36255366 wcdma ran planning and optimization book1 wrnpo basics
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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA RAN
Fundamental
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Page1Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Objectives
z Upon completion of this course, you will be able to:
Describe the development of 3G
Outline the advantage of CDMA principle
Characterize code sequence
Outline the fundamentals of RAN
Describe feature of wireless propagation
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Page2Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. 3G Overview
2. CDMA Principle
3. WCDMA Network Architecture and protocol structure
4. WCDMA Wireless Fundamental
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Page3Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. 3G Overview
2. CDMA Principle
3. WCDMA Network Architecture and protocol structure
4. WCDMA Wireless Fundamental
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Page4Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Different Service, Different Technology
AMPS
TACS
NMT
Others
1G 1980s
Analog
GSMGSM
CDMACDMAIS-95IS-95
TDMATDMA
IS-136IS-136
PDCPDC
2G 1990s
Digital
Technologies
drive
3G
IMT-2000
UMTSUMTS
WCDMAWCDMA
cdmacdma
20002000
Demands
drive
TD-
SCDMA
TD-
SCDMA
3G provides compositive services for both operators and subscribers
z The first generation is the analog cellular mobile communication network in the time
period from the middle of 1970s to the middle of 1980s. The most important
breakthrough in this period is the concept of cellular networks put forward by the BellLabs in the 1970s, as compared to the former mobile communication systems. The
cellular network system is based on cells to implement frequency reuse and thus
greatly enhances the system capacity.
z The typical examples of the first generation mobile communication systems are the
AMPS system and the later enhanced TACS of USA, the NMT and the others. The
AMPS (Advanced Mobile Phone System) uses the 800 MHz band of the analog
cellular transmission system and it is widely applied in North America, South America
and some Circum-Pacific countries. The TACS (Total Access Communication System)
uses the 900 MHz band. It is widely applied in Britain, Japan and some Asian
countries.
z The main feature of the first generation mobile communication systems is that they
use the frequency reuse technology, adopt analog modulation for voice signals and
provide an analog subscriber channel every other 30 kHz/25 kHz.
z However, their defects are also obvious:
Low utilization of the frequency spectrum
Limited types of services
No high-speed data services
Poor confidentiality and high vulnerability to interception and numberembezzlement
High equipment cost
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z To solve these fundamental technical defects of the analog systems, the digital
mobile communication technologies emerged and the second generation mobile
communication systems represented by GSM and IS-95 came into being in the
middle of 1980s. The typical examples of the second generation cellular mobile
communication systems are the DAMPS of USA, the IS-95 and the European GSMsystem.
z The GSM (Global System for Mobile Communications) is originated from Europe.
Designed as the TDMA standard for mobile digital cellular communications, it
supports the 64 kbps data rate and can interconnect with the ISDN. It uses the 900
MHz band while the DCS1800 system uses the 1800 MHz band. The GSM system
uses the FDD and TDMA modes and each carrier supports eight channels with the
signal bandwidth of 200 kHz.
z The DAMPS (Digital Advanced Mobile Phone System) is also called the IS-54 (NorthAmerica Digital Cellular System). Using the 800 MHz bandwidth, it is the earlier of the
two North America digital cellular standards and specifies the use of the TDMA mode.
z The IS-95 standard is another digital cellular standard of North America. Using the
800 MHz or 1900 MHz band, it specifies the use of the CDMA mode and has already
become the first choice among the technologies of American PCS (Personal
Communication System) networks.
z Since the 2G mobile communication systems focus on the transmission of voice and
low-speed data services, the 2.5G mobile communication systems emerged in 1996to address the medium-rate data transmission needs. These systems include GPRS
and IS-95B.
z The CDMA system has a very large capacity that is equivalent to ten or even twenty
times that of the analog systems. But the narrowband CDMA technologies come into
maturity at a time later than the GSM technologies, their application far lags behind
the GSM ones and currently they have only found large-scale commercial
applications in North America, Korea and China. The major services of mobile
communications are currently still voice services and low-speed data services.
z With the development of networks, data and multimedia communications have also
witnessed rapid development; therefore, the target of the 3G mobile communication is
to implement broadband multimedia communication.
z The 3G mobile communication systems are a kind of communication system that can
provide multiple kinds of high quality multimedia services and implement global
seamless coverage and global roaming. They are compatible with the fixed networks
and can implement any kind of communication at any time and any place with
portable terminals.
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Page6Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
3G Evolution
z Proposal of 3G
IMT-2000: the general name of third generation mobile
communication system
The third generation mobile communication was first proposed
in 1985and was renamed as IMT-2000 in the year of 1996
Commercialization: around the year of 2000
Work band : around 2000MHz
The highest service rate :up to 2000Kbps
z Put forward in 1985 by the ITU (International Telecommunication Union), the 3G
mobile communication system was called the FPLMTS (Future Public Land Mobile
Telecommunication System) and was later renamed as IMT-2000 (InternationalMobile Telecommunication-2000). The major systems include WCDMA, cdma2000
and UWC-136. On November 5, 1999, the 18th conference of ITU-R TG8/1 passed
the Recommended Specification of Radio Interfaces of IMT-2000 and the TD-SCDMA
technologies put forward by China were incorporated into the IMT-2000 CDMA TDD
part of the technical specification. This showed that the work of the TG8/1 in
formulating the technical specifications of radio interfaces in 3G mobile
communication systems had basically come into an end and the development and
application of the 3G mobile communication systems would enter a new and essential
phase.
z The 3GPP is an organization that develops specifications for a 3G system based on
the UTRA radio interface and on the enhanced GSM core network.
z The 3GPP2 initiative is the other major 3G standardization organization. It promotes
the CDMA2000 system, which is also based on a form of WCDMA technology. In the
world of IMT-2000, this proposal is known as IMT-MC. The major difference between
the 3GPP and the 3GPP2 approaches into the air interface specification development
is that 3GPP has specified a completely new air interface without any constraints from
the past, whereas 3GPP2 has specified a system that is backward compatible with IS-
95 systems.
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Page7Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
3G Spectrum Allocation
z ITU has allocated 230 MHz frequency for the 3G mobile communication system IMT-
2000: 1885 ~ 2025MHz in the uplink and 2110~ 2200 MHz in the downlink. Of them,
the frequency range of 1980 MHz ~ 2010 MHz (uplink) and that of 2170 MHz ~ 2200
MHz (downlink) are used for mobile satellite services. As the uplink and the downlink
bands are asymmetrical, the use of dual-frequency FDD mode or the single-frequency
TDD mode may be considered. This plan was passed in WRC92 and new additional
bands were approved on the basis of the WRC-92 in the WRC2000 conference in the
year 2000: 806 MHz ~ 960 MHz, 1710 MHz ~ 1885 MHz and 2500 MHz ~ 2690 MHz.
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Page8Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Bands WCDMA Used
z Main bands
1920 ~ 1980MHz / 2110 ~ 2170MHz
z Supplementary bands: different country maybe different
1850 ~ 1910 MHz / 1930 MHz ~ 1990 MHz (USA)
1710 ~ 1785MHz / 1805 ~ 1880MHz (Japan)
890 ~ 915MHz / 935 ~ 960MHz (Australia)
. . .
z Frequency channel numbercentral frequency5, for mainband:
UL frequency channel number96129888
DL frequency channel number : 1056210838
z The WCDMA system uses the following frequency spectrum (bands other than those
specified by 3GPP may also be used): Uplink 1920 MHz ~ 1980 MHz and downlink
2110 MHz ~ 2170 MHz. Each carrier frequency has the 5M band and the duplex
spacing is 190 MHz. In America, the used frequency spectrum is 1850 MHz ~ 1910
MHz in the uplink and 1930 MHz ~ 1990 MHz in the downlink and the duplex spacing
is 80 MHz.
