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HUAWEI TECHNOLOGIES CO., LTD.
www.huawei.com
Huawei Confidential
Internal
Principles of the WCDMA System
GSM-to-UMTS Training Series_V1.0
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 2
Date Version Description Author
2008-10-25 1.0 Draft Completed. Zang Liang
2008-12-31 1.1 Updated the access technology in the latest products in page 8. Added the comparison of frequency computation between the GSM and the WCDMA in page 13.
Added the comparison of encoding process in page 27.
Added explanations about closed loop power control in page 66.
Added explanations about handover in page 79.
Dong Qihuan
2009-01-14 1.11 Added information about EGSM/RGEM frequency bands in page 10.
Added handover modes and interference modes to the major differences between the GSM and the UMTS in page 11.
Added the method of computing frequencies at the EGSM/RGEM frequency bands in page 13.
Added association control channels in page 47.
Kuang Jun
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 3
Objectives
Know the similarities and differences between the GSM and the WCDMA technologies.
Master the basic principles of the CDMA technology.
Master the structure and radio interfaces of the WCDMA system.
Master the principle of WCDMA radio resource management.
Know technical features of the WCDMA FDD.
After studying this course, you will be able to:
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 4
Contents
Chapter 1 Introduction: GSM and WCDMA
Chapter 2 Overview of CDMA Principles
Chapter 3 WCDMA Radio Interface Physical Channel
Chapter 4 Overview of Radio Resource Management
Chapter 5 Technical Features of WCDMA FDD
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 5
Evolution from GSM to WCDMA
GSMMainly designed for the speech service Theoretical rate/actual rate: 64 kbit/s/9.6 kbit/s
GPRS
Supports higher data rates through the introduction of packet channels Theoretical rate/actual rate: 171.2 kbit/s/20 kbit/s-40 kbit/s
EDGEWith the introduction of new modulation mode, the theoretical rate is three times higher than that of the GPRS Theoretical rate/actual rate: about 473.6 kbit/s/100 kbit/s
WCDMA
Has the capability of high-speed data access and provide various servicesTheoretical rate/actual rate: R99 and R4: 2 Mbit/s/384 kbit/sR5 (HSDPA): 14.4 Mbit/s/1 Mbit/s higher
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 6
FrequencyTime
Power
FDMA
FrequencyTime
Power
TDMA
Multiple Access Technology - Distinguish Different Users
Power
Time
CDMA
Frequency
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 7
Comparison of Multiple Access Technology Between the GSM and the WCDMA
WCDMA: FDMA + CDMA
Bandwidth of a single carrier: 5 MHzStrong anti-interference capability. C/I: > -8 dBThe capacity is not fixed (soft capacity), closely related to user distribution, service type, and interference.Users interfere with each other. They must be well controlled.
Bandwidth of a single carrier: 200 kHzWeak anti-interference capability. C/I: > 9 dBWith eight timeslots for a single carrier, the system capacity is relatively fixed. It can be estimated according to the timeslot quantity.Since different users occupy different timeslots, they rarely interfere with each other.
GSM: FDMA + TDMA
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 8
Comparison of Radio Access Technology Between the GSM and the WCDMA
GSM WCDMA
Source coding
FR: RPE - LTP coding, 13 kbit/s EFR: enhancing the voice quality, 13 kbit/s HR: increasing the system capacity, 6.5 kbit/s AMR coding
AMR: eight types of speech ratesCompatible with the coding of current main-stream mobile communication systems, helpful for designing multimode terminals Provided with the traffic-adaptive capability: able to automatically adjust the speech rate so that the system can balance between the coverage, capacity, and speech quality
Channel coding Convolutional code (1/2) Speech service: convolutional code (1/2 and 1/3) High-speed data service: Turbo code
Channelization Packed in the pulse mode, data is sent out in different timeslots.
Through spread spectrum and scrambling, data is combined and outputted.
Modulation technology GMSK, 8PSK (EDGE) QPSK, 16QAM (HSDPA)
Power control technology Slow power control (2 Hz) Fast power control (1500 Hz): used to
restrain fadingTransmit diversity Transmit diversity (BTS3012) Transmit diversity
Receiving technology (anti-
fading)
Space diversity and polarization diversityThe effect similar to that of the frequency diversity can be realized through frequency hopping.
Space diversity and polarization diversityFrequency diversity: rake receiver
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 9
Comparison Between GSM and WCDMA Network Interfaces
RNS
RNC
RNS
RNC
WCDMA Core Network
Node B Node B Node B Node B
Iu - CS Iu
Iur
Iub IubIub Iub
Iu - PS
BSS
BSC
GSM NSS
BTS BTS
A
AbisAbis
Gb
Sector = Cell. One cell can include multiple carriers.
