te-440 universal mobile telecommunication system (umts)marcp
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Universal Mobile
Telecommunication System
1TE 440 Next Generation Wireless Networks
College of Engineering
PAF – Karachi Institute of Economics and Technology
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TE 440 Next Generation Wireless Networks 2
UMTS
“UMTS will be a mobile communications system that can offer significant user
benefits including high-quality wireless multimedia services to a convergent
network of fixed, cellular and satellite components.
It will deliver information directly to users and provide them with access to new
and innovative services and applications.
It will offer mobile personalized communications to the mass market regardless of
location, network and terminalused”
.
UMTS Forum 1997
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TE 440 Next Generation Wireless Networks 3
Second Generation Third Generation
GSM - 900
GSM -1800
DECT
TETRA
HIPERLAN
Satellite
UMTS
MBS
WLL
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TE 440 Next Generation Wireless Networks 4
UMTS Main Requirements (3 Ms)
• Multi-media
• Multi-environment
• Multi-operator Virtual operators
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TE 440 Next Generation Wireless Networks 5
Mobile Multimedia Services
VideoConference
(High quality)
VideoConference
(Low quality)
Telephone
Conference
Telephone
VoiceMail
Electronic
Mail FAX
Electronic
Publishing
Electronic
Newspaper
ISDNKaraoke
VideoCatalogshopping
Database AccessRemote medical
service(Medical image) Video on
demand-Sports-News-Movies
Mobile TV
MobileRadio
Image
Data
Voice
Multicast
Multi Point
AsymmetricSymmetric
Point to Point
Broadcast
2M
384K
64K
32K
16K
9.6K
2.4K
1.2K
News
Weatherforecast
Trafficinformation
Sportsinformation
LeisureInformation
Mobile Multimedia
WWW
ftp
IP
telephony
etc
Information
Distribution
Services
Internet
Access
pager
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TE 440 Next Generation Wireless Networks 6
Different Environments for UMTS
Global
Suburban
Macro-Cell
Urban
Micro-CellIn- Building
Pico-Cell
Home-Cell
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UMTS Bearer Services
The UMTS radio access network and fixed network are expectedto provide four classes of bearer services:
• Class A - Circuit-switched bit pipe
• Class B - Circuit-switched bit pipe for variable bit rate
• Class C - Connection-oriented packet switched bearer
service
• Class D - Connectionless packet-switched bearer service
7TE 440 Next Generation Wireless Networks
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On the Air Interface
• Class A – LDD Low Delay Data (real time)
• Class B - LDD-VBR Low Delay Data – Variable Bit
Rate (real time)
• Class C – LCD Long Constrained Delay (50 ms)
• Class D – UDD Unconstrained Delay Data (300ms)
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TE 440 Next Generation Wireless Networks 9
First Phase of UMTS
• Europe has decided to adopt an evolutionary approach for theUMTS core network based on migration from the GSM/GPRSinfrastructure.
• For the actual air interface, a revolutionary approach has beenchosen. That is a new radio air interface for UMTS TerrestrialRadio Access (UTRA).
• There is another parallel activity concerning the UMTS airinterface using an evolutionary approach (an intermediateapproach).
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TE 440 Next Generation Wireless Networks 10
The Two Approaches
NewRadio
Access (UTRAN)
NSS
And
GSN’s
PSTNN-ISDNB-ISDN
IP-basedNetworks
Radio AccessGSM Infrastructure Public Network
Dual-mode
Dual-mode
EvolvedGSM
Radio Access
(GERAN)
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TE 440 Next Generation Wireless Networks 11
Evolutionary approach for the GSM
Air Interface
In this approach the GSM air interface has evolved within GSM phase 2+ to
support higher rate data services. The most important developments in this
approach are:
1. General Packet Radio Services (GPRS )
2. High Speed Circuit Switched Data (HSCSD )
3. Enhanced Data Rates for GSM Evolution (EDGE )
It is referred to GSM/EDGE Radio Access Network (GERAN)
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TE 440 Next Generation Wireless Networks 12
UMTS Terrestrial Radio Access(UTRA)
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TE 440 Next Generation Wireless Networks 13
ETSI SMG2 has selected the wideband CDMA concept for the
paired band (FDD mode) and the TD/CDMA concept for the
unpaired band (TDD mode) for UTRA.