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Page9Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
3G Application Service
Time Delay
ErrorRatio
background
conversational
streaming
interactive
z Compatible with abundant services and applications of 2G, 3G system has an open
integrated service platform to provide a wide prospect for various 3G services.
z Features of 3G Services
z 3G services are inherited from 2G services. In a new architecture, new service
capabilities are generated, and more service types are available. Service
characteristics vary greatly, so each service features differently. Generally, there are
several features as follows:
Compatible backward with all the services provided by GSM.
The real-time services (conversational) such as voice service
generally have the QoS requirement.
The concept of multimedia service (streaming, interactive,
background) is introduced.
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Page10Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
The Core technology of 3G: CDMA
CDMA
WCDMAWCDMA
CN: based on MAP and GPRSRTT: WCDMA
TD-SCDMACN: based on MAP and GPRS
RTT: TD-SCDMA
cdma2000CN: based on ANSI 41 and MIP
RTT: cdma2000
z Formulated by the European standardization organization 3GPP, the core network
evolves on the basis of GSM/GPRS and can thus be compatible with the existing
GSM/GPRS networks. It can be based on the TDM, ATM and IP technologies to
evolve towards the all-IP network architecture. Based on the ATM technology, the
UTRAN uniformly processes voice and packet services and evolves towards the IP
network architecture.
z The cdma2000 system is a 3G standard put forward on the basis of the IS-95
standard. Its standardization work is currently undertaken by 3GPP2. Circuit Switched
(CS) domain is adapted from the 2G IS95 CDMA network, Packet Switched (PS)
domain is A packet network based on the Mobile IP technology. Radio Access
Network (RAN) is based on the ATM switch platform, it provides abundant adaptationlayer interfaces.
z The TD-SCDMA standard is put forward by the Chinese Wireless Telecommunication
Standard (CWTS) Group and now it has been merged into the specifications related
to the WCDMA-TDD of 3GPP. The core network evolves on the basis of GSM/GPRS.
The air interface adopts the TD-SCDMA mode.
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Page11Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. 3G Overview
2. CDMA Principle
3. WCDMA Network Architecture and protocol structure
4. WCDMA Wireless Fundamental
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Page12Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Multiple Access and Duplex Technology
z Multiple Access Technology
Frequency division multiple access (FDMA)
Time division multiple access (TDMA)
Code division multiple access (CDMA)
z In mobile communication systems, GSM adopts TDMA; WCDMA, cdma2000 and TD-
SCDMA adopt CDMA.
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Page13Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Multiple Access Technology
Frequ
ency
Time
Power
FDMA
Frequ
encyTime
Power
TDMA
Power
Time
CDMA
Frequency
z Frequency Division Multiple Access means dividing the whole available spectrum into
many single radio channels (transmit/receive carrier pair). Each channel can transmit
one-way voice or control information. Analog cellular system is a typical example of
FDMA structure.
z Time Division Multiple Access means that the wireless carrier of one bandwidth is
divided into multiple time division channels in terms of time (or called timeslot). Each
user occupies a timeslot and receives/transmits signals within this specified timeslot.
Therefore, it is called time division multiple access. This multiple access mode is
adopted in both digital cellular system and GSM.
z CDMA is a multiple access mode implemented by Spreading Modulation. Unlike
FDMA and TDMA, both of which separate the user information in terms of time and
frequency, CDMA can transmit the information of multiple users on a channel at the
same time. The key is that every information before transmission should be
modulated by different Spreading Code to broadband signal, then all the signals
should be mixed and send. The mixed signal would be demodulated by different
Spreading Code at the different receiver. Because all the Spreading Code is
orthogonal, only the information that was be demodulated by same Spreading Code
can be reverted in mixed signal.
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Page14Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Multiple Access and Duplex
Technology
z Duplex Technology
Frequency division duplex (FDD)
Time division duplex (TDD)
z In third generation mobile communication systems, WCDMA and cdma2000 adopt
frequency division duplex (FDD), TD-SCDMA adopts time division duplex (TDD).
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Page15Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Duplex Technology
Time
Frequency
Power
TDD
USER 2
USER 1
DL
UL
DL
DLUL
FDD
Time
Frequency
Power
UL DL
USER 2
USER 1
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Page16Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. 3G Overview
2. CDMA Principle
3. WCDMA Network Architecture and protocol structure
4. WCDMA Wireless Fundamental
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Page17Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Network Architecture
RNS
RNC
RNS
RNC
Core Network
Node B Node B Node B Node B
Iu-CS Iu-PS
Iur
Iub IubIub Iub
CN
UTRAN
UEUu
CS PS
Iu-CSIu-PS
CSPS
z WCDMA including the RAN (Radio Access Network) and the CN (Core Network). The
RAN is used to process all the radio-related functions, while the CN is used to
process all voice calls and data connections within the UMTS system, and
implements the function of external network switching and routing.
z Logically, the CN is divided into the CS (Circuit Switched) Domain and the PS (Packet
Switched) Domain. UTRAN, CN and UE (User Equipment) together constitute the
whole UMTS system
z A RNS is composed of one RNC and one or several Node Bs. The Iu interface is
used between RNC and CN while the Iub interface is adopted between RNC and
Node B. Within UTRAN, RNCs connect with one another through the Iur interface.
The Iur interface can connect RNCs via the direct physical connections among them
or connect them through the transport network. RNC is used to allocate and control
the radio resources of the connected or related Node B. However, Node B serves to
convert the data flows between the Iub interface and the Uu interface, and at the
same time, it also participates in part of radio resource management.
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Page18Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Network Version Evolution
3GPP Rel993GPP Rel4
3GPP Rel5
2000 2001 2002
GSM/GPRS CN
WCDMA RTT
IMS
HSDPA 3GPP Rel6
MBMSHSUPA
2005
CS domain change toNGN
WCDMA RTT
z The overall structure of the WCDMA network is defined in 3GPP TS 23.002. Now,
there are the following three versions: R99, R4, R5.
z 3GPP began to formulate 3G specifications at the end of 1998 and beginning of 1999.
As scheduled, the R99 version would be completed at the end of 1999, but in fact it
was not completed until March, 2000. To guarantee the investment benefits of
operators, the CS domain of R99 version do not fundamentally change., so as to
support the smooth transition of GSM/GPRS/3G.
z After R99, the version was no longer named by the year. At the same time, the
functions of R2000 are implemented by the following two phases: R4 and R5. In the
R4 network, MSC as the CS domain of the CN is divided into the MSC Server and the
MGW, at the same time, a SGW is added, and HLR can be replaced by HSS (not
explicitly specified in the specification).
z In the R5 network, the end-to-end VOIP is supported and the core network adopts
plentiful new function entities, which have thus changed the original call procedures.
With IMS (IP Multimedia Subsystem), the network can use HSS instead of HLR. In
the R5 network, HSDPA (High Speed Downlink Packet Access) is also supported, it
can support high speed data service.
z In the R6 network, the HSUPA is supported which can provide UL service rate up to
5.76Mbps. And MBMS (MultiMedia Broadcast Multicast Service) is also supported.
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Page19Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Network Version Evolution
z Features of R6
MBMS is introduced
HSUPA is introduced to achieve the service rate up to 5.76Mbps
z Features of R7
HSPA+ is introduced, which adopts higher order modulation and MIMO
Max DL rate: 28Mbps, Max UL rate:11Mbps
z Features of R8
WCDMA LTE (Long term evolution) is introduced
OFDMA is adopted instead of CDMA
Max DL rate: 50Mbps, Max UL rate: 100Mbps (with 20MHz bandwidth)
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Page20Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. 3G Overview
2. CDMA Principle
3. WCDMA Network Architecture and protocol structure
4. WCDMA Wireless Fundamental
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Page21Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Processing Procedure of WCDMA System
Source
CodingChannel Coding& Interleaving Spreading Modulation
Source
Decoding
Channel Decoding
& Deinterleaving Despreading Demodulation
Transmission
Reception
chipmodulated
signalbi t symbol
Service
Signal
Radio
Channel
Service
Signal
Receiver
z Source coding can increase the transmitting efficiency.
z Channel coding can make the transmission more reliable.
z Spreading can increase the capability of overcoming interference.
z Through the modulation, the signals will transfer to radio signals from digital signals.
z Bit, Symbol, Chip
Bit : data after source coding
Symbol: data after channel coding and interleaving
Chip: data after spreading
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Page22Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Source Coding
z AMR (Adaptive Multi-Rate)
Speech
A integrated speech codec with 8
source rates
The AMR bit rates can be controlled
by the RAN depending on the system
load and quality of the speech
connections
z Video Phone Service
H.324 is used for VP Service in CSdomain
Includes: video codec, speech codec,
data protocols, multiplexing and etc.