One sector can include multiple cells. Cell = Carrier
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 10
Comparison Between GSM and WCDMA Protocols
GSM WCDMA
A/Iu-CS
L3: BSSAP L3: RANAPL2: MTP L2: ATML1: E1 L1: E1 or STM - 1
Abis/Iub
L3: BTSM L3: NBAPL2: LAPD L2: ATML1: E1 L1: E1 or STM - 1
Radio interface
L3: RR RRC
L2 (data link layer): LAPDm L2 (data link layer): RLC/MAC
L1 (radio frequency band) (MHz):
890-915/935-960
1710-1785/1805-1880
L1 (radio frequency band) (MHz):
Major frequency band: 1920-1980 / 2110-2170
Supplementary frequency band: 1710-1785/1805-1880
(In China, only 30 MHz in the high frequency band serves as a supplementary frequency band.)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 11
Major Differences Between WCDMA and GSM Air Interfaces
GSM WCDMA
Carrier spacing 200 kHz 5 MHz
Frequency reuse coefficient 1-18 1
Method for differentiating cells Frequency + BSIC Frequency + Scrambling code
Power control frequency 2 Hz or lower 1500 Hz
QoS control Network planning (frequency planning)
Algorithm of radio resource management
Frequency diversity Frequency hoppingThe 3.84-MHz bandwidth enables the network to use the rake receiver for multipath diversity
Packet data Timeslot-based scheduling in the GPRS
Packet scheduling based on loads
Downlink transmit diversity
Not supported by the standards but applicable
Supported for increasing the capacity of downlinks
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 12
1850 1900 1950 2000 2050 2100 2150 2200 2250
ITU
Europe
USA MSSPCS
A D B BC D CE F A FE MSSReserveBroadcast auxiliary
2165 MHz1990 MHz
1850 1900 1950 2000 2050 2100 2150
2200 2250
1880 MHz 1980 MHz
UMTSGSM 1800 DECT MSS
1885 MHz 2025 MHz
2010 MHz
IMT 2000
MSSUMTS
Japan MSSIMT 2000MSSIMT 2000PHS
1895
1918
BC
1885
A A.
2170 MHz
IMT 20002110 MHz 2170 MHz
MSS MSS
CDMATDDWLL
FDDWLL
1980
2025 MHz
GSM1800
CDMA FDDWLL
1960
1920
1945
Chinacellular(1) cellular(2) cellular(2)
1805 MHz
1865
1865
1870
1885
1890
1895
1910
1930
1945
1965
1970
1975
Allocation of 3G Spectrum
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 13
Comparison of Frequency Computation Between the WCDMA and the GSM
Main working bands: 1920 - 1980 MHz/2110 - 2170 MHzFormula for computing WCDMA frequencies:Frequency number = Frequency x 5Central frequency number of uplink: 9612 - 9888Central frequency number of downlink: 10562 - 10838
Supplementary working bands: 1755 - 1785 MHz/1850 - 1880 MHz The currently existing GSM frequency bands of China Mobile and China Union can be used for the WCDMA later.
Computing WCDMA frequencies
GSM900: BS reception: f1 (n) = 890 + n x 0.2 MHzBS transmission: f2 (n) = f1 (n) + 45 MHz
GSM1800: BS reception: f1 (n) = 1710 + (n - 511) x 0.2 MHzBS transmission: f2 (n) = f1 (n) + 95 MHz
Computing GSM frequencies
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 14
Contents
Chapter 1 Introduction: GSM and WCDMA
Chapter 2 Overview of CDMA Principles
Chapter 3 WCDMA Radio Interface Physical Channel
Chapter 4 Overview of Radio Resource Management
Chapter 5 Technical Features of WCDMA FDD
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 15
Overview of CDMA Principles
Radio Propagation EnvironmentRadio Propagation Environment
Multiple Access Technology and Multiple Access Technology and Duplex TechnologyDuplex Technology
CDMA Principles and Rake ReceiverCDMA Principles and Rake Receiver
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 16
Multipath Environment
Time
Rx signals
Tx signals
Intensity
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 17
FadingTx data
-40-35-30-25-20-15-10-50
dB
Rx data
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 18
Fading
Distance (m)
Rx power (dBm)
10 20 30
-20
-40
-60
Slow fading
Fast fading
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 19
Frequency-Selective Fading
Narrowband system (GSM)
Large fading
Tx signals Rx fading signalsFrequencyFrequency
Intensity Intensity
Large fading
Tx signals Rx fading signalsFrequencyFrequency
Intensity Intensity
Broadband system (CDMA)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 20
Classification of Typical Radio Mobile Channels
Static channels (static)
Pedestrian channels in typical urban areas (TU3)
Vehicle-mounted channels in typical urban areas (TU30)
Vehicle-mounted channels in rural areas (RA50)
Vehicle-mounted channels on expressways (HT120)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 21
Overview of CDMA Principles
Radio Propagation EnvironmentRadio Propagation Environment
Multiple Access Technology and Multiple Access Technology and Duplex TechnologyDuplex Technology
CDMA Principles and Rake ReceiverCDMA Principles and Rake Receiver
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 22
Duplex Technology – Distinguish User’s UL and DL Signal Frequency division duplex (FDD): Distinguish uplink and downlink according to
frequencies. Adopted by the WCDMA and CDMA2000 Advantage: It can be easily implemented. Disadvantage: The spectrum utilization is low when the uplink and downlink services
(mainly the data services) are asymmetrical. Time division duplex (TDD): Distinguish uplink and downlink according to timeslots.
