42164892 intoduction wcdma fundamantels[1]
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MobileComm Technologies India Pvt. Ltd.
Dallas . Atlanta . Washington . LA . Sao Paulo . New Delhi . Toronto . Muscat. Sydney
Introduction & WCDMA Fundamentals
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Copyright 2010 MobileComm Technologies India Pvt. Ltd.
All rights reserved
MobileComm is committed to providing our customers with quality instructor led
Telecommunications Training.
This documentation is protected by copyright. No part of the contents of this
documentation may be reproduced in any form, or by any means, without the prior written consent of MobileComm Technologies .
Document Number: RK/CT/3/2010
This manual prepared by: MobileComm Technologies
MobileComm Technologies(India)Pvt. Ltd.424, First Floor, Udyog Vihar Phase -4,
Gurgaon-122002
Headquarter:MobileComm Professionals Inc.1255 West 15th Street, Suite 440
Plano, TX, 75075Tel: (972) 633-5100Fax: (972) 633-5106www.mcpsinc.com
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• Understand why 3G was created
• Different services in 3G
• How QoS is ensured by 3G
Objectives
At the end of this session, you will be able to:
Introduction
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Mobile Network Evolution
1G
Analogue
2G
Digital
2.5G
Packet Data
2.75G
Enhanced Data
NMT
TACS
AMPS
GSM
CDMA
TDMA
GPRS
EDGE
CDMA 1X
WCDMA
TD-SCDMA
cdma2000
1X EV-DO
2M, 14M
2M
2.4M
384K
144K
1982-1996+ 1992-2002+ 2001+ 2004+ 2002-2004+
115K
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A Third Generation of Mobile Systems: What for?
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• Concepts of 3G - Mobiles
Voice & Music phone
Mobile Audio Video
Communicator
PC / PDA PCMCIA card
A Third Generation of Mobile Systems: What for?
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Standardization Bodies
T1 ETSI TTC / ARIB TTA CWTS TIA
= 3GPP2
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Standardisation of 3G cellular networks
– ITU (Global guidelines and recommendations)
• IMT-2000: Global standard for third generation (3G) wireless communications
– 3GPP is a co-operation between standardisation bodiesETSI (Europe), ARIB/TTC (Japan), CCSA (China), ATIS (North America) and TTA (South Korea)
• GSM
– EDGE
• UMTS
– WCDMA - FDD
– WCDMA - TDD
• TD-SCDMA
– 3GPP2 is a co-operation between standardisation bodiesARIB/TTC (Japan), CCSA (China), TIA (North America) and TTA (South Korea)
• CDMA2000
– CDMA2000 1x
– CDMA2000 1xEV-DO
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2 Mbit/s 384 kbit/s 144 kbit/s
Indoor
low mobility
Urban
reduced mobility
Rural outdoor
high mobility
• Variable bit rate capability
• Variable Quality Of Service (BER, delay)
• Support of asymmetric traffic
• Service multiplexing
• High spectrum efficiency
• European objective: ensure compatibility with GSM
3GPP Objectives
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Added Value of UMTS
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Mobile Networks and Data Services
2G Mobile
3G (UMTS)
3.5G or 3G+ (HSDPA and HSUPA)
2.5G (GPRS)
2.75G (EDGE)
3G Mobile
LTE
WiMAX
HSDPA
UMTS
EDGE
GPRS 160kbps
384Kbps
2Mbps *
14.4Mbps *
75Mbps *
100Mbps ? *
* : Per cell bandwidth (not per user)WiMAX ("3G" or "4G" depending on manufacturer)
Future: 4G (LTE)
HSUPA 5.7Mbps *
Maximum Theoretical Bandwidth
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UMTS QoS class
NRT Data Call
Background Class
PS Data Call
Interactive Class
PS Data Call
Streaming Class
PS Data Call
Conversational Class
CS Data Call
CS Data Call CS Voice Call
CS Call
RT Data Call
PS Call
Call
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Why do we need QoS?
• UMTS networks support services with very different performance requirements
– Real-time services require performance guarantees
– Customer acceptance closely tied to service quality
• Optimal usage of network resources
– Radio resources scarce
– Cost-effectiveness
– Return of investment
• Service and user differentiation
– Meet different needs of customers (e.g. business vs. consumer)
– Support different services (real-time vs. best effort)
• Competitive advantage! Delay Jitter Loss
Video call High High High Med
Streaming High Med Med Med
Web browsing Med Med Low High
E-mail Low Low Low High
Application BandwidthSensitivity
Performance Requirements
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QoS Traffic Classes
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QoS Traffic Classes
Traffic class Characteristics Example
application
Conversational Preserve time relation between
information entities of the stream.
Conversational pattern (stringent and
low delay)
Speech
Video calls
Streaming Preserve time relation between
information entities of the stream.
Real-time
streaming
video
Interactive Request-response pattern. Preserve
payload content.
Web browsing
Background Destination is not expecting the data
within a certain time. Preserve
payload content.
File
downloading
Demanding
• Delay
• Jitter
Demanding
• Bit rate
• Jitter
Tolerant
• Delay and bit rate can vary
• Integrity
Easiest
• Delay and bit ratecan vary
• Integrity
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QoS for different services
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UMTS BEARERS
The Attributes (QoS Parameters) of a Bearer Service can be negotiated at the beginning of connection and during a connection Several different Bearer Services can be established simultaneously by one UE
Important Quality Parameters are– Maximum transfer delay – Delay variation – Bit error ratio– Data rate
“A bearer is a logical connection between two end points with specific service
capabilities”
A bearer service includes all aspects to enable the provision of a contracted QoS (e.g.,
controlling, signalling, user plane transport, management functionalities).