5.15AMR_5.15
4.75AMR_4.75
5.9AMR_5.90
6.7 (PDC EFR)AMR_6.70
7.4 (TDMA EFR)AMR_7.40
7.95AMR_7.95
10.2AMR_10.20
12.2 (GSM EFR)AMR_12.20
Bit Rate (kbps)CODEC
z AMR is compatible with current mobile communication system (GSM, IS-95, PDC and
so on), thus, it will make multi-mode terminal design easier.
z The AMR codec offers the possibility to adapt the coding scheme to the radio channel
conditions. The most robust codec mode is selected in bad propagation conditions.
The codec mode providing the highest source rate is selected in good propagation
conditions.
z During an AMR communication, the receiver measures the radio link quality and must
return to the transmitter either the quality measurements or the actual codec mode the
transmitter should use during the next frame. That exchange has to be done as fast
as possible in order to better follow the evolution of the channels quality.
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Page23Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Processing Procedure of WCDMA System
Transmitter
Source
CodingChannel Coding& Interleaving Spreading Modulation
Source
Decoding
Channel Decoding
& Deinterleaving Despreading Demodulation
Transmission
Reception
chipmodulated
signalbi t symbol
Service
Signal
Radio
Channel
Service
Signal
Receiver
z Source coding can increase the transmitting efficiency.
z Channel coding can make the transmission more reliable.
z Spreading can increase the capability of overcoming interference.
z Scrambling can make transmission in security.
z Through the modulation, the signals will transfer to radio signals from digital signals.
z Bit, Symbol, Chip
Bit : data after source coding
Symbol: data after channel coding and interleaving
Chip: data after spreading
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Page24Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Block Coding - CRC
z Block coding is used to detect if there are any uncorrected
errors left after error correction.
z The cyclic redundancy check (CRC) is a common method of
block coding.
z Adding the CRC bits is done before the channel encoding
and they are checked after the channel decoding.
z During the transmission, there are many interferences and fading. To guarantee
reliable transmission, system should overcome these influence through the channel
coding which includes block coding, channel coding and interleaving.
z Block coding: The encoder adds some redundant bits to the block of bits and the
decoder uses them to determine whether an error has occurred during the
transmission. This is used to calculate Block Error Ratio (BLER) used in the outer
loop power control.
z The CRC (Cyclic Redundancy Check) is used for error checking of the transport
blocks at the receiving end. The CRC length that can be inserted has four different
values: 0, 8, 12, 16 and 24 bits. The more bits the CRC contains, the lower is the
probability of an undetected error in the transport block in the receiver.
z Note that certain types of block codes can also be used for error correction, although
these are not used in WCDMA.
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Page25Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Channel Coding
z Effect
Enhance the correlation among symbols so as to recover the signal when
interference occurs
Provides better error correction at receiver, but brings increment of the delay
z Types
No Coding
Convolutional Coding (1/2, 1/3)
Turbo Coding (1/3)
Code Block
of N Bits
No Coding
1/2 Convolutional
Coding
1/3 Convolutional
Coding
1/3 Turbo Codi ng
Uncoded N bits
Coded 2N+16 bits
Coded 3N+24 bits
Coded 3N+12 bits
z UTRAN employs two FEC schemes: convolutional codes and turbo codes. The idea
is to add redundancy to the transmitted bit stream, sO that occasional bit errors can
be corrected in the receiving entity.
z The first is convolution that is used for anti-interference. Through the technology,
many redundant bits will be inserted in original information. When error code is
caused by interference, the redundant bits can be used to recover the original
information. Convolutional codes are typically used when the timing constraints are
tight. The coded data must contain enough redundant information to make it possible
to correct some of the detected errors without asking for repeats.
z Turbo codes are found to be very efficient because they can perform close to the
theoretical limit set by the Shannons Law. Their efficiency is best with high data rate
services, but poor on low rate services. At higher bit rates, turbo coding is more
efficient than convolutional coding.
z In WCDMA network, both Convolution code and Turbo code are used. Convolution
code applies to voice service while Turbo code applies to high rate data service.
z Note that both block codes and channel codes are used in the UTRAN. The idea
behind this arrangement is that the channel decoder (either a convolutional or turbo
decoder) tries to correct as many errors as possible, and then the block decoder
(CRC check) offers its judgment on whether the resulting information is good enough
to be used in the higher layers.
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Page26Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Interleaving
z Effect
Interleaving is used to reduce the probability of consecutive bits error
Longer interleaving periods have better data protection with more delay
1110
1.........
............
...000
0100
0 0 1 0 0 0 0 . . . 1 0 1 1 1
1110
1.........
............
...0000010 0 0 0 1 0 1 0 0 1 0 1 1
Inter-columnpermutation
Output bits
Input bits
Interleaving periods:
20, 40, or 80 ms
z Channel coding works well against random errors, but it is quite vulnerable to bursts
of errors, which are typical in mobile radio systems. The especially fast moving UE in
CDMA systems can cause consecutive errors if the power control is not fast enough
to manage the interference. Most coding schemes perform better on random data
errors than on blocks of errors. This problem can be eased with interleaving, which
spreads the erroneous bits over a longer period of time. By interleaving, no two
adjacent bits are transmitted near to each other, and the data errors are randomized.
z The longer the interleaving period, the better the protection provided by the time
diversity. However, longer interleaving increases transmission delays and a balance
must be found between the error resistance capabilities and the delay introduced.
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Page27Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Processing Procedure of WCDMA System
Source
CodingChannel Coding& Interleaving Spreading Modulation
Source
Decoding
Channel Decoding
& Deinterleaving Despreading Demodulation
Transmission
Reception
chipmodulated
signalbi t symbol
Service
Signal
Radio
Channel
Service
Signal
Receiver
z Source coding can increase the transmitting efficiency.
z Channel coding can make the transmission more reliable.
z Spreading can increase the capability of overcoming interference.
z Scrambling can make transmission in security.
z Through the modulation, the signals will transfer to radio signals from digital signals.
z Bit, Symbol, Chip
Bit : data after source coding
Symbol: data after channel coding and interleaving
Chip: data after spreading
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Page28Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Correlation
z Correlation measures similarity between any two arbitrary signals.
z Identical and Orthogonal signals:
Correlation = 0
Orthogonal signals
-1 1 -1 1-1 1 -1 1
1 1 1 1
+1
-1
+1
-1
+1
-1
+1
-1
Correlation = 1
Identical signals
-1 1 -1 11 1 1 1
-1 1 -1 1
C1
C2 +1
+1
C1
C2
z Correlation is used to measure similarity of any two arbitrary signals. It is computed
by multiplying the two signals and then summing (integrating) the result over a
defined time windows. The two signals of figure (a) are identical and therefore their
correlation is 1 or 100 percent. In figure (b) , however, the two signals are
uncorrelated, and therefore knowing one of them does not provide any information on
the other.
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Page29Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Orthogonal Code Usage - Coding
UE1: 1 1
UE2: 1 1
C1 : 1111 1111C2 : 1111 1111UE1c1 1111 1111UE2c2 1111 1111
UE1c1 UE2c2 2 02 0 2 0 2 0
UE1: 1 1
UE2: 1 1
C1 : 1111 11 11C2 : 1111 1111UE1c1 1111 11 11UE2c2 1111 1111
UE1c1 UE2c2 2 02 0 2 0 2 0
z By spreading, each symbol is multiplied with all the chips in the orthogonal sequence
assigned to the user. The resulting sequence is processed and is then transmitted
over the physical channel along with other spread symbols. In this figure, 4-digit
codes are used. The product of the user symbols and the spreading code is a
sequence of digits that must be transmitted at 4 times the rate of the original encoded
binary signal.