Adopted by the TD-SCDMA Advantage: The uplink and downlink can be allocated with different numbers of timeslots
when the uplink and downlink services are asymmetrical. Therefore, the spectrum utilization is high.
Disadvantage:
− It cannot be easily implemented and needs precise synchronization. In the CDMA system, GPS synchronization is needed.
− When it is used with the CDMA technology, it is difficult to control interference between the uplink and the downlink.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 23
Code Division Multiple Access (CDMA) Multiple users share a same frequency at the same time. This greatly
improves spectrum utilization. Users are identified through pseudo numbers.
The CDMA system supports soft capacity. For all the users, the system performance deteriorates when the number of users
increases. Contrarily, the system performance improves when the number of users decreases.
That is, the CDMA system can obtain larger capacity by deteriorating parts of the system performance.
Disadvantages of the CDMA system: It occupies a wide bandwidth.
It is a self-interference system. This causes mutual interference between users.
It is difficult to implement such technologies as power control and load control.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 24
Overview of CDMA Principles
Radio Propagation EnvironmentRadio Propagation Environment
Multiple Access Technology and Multiple Access Technology and Duplex TechnologyDuplex Technology
CDMA Principles and Rake ReceiverCDMA Principles and Rake Receiver
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 25
Common Terms Bit, symbol and chip
Bit (bit/s): the data that is obtained upon source coding and contains information.
Symbol (sps): the data obtained upon channel coding and interleaving.
Chip (cps): the data obtained upon final spreading.
− The spreading rate of WCDMA is: 3.84 Mcps
Processing gain It refers to the ratio of the final spreading rate to the bit rate (cps/bit/s).
In the WCDMA system, the processing gain depends on the specific service.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 26
Spreading Factor and Service Rate Symbol rate = (service rate + check code) × channel code
×repetition or punching rate For WCDMA, if the service rate is 384 Kbit/s and the channel code is
1/3 Turbo, the symbol rate is 960 Kbit/s.
For CDMA2000-1x, if the service rate is 9.6 Kbit/s and the channel code is 1/3 convolutional code, the symbol rate is 19.2 Kbit/s.
Chip rate = symbol rate spreading factor For WCDMA, if the chip rate is 3.84 MHz and the spreading factor is
4, the symbol rate is 960 Kbit/s.
For CDMA2000-1x, if the chip rate is 1.2288 MHz and the spreading factor is 64, the symbol rate is 19.2 Kbit/s.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 27
Basic Block Diagram of CDMA System
Source coding
InterleavingChannel coding
and interleaving
ScramblingSpreading ModulationRF
emission
Source decoding
deinterleavingDe-
interleavingChannel decoding
DescramblingDe-spreading Demodulation RF reception
Radio channel
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 28
Source Coding in WCDMA
Source coding InterleavingChannel
coding and interleaving
ScramblingSpreading ModulationRF
emission
The WCDMA system adopts the adaptive multi-rate (AMR) speech coding. A total of eight coding modes are available. The coding rate ranges from 12.2
Kbit/s to 4.75 Kbit/s. Multiple voice rates are compatible with the coding modes used by current
mainstream mobile communication systems. This facilitates the design of multi-mode terminals.
The system automatically adjusts the voice rate according to the distance between the user and the NodeB, thus reducing the number of handovers and call drop.
The system automatically decreases the voice rate of some users according to the cell load, thus saving power and containing more users.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 29
Source coding
InterleavingChannel coding and interleaving
ScramblingSpreading ModulationRF
emission
Channel Coding in WCDMA
Channel coding can enhance symbol correlation to recover signals in the case of interference.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Code type
Voice service: convolutional code (1/2 and 1/3).
Data service: Turbo code (1/3).
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 30
Interleaving Interleaving is used to disarrange symbol correlation and reduce the impact
caused by fast fading and interference of the channel.
1 2 3 4 5 6 7 8 ... ... 452 453 454 ……
8162432..
456
2101826..
450
6142230..
454
19
1725..
449
4122028..
452
7152331..
455
3111927..
451
5132129..
453
.... ....
A4 A5 A6 A7 B0 B1 B2 B3 B4 B5 B6 B7 C0 C1 C2 C3
{A4,B0} {A5,B1} {A6,B2} {A7,B3} {B4,C0} {B5,C1} {B6,C2} {B7,C3}
Ist interleaving
2nd interleaving
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 31
Spreading Principle
Source coding
InterleavingChannel coding and interleaving
ScramblingSpreading ModulationRF
emission
Users who need to send information: UE1, UE2 and UE3
UE1 uses c1 for spreading: UE1 x c1
UE2 uses c2 for spreading: UE2 x c2
UE3 uses c3 for spreading: UE3 x c3
c1, c2 and c3 are orthogonal to each other
Information sent: UE1 x c1 + UE2 x c2 + UE3 x c3
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 32
De-spreading Principle
UE1 uses c1 for de-spreading.