“QoS support in UMTS is based on the concept of bearer service”
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UMTS BEARERS : Example
RAB Class Usage
AMR 12.2 Conversational Voice
CS C 64 Conversational Video conferencing
PS I/B 8/8 Interactive / Background Email/Internet
PS I/B 16/16 Interactive / Background Email/Internet
PS I/B 64/64 Interactive / Background Email/Internet
PS I/B 64/128 Interactive / Background Email/Internet
PS I/B 64/384 Streaming Live Audio/Video
PS I/B 128/128 Streaming Live Audio/Video
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QoS Differentiation
Conversational RAB
Streaming RAB
Interactive RAB
Interactive RAB
Background RAB
MMS
Web
browsing
Push-to-talk
Streaming
Video
telephony
• Each service gets the treatment it requires according to the QoS profile
• Network resources are shared according to the service needs
• Network resources can be used more efficiently
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WCDMA Network Structure
GSM /GPRS BSS
BTS
BSC
PCUSS7
SCP
SMS
SCE
PSTN/other PLMN
Internet,
Intranet
MSC/VLR GMSC
HLR/AUC
SGSN
CG BG
GGSN
PS backbone
Other PLMN
CS domain
PS domain
NodeB
RNC
UTRAN
Iu-CS
Iu-PS
A
Gb
GERAN
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WCDMA Interfaces
A Interface
A-bis
Um
MSC
BSC
BTS
UE
SGSN
Gb
GSM
Iub
Uu
MSC
RNC
NodeB
UE
SGSN
Iu-PSIu-CS
Iub
Uu
RNC
NodeB
UE
Iur
WCDMA
UTRANBSS
GERAN
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Radio Network Interfaces
• Iu
– Iu PS
• Connection to the packet switched core network domain
– SGSN/GGSN
– Iu CS
• Connection to the circuit switched core network domain
– MSC
– Protocol RANAP
• Iur
– RNC interconnection [eg: for SHO support ]
– Protocol RNSAP
• Iub
– Connection for the RBS to the RNC
– Protocol NBAP
• Uu
– Air Interface to the UE
– Protocol RRC, RLC, MAC
Core Network
RNC
RNC
Iu
Iur
Iub
UuNode
B
NodeB
NodeB
UE
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•WCDMA Air Interface
•WCDMA Principles & Spreading codes
•Overview of Radio Resource Management (RRM)
•Load control
•Admission Control
•Packet Scheduler
•Resource Manager
•Power Control
•Handover Control
•Capacity limitation and Cell breathing
•Rake receiver
Objectives
At the end of this session, you will be able to:
W-CDMA Fundamantels
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Agenda
•WCDMA Air Interface
•WCDMA Principles & Spreading codes
• Overview of Radio Resource Management (RRM)
•Capacity limitation and Cell breathing
•Rake receiver
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Power
PowerPower
FDMA TDMA
W-CDMA
Access Technologies
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What do YOU hear...
•If you only speak Japanese?
•If you only speak English?
•If you only speak Italian?
•If you only speak Japanese, but the Japanese-speaking person is all the way across the room?
•If you only speak Russian, but the Spanish-speaking person is talking very loudly?
WCDMA Cocktail Party
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UMTS Air Interface technologies
– UMTS Air interface is built based on two technological solutions• WCDMA – FDD• WCDMA – TDD
– WCDMA – FDD is the more widely used solution• FDD: Separate UL and DL frequency band
– WCDMA – TDD technology is currently used in limited number of networks
• TDD: UL and DL separated by time, utilizing same frequency
– Both technologies have own dedicated frequency bands
– This course concentrates on design principles of WCDMA – FDD solution, basic planning principles apply to both technologies
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Duplex Spacing: 190 MHz
FDD
Time
Frequency
Power
5 MHz 5 MHz
Code Multiplex
UL DL
UMTS USER 1
UMTS USER 2
Time
Frequency
Power
TDD
5 MHz
Code Multiplex
&
Time Division
666.67 ms
DL
UL
DL
DL
UL
UMTS USER 2
UMTS USER 1
• W-CDMA: FDD or TDD
UMTS Air Interface technologies
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• W-CDMA FDD mode for the paired band
– uplink and downlink are separated in frequency
TD-CDMA TDD mode for the unpaired band
– uplink and downlink are separated in time
– flexible time duration for uplink and downlink for asymmetrical traffic
UMTS Air Interface technologies
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WCDMA Technology
5 MHz
3.84 MHz
f
5+5 MHz in FDD mode5 MHz in TDD mode
Fre
qu
ency
TimeDirect Sequence (DS) CDMA
WCDMA Carrier
WCDMA5 MHz, 1 carrier
TDMA (GSM)5 MHz, 25 carriers
Users share same time and frequency
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IMT-2000 frequency allocations
2200 MHz20001900 1950 2050 2100 21501850
JapanIMT-2000
PH
S IMT-2000
ITU
Mo
bil
e
Sate
llit
e
IMT-2000 IMT-2000
EuropeUMTS(FDD)
DE
CT
UM
TS
(T
DD
)
GSM1800
UM
TS
(T
DD
)
UMTS(FDD)
USA
PC
S
un
lic
en
se
d
PCSPCS
UM
TS
(T
DD
)IM
T-2
000 (
TD
D)
Mo
bil
e
Sate
llit
eM
ob
ile
Sate
llit
e
Mo
bil
e
Sate
llit
eM
ob
ile
Sate
llit
e
Mo
bil
e
Sate
llit
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Mo
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ITU-R
•responsible for world-wide Radio Communication aspects
• setting requirements for 3G / 4G Mobile Communication (IMT-2000 / IMT-Advanced)
•World Radio ConferenceWRC 1992: IMT-2000 frequency allocation proposals
national regulation authorities:
• responsible for national frequency allocation & licensing process
•GSM spectrum refarming is also possible
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UMTS – FDD Frequency band evolution
– Release 99• I 1920 – 1980 MHz 2110 –2170 MHz UMTS only in Europe, Japan, India• II 1850 –1910 MHz 1930 –1990 MHz US PCS, GSM1900
– New in Release 5• III 1710-1785 MHz 1805-1880 MHz GSM1800
– New in Release 6• IV 1710-1755 MHz 2110-2155 MHz US 2.1 GHz band• V 824-849MHz 869-894MHz US cellular, GSM850• VI 830-840 MHz 875-885 MHz Japan
– New in Release 7• VII 2500-2570 MHz 2620-2690 MHz• VIII 880-915 MHz 925-960 MHz GSM900• IX 1749.9-1784.9 MHz 1844.9-1879.9 MHz Japan
