Download Radio Access Network Architecture

RADIO ACCESS NETWORK
ARCHITECTURE
5.1 System Architecture
5.2 UTRAN Architecture
5.3 General Protocol Model for UTRAN Terrestrial
Interfaces
5.4 Iu, The UTRAN–CN Interface
5.5 UTRAN Internal Interfaces
5.6 UTRAN Enhancements and Evolution
5.7 UTRAN CN Architecture and Evolution
5.1 SYSTEM ARCHITECTURE

Functional network elements

User Equipment (UE)


Radio Access Network (RAN, UMTS Terrestrial RAN
= UTRAN)


interfaces with user and radio interface
handles all radio-related functionality
Core Network

switches and routes calls and data connections
to external networks

PLMN (Public Land Mobile Network)
operated by a single operator
 distinguished from each other with unique identities
 operational either on their own or together with other
sub-networks
 connected to other PLMNs as well as to other types of
network, such as ISDN, PSTN, the Internet, etc.


UE consists of two parts

Mobile Equipment (ME)


the radio terminal used for radio communication
over Uu interface
UMTS Subscriber Identity Module (USIM)
a smartcard that holds the subscriber identity
 performs authentication algorithms
 stores authentication and encryption keys
 some subscription information that is needed at the
terminal


UTRAN consists of two elements

Node B
converts data flow between Iub and Uu interfaces
 participates in radio resource management


Radio Network Controller (RNC)
owns and controls radio resources in its domain
 the service access point (SAP) for all services that
UTRAN provides the CN
 e.g., management of connections to UE


Main elements of CN
a)
b)
c)
d)
e)
HLR (Home Location Register)
MSC/VLR (Mobile Services Switching Centre/Visitor
Location Register)
GMSC (Gateway MSC)
SGSN (Serving GPRS (General Packet Radio Service)
Support Node)
GGSN (Gateway GPRS Support Node)
(a) HLR (Home Location Register)
a database located in user’s home system that stores
the master copy of user’s service profile
 service profile consists of, e.g.,

information on allowed services, forbidden
roaming areas
 supplementary service information such as
status of call forwarding and the call
forwarding number

it is created when a new user subscribes to the
system, and remains stored as long as the
subscription is active
 for the purpose of routing incoming transactions to
UE (e.g. calls or short messages)


HLR also stores the UE location on the level of
MSC/VLR and/or SGSN
(b) MSC/VLR (Mobile Services Switching
Centre/Visitor Location Register)
the switch (MSC) and database (VLR) that serve the
UE in its current location for Circuit Switched (CS)
services
◦ the part of the network that is accessed via MSC/VLR
is often referred to as CS domain
◦ MSC
◦

◦
used to switch CS transactions
VLR

holds a copy of the visiting user’s service profile,
as well as more precise information on the
UE’s location within the serving system
(c) GMSC (Gateway MSC)
the switch at the point where UMTS PLMN is
connected to external CS networks
 all incoming and outgoing CS connections go through
GMSC

(d) SGSN (Serving GPRS (General Packet Radio
Service) Support Node)
functionality is similar to that of MSC/VLR but is
typically used for Packet Switched (PS) services
 the part of the network that is accessed via SGSN is
often referred to as PS domain

(e) GGSN (Gateway GPRS Support Node)

functionality is close to that of GMSC but is in
relation to PS services

External networks can be divided into two groups

CS networks
provide circuit-switched connections, like the existing telephony
service
 ISDN and PSTN are examples of CS networks


PS networks
provide connections for packet data services
 Internet is one example of a PS network


Main open interfaces

Cu interface


the electrical interface between USIM smartcard
and ME
Uu interface
the WCDMA radio interface
 the interface through which UE accesses the fixed
part of the system
 the most important open interface in UMTS


Iu interface


Iur interface


connects UTRAN to CN
allows soft handover between RNCs
Iub interface

connects a Node B and an RNC
5.2 UTRAN ARCHITECTURE
5.2.1 Radio Network Controller
5.2.2 Node B (Base Station)

UTRAN


consists of one or more Radio Network Sub-systems (RNS)
RNS
a subnetwork within UTRAN
 consists of one Radio Network Controller (RNC) and one or
more Node Bs



