UMTS Network Architecture OSI Communication model UMTS Protocol stack Circuit switched-control plane/user plane Packet switched-control plane/user plane Generic protocol model for UTRAN interfaces Iu-CS interface protocol structure Iu-PS interface protocol structure Iurinterface protocol structure Iubinterface protocol structure

1. Radio and Core Network
Protocols in UMTS
Presented by:
Naveen Jakhar, ITS

2. Topics:
UMTS Network Architecture
OSI Communication model
UMTS Protocol stack
Circuit switched-control plane/user plane
Packet switched-control plane/user plane
Generic protocol model for UTRAN interfaces
Iu-CS interface protocol structure
Iu-PS interface protocol structure
Iur interface protocol structure
Iub interface protocol structure
Summary
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3. UMTS Network Architecture
3

4. OSI Communication model
• Each layer communicates only with two
adjacent layers and its peer on the other side
• Each layer receives services from the layer
below and provides services to the layer
above
Page 4
• Intermediate communication nodes
require layers 1 through 3
• Internal operation within each layer is
independent of the internal operation
in any other layer
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical LayerPhysical Layer
Data Link Layer
Network Layer
Physical Medium Physical Medium
Node A Node B Node C
Peer to peer protocols
• WCDMA interfaces
described using OSI model
• OSI = Open System
Interconnect
• Developed by ISO as a
general model for computer
communication
• Used as a framework for
development and
presentation of most
contemporary
communication standards
Note: WCDMA covers Layers 1-3 of OSI Model

5. 5
UMTS Protocol stack
• First three layers of the
protocol stack are part of
UTRAN
Note: SMS exists on
both circuit switched
and packet switched
side

6. NAS or the Non Access Stratum is a set of protocols in the
UMTS that is used to convey non-radio signalling between the User
Equipment (UE) and the core network.
From a protocol stack perspective, the NAS is the highest stratum of
the control plane
The NAS procedures consist of MM, CC, GMM, SM
Access Stratum signalling is between UTRAN and the terminal.
Eg. RRC Connection setup
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7. UMTS CS protocols – control plane
• RNC terminates
the Access
Stratum (AS)
• RRC, RLC and
MAC terminate at
RNC
• PHY terminates at
Node B except for
outer loop power
control
• RAN (access
stratum) acts as
transport for NAS
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Note: UTRAN protocols are layered in an architecture that follows OSI
model

8. RRC: RRC connection management(setup, release, reconfiguration), –
Radio Bearers management(setup, release, reconfiguration),
Management of radio resources for the RRC connection, RRC
connection mobility functions, Paging/notification
Radio Link Control (RLC): The RLC protocol offers logical link control
over the radio interface for the transmission of higher layer-signalling
messages and SMS. RLC is defined in TS 25.322.
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9. UMTS CS protocols – user plane
• User plane –
caries user
data
• Application –
end to end
protocol
• Access stratum
the same for
both control
plane and user
plane
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10. UMTS PS protocols – control plane
• Control plane
for packet data
• Very similar to
control plane
for PS
• Identical
access stratum
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11. UMTS PS protocols – user plane
• Additional protocol
PDCP
• PDCP –
compression of IP
headers
• PDCP may or may
not be used
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12. • PDCP:
– provides protocol transparency
(wrt the underlying radio-
interface protocols) for higher-
layer protocols
– support for e.g., IPv4, PPP and
IPv6 (easy introduction of new
higher layer protocols)
– compression of control
information (header
compression)
– no user data compression in Iu
mode
■ RLC:
– RLC protocol provides
logical link control
over the radio
interface.
■ MAC
– MAC protocol controls
the access signaling
(request and grant)
procedures for the
radio channel

13. Figure :Generic protocol model for UTRAN interfaces

14. The structure consists of two horizontal layers:
1)The Radio Network Layer and
2) The Transport Network Layer.
The Radio Network Layer is concerned with application information
to be carried either user data and control information.
The Transport Network Layer is concerned with the transport
technologies used for the UTRAN interfaces.
The two layers are logically independent of each other. This makes it
possible to change the Transport Network Layer without affecting
Radio Network Layer, if required. In Release 99, the Transport
Network Layer is based on ATM. In Release 5, IP is used.
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15. •The user plane includes the user data between the UE and the
network and the data bearers. The user data consists of data streams
characterized by frame protocols specific to a UTRAN interface.
•The control plane includes the application protocols and the signaling
bearers, which transport the control information.
The application protocols used at different UTRAN interfaces are:
■ Iu-CS: Radio access network application protocol (RANAP)
■ Iu-PS: RANAP
■ Iub: Node B application protocol (NBAP)
■ Iur: Radio network system application protocol (RNSAP)
•The transport network control plane includes the access link control
application protocol (ALCAP). ALCAP is used to set up transport
bearers to carry user and control plane information. It is not visible to the
Radio Network Layer.
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16. Figure : Iu-CS interface protocol structure.
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17. IUcs interface protocol structure
• In UMTS, the interface between RAN and CN is Iu.
•Iu-CS is the interface specified between the RAN and the 3G MSC.
•The Iu-PS interface is defined between the RAN and the 3G SGSN.
•In order to have uniformity, 3GPP specifies a single protocol at Radio Network
Layer for the Iu-CS and the Iu-PS interfaces.
The radio access network application protocol (RANAP) is the Radio Network
Layer protocol for the Iu interface. The RANAP peer entities reside in 3G
MSC/SGSN and the SRNC. The RANAP functions are specified in 3GPP TS
25.413 in detail. In summary, RANAP procedures support the following key
functions:
■ Radio access bearer (RAB) management including RAB setup, modification,
and release
■ Iu connection management
■ Facilitate general UTRAN procedures from the core network, e.g., paging
requests from the CN to UE
■ Services to upper layers including the transportation of upper layer
nonstratum protocols (i.e., call control, session management, and mobility
management) messages between the UE and CN
■ Overload and error handling
■ SRNS relocation
■ UE location reporting 17