(UE1 x c1 + UE2 x c2 + UE3 x c3) x c1
= UE1 x (c1 x c1) + UE2 x (c2 x c1) + UE3 x (c3 x c1)
= UE1 x 1 + UE2 x 0 + UE3 x 0
= UE1
In the same way, UE2 uses c2 for de-spreading and UE3 uses c3 for de-spreading to get their own signals.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 33
Spreading and De-spreading (DS-CDMA)
Spreading
De-spreading
Chip
Symbol
Data
Spreading code
Spreading signal = Data x Code word
Spreading code
Data = Spreading signal x
Code word
1
-1
1
-1
1
-1
1
-1
1
-1
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 34
____________
UE1: + 1 - 1 1
_____________
UE2: - 1 + 1
c1: + 1 - 1 + 1 - 1 + 1 - 1 + 1 - 1
c2: + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1
UE1×c1: + 1 - 1 + 1 - 1 - 1 + 1 - 1 + 1
UE2×c2: - 1 - 1 - 1 - 1 + 1 + 1 + 1 + 1
UE1×c1 + UE2×c2: 0 - 2 0 - 2 0 + 2 0 + 2
Spreading Principle
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 35
UE1×c1 + UE2×c2 : 0 -2 0 -2 0 +2 0 +2
De-spreading Principle
Question: How to generate those orthogonal codes like c1 and c2?
UE1 de-spreading with c1: +1 -1 +1 -1 +1 -1 +1 -1
De-spreading result: 0 +2 0 +2 0 -2 0 -2
Integral: +4 -4
Decision: +4/4 = +1 -4/4 = -1
UE2 de-spreading with c2: +1 +1 +1 +1 +1 +1 +1 +1
De-spreading result: 0 -2 0 -2 0 +2 0 +2
Integral: -4 +4
Decision : -4/4 = -1 +4/4 = +1
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 36
UE1 × c1 + UE2 × c2: 0 - 2 0 - 2 0 + 2 0 + 2
UE1 × c1 + UE2 × c2 error code: 2 - 2 0 - 2 1 + 2 0 + 2
If error codes occur in the propagation process
UE1 uses c2 for de-spreading: c2 + 1 - 1 + 1 - 1 + 1 - 1 + 1 -1
De-spreading result: 2 - 2 0 - 2 0 + 2 0 + 2
Integral detection: - 2 + 4
Normalization: - 2/4= - 0.5 + 4/4=1
UE1 uses c1 for de-spreading: c1 + 1 - 1 + 1 - 1 + 1 - 1 + 1 -1
De-spreading result: 2 + 2 0 + 2 0 - 2 0 - 2
Integral detection: + 6 - 4
Normalization: +6/4=1.5 - 4/4= -1
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 37
OVSF and Walsh
OVSF codes (Walsh) are completely orthogonal and their mutual correlation is zero.
SF = 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)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 38
Use of OVSF Code
Over downlink channels, OVSF codes are used to differentiate users.
Over uplink channels, OVSF codes are used to differentiate the services of a user.
Typical Service Data Rate (bit/s) Downlink SF Uplink SF
AMR 12.2 + 3.4 128 64
Modem 28.8 kbit/s 28.8 + 3.4 64 32
12.2 kbit/s AMR and 64 kbit/s packet data
12.2 + 64 + 3.4 32 16
12.2 kbit/s AMR and 144 kbit/s packet data
12.2 + 144 + 3.4 16 8
12.2 kbit/s AMR and 384 kbit/s packet data
12.2+384+3.4 8 4
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 39
Scrambling in the WCDMA System
Source coding
InterleavingChannel coding and interleaving
ScramblingSpreading ModulationRF
emission
Downlink: Different cells (sector carrier frequencies) have different downlink scrambling codes.
Each cell is configured with a unique downlink scrambling code. The UE identifies a cell based on the scrambling code.
OVSF codes are used to differentiate different users in a cell.
Uplink: Scrambles are used to differentiate different users.
In a cell, each user is configured with a unique uplink scrambling code.
OVSF codes are used to differentiate the services of a user.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 40
WCDMA Scrambling Code: Gold Sequence
Over downlink channels, OVSF codes are used to differentiate users.
There are 224 uplink long scrambling codes and 224 uplink short scrambling codes.
Over downlink channels, scrambling codes are used to differentiate cells (sectors/carriers).
There are (218 - 1 = ) 262143 scrambling codes on the downlink. Currently, however, only the primary scrambling codes in the scrambling codes from No.0 to No.8191 are used.
A scrambling code is repeated every 10 ms. It is 38400 chips long.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 41
Dow
nlink scram
bling code
Set 0
Set 1…
Set 511
Primary scrambling code 0
Secondary scrambling code 1
…
Secondary scrambling code 15
Primary scrambling code 511×16
…
Secondary scrambling code 511×16 + 1
Secondary scrambling code 511×16 + 15
8192 scrambling codes
512 sets
Each set contains 1 primary scrambling
code and 15 secondary
scrambling codes.