RNCs
 may be connected to each other via Iur interface
 RNCs and Node Bs are connected with Iub interface
Main characteristics of UTRAN
 support of UTRA and all related functionality
 support soft handover and WCDMA-specific Radio Resource
Management algorithms
 use of ATM transport as the main transport mechanism in
UTRAN
 use of IP-based transport as the alternative transport
mechanism in UTRAN from Release 5 onwards
5.2.1 RADIO NETWORK
CONTROLLER

RNC (Radio Network Controller)
the network element responsible for radio resources control
of UTRAN
 it interfaces CN (normally to one MSC and one SGSN)
 terminates RRC (Radio Resource Control) protocol that
defines the messages and procedures between mobile and
UTRAN
 it logically corresponds to the GSM BSC

註：RADIO
RESOURCE
CONTROL

Radio Resource Control (RRC) messages
the major part of the control signaling between UE and
UTRAN
 carry all parameters required to set up, modify and release
Layer 2 and Layer 1 protocol entities


The mobility of user equipment in the connected mode
is controlled by RRC signaling

measurements, handovers, cell updates, etc.
3GPP BEARERS FOR SUPPORTING
PACKET-SWITCHED SERVICES
UTRAN
CN
TRAFFIC BEARERS STRUCTURE SUPPORTING
PACKET-SWITCHED SERVICES

3GPP Bearer
a dedicated path between mobile and its serving GGSN
 for a mobile to send or receive packets over a 3GPP PS CN
 a 3GPP Bearer in a UMTS network would be a UMTS
Bearer


Constructed by concatenating
Radio Access Bearer (RAB)
 connects a mobile over a RAN to the edge of
CN (i.e., a SGSN)
 CN Bearer
 carries user traffic between the edge of CN
and a GGSN

SIGNALING AND TRAFFIC
CONNECTIONS BETWEEN MOBILE
AND SGSN


The signaling connection between mobile and SGSN is
constructed by concatenating
 Signaling Radio Bearer
 between mobile and RAN (e.g., the RNC in UTRAN)
 Iu Signaling Bearer
 between RAN and SGSN
Signaling and traffic connections between mobile and
SGSN
 Radio Resource Control (RRC) connection
 Radio Access Network Application Part (RANAP)
connection

Radio Resource Control (RRC) connection
includes Signaling Radio Bearers and Traffic Radio
Bearers for the same mobile
 used to establish, maintain, and release Radio
Bearers
 a mobile will use a common RRC connection to carry
signaling and user traffic for both PS and CS services


Radio Access Network Application Part (RANAP)
connection
includes Iu Signaling Bearers and Iu Traffic Bearers
for the same mobile
 used to establish, maintain, modify, change, and
release all these Iu Bearers

5.2.1.1 LOGICAL ROLE OF THE RNC
The RNC controlling one Node B is indicated as
the Controlling RNC (CRNC) of Node B
 Controlling RNC

responsible for load and congestion control of its own
cells
 executes admission control for new radio links


In case one mobile–UTRAN connection uses
resources from more than one RNS (due to
handover), the RNCs involved have two separate
logical roles
Serving RNC (SRNC)
 Drift RNC (DRNC)


Serving RNC



SRNC for one mobile is the RNC that terminates
both the Iu link for the transport of user data and the
corresponding RANAP (RAN Application Part)
signaling to/from the core network
SRNC also terminates the Radio Resource Control
Signaling, that is the signaling protocol between the
UE and UTRAN
it performs L2 processing of the data to/from the
radio interface
basic Radio Resource Management operations are
executed in SRNC
 map Radio Access Bearer (RAB) parameters into
air interface transport channel parameters
 handover decision
 outer loop power control
 one UE connected to UTRAN has one and only one
SRNC


Drift RNC
DRNC is any RNC, other than the SRNC, that
controls cells used by the mobile
 DRNC does not perform L2 processing of the user
plane data, but routes the data transparently
between Iub and Iur interfaces
 one UE may have zero, one or more DRNCs

5.2.2 NODE B (BASE STATION)

Main function of Node B
perform the air interface L1 processing, e.g.,
 channel coding and interleaving
 rate adaptation
 spreading
 also performs some basic Radio Resource
Management operations, e.g.
 inner loop power control
◦