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UMTS-2100 Uplink Downlink
1980 MHz1920 MHz 2110 MHz 2170 MHz
UMTS frequency allocations
Duplex Frequency : 2110-1920 = 190 MHz
Bandwidth :1980-1920 = 60 MHz
Carriers : 60 / 5 = 12
UL : 1959 MHz – 1979 MHz
DL : 2149 MHz – 2169 MHz
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Frequency channel numbering
UTRA Absolute Radio Frequency Channel Number (UARFCN)
UARFCN formula (3GPP 25.101 and 25.104):
UARFCN = 5 . f [MHz]Uplink/Downlink Center Uplink/Downlink
with
0.0 MHz <= fCenter Uplink/Downlink
UARFCN is integer:
0 <= UARFCN <= 16383
<=3276.6 [MHz]
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Center Frequency
Center Frequency fcenter
Consequence of UARFCN formula (see previous slide):
• fcenter must be set in steps of 0.2MHz (Channel Raster=200 kHz)
• fcenter must terminate with an even number (e.g 1927.4 not 1927.5)
fcenter values
Uplink (1920Mhz-1980MHz)
1922.4MHz <= fcenter <= 1977.6MHz
9612 <= UARFCN Uplink <= 9888
Downlink (2110Mhz-2170MHz)
2112.4MHz <= fcenter <= 2167.6MHz
10562 <= UARFCN Downlink <= 10838
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WCDMA – FDD technology
– Multiple access technology is wideband CDMA (WCDMA)• All cells at same carrier frequency• Spreading codes used to separate cells and users• Signal bandwidth 3.84 MHz
– Multiple carriers can be used to increase capacity• Inter-Frequency functionality to support mobility between
frequencies
– Compatibility with GSM technology• Inter-System functionality to support mobility between GSM and
UMTS
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UMTS & GSM Network Planning
GSM900/1800: 3G (WCDMA):
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Differences between WCDMA & GSM
WCDMA GSM
Carrier spacing 5 MHz 200 kHz
Frequency reuse factor 1 1–18
Power controlfrequency
1500 Hz 2 Hz or lower
Quality control Radio resourcemanagement algorithms
Network planning(frequency planning)
Frequency diversity 5 MHz bandwidth givesmultipath diversity with
Rake receiver
Frequency hopping
Packet data Load-based packetscheduling
Timeslot basedscheduling with GPRS
Downlink transmitdiversity
Supported forimproving downlink
capacity
Not supported by thestandard, but can be
applied
High bit rates
Services withDifferent quality
requirements
Efficient packet data
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Agenda
•WCDMA Air Interface
•WCDMA Principles & Spreading codes
•Channelization Code
•Scrambling Code
• Overview of Radio Resource Management (RRM)
•Capacity limitation and Cell breathing
•Rake receiver
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WCDMA Features
• Separate users through different codes
• Large bandwidth
• Continuous transmission and reception
• Code planning - Frequency reuse is 1
• No frequency planning
• Scrambling code planning
• 5 MHz carrier separation
• Fast Power Control
• Soft/Softer Handover
• Admission Control
• Congestion Controlfrequency
Code-Division Multiple Access
codeCDMA
3GPP : 3rd Generation Partnership Projecthttp://www.3gpp.org
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• Separates users through different codes
• Codes are used for two purposes:
• Differentiate channels/users
• Spreading the data over the entire bandwidth
f
Code
t
MS 1MS 2MS 3
5 MHz
• WCDMA (5 MHz)
• IS-95 (1.25 MHz)
• CDMA2000 (1.25, 3.75 MHz)
Spreading Principle
Direct Sequence Spreading - Code Division Multiple Access (DS-CDMA)
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Spreading Principle
Spreading code = Scrambling code + Channelization code
• Scrambling codes (Repeat period 10 ms=38400 chips)– Separates different mobiles (in uplink)
– Separates different cells (in downlink)
• Channelization codes– Separates different channels that are transmitted on the same scrambling code
– Orthogonal Variable Spreading Factor (OVSF) codes
– Period depends on data rate
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Spreading Code
Spread Signal
Data
Air Interface
Bits (In this drawing, 1 bit = 8 Chips SF=8)
Baseband Data
-1
+1
+1
+1
+1
+1
-1
-1
-1
-1
ChipChip
CDMA principle - Chips & Bits & Symbols
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Common Technical Terms
Bit, Symbol, Chip:
A bit is the input data which contain information
A symbol is the output of the convolution, encoder, and the block interleaving
A chip is the output of spreading
Processing Gain:
Processing gain is the ratio of chip rate to the bit rate.
Closely related to spreading factor, SF.
Forward direction/ Downlink : Information path from base station to mobile station
Reverse direction/ Uplink : Information path from mobile station to base station
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Block Diagram of WCDMA System
Source coding Channel
codingSpreading Modulation
Source
decoding
Channel
decodingDespreading Demodulation
Radio channel
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WCDMA System
Source Coding
Voice : Adaptive multirate technique with rate 4.75kbps – 12.2kbps
Channel Coding
CRC Attachment.
Check for error during transmission.
Voice : CRC check returns error, discard information
Data : CRC check returns error; ask for retransmission
Convolutional or Turbo Coding
Convolution coding for voice and low speed signaling
Turbo Coding for large data transmission. Better performance than convolutional coding
Interleaving
Distribute error over data transmitted
Rate Matching
Match symbol rate to that accepted by spreading
Rate matching technique : Repeat or puncturing
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Spreading Principle
User information bits are spread into a number of chips by multiplying them with a spreading code
The chip rate for the system is 3.84 Mchip/s and the signal is spread in 5 MHz
The Spreading Factor (SF) is the ratio between the chip rate and the symbol rate
The same code is used for de/spreading the information after it is sent over the air interface.