Currently, the system mainly uses primary scrambling codes.
Primary and Secondary Scrambling Codes
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 42
Dow
nlink scram
bling code
Group 0
Group 1…
Group 63
Primary scrambling code 0
Primary scrambling code 1
…
Primary scrambling code 7
Primary scrambling code 504
…
Primary scrambling code 505
Primary scrambling code 511
512 scrambling codes
64 groups
Each group contains eight scrambling codes, one of which is the primary scrambling code.
Scrambling code planning in the network planning is to plan and allocate the 512 primary scrambling codes.
Primary Scrambling Codes and Scrambling Code Groups
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 43
Allowed maximum interference level
Eb/No required
Spreading/De-spreading Principle — Explanations for Frequency Domain
Power spectrum
Power sharable for all users
a2Tbit = Ebit
Gain
Other user interference signals Echip
Eb/No = Ec/Io × Gain
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 44
The CDMA broadband spreading technology effectively avoids frequency-selective fading of radio channels.
Spreading code
Spreading code
Signal combination
Spectrum Change in CDMA
Narrowband signalf
P(f)
Broadband signal
P(f)
f
Noise
P (f)
f
Noise + broadband signal
P (f)
f
Separation of signals and noise
P (f)
f
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 45
Rake Receiver
Front-end receiver
Receiving path 1
Receiving path 2
Receiving path 3
Delay estimator Compute delay and phase deflection
Signal synthesizer Consolidate signals
tt
s(t) s(t)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 46
Contents
Chapter 1 Introduction: GSM and WCDMA
Chapter 2 Overview of CDMA Principles
Chapter 3 WCDMA Radio Interface Physical Channel
Chapter 4 Overview of Radio Resource Management
Chapter 5 Technical Features of WCDMA FDD
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 47
Mapping of Channel Function Between the GSM and the WCDMA
GSM WCDMA
Cell search
FCCH: frequency correction channel (P - )CPICH: (Primary) common pilot channel
SCH: synchronization channel SCH: synchronization channel, but has different functions from that in the GSM system
BCCH: broadcast control channel P-CCPCH: primary common control physical channel
Paging PCH: paging channel
PICH: page indicator channel, helpful for power saving on a terminalS-CCPCH: secondary common control physical channel
Access
Uplink: RACH: random access channelSDCCH: stand-alone dedicated control channel
Uplink: PRACH: physical random access channel
Downlink: AGCH: access grant channel SDCCH: stand-
alone dedicated control channel
Downlink: AICH: acquisition indication channel S-CCPCH: secondary common control physical channel
Speech service TCH: traffic channel DPDCH: dedicated physical data control channel
DPDCH: dedicated physical data control channel
Data service PDCH: packet data channel
HS-PDSCH: high-speed physical downlink shared channelHS-SCCH: high-speed shared control channelHS-DPCCH: high-speed dedicated control channel
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 48
Classification of WCDMA Channels In terms of protocol layer, the WCDMA radio interface has three
channels:
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.
Transport channel : Provided service 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.
Physical channel: It is the final form of all kinds of information when they are transmitted on radio interfaces.
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 49
TCH
CCH
Logical Channels
Broadcast Control Channel ( BCCH)Paging control channel (PCCH)
Dedicate control channel (DCCH)
Common control channel (CCCH)
Dedicated traffic channel (DTCH)
Common traffic channel (CTCH)
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 50
Dedicated Channel (DCH)
-DCH can be uplink or downlink channel
Broadcast channel (BCH)
Forward access channel (FACH)
Paging channel (PCH)
Random access channel (RACH)
Common transport channel
Dedicated transport channel
Transport Channels
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 51
The timeslot concept in the WCDMA system differs greatly from that
in the GSM system.
Physical Channels
Physical channels are divided into uplink and down physical channels.
A physical channel can be determined by a carrier, codes (channel code and scrambling code), and a phase. Most channels consist of radio frames and timeslots. Each radio frame has 10 ms and consists of 15 timeslots.