It logically corresponds to the GSM Base Station
註：INTERLEAVING

The transmission of pulses from two or more
digital sources in time-division sequence over a
single path
5.3 GENERAL PROTOCOL MODEL
FOR UTRAN TERRESTRIAL
INTERFACES
5.3.1 General
5.3.2 Horizontal Layers
5.3.3 Vertical Planes
5.3.1 GENERAL

The general protocol model for UTRAN
terrestrial interfaces
the layers and planes are logically independent of
each other
 parts of the protocol structure may be changed in the
future while other parts remain intact

5.3.2 HORIZONTAL LAYERS

The protocol structure consists of two main layers
Radio network layer
 Transport network layer

5.3.3 VERTICAL PLANES
5.3.3.1 Control Plane
5.3.3.2 User Plane
5.3.3.3 Transport Network Control Plane
5.3.3.4 Transport Network User Plane
5.3.3.1 CONTROL PLANE

Control Plane
 used for all UMTS-specific control signaling
 includes two parts
 application protocol
 RANAP (RAN application part) in Iu
 RNSAP (RNS application part) in Iur
 NBAP (Node B application part) in Iub
 signaling bearer
 transport the application protocol messages

Application protocol is used for

setting up bearers to UE, i.e.
 radio access bearer in Iu
 radio link in Iur and Iub
5.3.3.2 USER PLANE

User Plane
 transport all information sent and received by the
user, such as
 coded voice in a voice call
 packets in an Internet connection
 includes two parts
 data stream(s)
 data bearer(s) for data stream(s)
5.3.3.3 TRANSPORT NETWORK
CONTROL PLANE
Used for all control signaling within transport layer
 Does not include any radio network layer information
 Includes ALCAP (Access Link Control Application Part)
protocol used to set up the transport bearers (data
bearer) for user plane

Includes signaling bearer needed for ALCAP
 Transport network control plane

acts between control plane and user plane
 makes it possible for application protocol in radio
network control plane to be completely independent
of the technology selected for data bearer in user
plane

5.3.3.4 TRANSPORT NETWORK USER
PLANE

Transport Network User Plane
data bearer(s) in user plane
 signaling bearer(s) for application protocol

5.4 IU, THE UTRAN–CN INTERFACE
5.4.1 Protocol Structure for Iu CS
5.4.2 Protocol Structure for Iu PS
5.4.3 RANAP Protocol
5.4.4 Iu User Plane Protocol
5.4.5 Protocol Structure of Iu BC, and the SABP
Protocol

Iu interface
an open interface that divides the system into radiospecific UTRAN and CN
 handles switching, routing and service control


Iu can have two main different instances and one
additional instance
Iu CS
 connect UTRAN to Circuit Switched (CS) CN
 Iu PS
 connect UTRAN to Packet Switched (PS) CN
 Iu BC (Broadcast)
 support Cell Broadcast Services
 connect UTRAN to the Broadcast domain of CN

5.4.1 PROTOCOL STRUCTURE FOR IU
CS
5.4.1.1 Iu CS Control Plane Protocol Stack
5.4.1.2 Iu CS Transport Network Control Plane
Protocol Stack
5.4.1.3 Iu CS User Plane Protocol Stack

The following figure
depicts the Iu CS overall protocol structure
 the three planes in the Iu interface share a common
ATM (Asynchronous Transfer Mode) transport
 physical layer is the interface to physical medium
 optical fiber
 radio link
 copper cable

5.4.1.1 Iu CS CONTROL PLANE
PROTOCOL STACK
Control Plane protocol stack consists of RANAP,
on top of Broadband (BB) SS7 (Signaling System
#7) protocols
 The applicable layers are
 Signaling Connection Control Part (SCCP)
 Message Transfer Part (MTP3-b)
 SAAL-NNI (Signaling ATM Adaptation Layer
for Network to Network Interfaces)

註：SS7

MTP (Message Transfer Part，訊息轉送部)

SS7的第一層為信號數據鏈路層(Signaling Data Link
Level)又稱為實體層(Physical Level)


SS7的第二層為信號鏈路層(Signaling Link Level)


定義信號鏈路之實體、電氣與功能，以提供實體
鏈路收送SS7信號
確保SS7信號訊息在實體層上收送的可靠度
SS7的第三層為信號網路層(Signaling Network Level)
處理信號訊息及管理信號網路
 MTP3-b


