches are mixed using complex scrambling
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Uplink Multiplexing
CRC attachment
Transport block
concatenation/Code
block segmentation
Channel coding
Radio frame equalization
First Interleaving
(20, 40, or 80ms)
Radio frame segmentation Rate Matching
Transport Channel
Multiplexing
Other Transport
ChannelsPhysical channel
segmentation
Second interleaving
(10ms)
Physical channel mapping
DPDCH #1 DPDCH #2 DPDCH #N
Source: Harri Homa andAntti Toskala, WCDMA
for UMTS
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Downlink (1)
Spreading factors: 4-512 modulation scheme: QPSK
One type of downlink dedicated physical channel
– downlink dedicated physical channel (downlink DPCH)
– dedicated data (downlink DPDCH) and control information (downlink DPCCH)(pilot bits, TPC, TFCI) are transmitted on DPCH in time multiplex mode
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Downlink (2)
Common downlink pilot channels (CPICH)
– fixed rate, SF=256, 30kbps
– carry predefined symbol/bit sequence
– Primary Common Pilot Channel (P-CPICH): a phase reference for the downlink
channels
– Secondly Common Pilot Channel (S-CPICH): a phase reference for a secondary
CCPCH carrying downlink access channels only and /or a downlink DPCH
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Downlink (3)
downlink DPDCH and DPCCH: Why time-multiplexed?
– Time multiplexed: the common channels have continuous transmission, no audible
interference
– I/Q code multiplexed: downlink multicode transmission: no need for optimization of
PAPR as with single code (pair) transmission
– Code multiplexed: reserving a code for DPCCH results in worse code resource
utilization
D li k (4)
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Downlink (4)
downlink spreading: one scrambling code (one code tree) per sector in the base
station
– Variable data rate: rate matching operation or discontinuous transmission
– Why cannot the spreading factor on DPDCH vary on a frame-by-frame basis?
downlink scrambling: long codes
– number of scrambling codes: limited to 512 codes, otherwise the cell search
procedure would become too excessive
scramble
code #0
scramble
code #1scramble
code #0
scramblecode #1
scramble
code #2scramble
code #3
scramble
code #4
scramble
code #5scramble
code #6
scramble
code #7
scramble
code #8
D li k M lti l i
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Downlink Multiplexing
CRC attachment
Transport block
concatenation/Code
block segmentation
Channel coding
Rate matching
Insertion of DTX indication
(with fixed bit positions only)
First Interleaving
(20,40 or 80ms)Radio frame
segmentation
Transport Channel
Multiplexing
Other Transport
Channels
Physical channel segmentation
Second interleaving
(10ms)
Physical channel mapping
DPDCH #1 DPDCH #2 DPDCH #N
Insertion of DTX indication
(with flexible positions only)
Source: Harri Homa andAntti Toskala, WCDMA
for UMTS
S bli C d (1)
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Scrambling Codes (1)
Scrambling in WCDMA is used on top of spreading– does not change the signal bandwidth and symbol rate
– to separate terminals or base stations from each other; use pseudo-noise (PN) codes
Spreading in WCDMA
– increase signal bandwidth– to separate channels from each other (channelisation); use orthogonal codes
(channelisation codes)
S bli C d (2)
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Two types of scrambling codes: long and short scrambling codes
Scrambling Codes (2)
Scrambling Codes (3)
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Uplink physical channels: complex-valued scrambling code, either long or short
– Long scrambling codes: used if the base station uses a Rake receiver
– Short scrambling codes: used if the base station uses advanced multiuser detectors or
interference cancellation receivers
Scrambling Codes (3)
long scrambling
code, shift #1
long scrambling
code, shift #0
long
scrambling
code #1
long
scrambling
code #0
long: BS has a Rake
receiver
short: BS uses multiuser
detection
GPS
IS-95 or CDMA2000WCDMA
Scrambling Codes (4)
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Signal detection at BS
Scrambling Codes (4)
Slot #0
Time
Slot #15Slot #1
long scrambling code: one frame: 10ms, 38400 chips
Slot #0 Slot #15Slot #1
Time
Slot #0 Slot #15Slot #1
Time
Received signal at BS
Terminal #0
(Scrambling code #0)
Terminal #1
(Scrambling code #1)
Terminal #2(Scrambling code #2)
Scrambling Codes (5)
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Descrambling using
scrambling code #0
Descrambling usingscrambling code #1
Descrambling using
scrambling code #2
Signal detection
for user #0
Signal detectionfor user #1
Signal detection
for user #2
Receivedsignal at BS
Recovered data
symbols for user #0
Recovered datasymbols for user #1
Recovered data
symbols for user #2
Interference
Regenerator for user #0
Delay
Descrambling using
scrambling code #0
Signal detection
for user #0
Recovered data
symbols for user #0
Multiuser detectors or interference cancellation receivers
Scrambling Codes (5)
Advantage of short scrambling codes: reduce of processing delay
Channelisation Codes (1)
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Channelisation Codes (1)
Transmissions from a single source are separated by channelisation codes
– downlink connection within one sector
– dedicated channels in the uplink from one terminal
WCDMA uses Orthogonal Variable Spreading Factor (OVSF) codes
OVSF allows the spreading factor to be changed and orthogonality between
different spreading codes of different lengths to be maintained
c1,1=(1)
c2,1=(1,1)
c2,2=(1,-1)
c4,1=(1,1,1,1)
c4,2=(1,1,-1,-1)
c4,3=(1,-1,1,-1)
c4,4
=(1,-1,-1,1)
c
(c,c)
(c,-c)