Data
Timeslot 0 Timeslot 1 Timeslot 14
T timeslot = 2560 chips
T = 10 ms, 38400 chips
Data
Timeslot i
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 52
Uplink Common Physical Channel
Physical Random Access Channel (PRACH)
Uplink Dedicated Physical Channel
Uplink Dedicated Physical Data Channel
(Uplink DPDCH)
Uplink Dedicated Physical Control
Channel (uplink DPCCH)Uplink Physical
Channel
Uplink Physical Channel
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 53
Downlink Common Physical Channel
Common Control Physical Channel (CCPCH)
Synchronization Channel (SCH)
Paging Indicator Channel (PICH)
Acquisition Indicator Channel (AICH)
Common Pilot Channel (CPICH)
Downlink Dedicated Physical Channel
(downlink DPCH)
Downlink Physical Channel
Downlink Physical Channel
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 54
Configuration Example of Downlink Physical Channel
SF 4 8 16 32 64 128 256 512 ┏ ━ ●C(256, 0): PCPI CH 2 ┏ 0 ┫ ┃ ┗ ━ ●C(256, 1): PCCPCH 3 ┏ 0 ┫ ┃ ┃ ┏ ━ ●C(256, 2): AI CH 6 ┃ ┗ 1 ┫ ┃ ┗ ━ ●C(256, 3): PI CH 10 ┏ 0 ┫ ┃ ┗ ━ ●C(64, 1): SCCPCH 8 ┏ 0 ┫ ┃ ┃ ┏ ━ ●C(64, 2): SCCPCH 9 ┃ ┗ 1 ┫ ┃ ┗ ━ ○3 ┏ 0 ┫ ┃ ┗ ━ ○1 ┏ 0 ┫ ┃ ┗ ━ ○1 ┃ ┗ ━ ○1
┏ ━ ○2 ┃ ┗ ━ ○3
Pilot channel (PICH)
Used to bear broadcast channels (BCHs)
Used to bear forward access channels
(FACHs) and paging channels (PCHs)
Allocated to dedicated physical channels
(DPCHs) in real time
Synchronization channel (SCH)
SCH 0,1
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Functions of Physical Channels
NodeB (BS)
User equipment (UE)
P-CCPCH: primary common control physical channel SCH: synchronization channel
P-CPICH: primary common pilot channel S-CPICH: secondary common pilot channel
Cell broadcast channel (CBCH)
DPDCH: dedicated physical data channel
DPCCH: dedicated physical control channel
Dedicated access channel
Paging channel (PCH)
PICH: paging indicator channel
S-CCPCH: secondary common control physical channel
PRACH: physical random access channel
AICH: acquisition indication channel
Random access channel (RACH)
HS-DPCCH: high-speed dedicated control channel
HS-SCCH: high-speed shared control channel
HS-PDSCH: high-speed physical downlink shared channel
High-speed downlink shared channel
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Functions of Common Physical Channels
SCH: used for cell search Divided into P-SCH and S-SCH
CPICH: used to identify scrambling codes Divided into P-CPICH and S-CPICH
− P-CPICH: Their channel codes are fixed to be Cch,256,0. They
use primary scrambling codes.
− P-CPICH is the power benchmark of other physical downlink channels. S-CPICH: used for smart antennas
P-CCPCH: used to carry system messages
channel codes are fixed to be Cch,256,1.
Each cell must be configured with all these channels, but only one for each type.
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Functions of Common Physical Channels
S-CCPCH: used to carry downlink signaling messages
PICH: used to carry paging indicators. A PICH must be configured with an S-CCPCH as a pair.
PRACH: used to carry uplink signaling messages
The interval for timeslot access is 5120 chips, indicating that the maximum coverage radius of a WCDMA BS is 200 km.
AICH: used to carry acquisition indications of PRACH prefix. An AICH must be configured with a PRACH as a pair.
Each cell must be configured with all these channels, at least one for each type.
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Functions of Dedicated Physical Channels DPDCH: used to carry users' service data. The maximum data rate of a single code
channel is 384 kbit/s.
DPCCH: used to carry control information, and provide control data such as demodulation and power control for DPDCHs
On the uplink, DPDCHs and DPCCHs transmit signals over different code channels. On the downlink, DPDCHs and DPCCHs transmit signals in the mode of time multiplexing.
When the required data rate is higher than the maximum data rate of a single code channel, the system can use multiple code channels for transmission.
Maximum uplink data rate: 384 kbit/s x 6 code channels
Maximum downlink data rate: 384 kbit/s x 7 code channels
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Mapping Between Logical Channels and Transport Channels
Logical Channels Transport Channels CCCH (uplink) RACH DCCH/DTCH (uplink) RACH DCH BCCH (downlink) BCH PCCH (downlink) PCH CCCH/CTCH (downlink) FACH DCCH/DTCH (downlink) DCH FACH
DTCH (downlink) HS-DSCH
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Mapping Between Transport Channels and Physical Channels Transport Channels Physical Channels DCH Dedicated Physical Data Channel (DPDCH)
Dedicated Physical Control Channel (DPCCH) RACH Physical Random Access Channel (PRACH) BCH Primary Common Control Physical Channel (P-CCPCH) FACH Secondary Common Control Physical Channel (S-CCPCH) PCH
Synchronization Channel (SCH)Acquisition Indicator Channel (AICH)Paging Indicator Channel (PICH)
HS-DSCH High Speed Physical Downlink Shared Channel (HS-PDSCH)
HS-DSCH-related Shared Control Channel (HS-SCCH)Dedicated Physical Control Channel (uplink) for Hs-DSCHHS-DPCCH
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 61
Contents
Chapter 1 Introduction: GSM and WCDMA
Chapter 2 Overview of CDMA Principles
Chapter 3 WCDMA Radio Interface Physical Channel
Chapter 4 Overview of Radio Resource Management
Chapter 5 Technical Features of WCDMA FDD
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Overview of Radio Resource Management
RRM - Radio Resource Management
Since the WCDMA system is a self-interference system, the use of power is incompatible in WCDMA system.