提供訊息繞送、識別，通訊裝置間的訊號鏈結管理、分
享與轉換

SCCP：協助ISUP做端對端之交換
 供ISDN-UP (ISUP)建立端對端的信號接續(Signaling
Connection)
 供網管、維護中心與各交換局間(有SP功能者)建立信號接
續
 供將來用戶(User)(如帳務中心)與各交換局(SP點)間建立
信號接續，可直接傳送帳務資料，而不用再運送磁帶
 供將來其他用戶部(User Part)建立信號接續使用

TCAP
交易能力(Transaction Capabilities；TC)或稱交易能力應
用部(Transaction Capabilities Application Part；TCAP)
 在SS7網路中是屬於應用層(Application Layer)中的一個
應用服務元件(Application Service Element；ASE)


目的
 提供SS7網路中之信號節點對信號節點間非電路接續相
關訊息的傳送
 為它們之間的各種應用提供一般性服務
 例如
 交換機與交換機間非電路接續相關訊息的交換
 交換機對網路服務中心資料庫作號碼翻譯(例如080
服務號碼)皆可由TCAP所提供的服務來達成



SAAL-NNI is further divided into
 Service Specific Coordination
Function (SSCF)
 Service Specific Connection Oriented
Protocol (SSCOP)
 ATM Adaptation Layer 5 (AAL) layers
SSCF and SSCOP layers
 designed for signaling transport in
ATM networks
 take care of signaling connection
management
AAL5 is used for segmenting the data to
ATM cells
註：


SSCF (Service Specific Coordination Function)
 為特定服務協調功能
 包括UNI (User-to-Network Interface)與NNI
(Network-to-Network Interface)
 負責連線管理(connection management)與鏈結狀態
(link status)等管理
SSCOP (Service Specific Connection Oriented Protocol)
 為特定服務連結導向通訊協定，提供可靠的訊號傳輸
服務
 包括流量控制、重送機制、連線控制與錯誤偵測等
 透過SSCOP傳送資料，如發生資料內容錯誤，可透過
重送機制來修正錯誤；也提供上層通訊協定可靠的傳
輸服務
註：ATM IN BRIEF
註：AAL2 AND AAL5
Above the ATM layer we usually find an ATM
adaptation layer (AAL)
 AAL

process the data from higher layers for ATM
transmission
 segment the data into 48-byte chunks and
reassemble the original data frames on the receiving
side


Five different AALs (0, 1, 2, 3/4, and 5)

AAL0


no adaptation is needed
the other adaptation layers have different properties
based on three parameters
real-time requirements
 constant or variable bit rate
 connection-oriented or connectionless data
transfer


Iu interface uses two AALs
AAL2
 主要特色為需要建立連線(connection-oriented
services)、即時傳輸(real-time data streams)及非固定
的傳輸速率(variable bit rate，VBR)，適合用來傳送經
過壓縮的影音資料
 每個經過壓縮的影音資料傳輸速率並不固定，會隨著
每個畫面的複雜度不同而有所改變，此類服務需要即
時性傳輸，適用於AAL2的傳輸服務
 AAL5
 主要的特色為無需建立連線、非即時傳輸以及非固定
的傳輸速率

5.4.1.2 IU CS TRANSPORT NETWORK
CONTROL PLANE PROTOCOL STACK

Transport Network Control Plane
protocol stack consists of
 Signaling Protocol on top of BB SS7
protocols for setting up
 AAL2 connections (Q.2630.1 [Q.aal2
CS1])
 adaptation layer (Q.2150.1 [AAL2
Signaling Transport Converter for
MTP3b])
 BB SS7 are those described above
without SCCP layer
5.4.1.3 IU CS USER PLANE
PROTOCOL STACK
A dedicated AAL2 connection is reserved for each
individual CS service
 Iu User Plane Protocol residing directly on top of AAL2

5.4.2 PROTOCOL STRUCTURE FOR IU
PS
5.4.2.1 Iu PS Control Plane Protocol Stack
5.4.2.2 Iu PS Transport Network Control Plane Protocol
Stack
5.4.2.3 Iu PS User Plane Protocol Stack