Information signal
Spreading signal
Transmission signal
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Spreading Technology
Spreading consists of 2 steps: Channelization operation: Transforms data symbols into chips. Thus
increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading Factor(SF).The operation is done through multiplication with OVSF code.
Scrambling operation is applied to the spreading signal.
Data bit
OVSF code
Scrambling code
Chips after spreading
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DL & UL Channelisation Codes
– Walsh-Hadamard codes: orthogonal variable spreading factor codes (OVSF codes)
• SF for the DL transmission in FDD mode = {4, 8, 16, 32, 64, 128, 256, 512}
• SF for the UL transmission in FDD mode = {4, 8, 16, 32, 64, 128, 256}
– Good orthogonality properties: cross correlation value for each code pair in the code set equals 0
• In theoretical environment users of one cell do not interfere each other in DL
• In practical multipath environment orthogonality is partly lost Interference between users of same cell
– Orthogonal codes are suited for channel separation, where synchronisation between different channels can be guaranteed
• Downlink channels under one cell
• Uplink channels from a single user
– Orthogonal codes have bad auto correlation properties and thus not suited in an asynchronous environment
• Scrambling code required to separate signals between cells in DL and users in UL
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Channelisation Code Tree
C0(0)=[1]
C2(1)=[1-1]
C2(0)=[11]
C4(0)=[1111]
C4(1)=[11-1-1]
C4(2)=[1-11-1]
C4(3)=[1-1-11]
C8(0)=[11111111]
C8(1)=[1111-1-1-1-1]
C8(2)=[11-1-111-1-1]
C8(3)=[11-1-1-1-111]
C8(0)=[1-11-11-11-1]
C8(5)=[1-11-1-11-11]
C8(6)=[1-1-111-1-11]
C8(7)=[1-1-11-111-1]
C16(0)=[............]
C16(1)=[............]
C16(15)=[...........]
C16(14)=[...........]
C16(13=[...........]
C16(12)=[...........]
C16(11)=[...........]
C16(10)=[...........]
C16(9)=[............]
C16(8)=[............]
C16(7)=[............]
C16(6)=[............]
C16(5)=[............]
C16(4)=[............]
C16(3)=[............]
C16(2)=[............]
SF=1 SF=2 SF=4 SF=8 SF=16 SF=256 SF=512...
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SF and Service Rate
Symbol Rate*SF=Chip Rate
In WCDMA system, if chip rate=3.84MHz, SF=4, then symbol rate=960Kbps.
Symbol Rate=(Service Rate + Checking Code)*Channel Coding Rate* Repeat or Puncture Rate
In WCDMA system, if service rate=384Kbps, channel coding=1/3 Turbo coding, then symbol rate=960Kbps;
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Correlation Function
Input Data +1 - 1 +1
-1 +1 –1 +1 +1 –1 +1 - 1 -1 +1 –1 +1 +1 –1 +1 - 1 -1 +1 –1 +1 +1 –1 +1 - 1
-1 +1 –1 +1 +1 –1 +1 - 1 +1 –1 +1 –1 –1 +1 –1 +1 -1 +1 –1 +1 +1 –1 +1 - 1
-1 +1 –1 +1 +1 –1 +1 - 1 +1 +1 +1 +1 +1 +1 +1 +1 -1 -1 +1 –1 +1 +1 –1 +1
+1 +1 +1 +1 +1 +1 +1 +1 +1 –1 +1 –1 –1 +1 –1 +1 +1 –1 –1 –1 +1 –1 –1 - 1
Channelization code
in Transmitter
Transmitted
Sequence
Channelization Code
used in Receiver
8 0 - 4
Integrate
Result
+1 0 - 0.5Divide by
Code Length
Correlation using channelization codes
(a) Same channelization code; (b) Different channelization codes ; (c) Same code with non zero time offset
x x x
Integrate Integrate Integrate
= = =
x x x
= = =
Transmitter
Receiver
Input Data +1 - 1 +1
-1 +1 –1 +1 +1 –1 +1 - 1 -1 +1 –1 +1 +1 –1 +1 - 1 -1 +1 –1 +1 +1 –1 +1 - 1
-1 +1 –1 +1 +1 –1 +1 - 1 +1 –1 +1 –1 –1 +1 –1 +1 -1 +1 –1 +1 +1 –1 +1 - 1
-1 +1 –1 +1 +1 –1 +1 - 1 +1 +1 +1 +1 +1 +1 +1 +1 -1 -1 +1 –1 +1 +1 –1 +1
+1 +1 +1 +1 +1 +1 +1 +1 +1 –1 +1 –1 –1 +1 –1 +1 +1 –1 –1 –1 +1 –1 –1 - 1
Channelization code
in Transmitter
Transmitted
Sequence
Channelization Code
used in Receiver
8 0 - 4
Integrate
Result
+1 0 - 0.5Divide by
Code Length
-
x x x
Integrate Integrate Integrate
= = =
x x x
= = =
Transmitter
Receiver
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Desp
read
ing
User
data
Spreading code
Chip
sequence
0 1
1 1 0 0 1 1 0 0
+1
0
-1
+1
0
-1
+1
0
-1
Spreading
1 1 0 0 1 1 0 0
+1
0
-1
+1
0
-1
+1
0
-1
Case 1
1 0 1 0 1 0 1 0
+1
0
-1
+1
0
-1
+1
0
-1
Case 2
Spreading Principle
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Spread Spectrum Gain
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Benefits of Spreading
MOD DEM DETF
MOD - modulation
DEM - demodulation
F - filtering
DET - detection
NBI - narrow-band interference
WBI - wide-band interference
384 kbps
1
1
f
P
Spreading code3.84 Mcps
2
Spreading factor
Processing gain
G =Rchip
Rbit
f
P
2
WBI
NBI3
f
P
WBI
NBI 3
4
P
f
4
5
f
P
5
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Frequency (Hz)
Voice user (R=12,2 kbit/s)
Packet data user (R=384 kbit/s)
Po
wer
den
sit
y (
W/H
z)
R
Frequency (Hz)
Gp=W/R=24.98dB
Po
wer
den
sit
y (
W/H
z)
R
Gp=W/R=10 dB
• Spreading sequences have a different length
• Processing gain depends on the user
data rate
Processing Gain Examples
R
WdBGp Processing gain:
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•The more processing gain the system has, the more the power of uncorrelated interfering signals is suppressed in the despreading process.