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Page30Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Orthogonal Code Usage - Decoding
UE1C1 UE2C2: 2 02 0 2 0 2 0
UE1 Dispreading by c1: 1111 1111Dispreading result: 2 02 0 2 0 2 0Integral judgment: 4 (means1) 4 (means1)
UE2 Dispreading by c2: 11 11 11 11
Dispreading result: 2 0 2 0 2 0 2 0Integral judgment: 4 (means1) 4 (means1)
UE1C1 UE2C2: 2 02 0 2 0 2 0
UE1 Dispreading by c1: 111 1 1111Dispreading result: 2 02 0 2 0 2 0Integral judgment: 4 (means1) 4 (means1)
UE2 Dispreading by c2: 11 11 11 11
Dispreading result:
2 0
2 0
2 0
2 0Integral judgment: 4 (means1) 4 (means1)
z The receiver dispreads the chips by using the same code used in the transmitter.
Notice that under no-noise conditions, the symbols or digits are completely recovered
without any error. In reality, the channel is not noise-free, but CDMA system employ
Forward Error Correction techniques to combat the effects of noise and enhance the
performance of the system.
z When the wrong code is used for dispreading, the resulting correlation yields an
average of zero. This is a clear demonstration of the advantage of the orthogonal
property of the codes. Whether the wrong code is mistakenly used by the target user
or other users attempting to decode the received signal, the resulting correlation is
always zero because of the orthogonal property of codes.
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Page31Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Spectrum Analysis of Spreading & Dispreading
Spreading code
Spreading code
Signal
Combination
Narrowband signal
f
P(f)
Broadband signal
P(f)
f
Noise & Other Signal
P(f)
f
Noise+Broadband signal
P(f)
f
Recovered signal
P(f)
f
z Traditional radio communication systems transmit data using the minimum bandwidth
required to carry it as a narrowband signal. CDMA system mix their input data with a
fast spreading sequence and transmit a wideband signal. The spreading sequence is
independently regenerated at the receiver and mixed with the incoming wideband
signal to recover the original data. The dispreading gives substantial gain proportional
to the bandwidth of the spread-spectrum signal. The gain can be used to increase
system performance and range, or allow multiple coded users, or both. A digital bit
stream sent over a radio link requires a definite bandwidth to be successfully
transmitted and received.
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Page32Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Spectrum Analysis of Spreading & Dispreading
Max allowed interference
Eb/No
Requiremen
t
Power
Max interference caused
by UE and others
Processing Gain
Ebi t
Interference from
other UE Echip
Eb / No = Ec / NoPG
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Page33Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Process Gain
z Process Gain
Process gain differs for each service.
If the service bit rate is greater, the process gain is smaller, UE
needs more power for this service, then the coverage of this
service will be smaller, vice versa.
)ratebitratechiplog(10GainocessPr =
z For common services, the bit rate of voice call is 12.2kbps, the bit rate of video phone
is 64kbps, and the highest packet service bit rate is 384kbps(R99). After the
spreading, the chip rate of different service all become 3.84Mcps.
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Page34Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Spreading Technology
z Spreading consists of 2 steps:
Channelization operation, which transforms data symbols into chips
Scrambling operation is applied to the spreading signal
scramblingchannelization
Data
symbol
Chips after
spreading
z Spreading means increasing the bandwidth of the signal beyond the bandwidth
normally required to accommodate the information. The spreading process in UTRAN
consists of two separate operations: channelization and scrambling.
z The first operation is the channelization operation, which transforms every data
symbol into a number of chips, thus increasing the bandwidth of the signal. The
number of chips per data symbol is called the Spreading Factor (SF). Channelization
codes are orthogonal codes, meaning that in ideal environment they do not interfere
each other.
z The second operation is the scrambling operation. Scrambling is used on top of
spreading, so it does not change the signal bandwidth but only makes the signals
from different sources separable from each other. As the chip rate is already achieved
in channelization by the channelization codes, the chip rate is not affected by the
scrambling.
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Page35Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Channelization Code
z OVSF Code (Orthogonal Variable Spreading Factor) is used as
channelization code
SF = 8SF = 1 SF = 2 SF = 4
Cch,1,0 = (1)
Cch,2,0 = (1,1)
Cch,2,1 = (1, -1)
Cch,4,0 = (1,1,1,1)
Cch,4,1 = (1,1,-1,-1)
Cch,4,2 = (1,-1,1,-1)
Cch,4,3 = (1,-1,-1,1)
Cch,8,0 = (1,1,1,1,1,1,1,1)
Cch,8,1 = (1,1,1,1,-1,-1,-1,-1)
Cch,8,2 = (1,1,-1,-1,1,1,-1,-1)
Cch,8,3 = (1,1,-1,-1,-1,-1,1,1)
Cch,8,4 = (1,-1,1,-1,1,-1,1,-1)
Cch,8,5 = (1,-1,1,-1,-1,1,-1,1)
Cch,8,6 = (1,-1,-1,1,1,-1,-1,1)
Cch,8,7 = (1,-1,-1,1,-1,1,1,-1)
z Orthogonal codes are easily generated by starting with a seed of 1, repeating the 1
horizontally and vertically, and then complementing the -1 diagonally. This process is
to be continued with the newly generated block until the desired codes with the proper
length are generated. Sequences created in this way are referred as Walsh code.
z Channelization uses OVSF code, for keeping the orthogonality of different subscriber
physical channels. OVSF can be defined as the code tree illustrated in the following
diagram.
z Channelization code is defined as Cch SF, k,, where, SF is the spreading factor of the
code, and k is the sequence of code, 0kSF-1. Each level definition length of code
tree is SF channelization code, and the left most value of each spreading code
character is corresponding to the chip which is transmitted earliest.
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Page36Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Channelization Code
z SF = chip rate / symbol rate
High data rates low SF code
Low data rates high SF code
16Data 128 kbps DL8Data 128 kbps UL
32Data 64 kbps DL16Data 64 kbps UL
8Data 384 kbps DL4Data 384 kbps UL
16Data 144 kbps DL8Data 144 kbps UL
128Speech 12.2 DL64Speech 12.2 UL
SFRadio bearerSFRadio bearer
z The channelization codes are Orthogonal Variable Spreading Factor (OVSF)
codes. They are used to preserve orthogonality between different physical channels.
They also increase the clock rate to 3.84 Mcps. The OVSF codes are defined using a
code tree.
z In the code tree, the channelization codes are individually described by Cch,SF,k, where
SF is the Spreading Factor of the code and k the code number, 0 k SF-1.
z A channelization sequence modulates one users bit. Because the chip rate is
constant, the different lengths of codes enable to have different user data rates. Low
SFs are reserved for high rate services while high SFs are for low rate services.
z The length of an OVSF code is an even number of chips and the number of codes (for
one SF) is equal to the number of chips and to the SF value.
z
The generated codes within the same layer constitute a set of orthogonal codes.Furthermore, any two codes of different layers are orthogonal except when one of the
two codes is a mother code of the other. For example C4,3 is not orthogonal with C1,0and C2,1, but is orthogonal with C2,0.
z SF in uplink is from 4 to 256.
z SF in downlink is from 4 to 512.
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Page37Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Purpose of Channelization Code
z Channelization code is used to distinguish different physical
channels of one transmitter
For downlink, channelization code ( OVSF code ) is used to
separate different physical channels of one cell
For uplink, channelization code ( OVSF code ) is used to
separate different physical channels of one UE
z For voice service (AMR), downlink SF is 128, it means there are 128 voice services
maximum can be supported in one WCDMA carrier;
z For Video Phone (64k packet data) service, downlink SF is 32, it means there are 32
voice services maximum can be supported in one WCDMA carrier.