The following figure
 depicts Iu PS protocol
structure
 a common ATM transport is
applied for both User Plane
and Control Plane
 the physical layer is as
specified for Iu CS
5.4.2.1 IU PS CONTROL PLANE
PROTOCOL STACK

Control Plane protocol stack
consists of
 RANAP
 signaling bearers
 BB SS7-based signaling bearer
 an alternative IP-based
signaling bearer
 SCCP layer is used for both
bearer


IP-based signaling bearer consists
of
 M3UA (SS7 MTP3 – User
Adaptation Layer)
 SCTP (Stream Control
Transmission Protocol)
 designed for signaling
transport in the Internet
 ensure reliable, in-sequence
transport of messages with
congestion control
 IP (Internet Protocol)
AAL5 (common to both
alternatives)
註：


SCTP (RFC 2960)
 提供可靠的傳輸服務，主要存在於
IuPS介面
 運作於完整的IP網路環境中，並可適
用於IPv4與IPv6
 提供流量控制、重送機制，以供上
層M3UA一個穩定可靠的傳輸介面
M3UA
 基於SCTP，提供上層SCCP訊號傳送
機制


SCCP
 原本以MTP3作為它下層的通訊協定
 為順利透過IP或ATM等通訊協定，在
其下層提供一個類似MTP3的通訊協
定，以便順利運作在這些通訊協定上
RANAP
 本身並無處理錯誤能力
 它假設所有送出的訊息都會被正確接
收，即其下層通訊協定(Transport
Network Layer)需有處理錯誤能力
 如SSCOP與SCTP具有錯誤偵測與資
料重送機制
5.4.2.2 IU PS TRANSPORT NETWORK
CONTROL PLANE PROTOCOL STACK
Transport Network Control Plane is not applied
to Iu PS
 Setting up of GTP tunnel

requires an identifier for the tunnel and IP addresses
for both directions
 these are already included in RANAP RAB
Assignment messages

5.4.2.3 IU PS USER PLANE
PROTOCOL STACK

Iu PS User Plane
multiple packet data flows are
multiplexed on one or several AAL5
PVCs (Permanent Virtual Circuit)
 GTP-U (User Plane part of GPRS
Tunneling Protocol) is the
multiplexing layer that provides
identities for individual packet data
flow
 each flow uses UDP connectionless
transport and IP addressing

5.4.3 RANAP PROTOCOL

RANAP
defines interactions between RNS and CN
 the signaling protocol in Iu that contains all the
control information specified for Radio Network
Layer
 implemented by various RANAP Elementary
Procedures (EP)
 each RANAP function may require execution of one
or more EPs


three classes of EP
class 1 EP
 request and response (failure or success)
 class 2 EP
 request without response
 class 3 EP
 request and possibility for one or more
responses


RANAP functions






relocation
RAB (Radio Access Bearer) management
Iu release
report unsuccessfully transmitted data
common ID management
paging






management of tracing
UE–CN signaling transfer
security mode control
management of overload
reset
location reporting
RANAP FUNCTION-
Relocation：handles both SRNS relocation and
hard handover (including inter-system case
to/from GSM)

SRNS relocation
the serving RNS functionality is relocated
from one RNS to another without changing the
radio resources and without interrupting the
user data flow
 prerequisite：all Radio Links are already in
the same DRNC that is the target for the
relocation


Inter-RNS hard handover
relocate the serving RNS functionality from
one RNS to another and to change the radio
resources correspondingly by a hard handover
in Uu interface
 prerequisite：UE is at the border of the source
and target cells

RANAP FUNCTION-

RAB (Radio Access Bearer) management：combines
all RAB handling
 RAB set-up
 modification of the characteristics of an existing
RAB
 clearing an existing RAB
Iu release
 releases all resources (Signaling link and U-Plane)
from a given instance of Iu related to the specified
UE
RANAP FUNCTION-
Reporting unsuccessfully transmitted data


allows CN to update its charging records with
information from UTRAN if part of the data sent was
not successfully sent to UE
Common ID management

the permanent identification of the UE is sent from
CN to UTRAN to allow paging coordination from
possibly two different CN domains
RANAP FUNCTION-
Paging
used by CN to page an idle UE for a UE terminating
service request, such as a voice call
 a paging message is sent from CN to UTRAN with
the UE common identification (permanent Id) and
the paging area
 UTRAN will either use an existing signaling
connection, if one exists, to send the page to UE or
broadcast the paging in the requested area