Introduction
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TE 440 Next Generation Wireless Networks 14
Frequency allocation in Europe
1880 1900 1980 2010 2025 2110 2170 2200
DECT UMTSMSS MSS
FDDFDD TDDTDD
UMTSUMTS
1920
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TE 440 Next Generation Wireless Networks 15
Wideband CDMA Specifications
Multiple access DS-CDMA
Transmission mode FDD
Chip rate 3.84 Mchips/s
Carrier spacing 5 MHz
Frame size 10 ms
Spreading technique Variable-spreading factor+multi-code
Channel Coding 1/2-1/3 rate convolutional coding and
Turbo CodingModulation QPSK with roll-off factor a= 0.22
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Main Parameters [1]
• WCDMA is a wideband Direct-Sequence Code Division
Multiple Access (DS-CDMA) system
• user information bits are spread over a wide bandwidth by
multiplying the user data with quasi-random bits (called chips)
• to support very high bit rates (up to 2 Mbps), the use of a
variable spreading factor and multi-code connections is
supported
• The chip rate of 3.84 Mcps leads to a carrier bandwidth of
approximately 5 MHz
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Allocation of bandwidth in WCDMA in the time-
frequency-code space
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Main Parameters [2]
• wide carrier bandwidth
• high user data rates
• multiple 5 MHz carriers to increase capacity
• highly variable user data rates
• data capacity can change from frame to frame• Frequency Division Duplex (FDD)
• Time Division Duplex (TDD)
• asynchronous base stations
•
coherent detection on uplink and downlink using common pilot• Multiuser detection and smart adaptive antennas
• deployed in conjunction with GSM
• handovers between GSM and WCDMA are supported
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Spreading and Despreading [1]
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Spreading and Despreading [2]
TE 440 Next Generation Wireless Networks 20
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TE 440 Next Generation Wireless Networks 21
Spreading and Despreading [3]
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Definition of Channels
Logical Channel – Type of information to be transmitted e.g., traffic or controllogical channels.
Transport Channel – How and with what format data is transmitted through
physical links.
Physical Channel – Unit of radio resource of a radio system e.g., frequency
band, time slot, code, etc.
RF Channel – Fixed frequency band of a radio system.
The MAC sublayer is responsible for mapping logical channels onto transport
channels.
The physical layer is responsible for mapping transport channels onto physical
channels.
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Transport Channels [1]
Common Channels (CCHs) Dedicated Channel (DCH)(Uplink/Downlink)
Common PacketChannel(CPCH)(Uplink)
Broadcast
Channel (BCH)
(Downlink)
Forward-Access
Channel (FACH)
(Downlink)
Paging
Channel (PCH)
(Downlink)
Random-Access
Channel (RACH)
(Uplink)
Downlink SharedChannel(DSCH)(Downlink)
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Transport Channels [2]
Dedicated Transport Channel
1. DCH – Dedicated Channel
• Downlink/uplink Transport channel
• A point-to-point channel allocated to a specific user
• Carries information intended for the given user including data and higher
layer control information
• Characterised by features such as
–
fast power control – fast data rate change on a frame-by-frame basis
– possibility of transmission to a certain part of the cell
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Transport Channels [3]
Common Transport Channels
1. BCH – Broadcast Channel
• It is a downlink channel
• System and cell-specific information over the entire cell
• The terminal cannot register to the cell without the possibility of decoding
the broadcast channel
– transmit with relatively high power
–
low and fixed data rate
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Transport Channels [4]
2. FACH – Forward Access Channel
• It is a downlink channel
• Used to carry control information to a mobile station when the system
knows the location cell of the mobile station