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Page38Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Purpose of Scrambling Code
z Scrambling code is used to distinguish different transmitters
For downlink, scrambling code is used to separate different
cells in one carrier
For uplink, scrambling code is used to separate different UEs
in one carrier
z In addition to spreading, part of the process in the transmitter is the scrambling
operation. This is needed to separate terminals or base stations from each other.
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Page39Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Scrambling Code
z Scrambling code: GOLD sequence.
z There are 224 long uplink scrambling codes which are used for
scrambling of the uplink signals. Uplink scrambling codes are
assigned by RNC.
z For downlink, 512 primary scrambling codes are used.
z Different scrambling codes will be planned to different cells in downlink.
z Different scrambling codes will be allocated to different UEs in uplink.
z The scrambling code is always applied to one 10 ms frame.
z In UMTS, Gold codes are chosen for their very low peak cross-correlation.
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Page40Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Primary Scrambling Code Group
Primary
scrambling
codes for
downlink
physical
channels
Group 0
Primaryscrambling code 0
Primaryscrambling code
8*63
Primaryscrambling code
8*63 +7512 primary
scrambling
codes
Group 1
Group 63
Primaryscrambling code 1
Primaryscrambling code 8
64 primary
scrambling code
groups
Each group consists of 8
primary scrambling codes
z There are totally 512 primary scrambling codes defined by 3GPP. They are further
divided into 64 primary scrambling code groups. There are 8 primary scrambling
codes in every group. Each cell is allocated with only one primary scrambling code.
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Page41Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Code Multiplexing
z Downlink Transmission on a Cell Level
Scrambling code
Channelization code 1
Channelization code 2
Channelization code 3
User 1 signal
User 2 signal
User 3 signal
NodeB
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Page42Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Code Multiplexing
z Uplink Transmission on a Cell Level
NodeB
Scrambling code 3
User 3 signal
Channelization code
Scrambling code 2
User 2 signal
Channelization code
Scrambling code 1
User 1 signal
Channelization code
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Page43Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Processing Procedure of WCDMA System
Source
CodingChannel Coding& Interleaving Spreading Modulation
Source
Decoding
Channel Decoding
& Deinterleaving Despreading Demodulation
Transmission
Reception
chipmodulated
signalbi t symbol
Service
Signal
Radio
Channel
Service
Signal
Receiver
z Source coding can increase the transmitting efficiency.
z Channel coding can make the transmission more reliable.
z Spreading can increase the capability of overcoming interference.
z Scrambling can make transmission in security.
z Through the modulation, the signals will transfer to radio signals from digital signals.
z Bit, Symbol, Chip
Bit : data after source coding
Symbol: data after channel coding and interleaving
Chip: data after spreading
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Page44Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Modulation Overview
1 00 1
time
Basic steady radio
wave:
carrier = A.cos(2Ft+)Ampl itude Shif t
Keying:
A.cos(2Ft+)Frequency Shift
Keying:
A.cos(2Ft+)Phase Shift Keying:
A.cos(2Ft+)
Data to be transmitted:
Digital Input
z A data-modulation scheme defines how the data bits are mixed with the carrier signal,
which is always a sine wave. There are three basic ways to modulate a carrier signal
in a digital sense: amplitude shift keying (ASK), frequency shift keying (FSK), and
phase shift keying (PSK).
z In ASK the amplitude of the carrier signal is modified by the digital signal.
z In FSK the frequency of the carrier signal is modified by the digital signal.
z The PSK family is the most widely used modulation scheme in modern cellular
systems. There are many variants in this family, and only a few of them are
mentioned here.
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Page45Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Modulation Overview
z Digital Modulation - BPSK
1
t
1 10
1
t-1
NRZ coding
fo
BPSK
Modulated
BPSKsignal
Carrier
Informationsignal
=0 = =0
1 102 3 4 9875 6
1 102 3 4 9875 6
Digital Input
High Frequency
Carrier
BPSK Waveform
z In binary phase shift keying (BPSK) modulation, each data bit is transformed into a
separate data symbol. The mapping rule is 1 > + 1 and 0 > 1. There are only
two possible phase shifts in BPSK, 0 and radians.
z NRZ means none return zero.
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Page46Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Modulation Overview
z Digital Modulation - QPSK
-1 -1
1 102 3 4 9875 6
1 102 3 4 9875 6
NRZ Input
I di-Bit Stream
Q di-Bit Stream
I
Component
Q
Component
QPSK Waveform
1
1
-1
1
-1
1
1
-1
-1
-1
1 1 -1 1 -1 1 1 -1
z The quadrature phase shift keying (QPSK) modulation has four phases: 0, /2, , and
3/2 radians. Two data bits are transformed into one complex data symbol; A symbol
is any change (keying) of the carrier.
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Page47Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Modulation Overview
NRZcoding
90o
NRZcoding
QPSK
Q(t)
I(t)
fo
A
A Acos(ot)
Acos(ot + /2)
1 1 /41 -1 7/4-1 1 3/4-1 -1 5/4
)cos(2: +oAQPSK
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Page48Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Demodulation
z QPSK Constellation Diagram
1 102 3 4 9875 6
QPSK Waveform
1,1
-1,-1
-1,1
1,-1
1 -11 -1 1 -1-11-1 1
-1,1
NRZ Output
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Page49Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Modulation
z Different modulation methods corresponding to different
transmitting abilities in air interface
HSDPA: QPSK or 16QAMR99/R4: QPSK
z The UTRAN air interface uses QPSK modulation in the downlink, although HSDPA
may also employ 16 Quadrature Amplitude Modulation (16QAM). 16QAM requires
good radio conditions to work well. As seen, with 16QAM also the amplitude of the
signal matters.
z As explained, in QPSK one symbol carries two data bits; in 16QAM each symbol
includes four bits. Thus, a QPSK system with a chip rate of 3.84Mcps could
theoretically transfer 2 3.84 = 7.68 Mbps, and a 16QAM system could transfer 4
3.84 Mbps = 15.36 Mbps. In 3GPP also the usage of 64QAM with HSDPA has been
studied.
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Page50Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Processing Procedure of WCDMA System
Source
CodingChannelCoding Spreading Modulation
Source
Decoding
Channel
Decoding Despreading Demodulation
Transmission
Reception
chipmodulated
signalbi t symbol
Service
Signal
Radio
Channel
Service
Signal
Transmitter
Receiver
z Source coding can increase the transmitting efficiency.
z Channel coding can make the transmission more reliable.
z Spreading can increase the capability of overcoming interference.
z Scrambling can make transmission in security.
z Through the modulation, the signals will transfer to radio signals from digital signals.
z Bit, Symbol, Chip
Bit : data after source coding
Symbol: data after channel coding and interleaving
Chip: data after spreading
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Page51Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Wireless Propagation
ReceivedSignal
Transmitted
Signal
Transmission Loss:
Path Loss + Multi-path Fading
Time
Amp li tude
z A mobile communication channel is a multi-path fading channel and any transmitted
signal reaches a receive end by means of multiple transmission paths, such as direct
transmission, reflection, scatter, etc.
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Page52Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Propagation of Radio SignalSignal at Transmitter
Signal at Receiver
-40
-35
-30
-25
-20
-15
-10
-5
dB
0
0dBm
-20
-15
-10
-5
5
10
15
20
Fading
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Page53Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Fading Categories
z Fading Categories
Slow Fading Fast Fading
z Furthermore, with the moving of a mobile station, the signal amplitude, delay and
phase on various transmission paths vary with time and place. Therefore, the levels of
received signals are fluctuating and unstable and these multi-path signals, if overlaid,
will lead to fast fading. Fast fading conforms to Rayleigh distribution. The mid-value
field strength of fast fading has relatively gentle change and is called slow fading.
Slow fading conforms to lognormal distribution.