RANAP FUNCTION-
Management of tracing

CN may, for operation and maintenance purposes,
request UTRAN to start recording all activity related
to a specific UE–UTRAN connection
RANAP FUNCTION-
UE–CN signaling transfer
transfer of the first UE message from UE to UTRAN
 example
 a response to paging
 a request of a UE-originated call
 a registration to a new area
 it also initiates the signaling connection for Iu
 direct transfer
 used for carrying all consecutive signaling
messages over the Iu signaling connection in both
uplink and downlink directions

RANAP FUNCTION-
Security mode control
used to set the ciphering or integrity checking on or
off
 when ciphering is on
 the signaling and user data connections in the
radio interface are encrypted with a secret key
algorithm

when integrity checking is on
 an integrity checksum, further secured with a
secret key, is added to some or all of the Radio
Interface signaling messages
 this ensures that the communication partner has not
changed, and the content of the information has not
been altered

RANAP FUNCTION-
Management of overload
control the load over Iu interface against overload
due
 example, to process overload at the CN or UTRAN


a simple mechanism is applied that allows
stepwise reduction of the load and its stepwise
resumption [(中斷後的)重新開始], triggered by a timer
RANAP FUNCTION-
Reset
reset the CN or the UTRAN side of Iu interface in
error situations
 one end of the Iu may indicate to the other end that it
is recovering from a restart, and the other end can
remove all previously established connections

RANAP FUNCTION-
Location reporting
allows CN to receive information on the location of a
given UE
 includes two elementary procedures
 control the location reporting in RNC
 send the actual report to CN

5.4.4 IU USER PLANE PROTOCOL

Iu User Plane protocol
 in the Radio Network Layer of Iu
User Plane
 defined to be independent of CN
domain
 purpose
 carry user data related to RABs
over Iu interface
 the protocol performs either a fully
transparent operation, or framing for
user data segments
 the protocol also performs some basic
control signaling to be used for
initialization and online control

the protocol has two modes
 transparent mode
 本身並不會加入任何協定檔頭，亦即上層所傳送的
通訊協定會直接加上GTP-U檔頭後送出，Iu FP本
身並不加入任何資料
 applied for RABs that assume fully transparent
operation
 support mode
 所提供的傳輸協定，包含速率控制與時間限制，可
用於支援real-time的語音傳輸
 for predefined SDU (Service Data Unit) sizes
 performs framing of user data into segments of
predefined size
the SDU sizes typically correspond to
 AMR (Adaptive Multirate Codec) speech
frames, or
 the frame sizes derived from the data rate of a
CS data call
 control procedures for initialization and rate
control are defined, and a functionality is
specified for indicating the quality of the frame
based, for example, on CRC from radio interface

5.4.5 PROTOCOL STRUCTURE OF IU
BC, AND THE SABP PROTOCOL

Iu BC interface
connects RNC in UTRAN with the broadcast domain
of Core Network, namely with Cell Broadcast Centre
 used to define Cell Broadcast information that is
transmitted to mobile user via Cell Broadcast Service
 e.g. name of city/region visualized on the mobile
phone display

Iu BC is a control plane only interface
 the protocol structure of Iu BC is shown as follows



SABP (Service Area Broadcast Protocol)
 provides the capability for Cell Broadcast
Centre in CN to define, modify and
remove cell broadcast messages from RNC
SABP has the following functions
 message handling
 broadcast of new messages
 amendment [修正] of existing broadcast
messages
 prevention of broadcasting of specific
messages

load handling


responsible for determining the loading of the broadcast
channels at any particular point in time
reset

permits CBC to end broadcasting in one or more Service
Areas
5.5 UTRAN INTERNAL INTERFACES
5.5.1 RNC–RNC Interface (Iur Interface) and the
RNSAP Signaling
5.5.2 RNC–Node B Interface and the NBAP
Signaling
5.5.1 RNC–RNC INTERFACE (IUR
INTERFACE) AND THE RNSAP
SIGNALLING
5.5.1.1 Iur1：Support of the Basic Inter-RNC
Mobility
5.5.1.2 Iur2：Support of Dedicated Channel Traffic
5.5.1.3 Iur3：Support of Common Channel Traffic
5.5.1.4 Iur4：Support of Global Resource
Management