On one hand, increasing the Tx power for a user can improve the quality of service (QoS) of this user.
On the other hand, as WCDMA is self interference system, power enhancement will interfere other user and make the reception quality worse. .
Power is a final radio resource. The only way to make radio resources utility is to strictly control the use of power.
The RRM is to manage the power by combining QoS objectives.
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Purposes of RRM
The RRM is intended to: Ensure the QoS requested by the CN
Enhance the system coverage
Improve the system capacity
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Tasks of RRM
Channel configuration: To ensure the QoS requested by the CN, the RRM maps the QoS into some features of the access stratum and thus uses the resources at the access stratum to serve the local connection.
Power control: When the QoS requested by the CN is ensured, the RRM minimizes the Tx power of a UE to reduce the interference of this UE to the entire system, and to improve the system capacity and coverage.
Mobility management: The RRM maintains the QoS when a UE moves.
Load control: After a certain number of UEs access to the system, the RRM must ensure that the load of the entire system retains at a stable level to ensure the QoS of each connection in the system.
QoS assurance and power saving run through the entire RRM.
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Power Control—Near-Far Effect The CDMA has not been put into commercial use in a large scale since it
was put forward. That is because it cannot overcome the near-far effect.
All other signals are overwhelmed by the signals of a UE closest to the BS. Communications fail.
One UE can congest an entire cell
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Purpose and Classification of Power Control
Owing to the near-far effect, the WCDMA system must introduce power control. In addition, power control can also bring many other benefits:
Adjust the transmit power to maintain the uplink and downlink communication quality.
Overcome slow and fast fading.
Reduce network interference and improve the system quality and capacity.
Power control is classified into:
Open loop power control
Closed loop power control
- Uplink and downlink inner loop power control
- Uplink and downlink outer loop power control
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Principles of Open Loop Power Control
Basic principle Suppose the coupling loss between the transmit power and the received power
is the same as the interference level between them. Use the previously-measured received power to determine the initial transmit power.
If the BS fails to receive the initial transmit power, there is a retransmission mechanism for improving the power.
Basic function To overcome slow fading and path loss
Major disadvantage Asymmetry between the wave power of the uplink and downlink channels is not
considered, so accuracy cannot be guaranteed.
Major application Uplink: applied to PRACHs and DPCCHs Downlink: applied to DPCCHs
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Principles of Open Loop Power Control
Principles of setting initial transmit powerPrinciples of setting initial transmit power
DL
UL UL
DL UL
_ _ ............................(1)_ _ ....................(2)
Suppose the uplink and downlink path losses are the same: ....................(3
CPICH RSCP CPICH Pow PLX EcNo X Pow PL Interference
PL PL
UL
)
_ _ _ _X Pow CPICH Pow CPICH RSCP Interference X EcNo
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Open Loop Power Control over the PRACH
NodeB UERACH
BCH: Transmit power of CPICH UL interference level
The open loop power control is intended to roughly estimate the initial transmit power. It estimates the path loss and interference level according to measurement results, and thus calculates the initial transmit power.
The UE measures the received power of the CPICH and calculates the initial uplink transmit power.
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Open Loop Power Control over the PRACHOne access slot
p-a
p-m
p-p
Pre-amble
Pre-amble Message part
Acq.Ind.AICH access
slots RX at UE
PRACH accessslots TX at UE
Access process of the PRACH: A UE transmits a PRACH preamble signal over the PRACH. After a BS successfully captures the preamble signal, the BS responds with an AI over the downlink AICH. If the UE receives the AI signal, the UE transmits a PRACH message. If the UE fails to receive the AI signal at the time point τp-
a, the UE will increase the power and transmit next preamble signal after a certain time τp-p. The UE will continue such an action over and over until it receives the AI signals.
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Open Loop Power Control over the PRACH
Preamble_Initial_Power = PCPICH DL TX power - CPICH_RSCP + UL interference + Constant Value
Note: The PCPICH DL TX power, UL Interference, and Constant Value are delivered in system messages. The CPICH_RSCP is measured by the UE.
In the early stage of network construction, the coverage is limited, so the Constant Value can be set to a larger value (-16 dB or -15dB).
In this way, the network can receive the preamble signals sent by the UE in time. In addition, the parameter Power Ramp Step can also be set to a larger value to increase the network probability of capturing preamble signals.
Method for setting the transmit power of the first preamble signal over the uplink PRACH:
Default settings: Constant Value: -20 dB
PowerRampStep: 2 dB
PreambleRetransMax: 20
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Open Loop Power Control over the Uplink DPCCH
DPCCH_Initial_power = DPCCH_Power_offset - CPICH_RSCPNote: The CPICH_RSCP is measured by a UE.