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Page54Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Diversity Technique
z Diversity technique is used to obtain uncorrelated signals for
combining
Reduce the effects of fading
Fast fading caused by multi-path
Slow fading caused by shadowing
Improve the reliability of communication
Increase the coverage and capacity
z Diversity technology means that after receiving two or more input signals with
mutually uncorrelated fading at the same time, the system demodulates these signals
and adds them up. Thus, the system can receive more useful signals and overcome
fading.
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Page55Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Diversity
z Time diversity
Channel coding, Block interleaving
z Frequency diversity
The user signal is distributed on the whole bandwidth
frequency spectrum
z Space diversity
z
Polarization diversity
z Diversity technology is an effective way to overcome overlaid fading. Because it can
be selected in terms of frequency, time and space, diversity technology includes
frequency diversity, time diversity and space diversity.
z Time diversity: Channel coding
z Frequency diversity: WCDMA is a kind of frequency diversity. The signal energy is
distributed on the whole bandwidth.
z Space diversity: using two antennas
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Page56Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Principle of RAKE Receiver
Receive set
Correlator 1
Correlator 2
Correlator 3
Searcher correlator Calculate the
time delay and
signal strength
CombinerThe
combined
signal
tt
s(t) s(t)
RAKE receiver help to overcome on the multi-path fading and enhance the receive
performance of the system
z The RAKE receiver is a technique which uses several baseband correlators to
individually process multipath signal components. The outputs from the different
correlators are combined to achieve improved reliability and performance.
z When WCDMA system is designed for cellular system, the inherent wide-bandwidth
signals with their orthogonal Walsh functions were natural for implementing a RAKE
receiver. In WCDMA system, the bandwidth is wider than the coherence bandwidth of
the cellular. Thus, when the multi-path components are resolved in the receiver, the
signals from different paths are uncorrelated with each other. The receiver can then
combine them using some combining schemes. So with RAKE receiver WCDMA
system can use the multi-path characteristics of the channel to get signal with better
quality.
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Page57Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Summary
z In this course, we have discussed basic concepts of WCDMA:
Spreading / Despreading principle
UTRAN Voice Coding
UTRAN Channel Coding
UTRAN Spreading Code
UTRAN Scrambling Code
UTRAN Modulation
UTRAN Transmission/Receiving
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Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA RadioInterface Physical Layer
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Page1Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Foreword
z The physical layer offers data transport services to higher layers.
z The physical layer is expected to perform the following functions inorder to provide the data transport service, for example: spreading,
modulation and demodulation, despreading, Inner-loop power
control and etc.
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Page2Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Objectives
z Upon completion of this course, you will be able to:
Outline radio interface protocol Architecture
Describe structure and functions of different physical channels
Describe UMTS physical layer procedures
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Page3Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Physical Layer Overview
2. Physical Channels
3. Physical Layer Procedure
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Page4Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Physical Layer Overview
2. Physical Channels
3. Physical Layer Procedure
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Page5Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
UTRAN Network Structure
RNS
RNC
RNS
RNC
Core Network
NodeB NodeB NodeB NodeB
Iu-CS Iu-PS
Iur
Iub IubIub Iub
CN
UTRAN
UEUu
CS PS
Iu-CSIu-PS
CSPS
z UTRAN: UMTS Terrestrial Radio Access Network.
z The UTRAN consists of a set of Radio Network Subsystems connected to the Core
Network through the Iu interface.
z A RNS consists of a Radio Network Controller and one or more NodeBs. A NodeB is
connected to the RNC through the Iub interface.
z Inside the UTRAN, the RNCs of the RNS can be interconnected together through the
Iur. Iu(s) and Iur are logical interfaces. Iur can be conveyed over direct physical
connection between RNCs or virtual networks using any suitable transport network.
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Page6Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Uu Interface Protocol Structure
L3
control
control
control
control
C-plane signaling U-plane information
PHY
L2/MAC
L1
RLC
DCNtGC
L2/RLC
MAC
RLCRLC
RLC
Duplication avoidance
UuS boundary
L2/BMC
control
PDCPPDCP L2/PDCP
DCNtGC
RRC
RLCRLC
RLCRLC
BMC
radio bearer
logical channel
transport channel
z The layer 1 supports all functions required for the transmissionof bit streams on the
physical medium. It is also in charge of measurements function consisting in indicating
to higher layers, for example, Frame Error Rate (FER), Signal to Interference Ratio(SIR), interference power, transmit power, It is basically composed of a layer 1
managemententity, a transport channelentity, and a physical channelentity.
z The layer 2 protocol is responsible for providing functions suchas mapping, ciphering,
retransmission and segmentation. It is made of four sub-layers: MAC (Medium
Access Control), RLC (Radio Link Control), PDCP (Packet Data Convergence
Protocol) and BMC (Broadcast/Multicast Control).
z The layer 3 is split into 2 parts: the access stratum and the non access stratum. The
access stratum part is made of RRC (Radio Resource Control)entity and
duplication avoidanceentity. duplication avoidance terminates in the CN but is part
of the Access Stratum. The higher layer signalling such as Mobility Management (MM)
and Call Control (CC) is assumed to belong to the non-access stratum, and therefore
not in the scope of 3GPP TSG RAN. In the C-plane, the interface between 'Duplication
avoidance' and higher L3 sub-layers (CC, MM) is defined by the General Control (GC),
Notification (Nt) and Dedicated Control (DC) SAPs.
z Not shown on the figure are connections between RRC and all the other protocol
layers (RLC, MAC, PDCP, BMC and L1), which provide local inter-layer control
services.
z The protocol layers are located in the UE and the peer entities are in the NodeB or the
RNC.
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z Many functions are managed by the RRC layer. Here is the list of the most important:
Establishment, re-establishment, maintenance and release of an RRC
connection between the UE and UTRAN: it includes an optional cell re-
selection, an admission control, and a layer 2 signaling link establishment.
When a RNC is in charge of a specific connection towards a UE, it acts as theServing RNC.
Establishment, reconfiguration and release of Radio Bearers: a number of
Radio Bearers can be established fora UE at the same time. These bearers are
configured depending on the requested QoS. The RNC is also in charge of
ensuring that the requested QoS can be met.
Assignment, reconf iguration and release of radio resources for the RRC
connection: it handles the assignment of radio resources (e.g. codes, shared
channels). RRC communicates with the UE to indicate new resources allocation
when handovers are managed.
Paging/Notification: it broadcasts paging information from network to UEs.
Broadcasting of i nformation provided by the non-access stratum (Core
Network) or access Stratum. This corresponds to system informationregularly
repeated.
UE measurement reporting and cont rol of the reporting: RRC indicates
what to measure, when and how to report.
Outer loop power control: controls setting of the target values.
Control of ciphering: provides procedures for setting of ciphering.
z The RRC layer is defined in the 25.331 specification from 3GPP.
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z The RLCs main function is the transfer of data from either the user or the control
plane over the Radio interface. Two different transfer modes are used: transparent
and non-transparent. In non-transparent mode, 2 sub-modes are used:
acknowledged orunacknowledged.
z
RLC provides services to upper layers: data transfer(transparent, acknowledged and unacknowledged modes).
QoS setting: the retransmission protocol (for AM only) shall be configurable by
layer 3 to provide different QoS.
notification of unrecoverable errors: RLC notifies the upper layers of errors
that cannot be resolved by RLC.
z The RLC functions are:
mapping between higher layer PDUs and logical channels.
ciphering: prevents unauthorized acquisition of data; performed in RLC layer
for non-transparent RLC mode.
segmentation/reassembly: this function performs segmentation/reassembly of
variable-length higher layer PDUs into/from smaller RLC Payload Units. The
RLC size is adjustable to the actual set of transport formats (decided when
service is established). Concatenation and padding may also be used.
error correction: done by retransmission (acknowledged data transfer mode
only).
flow control: allows the RLC receiver to control the rate at which the peer RLC
transmitting entity may send information.