The following figure shows the protocol stack of RNC
to RNC interface (Iur interface)
Iur interface provides four distinct functions
 support of basic inter-RNC mobility (Iur1)
 support of dedicated channel traffic (Iur2)
 support of common channel traffic (Iur3)
 support of global resource management (Iur4)
5.5.1.1 IUR1：SUPPORT OF THE
BASIC INTER-RNC MOBILITY

This functionality requires the basic module of
RNSAP signaling
provides the functionality needed for the mobility of
the user between two RNCs
 does not support the exchange of any user data traffic


If this module is not implemented


the only way for a user connected to UTRAN via
RNS1 to utilize a cell in RNS2 is to disconnect itself
temporarily from UTRAN (release the RRC
connection)
The functions offered by Iur basic module include
support of SRNC relocation
 support of inter-RNC cell and UTRAN registration
area update
 support of inter-RNC packet paging
 reporting of protocol errors


Since this functionality does not involve user
data traffic across Iur

User Plane and Transport Network Control Plane
protocols are not needed
5.5.1.2 IUR2：SUPPORT OF
DEDICATED CHANNEL TRAFFIC

This functionality
requires dedicated channel module of RNSAP signaling
 allows dedicated and shared channel traffic between two
RNCs


This functionality requires also
User Plane Frame Protocol (FP) for dedicated and
shared channel
 Transport Network Control Plane protocol (Q.2630.1
[Q.aal2 CS1]) used for the set-up of transport
connections (AAL2 connections)


Frame Protocol for dedicated
channels (DCH FP) defines the
structure of
the data frames carrying the user
data
 the control frames used to
exchange measurements and
control information


Frame Protocol for common
channels (CCH FP) describes

the User plane procedure for the
shared channel

The functions offered by Iur DCH module
establishment, modification and release of the dedicated
and shared channel in DRNC due to handovers in dedicated
channel state
 set-up and release of dedicated transport connections across
Iur interface
 transfer of DCH Transport Blocks between SRNC and
DRNC
 management of the radio links in DRNS via
 dedicated measurement report procedures
 power setting procedures
 compress mode control procedures

5.5.1.3 IUR3：SUPPORT OF COMMON
CHANNEL TRAFFIC

This functionality
allows the handling of common channel (i.e. RACH,
FACH and CPCH) data streams across Iur interface
 Note
 CPCH：Common Packet CHannel
 RACH：Random Access CHannel
 FACH：Forward Access CHannel


It requires
Common Transport Channel module of RNSAP
protocol
 Iur Common Transport Channel Frame Protocol
(CCH FP)


If signaled AAL2 connections are used

Q.2630.1 [Q.aal2 CS1] signaling protocol of the
Transport Network Control Plane is needed

The functions offered by Iur common transport
channel module
set-up and release of the transport connection across
Iur for common channel data streams
 splitting of the MAC layer between SRNC (MAC-d)
and DRNC (MAC-c)
 flow control between MAC-d and MAC-c

註：

負責處理傳輸通道的MAC層可細分為MAC的三個子
層

MAC-b
負責將要廣播(broadcast)的邏輯通道(logical channel)對應到相
對的傳輸通道(transport channel)
 在UE都有MAC-b層
 在Node B上有負責每個cell的MAC-b層

MAC-d
 負責管理專屬(dedicated)通道
 在UE都有一個MAC-d層
 在SRNC上有負責每個UE的MAC-d層
 MAC-c/sh
 負責處理在一般(common)與共享(shared)通道中的資
訊
 在UE上都有MAC-c/sh層
 在CRNC (Controlling RNC)上有負責一個cell的MACc/sh層

5.5.1.4 IUR4：SUPPORT OF GLOBAL
RESOURCE MANAGEMENT
This provides signaling to support enhanced
radio resource management and O&M features
across Iur interface
 The function is considered optional
 This function has been introduced in subsequent
releases for the support of

common radio resource management between RNCs
 advanced positioning methods
 Iur optimization


The functions offered by Iur global resource
module
transfer of cell information and measurements
between two RNCs
 transfer of positioning parameters between controller
 transfer of Node B timing information between two
RNCs