The DPCCH_Power_offset is the offset of the initial transmit power of the DPCCH. The RNC allocates it to a UE at the beginning of an RRC connection setup. The formula for computing it is as follows:
DPCCH_Power_offset = Primary CPICH DL TX power + UL Interference
+ Default Constant Value
In the formula,
the Primary CPICH DL TX power is the downlink transmit power of the P-CPICH.
The UL interference is the uplink interference.
The Default Constant Value is the default constant value of the initial transmit power of the DPCCH.
Method for setting the initial power of the uplink DPCCH:
Understanding
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Open Loop Power Control over the Downlink DPCCH
P = (Ec/Io) Req - CPICH_Ec/Io + PCPICH
Note: The (Ec/Io) Req is the required Ec/Io for a UE to correctly receive the dedicated
channel. The CPICH_Ec/Io is the Ec/Io of the CPICH measured by the UE, and it
is reported to the UTRAN through the RACH. The PCPICH is the transmit power
of the CPICH.
Method for setting the initial power of the downlink DPCCH:
Understanding
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 74
Uplink Inner Loop Power Control
NodeB UE
Send TPC bits
Measure SIRs of received signals and compare them
Inner loop
Set SIRtar
1500 Hz
The inner loop power control is intended to ensure equal bit energy for each UE signal received at the NodeB.
Each UE has its own control loop.
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Uplink Inner Loop Power Control
NodeB UE
Send TPC bits
Measure SIRs of received signals and compare them
Inner loop
Set SIRtar
Obtain the service data with a stable BLER
Measure the BLER over the transport channel
Outer loop
RNC
Measure BLERs of received data and
compare them
Set SIRtar
10-100Hz
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Downlink Inner Loop Power Control
NodeB
Set SIRtar
Send TPC
Measure SIRs and compare them
Measure BLERs and compare them
Outer
loopInner loop
Physical layer of the UE
Layer 3 of the UE
Downlink inner loop and outer loop power control
1500 Hz 10-100 Hz
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Physical Channel
Open Loop Power
Control
Inner Closed Loop
Outer Closed Loop
No Power
Control
PRACH √
DPCCH √ √ √
DPDCH √ √
PCPICH √
PCCPCH √
SCCPCH √
AICH √
PICH √
Power Control Application in the WCDMA System
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MML Commands Related to Power Control
MML commands related to open loop power control:
ADD PRACHBASIC
SET FRC
MML commands related to inner loop power control:
SET FRC
ADD CELLSETUP
MML commands related to outer loop power control:
ADD TYPRABOLPC
SET OLPC
MML commands related to power balance:
SET DPB
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 79
Classification of WCDMA Handover
Soft handover:
Soft handover
Softer handover
Hard handover:
Intra-frequency hard handover
Inter-frequency hard handover
Inter-system handover
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 80
Soft Handover
Time
Data received/sent by the UE
The UE movesTarget BSSource BS
Time
Data received/sent by the UE
The UE movesTarget BSSource BS
No “GAP” of communication
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Hard Handover
The UE movesTarget BSSource BS
Time
Data received/sent by the UE
The UE movesTarget BSSource BS
Time
Data received/sent by the UE
“GAP” of communication
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 82
Contents
Chapter 1 Introduction: GSM and WCDMA
Chapter 2 Overview of CDMA Principles
Chapter 3 WCDMA Radio Interface Physical Channel
Chapter 4 Overview of Radio Resource Management
Chapter 5 Technical Features of WCDMA FDD
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 83
Technical Specifications of WCDMA FDD
Modulation mode: QPSK for both the uplink and the downlink
Speech coding: AMR
Channel coding: convolutional code and Turbo code
Demodulation mode: coherence demodulation assisted by pilots
Transmit diversity mode: TSTD, STTD, and FBTD
Power control: uplink and downlink closed and open loop power control
BS synchronous mode: supports asynchronous and synchronous BS operation
Signal bandwidth: 5 MHz; chip rate: 3.84 Mcps
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Adopts AMR speech coding and supports the voice quality of 4.75 kbit/s to 12.2 kbit/s
Adopts soft handover and transmit diversity to improve the capacity
Provides high-fidelity voice modes
Supports fast power control
Speech Evolution of the WCDMA System
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 85
Supports up to 14.4 Mbit/s data services (HSDPA)
Supports packet switching
Evolves from the ATM platform to All-IP gradually
Provides QoS control
Better supports Internet packet services (HSDPA) through the CPCH and DSCH.
Provides mobile IP services (dynamic assignment of IP addresses)
Determines dynamic data rates provided by the TFCI domain.
Provides high quality support for symmetric uplink and downlink data services, including the voice, videophone, and video conference.
Data Evolution of the WCDMA System
HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 86
Summary
This course introduces the WCDMA system briefly.
The course contents include the basic key technologies of mobile communication systems, basic principles of the CDMA system, and the FDD mode of the WCDMA system.
After studying this course, you can have a general understanding of the 3G system, thus make a good foundation for further study.
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