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z MAC services include:
Data transfer: service providing unacknowledged transfer of MAC SDUs
between peer MAC entities.
Reallocation of radio resources and MAC parameters: reconfiguration of
MAC functions such as change of identity of UE. Requested by the RRC layer.
Reporting of measurements: local measurements such as traffic volume and
quality indication are reported to the RRC layer.
z The functions accomplished by the MAC sub-layer are listed above. Heres a quick
explanation for some of them:
Priority handling between the data flows of one UE: since UMTS is
multimedia, a user may activate several services at the same time, having
possibly different profiles (priority, QoS parameters...). Priority handling
consists in setting the right transport format for a high bit rate service and for alow bit rate service.
Priority handl ing between UEs: use for efficient spectrum resources utilization
for bursty transfers on common and shared channels.
Ciphering: to prevent unauthorized acquisition of data. Performed in the MAC
layer for transparent RLC mode.
Access Service Class (ACS) select ion for RACH transmission: the RACH
resources are divided between different ACSs in order to provide different
priorities on a random access procedure.
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z PDCP
UMTS supports several network layer protocols providing protocol transparency
for the users of the service.
Using these protocols (and new ones) shall be possible without any changes to
UTRAN protocols. In order to perform this requirement, the PDCP layer hasbeen introduced. Then, functions related to transfer of packets from higher
layers shall be carried out in a transparent way by the UTRAN network entities.
PDCP shall also be responsible for implementing different kinds of optimization
methods. The currently known methods are standardized IETF (Internet
Engineering Task Force) header compression algorithms.
Algorithm types and their parameters are negotiated by RRC and indicated to
PDCP.
Header compression and decompression are specific for each network layerprotocol type.
In order to know which compression method is used, an identifier (PID: Packet
Identifier) is inserted. Compression algorithms exist for TCP/IP, RTP/UDP/IP,
Another function of PDCP is to provide numbering of PDUs. This is done if
lossless SRNS relocation is required.
To accomplish this function, each PDCP-SDUs (UL and DL) is buffered and
numbered. Numbering is done after header compression. SDUs are kept until
information of successful transmission of PDCP-PDU has been received from
RLC. PDCP sequence number ranges from 0 to 65,535.
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z BMC (broadcast/multicast control protocol)
The main function of BMC protocol are:
Storage of cell broadcast message. the BMC in RNC stores the cell
broadcast message received over the CBC-RNC interface for scheduled
transmission.
Traffic vo lume monitoring and radio resource request for CBS. On the
UTRAN side, the BMC calculates the required transmission rate for the cell
broadcast service based on the messages received over the CBC-RNC
interface, and requests appropriate .CTCH/FACH resources from fromRRC
Scheduling of BMC message.The BMC receives scheduling information
together with each cell broadcast message over the CBC-RNC interface. Based
on this scheduling information, on the UTRAN side the BMC generates schedule
message and schedules BMC message sequences accordingly. On the UE
side ,the BMC evaluates the schedule messages and indicates scheduling
parameters to RRC, which are used by RRC to configure the lower layers for
CBS discontinuous reception.
Transmission of BMC message to UE.The function transmits the BMC
messages according to the schedule
Delivery of cell broadcast messages to the upper layer.This UE function
delivers the received non-corrupted cell broadcast messages to the upper layer
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z The layer 1 (physical layer) is used to transmit information under the form of
electrical signals corresponding to bits, between the network and the mobile user.
This information can be voice, circuit or packet data, and network signaling.
z The UMTS layer 1 offers data transport services to higher layers. The access to these
services is through the use of transport channels via the MAC sub-layer.z These services are provided by radio links which are established by signaling
procedures. These links are managed by the layer 1 management entity. One radio
link is made of one or several transport channels, and one physical channel.
z The UMTS layer 1 is divided into two sub-layers: the transport and the physical sub-
layers. All the processing (channel coding, interleaving, etc.) is done by the transport
sub-layer in order to provide different services and their associated QoS. The physical
sub-layer is responsible for the modulation, which corresponds to the association of
bits (coming from the transport sub-layer) to electrical signals that can be carried over
the air interface. The spreading operation is also done by the physical sub-layer.
z These two parts of layer 1 are controlled by the layer 1 management (L1M) entity. It is
made of several units located in each equipment, which exchange information through
the use of control channels.
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Page13Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
RAB, RB and RL
RAB
RB
RLNodeB
RNC CNUE
UTRAN
z RAB: The service that the access stratum provides to the non-access stratum for
transfer of user data between User Equipment and CN.
z RB: The service provided by the layer 2 for transfer of user data between UserEquipment and Serving RNC.
z RL: A "radio link" is a logical association between single User Equipment and a single
UTRAN access point. Its physical realization comprises one or more radio bearer
transmissions.
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Page14Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
1. Physical Layer Overview
2. Physical Channels
3. Physical Layer Procedure
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Page15Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Contents
2. Physical Channels
2.1 Physical Channel Structure and Functions
2.2 Channel Mapping
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Page16Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
WCDMA Radio Interface Channel Definition
z Logical Channel = information container
Defined by is transferred
z Transport Channel = characteristics of transmission
Described by and with data
is transmitted over the radio interface
z Physical Channel = specification of the information global
content
providing the real transmission resource, maybe a frequency ,
a specific set of codes and phase
z In terms of protocol layer, the WCDMA radio interface has three types of channels:
physical channel, transport channel and logical channel.
z Logical channel: Carrying user services directly. According to the types of the carried
services, it is divided into two types: control channel and service channel.
z Transport channel: It is the interface between radio interface layer 2 and layer 1, and it
is the service provided for MAC layer by the physical layer. According to whether the
information transported is dedicated information for a user or common information for
all users, it is divided into dedicated channel and common channel.
z Physical channel: It is the ultimate embodiment of all kinds of information when they
are transmitted on radio interface. Each channel which uses dedicated carrier
frequency, code (spreading code and scramble) and carrier phase (I or Q) can beregarded as a physical channel.
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Page17Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Logical Channel
Control channel
Traffic channel
Dedicated traffic channel (DTCH)
Common traffic channel (CTCH)
Broadcast control channel (BCCH)
Paging control channel (PCCH)
Dedicate control channel (DCCH)
Common control channel (CCCH)
z As in GSM, UMTS uses the concept of logical channels.
z A logical channel is characterized by the type of information that is transferred.
z As in GSM, logical channels can be divided into two groups: control channels forcontrol plane information and traffic channel for user plane information.
z The traffic channels are:
Dedicated Traff ic Channel (DTCH): a point-to-point bi-directional channel,
that transmits dedicated user information between a UE and the network. That
information can be speech, circuit switched data or packet switched data. The
payload bits on this channel come from a higher layer application (the AMR
codec for example). Control bits can be added by the RLC (protocol information)
in case of a non transparent transfer. The MAC sub-layer will also add a header
to the RLC PDU.
Common Traffic Channel (CTCH): a point-to-multipoint downlink channelfor transfer of dedicated user information for all or a group of specified UEs.
This channel is used to broadcast BMC messages. These messages can either
be cell broadcast data from higher layers or schedule messages for support of
Discontinuous Reception (DRX) of cell broadcast data at the UE. Cell broadcast
messages are services offered by the operator, like indication of weather, traffic,
location or rate information.
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Page18Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Logical Channel
Control channel
Traffic channel
Dedicated traffic channel (DTCH)
Common traffic channel (CTCH)
Broadcast control channel (BCCH)
Paging control channel (PCCH)
Dedicate control channel (DCCH)
Common control channel (CCCH)
z The control channels are:
Broadcast Contro l Channel (BCCH): a downlink channel that broadcasts all system
information types (except type 14 that is only used in TDD). For example, systeminformation type 3 gives the cell identity. UEs decode system information on the BCH
except when in Cell_DCH mode. In that case, they can decode system information type
10 on the FACH and other important signaling is sent on a DCCH.