•Thus, processing gain can be seen as an improvement factor in the SIR (Signal to Interference Ratio) of the signal after despreading.
Example: Voice AMR 12.2 Kbps
Gp= 10*log(3840000/12200)= 25 dB.
•After despreading the signal power has to be typically few dB above the interference and noise: Eb/No = 5dB; therefore the required wideband signal-to-interference ratio is 5dB –Gp= -20 dB.
•In other words, the signal power can be 20 dB under the interference and the WCDMA receiver can still detect the signal.
Processing gain
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Energy Box
Duration (t = 1/Rb)
Originating Bit Received Bit
Energy per bit = Eb = const
• Higher spreading factor Wider frequency band Lower power spectral density
• BUT
• Same Energy per Bit
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Transmission Power
Frequency
5MHz
Power density
Time
High bit rate user
Low bit rate user
Correlation between: Capacity, Interference, Load & Power
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Channelization Codes
CC1, CC2CC3, CC4
CC5, CC6, CC7
CC1 , CC2, CC3CC1, CC2
CC1, CC2, CC3, CC4
In the Uplink, Channelization Codes are used to distinguish between data (and control) channels from the same UE
In the Downlink, Channelization Codes are used to distinguish between data (and control) channels coming from the same NodeB
Channelization Codes have different length depending on the bit rate
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After the Channelization Codes, the data stream is multiplied by a special code to distinguish between different transmitters.
Scrambling codes are not orthogonal so they do not need to be synchronized
The separation of scrambling codes is proportional to the code length – longer codes, better separation (but not 100%)
Scrambling codes are 38400 chips long
Scrambling Codes
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Scrambling Codes
SC3 SC4
SC5 SC6
SC1 SC1
Cell “1” transmits using SC1
SC2 SC2
Cell “2” transmits using SC2
In the Downlink, the Scrambling Codes are used to distinguish each cell (assigned by operator – SC planning)
In the Uplink, the Scrambling Codes are used to distinguish each UE (assigned by network)
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Scrambling Code planning example
SC 0
SC 16 SC 40
SC 32
SC 56
SC 24 SC 1
SC 17 SC 41
SC 33
SC 64
SC 8
SC 48
SC 9 SC 25
SC 57
SC 65
SC 49
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Spreading factor
Channel symbol
rate
(ksps)
Channel bit rate
(kbps)
DPDCH channel bit rate range
(kbps)
Maximum user data rate with ½-
rate coding
(approx.)
512 7.5 15 3–6 1–3 kbps
256 15 30 12–24 6–12 kbps
128 30 60 42–51 20–24 kbps
64 60 120 90 45 kbps
32 120 240 210 105 kbps
16 240 480 432 215 kbps
8 480 960 912 456 kbps
4 960 1920 1872 936 kbps
4, with 3 parallel codes
2880 5760 5616 2.3 Mbps
Half rate speech
Full rate speech
128 kbps
384 kbps
2 Mbps
Symbolphyb RR 2_SF
WRSymbol
(QPSK modulation)
Physical Layer Bit Rates (DL)
Modulation :
DL : QPSK, 16 QAM.
UL : BPSK
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DL & UL Scrambling Codes
DL Scrambling Codes
– Pseudo noise codes used for cell separation
• 512 Primary Scrambling Codes
UL Scrambling Codes
– Two different types of UL scrambling codes are generated
• Long scrambling codes of length of 38 400 chips = 10 ms radio frame
• Short scrambling codes of length of 256 chips are periodically repeated to get the scrambling code of the frame length
– Short codes enable advanced receiver structures in future
•512 DL Primary Scrambling Codes•16.7 million UL Scrambling Codes
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Basic W-CDMA Terminologies
Eb/No
C
I
N
C
CEb/No
W-CDMATDMA-GSM
Power spectrum
1
1
11
1
1
1
2
2
2
2
3
3
3
3
3
2
4
4
4
4
4
Eb/Io is the Bit Energy we obtain after despreading in the presence of the Noise generated by all other users and the Noise from NodeB equipment.