•May also carry short user packets
3. PCH - Paging Channel
• It is a downlink channel
• Used to carry control information to a mobile station when the system
does not know the location cell of the mobile station
• It is used to inform the mobile station of incoming calls
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Transport Channels [5]
4. RACH –
Random Access Channel• It is an uplink channel
• Used to carry control information
• It is used for initiating a call (initial access to the serving BS)
• It may also carry short user packets
• must be heard from the whole desired cell coverage area
5. CPCH – Common Packet Channel
• It is a uplink channel used to carry infrequent medium sized packets
•the main differences to the RACH are: – the use of fast power control
– a physical layer-based collision detection mechanism
– a CPCH status monitoring procedure
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Transport Channels [6]
6. DSCH – Downlink Shared Channel
• Used to carry infrequent medium and large sized packets
• It can be shared in time between several users
• It is always associated with a downlink DCH
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Uplink Physical channels
Common Physical ChannelsDedicated Physical Channels
Dedicated Physical Data Channels(Uplink DPDCH)
Dedicated Physical Control Channel
(Uplink DPCCH)) Physical Random Access Channel(PRACH)
Physical Common Packet Channel(PCPCH)
Physical Channels
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Uplink Physical Channels
Dedicated Uplink Physical Channel
1. DPDCH - Dedicated Physical Data Channel
• Used to carry dedicated data i.e. the dedicated transport channel (DCH)
• There may be zero, one, or several uplink DPDCHs
2. DPCCH – Dedicated Physical Control Channel
• Used to carry control information consists of:
– pilot bits to support channel estimation
– transmit power-control (TPC) commands
– feedback information (FBI)
– an optional transport-format combination indicator (TFCI)
• One DPCCH and up to six parallel DPDCHs can be transmittedsimultaneously
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Uplink Scrambling Codes
• a complex-valued scrambling code.
• The long scrambling codes are from a set of Gold sequences of 38400
chips. There are 224 long uplink scrambling codes.
• The short scrambling codes are derived from a sequence of the family of
periodically extended S(2) codes. There are 224 short uplink scrambling
codes.
• assigned by higher layers.
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Common Uplink Physical Channel
1. PRACH - Physical Random Access Channel
• It is used to carry RACH
• Slotted ALOHA approach with fast acquisition indication
• A UE can start the transmission at a number of well-defined time-slotscalled access slots
• Consist of one or several preambles of length 4096 chips and a message
of length 10 or 20 ms
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TE 440 Next Generation Wireless Networks 33
#0 #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14
5120 chips
radio frame: 10 ms radio frame: 10 ms
Access slot #0 Random Access Transmission
Access slot #1
Access slot #7
Access slot #14
Random Access Transmission
Random Access Transmission
Random Access TransmissionAccess slot #8
RACH access slot numbers and their spacing
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2. PCPCH –
Physical Common Packet Channel
• Carries CPCH
• Its transmission is based on CSMA-CD approach with fast acquisition
indication
•
Access slot and timing structure is same as for RACH• In addition to Access Preamble it also has one Collision Detection
Preamble (CD-P)
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Downlink Physical Channels
Dedicated Downlink Physical Channels
1. DPCH - Dedicated Physical Channel
• Time multiplexed
• spreading factor SF:
SF = 512/2k
• In the downlink the spreading factors range from 4 to 512, with some
restrictions on the use of spreading factor 512 in the case of soft handover.
• The downlink DPDCH consists of QPSK symbols. Each symbol consists
of two bits while in the case of uplink the DPDCH consists of BPSK
symbol (one symbol corresponds to one bit).