18. The Service Connection and Control Part (SCCP) offers both connectionless and
connection-oriented services. Each active UE is assigned a separate logical link in case of
connection-oriented service between two RANAP entities.
The SCCP utilizes services provided by the lower layers to transport messages between two
entities.
 Layer 3 Broadband Message Transfer Part (MTP3b) provides message routing,
discrimination, and distribution. It also provides link management functions including load
sharing between linksets.
The SSCF-NNI(Service-Specific Coordination Function for Signaling at the Network Node
Interface) maps the requirements of above layers to the requirements of SSCOP.
The SSCOP (Service-Specific Connection-Oriented Protocol)provides the mechanism for
the establishment and release of connections and the reliable exchange of signalling
information between the signalling entities.
In cases where the IP transport option is chosen, the services are provided by M3UA(MTP 3
User Adaptation Layer), SCTP (Stream Control Transmission Protocol) and IP.
 AAL5 (ATM Adaptation Layer 5)is used to adapt the upper layer protocol to the
requirements of the lower ATM cells.
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19. As described in the previous section, the purpose of the transport network
control plane is to set up, maintain, and release bearers to transport the data
via the user plane.
The AAL2 signaling protocol capability set 1 (ALCAP), which is described in
ITU-T specification Q.2630.1, is used. ALCAP(Access Link Control Application
Part ) is a Layer 3 protocol. Its responsibility is to set up and manage ATM
Adaptation Layer 2 (AAL2) connections.
In the user plane, ATM Adaptation Layer 2 (AAL2) is used as the user data
bearer. AAL2 has been specifically designed to transport short-length packets.
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20. Figure: Iu-PS interface protocol structure. 20

21. IUps interface protocol structure
The Iu-PS interface is specified between the RAN and the 3G SGSN.
As described in the previous section, 3GPP specifies a single protocol at
the Radio Network Layer for the Iu-CS and the Iu-PS interfaces, i.e.,
RANAP for the control plane and Iu for the user plane.
No transport network control protocol is needed. Unlike GPRS, where
the GTP tunnel ends at the SGSN, the GTP tunnel in UMTS extends up
to RNC. The tunnel ID and IP address, which is required to establish a
tunnel, is included in the upper layer protocols.
Like GPRS, GTP-U uses UDP/IP. AAL5 is used to carry the packet-
switched user traffic over the Iu-PS interface.
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22. Figure :Iur interface protocol structure. 22

23. Iur interface protocol structure
Iur is the interface between the RNCs.
One of the RNCs assumes the controlling role and is termed the serving
RNC (SRNC); the other RNC is termed the drifting RNC (DRNC).
The Radio Subsystem Application Part (RNSAP) is a Radio Network Layer
protocol used at the Iur interface. RNSAP includes procedures for network
control signaling between two RNC nodes:
■ Radio link management and reconfiguration
■ Radio link supervision
■ Common control channel (CCCH) signaling transfer
■ Paging
■ Relocation execution
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24. RNSAP uses the services of the Transport Layer for reliable
transfer of signaling messages in both connectionless and
connection-oriented modes.
The SCCP allows a separate independent logical connection with
individual UE. If the ATM transport option is chosen between two
RNCs, the SCCP uses MTP3-B, SSCF-NNI, and SSCOP services
for networking and routing of messages.
In cases where the IP transport option is chosen, these services
are provided by the M3UA, SCTP, and IP.
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25. 25

26. Iub interface protocol structure
Iub is the interface between the Node B and the RNC .
The Node B application protocol (NBAP) is a Radio Network Layer control
plane protocol at the Iub interface. NBAP includes the procedures to manage
the logical resources at Node B. NBAP procedures support the following
functions:
■ Cell configuration management
■ Radio link management and supervision
■ Common transport channel management
■ System information management
■ Configuration verification/alignment
■ Measurement of common and dedicated resources System network
protocols
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27. Summary
•UTRAN in WCDMA covers Layers 1-3 of OSI Model
•Complete UMTS architecture is divided into Non Access Stratum and Access
Stratum
•The application protocols used at different UTRAN interfaces are:
■ Iu-CS: Radio access network application protocol (RANAP)
■ Iu-PS: RANAP
■ Iub: Node B application protocol (NBAP)
■ Iur: Radio network system application protocol (RNSAP)
•In order to have uniformity, 3GPP specifies a single protocol at Radio Network Layer for
the Iu-CS and the Iu-PS interfaces.
•UMTS protocol structure is divided into horizontal layers and vertical planes
1)Radio network layer 1)User Plane
2)Transport network layer 2)control plane
3) Transport Network control Plane
•In Release 99, the Transport Network Layer is based on ATM. In Release 5, IP is used.
•There is no Transport Network control Plane in Iu-PS interface
•Unlike GPRS, where the GTP tunnel ends at the SGSN, the GTP tunnel in UMTS
extends up to RNC.
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Thank You!