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Eb/No -> Eb = Energy per bit, No = Noise Spectral Density
[ Sensitivity of Base Station]
Uplink Eb/No = Minimum Signal/Noise to achieve any Service
BER (Bit Error Rate) = Function of Eb/No
SNR = C/I = Eb/No - Processing Gain
CS 12.2 CS 64 PS 64 PS 128 PS 384
Bit rate (kbps) 12.2 64 64 128 384
UL Eb/No (dB) 4.9 3 3.2 2.6 2.1
Spreading Factor 256
Processing gain (dB) 25 18 18 15 10
UL C/I (dB) -20 -15 -15 -12 -8
Basic W-CDMA Terminologies
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Interference level
Example: 2 UEs at the same distance from the BTS using 2 data rates
Eb/No
requiredS
F =
12
8
Service provided: Speech
Interference level
Eb/No
required
Service provided: Data 144
User 2 needs more power for the UL & DL for the same quality as
user 1
UE2UE1
Speech 8 kbps Data 144 kbpsThe higher the SF, the less power required
Node B
Received powerReceived power
Coverage Limits
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SF = 128
Speech 8 kbps Data 64 kbps Data 384 kbps
Node B
SF = 32
SF = 4
The coverage limits are determined by
the Uplink link Budget
Coverage Limits
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Channelisation code Scrambling code
Usage Uplink: Separation of physical data (DPDCH) and control channels (DPCCH) from same terminal
Downlink: Separation of downlink connections to different users within one cell
Uplink: Separation of mobile
Downlink: Separation of sectors (cells)
Length 4–256 chips (1.0–66.7 ms)
Downlink also 512 chips
Different bit rates by changing the length of the code
Uplink: (1) 10 ms = 38400 chips or (2) 66.7 ms = 256 chips
Option (2) can be used with advanced base station receivers
Downlink: 10 ms = 38400 chips
Number of codes
Number of codes under one scrambling code = spreading factor
Uplink: 16.8 million
Downlink: 512
Code family Orthogonal Variable Spreading Factor
Long 10 ms code: Gold code
Short code: Extended S(2) code family
Spreading Yes, increases transmission bandwidth
No, does not affect transmission bandwidth
Channelisation and Scrambling Codes
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Scrambling code
Channelization code 1
Channelization code 2
Channelization code 3
User 1 signal
User 2 signal
User 3 signal
Node B
Codes Multiplexing
1 - Downlink Transmission on a Cell Level
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NodeB
Channelization code
2 - Uplink Transmission on a Cell Level
Scrambling code 2
User 2 signal
Scrambling code 3
User 3 signal
Channelization code
Channelization code
Scrambling code 1
User 1 signal
Codes Multiplexing
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Channelization and Scrambling Codes
2 data channels(voice, control)
SC3 + CC1 + CC2
2 data channels(14 kbps data, control)
SC4 + CC1 + CC2
3 data channels(voice, video, control)
SC2 + CC1 + CC2 + CC3
3 data channels(voice, video, control)
SC5 + CC1 + CC2 + CC34 data channels
(384 kbps data, voice, video, control)SC6 + CC1 + CC2 + CC3 + CC4
4 data channels(384 kbps data, voice, video, control)
SC2 + CC4 + CC5 + CC6 + CC7
2 data channels(voice, control)
SC1 + CC1 + CC2
1 data channels(control)
SC1 + CC3
VoiceConversation Uplink
Packet Data
Videoconference
Videoconference with Data
Pilot, BroadcastSC1 + CCP + CCB
Pilot, BroadcastSC2 + CCP + CCB
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DL Spreading and Multiplexing in WCDMA
User 3
User 2
User 1
BCCH
Pilot X
CODE 1
X
CODE 2
X
CODE 3
X
CODE 4
X
CODE 5
+
X
SCRAMBLINGCODE
RF
SUM
User 2
User 1
BCCH
Pilot
Radio frame = 15 time slots
Time
User 3
3.84 MHzRF carrier
3.84 MHz bandwidth
CHANNELISATION codes:
P-CPICH
P-CCPCH
DPCH1
DPCH2
DPCH3
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Physical Layer Structure
Frame #0 Frame #1 Frame #i Frame #4095
System frame = 4096 frames = 40.96 seconds
Slot #0 Slot #1 Slot #j Slot #14
Frame = 15 slots = 10 ms = 38400 chips
Slot = 0.667 ms = 2560 chips
UMTS Frame Format
(38400*1000/10 = 3.84 Mcps)
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Parameters WCDMAChip rate 3.84 Mcps
Frame length 10 or 2 ms
Modulation
Downlink: QPSK; 16QAM
Uplink: BPSK
Bandwidth 5 MHz
Vocoder
Algebraic Code Excited
Linear Prediction Coder(ACELP)
Base synchronization Asynchronization
Power control rate 1500 Hz
Cell identification
Unique scrambling code (Gold code)
Channelization code
OVSF code
WCDMA Parameters
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Agenda
•WCDMA Air Interface
•WCDMA Principles & Spreading codes
• Overview of Radio Resource Management (RRM)
•Load control
•Admission Control
•Packet Scheduler
•Resource Manager
•Power Control
•Handover Control
•Capacity limitation and Cell breathing
•Rake receiver
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Radio Resource Management
– RRM is responsible for optimal utilisation of the radio resources:
• Transmission power and interference
• Logical codes
– The trade-off between capacity, coverage and quality is done all the time
• Minimum required quality for each user (nothing less and nothing more)Maximum number of users
– The radio resources are continuously monitored and optimised by several RRM functionalities
service quality
cell coverage cell capacity
Optimizationand Tailoring
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Handover
Control
Power Control
Resource
Manager
Admission
control
Load control
Packet data
scheduling
Congestion Control
Radio Resource Management
RADIO RESOURCE UTILIZATION
To adjust the transmit powers in upilnk and downlink to the minimum level required to enshure the demanded QoS
Takes care that a connected user is handed over from one cell to another as he moves through the coverage area of a mobile network.
To ensure that the network stays within the planned condition
Let users set up or reconfigure a radio access bearer(RAB) only if these would not overload the system and if the necessary resources are available.
Takes care that a system temporarily going into overload is returned to a non-overloaded situation.
To handle all non-realtime traffic,allocate optimum bit rates and schedule transmission of the packet data, keeping the required QoS in terms of throughput and delays.
To control the physical and logical radio resources under one RNC;to coordinate the usage of the available hardware resouces and to manage the code tree.
Basic RRM functions
* Power Control
* Handover Control
* Congestion Control
* Resource Management
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RRM Functionalities
LC Load Control
AC Admission Control
PS Packet Scheduler
RM Resource Manager
PC Power Control
HC HO Control
PC
HCFor each connection/user
LC
AC
For each cell
PS
RM
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– LC performs the function of load control in association with AC & PS
– LC updates load status using measurements & estimations provided by AC and PS
– Continuously feeds cell load information to PS and AC;
• Interference levels (UL)
• BTS power level (DL)
LC
AC
PSNRT load
Load change info
Load status
Load Control (LC)
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Load Control – Load Status
– Load thresholds set by radio network planning parameters
Overloadthreshold x
Load Targetthreshold y
Po
wer
Time
Load Margin
Overload
Normal load
Measured loadFree capacity
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– Checks that admitting a new user will not sacrifice planned coverage or quality of existing connections
– Admission control handles three main tasks
• Admission decision of new connections
– Take into account current load conditions (from LC) and load increase by the new connection
– Real-time higher priority than non-real time
– In overload conditions new connections may be rejected
• Connection QoS definition
– Bit rate, BER target etc.