Paging Cont rol Channel (PCCH): a downlink channel that transfers paging
information. It is used to reach a UE (or several UEs) in idle mode or in connected mode
(Cell_PCH or URA_PCH state). The paging type 1 message is sent on the PCCH.
When a UE receives a page on the PCCH in connected mode, it shall enter Cell_FACH
state and make a cell update procedure.
Dedicated Control Channel (DCCH): a point-to-point bi-directional channel that
transmits dedicated control information between a UE and the network. This channel isused for dedicated signaling after a RRC connection has been done. For example, it is
used for inter-frequency handover procedure, for dedicated paging, for the active set
update procedure and for the control and report of measurements.
Common Control Channel (CCCH): a bi-directional channel for transmitting control
information between network and UEs. It is used to send messages related to RRC
connection, cell update and URA update. This channel is a bit like the DCCH, but will be
used when the UE has not yet been identified by the network (or by the new cell). For
example, it is used to send the RRC connection request message, which is the first
message sent by the UE to get into connected mode. The network will respond on the
same channel, and will send him its temporary identities (cell and UTRAN identities).After these initial messages, the DCCH will be used.
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Page19Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Transport Channel
Dedicated Channel (DCH)
Broadcast channel (BCH)
Forward access channel (FACH)
Paging channel (PCH)
Random access channel (RACH)
High-speed downlink shared channel
(HS-DSCH)
Common transport
channel
Dedicated transpor tchannel
z In order to carry logical channels, several transport channels are defined. They are:
Broadcast Channel (BCH): a downlink channel used for broadcast of system
information into the entire cell.
Paging Channel (PCH): a downlink channel used for broadcast of control
information into the entire cell, such as paging.
Random Access Channel (RACH): a contention based uplink channel used
for initial access or for transmission of relatively small amounts of data (non
real-time dedicated control or traffic data).
Forward Access Channel (FACH): a common downlink channel used for
dedicated signaling (answer to a RACH typically), or for transmission of
relatively small amounts of data.
Dedicated Channel (DCH): a channel dedicated to one UE used in uplink or
downlink.
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Page20Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Physical Channel
z A physical channel is defined by a specific carrier frequency, code
(scrambling code, spreading code) and relative phase.
z In UMTS system, the different code (scrambling code or spreading
code) can distinguish the channels.
z Most channels consist of radio frames and time slots, and each
radio frame consists of 15 time slots.
z Two types of physical channel: UL and DL
Physical Channel
Frequency, Code, Phase
z Now we will begin to discuss the physical channel. Physical channel is the most
important and complex channel, and a physical channel is defined by a specific carrier
frequency, code and relative phase. In CDMA system, the different code (scramblingcode or spreading code) can distinguish the channel. Most channels consist of radio
frames and time slots, and each radio frame consists of 15 time slots. There are two
types of physical channel: UL and DL.
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Page21Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Downlink Physical Channel
z Downlink Dedicated Physical Channel (DL DPCH)
z Downlink Common Physical Channel
Primary Common Control Physical Channel (P-CCPCH)
Secondary Common Control Physical Channel (S-CCPCH)
Synchronization Channel (SCH)
Paging Indicator Channel (PICH)
Acquisition Indicator Channel (AICH)
Common Pilot Channel (CPICH)
High-Speed Physical Downlink Shared Channel (HS-PDSCH)
High-Speed Shared Control Channel (HS-SCCH)
z The different physical channels are:
Synchronization Channel (SCH): used for cell search procedure. There is theprimary and the secondary SCHs.
Common Control Physical Channel (CCPCH): used to carry common controlinformation such as the scrambling code used in DL (there is a primary CCPCHand additional secondary CCPCH).
Common Pilot Channels (P-CPICH and S-CPICH): used for coherentdetection of common channels. They indicate the phase reference.
Dedicated Physical Data Channel (DPDCH): used to carry dedicated datacoming from layer 2 and above (coming from DCH).
Dedicated Physical Control Channel (DPCCH): used to carry dedicatedcontrol information generated in layer 1 (such as pilot, TPC and TFCI bits).
Page Indicator Channel (PICH): carries indication to inform the UE that paginginformation is available on the S-CCPCH.
Acquis it ion Indicator Channel (AICH): it is used to inform a UE that thenetwork has received its access request.
High Speed Physical Downlink Shared Channel (HS-PDSCH): it is used tocarry subscribers BE service data (mapping on HSDPA) coming from layer 2.
High Speed Shared Control Channel (HS-SCCH): it is used to carry controlmessage to HS-PDSCH such as modulation scheme, UE ID etc.
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Page22Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Uplink Physical Channel
z Uplink Dedicated Physical Channel
Uplink Dedicated Physical Data Channel (Uplink DPDCH)
Uplink Dedicated Physical Control Channel (Uplink DPCCH)
High-Speed Dedicated Physical Channel (HS-DPCCH)
z Uplink Common Physical Channel
Physical Random Access Channel (PRACH)
z The different physical channels are:
Dedicated Physical Data Channel (DPDCH): used to carry dedicated data
coming from layer 2 and above (coming from DCH).
Dedicated Physical Control Channel (DPCCH): used to carry dedicated
control information generated in layer 1 (such as pilot, TPC and TFCI bits).
Physical Random Access Channel (PRACH): used to carry random access
information when a UE wants to access the network.
High Speed Dedicated Physical Control Channel (HS-DPCCH): it is used to
carry feedback message to HS-PDSCH such CQI,ACK/NACK.
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Page23Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Function of Physical Channel
NodeB UE
P-CCPCH-Primary Common Control Physical ChannelP-CCPCH-Primary Common Control Physical Channel
P-CPICH--Primary Common Pilot ChannelSCH--Synchronisation Channel
P-CPICH--Primary Common Pilot ChannelSCH--Synchronisation Channel
Cell Search Channels
DPDCH--Dedicated Physical Data ChannelDPDCH--Dedicated Physical Data Channel
DPCCH--Dedicated Physical Control ChannelDPCCH--Dedicated Physical Control Channel
Dedicated Channels
Paging ChannelsPICH--Paging Indicator ChannelPICH--Paging Indicator Channel
SCCPCH--Secondary Common Control Physical ChannelSCCPCH--Secondary Common Control Physical Channel
PRACH--Physical Random Access ChannelPRACH--Physical Random Access Channel
AICH--Acquisition Indicator ChannelAICH--Acquisition Indicator Channel
Random Access Channels
HS-DPCCH--High Speed Dedicated Physical Control ChannelHS-DPCCH--High Speed Dedicated Physical Control Channel
HS-SCCH--High Speed Share Control ChannelHS-SCCH--High Speed Share Control Channel
HS-PDSCH--High Speed Physical Downlink Share ChannelHS-PDSCH--High Speed Physical Downlink Share Channel
High Speed Downlink Share Channels
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Page24Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.
Synchronization Channels (P-SCH & S-SCH)z Used for cell search
z Two sub channels: P-SCH and S-SCH
z SCH is transmitted at the first 256
chips of every time slot
z Primary synchronization code is
transmitted repeatedly in each time slot
z Secondary synchronization code
specifies the scrambling code groups of
the cell
Primary
SCH
Secondary
SCH
Slot #0 Slot #1 Slot #14
acsi,0
pac pac pac
acsi,1 acs
i,14
256 chips2560 chips
One 10 ms SCH radio frame
z When a UE is turned on, the first thing it does is to scan the UMTS spectrum and find
a UMTS cell. After that, it has to find the primary scrambling code used by that cell in
order to be able to decode the BCCH (for system information). This is done with the
help of the Synchronization Channel.
z Each cell of a NodeB has its own SCH timing, so that there is no overlapping.
z The SCH is a pure downlink physical channel broadcasted over the entire cell. It is
transmitted unscrambled during the first 256 chips of each time slot, in time multiplex
with the P-CCPCH. It is the only channel that is not spread over the entire radio
frame. The SCH provides the primary scrambling code group (one out of 64 groups),
as well as the radio frame and time slot synchronization.
z The SCH consists of