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Common Downlink Physical Channels
1. CPICH - Common Pilot Channel
• Fixed rate carries a pre-defined bit/symbol sequence
• Channel estimation
• Two types of CPICH
– Primary Common Pilot Channel
– Secondary Common Pilot Channel
TE 440 Next Generation Wireless Networks 36
Pre-defined symbol sequence
Slot #0 Slot #1 Slot #i Slot #14
Tslot = 2560 chips , 20 bits = 10 symbols
1 radio frame: Tf = 10 ms
Frame structure for Common Pilot Channel
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1.1 Primary CPICH
• Same channelization code always used
• Scrambled using primary scrambling code
• One per cell
•Broadcast over entire cell
1.2 Secondary CPICH
• Uses either primary or secondary scrambling code
• Zero, one or several per cell
• May be transmitted over a part of cell
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3. S-CCPCH - Secondary Common Control Physical Channel
• carry FACH and PCH
• SF = 256/2K
• FACH and PCH can be mapped to same secondary CCPCH
• Primary CCPCH has fixed pre-defined rate while secondary CCPCH has
variable rate
• Primary CCPCH is continuously transmitted over entire cell while
secondary CCPCH is only transmitted only when there is data available
4. SCH – Synchronisation Channel
• Used for cell search
• Consist of two sub channels
– Primary SCH
– Secondary SCH
• Primary SCH consist of a modulated code of length 256 chips
• Secondary SCH consists of repeatedly transmitting a length 15 sequence
of modulated codes of length 256 chipsTE 440 Next Generation Wireless Networks 38
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5. PDSCH – Physical Downlink Shared Channel
• Carry DSCH
• Shared by users based on code multiplexing
• As DSCH is always associated with DCH, PDSCH is always associated
with DPCH
• Spreading factor may vary frame-to-frame
•Control information is transmitted on the DPCCH part of the associatedDPCH
• SF = 256 to 4
6. AICH – Acquisition Indicator Channel
• Used to carry Acquisition Indicators (AI)
• Either corresponds to an access preamble or a CD preamble
• Access preamble is an AP-AICH and CD preamble is a CD-AICH
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7. PICH – Page Indicator Channel
• Used to carry Page Indicator (PI)
• PICH is always associated with a S-CCPCH to which PCH is mapped
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TE 440 Next Generation Wireless Networks 41
BCH FACH PCH RACH DCH DSCH
P-CCPCH
S-CCPCH
PRACH
Transport
channels CPCH
Physical
channels AICH
PICH
PDSCH
SCH
DPCCH
DPDCH
PCPCHCPICH
Mapping of Transport Channels
onto Physical Channels
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Initial Cell Search
The initial Cell Search is carried out in three steps:
Step 1: Slot synchronisation - using the primary synchronisation channel.
Step 2: Frame synchronisation and code-group identification using thesecondary synchronisation channel.
Step 3: Scrambling-code identification-identified through symbol-by-symbol
correlation over the primary CCPCH with all the scrambling codes within the
code group.
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Handovers [1]
1. Intra-frequency HO
2. Inter-frequency HO
3. Inter System HO
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Handovers [2]
1. Intra-frequency HO
1.1 Softer Handover
• Between two adjacent sectors of a base station
• Communication take place concurrently via two air interface
channels, one for each sector separately.
•The two signals combined at BS
• Only one power control loop per connection
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TE 440 Next Generation Wireless Networks 45
Handovers [3]
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Handovers [4]
1.2 Soft Handover
• Between cell coverage area of two different base stations
• The main difference between softer and soft HO is in the uplink direction
• Data at different BS from the MS is combined at RNC
• Frame reliability indicator is used to select the best frame
• Two power control loops per connection are active, one per BS
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TE 440 Next Generation Wireless Networks 47
Handovers [5]
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TE 440 Next Generation Wireless Networks 48
Backward Soft Handover Procedure Example
Target NB RNC MS Serving NB DCCH
Measurement report Measurement reports
Add
Phase
MS monitors the pilots level from neighbouringNBs and compares them to a set of thresholds and
reports them MS acquires the Target
NB and adds it to its active list
1
2
DTCH
DCCH DCCH
DCCH DCCH
Handover "add" request Handover "add" request
Handover "add" completion
Handover "add" request Handover "add" completion
Handover "add" request
DTCH
Handover "add" completion Handover "add" completion
Drop Phase
MS monitors the pilot levels of the serving NBs and compares it with a
Threshold and reports them
1
MS removes one of the