• Connection specific power allocation (Initial, maximum and minimum power)
Admission Control (AC)
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Packet Scheduler (PS)
– PS allocates available capacity after real-time (RT) connections to non-real time (NRT) connections
• Each cell separately
• Based on QoS priority level of the connection
• In overload conditions bit rates of NRT connections decreased
– PS selects allocated channel type (common, dedicated or HSPA)
– PS relies on up-to-date information from AC and LC
– Capacity allocated on a needs basis using ‘best effort’ approach
• RT higher priority
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Resource Manager (RM)
– Responsible for managing the logical radio resources of the RNC in co-operation with AC and PS
– On request for resources, from either AC(RT) or PS(NRT), RM allocates:
• DL spreading code
• UL scrambling code
Code Type Uplink Downlink
Scrambling codes
Spreading codes
User separation Cell separation
Data & control channels from same UE Users within one cell
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Agenda
•WCDMA Air Interface
•WCDMA Principles & Spreading codes
•Overview of Radio Resource Management (RRM)
•Load control
•Admission Control
•Packet Scheduler
•Resource Manager
•Power Control
•Handover Control
•Capacity limitation and Cell breathing
•Rake receiver
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Power Control
• Concept : Power is a common resource in WCDMA
• Goal : Ensure sufficient received energy per information bit for all communication links
• Strategy : Power control on COMMON CHANNELS ensures there is sufficient coverage to establish connections and transfer date on common transport channels
Power control on DEDICATED CHANNELS (DCH) ensures sufficient connection quality while minimizing impact on other connections.
• Power Control or Rate Control
– Power control strategy (R99): adjust transmitted power while keeping the data rate constant
– Rate control strategy (HSDPA): adjust the data rate while keeping the transmitted power constant
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UE 1
UE 2
Before despreading After despreading
Near-Far-Problem
– Up to around 80 dB attenuation between UE1 and UE2
– If UE1 and UE2 transmitted with the same power, UE1 would jam UE2 :
so-called “near-far” effect
– Solution : power control
– Need for an efficient power control able to fight against slow AND fast fading!
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Power Control Types
• Open loop power Control
– Initial power setting
• Outer Loop (RNC)
– Adjust quality target dependent on performance
• Inner Loop (fast power control-NodeB)
– compensates for fading channels
– needs dedicated control channel for power control commands
Without power control
PTX
tfading
channel
t
PRX
fading
channel
t
PTX
t
PRX
With power control
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UL Outer LoopPower Control
Open Loop Power Control (Initial Access)
Closed Loop Power Control
RNCNode B
UE
DL Outer LoopPower Control
Power Control types
BLER target
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Open Loop Power Control
• Controlled by UE.
• Determine UE initial transmission power for random access procedure.
• Not in use when inner loop power control running.
• UE obtain information from network on:
• CPICH power
• Uplink interference level
• Constant value (Default = 2dB)
UE Initial Power = CPICH power – CPICH_RSCP + UL interference + Constant
System information :
CPICH power, UL interference & constant
PRACH Tx power
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Power Ramping on PRACH
PRACH
AICH
Preamble Sequence
1st transmitted
preamble
Increase power
until heard
Once preamble is heard,
increase power for
message Message
(Control Part)
Preamble heard
and Acquisition
Indicator sent
UL
DL
powerOffsetP0
powerOffsetP0
powerOffsetPpm
Open Loop Power Control
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Inner Closed Loop Power Control
Power Control Bit• Located in UE & NodeB
• Controls power of dedicated physical channels
• Power controls occurs at 1500Hz, thus known as
fast power control
• NodeB and UE continuously measure and compare
SIRmeasured with SIRthreshold value, and inform each
other to increase /reduce its power accordingly.
UE1 UE2 UE3 UE4
With Optimum Power Control
UE1
UE2
UE3
UE4
Without Power Control
Receiv
ed
po
wer
at
No
deB
Receiv
ed
po
wer
at
No
deB
(SIR)measured
NodeB
UE2
UE3
UE1
UE4
SIR threshold
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Outer Closed Loop Power Control
• Adjust SIR for every user
• Needed to keep track of changes in radio environment
• Aims to provide required quality
• If SIRthreshold reaches its maximum, system has to perform
- inter-frequency/inter-system handover
- RRC connection release
BER/BLER Value
Change in (SIR)threshold
RNCSIR threshold
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Power Control
• TX Power is adjusted regularly so that each connection is received with the required Eb/No of its service– Uplink: Avoid ”Near-Far-Problem“ – Downlink: Power share allocation
• Policy: “No one gets a higher quality (Eb/No) than he needs. Everyone gets exactly the required quality or is not served at all“– no unnecessary increase of interference for other mobiles– no waste of common power resource in the downlink
PC Gain:Lower Eb/No
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Importance of Power Control
– Minimizes the Interference and there by enhances capacity and quality.
– It helps allowing as many users as possible while keeping the interference as
minimum as possible
– It maintains the quality of all radio connections by controlling the transmit power in
both the links.
– Power Control aims at using the minimum required SIR for the quality of connection
to remain sufficient. No excessive quality.
– Power Control on common channels ensures that their coverage is sufficient for call
setup
– It provides protection against slow fading and fast fading.
– Efficient power control avoids the near-far problem.
– Power control works efficiently during transmission gap in compressed mode by
bring the SIR back close to the target SIR.
– It helps reducing the battery consumption
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Agenda
•WCDMA Air Interface
•WCDMA Principles & Spreading codes
•Overview of Radio Resource Management (RRM)
•Load control
•Admission Control
•Packet Scheduler
•Resource Manager
•Power Control
•Handover Control
•Capacity limitation and Cell breathing
•Rake receiver
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Handover Control (HC)
– HC is responsible for:
• Managing the mobility aspects of an RRC connection as UE moves around the network coverage area
• Maintaining high capacity by ensuring UE is always served by strongest cell
– Soft handover
• MS handover between different base stations
– Softer handover
• MS handover within one base station but between different sectors
– Hard handover
• MS handover between different frequencies or between WCDMA and GSM
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Soft/Softer Handover
Soft/softer handover is important for efficient power control. Without soft/softer handover there would be near-far scenarios of a UE penetrating from one cell deeply into an adjacent cell without being power controlled by the latter.
Soft Handover: UE connected to two or more NodeBs at the same time.
Softer Handover: UE connected to two or more sector of the same NodeB.
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Macro-Diversity
Softer HandOver
Node B(BTS)
RNC
Data UL
Data UL1Data UL2 Data UL
Data UL
Data DLData DL
Data DL1
Data DL1Data DL2
Data DL
UE
Data DL2
Data UL
CoreNetwork
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Macro-Diversity
Soft HandOver Intra RNC
RNC
Data UL1
Data UL1Data UL2
Data UL
Data UL
Data DL
Data DL1
Data DL1
Data DL1Data DL2
Data DL
UE
CoreNetwork
Data DL2
Data UL
Data DL2
Data UL2
Data UL2
Data UL1
Node B(BTS)
Node B(BTS)
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• Soft Hand Over Inter RNC: Serving RNC (SRNC) and Drift RNC (DRNC)
Node B(BTS)
SRNC
DRNCNode B(BTS)
Data UL
Data UL
Data ULData UL1
Data UL2
Data UL2
Data UL1Data UL2 Data UL
Data UL
Data DLData DL2
Data DL2
Data DL1
Data DL2
Data DL1
Data DL1Data DL2 Data DL
UE
CoreNetwork
Soft HandOver Inter RNC
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Hard Handover
• Hard handovers are typically performed between WCDMA frequencies and between WCDMA and GSM cells
GSM/GPRSGSM/GPRS
f1
f2
f1
f2f2f2
Inter-System Handovers (ISHO)
Inter-Frequency Handovers (IFHO)
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In UL selection of the best signal on a frame basis at RNC level -
‘selection diversity’
In DL Maximum Ratio combining due to RAKE receiver at UE
For UL & DL good decorrelation due to different locations of Node Bs
many multipaths
In UL Maximum. Ratio Combining at Node B
In DL Maximum Ratio combining due to RAKE receiver at UE
For UL & DL less decorrelation due to “same” location of sectors less multipaths
Soft HO
Softer HO
Soft/Softer Handover
RNC
RNC
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Soft/Softer Handover Power Control
Uplink Power is based on information (TPC bits) from both NodeBs to which the UE is connected. The UE will decrease its output power in all cases except when both NodeBs send increase power commands.
Downlink Power control for both NodeBs is based on one signal (TPC bits) from the UE (it does not distinguish between NodeBs and the decision is base on the combined output from the RAKE receiver
UL Power control DL Power control
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Agenda
•WCDMA Air Interface
•WCDMA Principles & Spreading codes
•Overview of Radio Resource Management (RRM)
•Capacity limitation and Cell breathing
•Rake receiver
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Few Basics….
COVERAGE
CAPACITY QUALITY
POWER
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Understanding Power Control…
LOWER Power Per User – HIGHER Number of Users
HIGHER Power Per User – LOWER
Number of Users
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Interference…
No or Improper Power Control leads to High interference that impacts Coverage, Capacity and Quality
Power Ctrl
ON
OFF
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UL/DL Capacity Limitation
• Scenario 1: Capacity limitation due to UL interference
– The cell can’t serve UE1 because the increase in UL interference by adding the new user would be too high, resulting in a high risk of drops
• Scenario 2: Capacity limitation due to DL power
– The cell can’t serve UE2 because it’s using all its available power to maintain the connections to the other UEs
UE1
UE2
Scenario 1 Scenario 2
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Node B Node B
Fully loaded system
Unloaded system
Cell Breathing
The more traffic, the more interference and the shorter the distance must be between the Node B and the UE.
The traffic load changes in the system causes the cells to grow and shrink with time
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Agenda
•WCDMA Air Interface
•WCDMA Principles & Spreading codes
•Overview of Radio Resource Management (RRM)
•Capacity limitation and Cell breathing
•Rake receiver
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Multipath Propagation
2t
Time Dispersion
t1t
0t
2t
3t
Maximum ratio combining
1t
0t
3t
Multiple paths possibly cause destructive interference between different replica of the desired signal
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The Rake Receiver
• Each multi-path component is called a “finger”
• Estimation of radio channel properties for each finger:
– delay
– amplitude and
– Phase
• The Rake receiver combines multi-path components by coherent combining of multi-path components belonging to the respective user.
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Maximum ratio combining – RAKE
Each finger tracks a different multipath component and other cells during Soft Handover
A maximum ratio combining produces the output
Search Finger is used to determine when to perform handovers
C
O
M
B
I
N
E
R
Power measurements of neighbouring NodeBs
Sum of individual multipath components
Finger #1
Finger #2
Finger #3
Finger #N
Buffer/delay
CorrelatorsChannel
Searcher Finger
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TX
D(t)
Delay t0
Delay t1
C(t-t0)
+C(t-t1)
Delay (t1)
RX
C(t-tn)
Delay (t0)
Delay (tn)RX
RX
C(t)
t0
t1
tn
Take advantage of multipath diversity
BTS
Taking advantage of Multipath: Rake Receiver
UE
Spreading &
Scrambling
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