serving NBs, from its active list 2 Handover "drop" completion Handover "drop" completion
DCCH Measurement report Measurement report
Handover "drop" request DCCH
Handover "drop" request Handover "drop" request Handover "drop" request DCCH
Handover "drop" completion Handover "drop" completion
DCCH DCCH
DCCH DCCH
Handover "add" completion
DCCH Measurement report Measurement report
Traffic
Traffic Softhandoverphase
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Handovers [7]
2. Inter-frequency HO
• Hard handover
• The handover between two base stations operating at two different
frequencies
•
e.g. HO between two different UMTS operators
3. Inter System HO
• Hard handover
• take place between the WCDMA FDD system and another system
• e.g. such as HO between UMTS to GSM
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UMTS Architecture [1]
TE 440 Next Generation Wireless Networks 50
CN
UTRAN
UE
Uu
Iu
UTRAN UMTS Terrestrial Radio Access Network CN Core Network UE User Equipment
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UMTS Architecture [2]
TE 440 Next Generation Wireless Networks 51
UTRAN Architecture
RNS
RNC
Node B Node B
Iub Iub
Core Network
RNS
RNC
Node B Node B
Iub Iub
Iu Iu
Iur
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UMTS Architecture [3]
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Network Nodes
1. User Equipment
• Consist of ME and USIM
• The Mobile Equipment (ME) is the radio terminal used for radio
communication over the Uu interface• The UMTS Subscriber Identity Module (USIM) is a smartcard that holds:
– the subscriber identity,
– performs authentication algorithms,
– stores authentication and encryption keys
– subscription information that is needed at the terminal
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Core Network [1]
1. Home Location Register –
HLR
• is a database located in the user‟s home system that stores the master copy
of the user‟s service profile
• It is created when a new user subscribes to the system, and remains stored
as long as the subscription is active
2. Mobile Switching Centre/Visitor Location Register – MSC/VLR
• It is the switch (MSC) and database (VLR) that serves the UE in its current
location for Circuit Switched (CS) services
• MSC switches the CS transactions• VLR holds a copy of the visiting user‟s service profile and more precise
information on the UE‟s location within the serving system
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Core Network [2]
3. Gateway MSC –
GMSC
• It is the switch at the point where UMTS PLMN is connected to external
CS networks
• All incoming and outgoing CS connections go through GMSC
4. Serving GPRS Support Node – SGSN
• Its functionality is similar to that of MSC/VLR but is typically used for
Packet Switched (PS) services
5. Gateway GSN –
GGSN
• functionality is close to that of GMSC but is in relation to PS services
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Interfaces
1. Cu interface
• This is the electrical interface between the USIM smartcard and the ME.
• The interface follows a standard format for smartcards.
2. Uu interface• It is the WCDMA radio interface
• The UE accesses the fixed part of the system through this interface
3. Iu interface
• It connects UTRAN to the CN
• the open Iu interface gives UMTS operators the possibility of acquiring
UTRAN and CN from different manufacturers
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4. Iur interface
• The open Iur interface allows soft handover between RNCs
5. Iub interface
•It connects a Node B and an RNC
• UMTS is the first commercial mobile telephony system where the
Controller – Base Station interface is standardised as a fully open interface
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Radio Access Network [1]
1. Radio Network Controller
• It is responsible for control of the radio resources in its area
• One RNC can control multiple Node Bs
• Its functionality is equivalent to BSC in GSM/GPRS
•RNCs are more intelligent than BSCs
• RNCs can autonomously handles handovers without involving MSCs and
SGSNs
• RNCs are interconnected using the Iur Interface
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Radio Access Network [2]
2. Node B
• It is responsible for air interface L1 processing
• Also performs some RRM function such as inner loop power control
• It is equivalent to BTS in GSM/GPRS
•Node Bs are typically collocated with GSM BTSs
• The enigmatic term „Node B‟ was initially adopted as a temporary term
during the standardization process, but then never changed
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General Protocol Model for UTRAN
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RadioNetworkLayer
TransportNetworkLayer
Control Plane
ApplicationProtocol
User Plane
DataStream(s)
SignallingBearer(s)
SignallingBearer(s)
Data
Bearer(s)
ALCAP(s)
Transport NetworkUser Plane
Transport NetworkUser Plane
Transport NetworkControl Plane
Physical Layer
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