5.5.2 RNC–NODE B INTERFACE
AND THE NBAP SIGNALING
5.5.2.1 Common NBAP and the Logical O&M
5.5.2.2 Dedicated NBAP

Figure 5.10 shows the protocol stack of RNC–
Node B interface (Iub interface)

Figure 5.11 shows the logical model of Node B
seen from the controlling RNC
Figure 5.11 Logical Model of Node B

Logical model of Node B includes
 the logical resources provided by Node B to UTRAN (via
Controlling RNC) - depicted as "cells" which include the
following physical channel resources
 DPCH (Dedicated Physical Channel)
 PDSCH (Physical Downlink Shared Channel)
 PUSCH (Physical Uplink Shared Channel)
 the dedicated channels which have been established on
Node B
 the common transport channels that Node B provides to
RNC

Elements of the logical model
Node B Communication Contexts for dedicated and
shared channels
1.

corresponds to all the dedicated resources
that are necessary for a user in dedicated
mode and using dedicated and/or shared
channels as restricted to a given Node B

attributes (not exhaustive)
 list of Cells where dedicated and/or shared
physical resources are used
 list of DCH which are mapped on the
dedicated physical resources for that Node B
Communication Context
 list of DSCH and USCH [TDD] which are
used by the respective UE
the complete DCH characteristics for each
DCH, identified by its DCH-identifier
 the complete Transport Channel
characteristics for each DSCH and USCH,
identified by its Shared Channel identifier
 list of Iub DCH Data Ports
 list of Iub DSCH Data ports and Iub USCH
data ports
 FDD – up to one Iub TFCI2 Data Port

for each Iub DCH Data Port, the
corresponding DCH and cells which are
carried on this data port
 for each Iub DSCH and USCH data port, the
corresponding DSCH or USCH and cells
which serve that DSCH or USCH
 physical layer parameters (outer loop power
control, etc)

2.
Common Transport Channel


configured in Node B, on request of CRNC
attributes (not exhaustive)

Type (RACH, CPCH [FDD], FACH, DSCH,
USCH [TDD], PCH)

Associated Iub RACH Data Port for a RACH,
Iub CPCH Data Port for a CPCH [FDD], Iub
FACH Data Port for a FACH, Iub PCH Data
Port for PCH

Physical parameters
3.
Transport network logical resources
3.1 Node B Control Port

Functionality

exchange the signaling information for
the logical O&M of Node B

the creation of Node B Communication
Contexts
the configuration of the common transport
channels that Node B provides in a given
cell
 PCH and BCH control information
between the RNC and the Node B
 Node B Control Port corresponds to one
signaling bearer between the controlling
RNC and the Node B
 There is one Node B Control Port per Node B

3.2 Communication Control Port
 used to send the procedures for controlling the
connections between radio links and Iub DCH
data ports from RNC to Node B for control of Node
B Communication Contexts
 one signaling bearer between RNC and Node B
can at most correspond to one Communication
Control Port
 Node B may have multiple Communication
Control Ports (one per Traffic Termination Point)
3.3 Traffic Termination Point
 represents DCH, DSCH and USCH [TDD] data
streams belonging to one or more Node B
Communication Contexts (UE contexts), which are
controlled via one Communication Control Port
3.4 Iub RACH Data Port
3.5 Iub CPCH Data Port [FDD]
3.6 Iub FACH Data Port
3.7 Iub PCH Data Port
3.8 Iub FDD TFCI2 Data Port
3.9 Iub DSCH Data Port
3.10 Iub TDD USCH Data Port
3.11 Iub DCH Data Port
5.5.2.1 COMMON NBAP AND THE
LOGICAL O&M

Iub interface signaling (NBAP, Node B
Application Part) is divided into two essential
components

common NBAP


defines the signaling procedures across the
common signaling link
dedicated NBAP

used in the dedicated signaling link


User Plane Iub frame protocols
define
 the structures of the frames
 the basic inband control
procedures for every type of
transport channel (i.e. for
every type of data port of
the model)
Q.2630.1 [Q.aal2 CS1]
signaling
 used for dynamic
management of AAL2
connections used in User
Plane

Common NBAP (C-NBAP) procedures
used for the signaling that is not related to one
specific UE context already existing in Node B
 defines all the procedures for the logical O&M
(Operation and Maintenance) of Node B


such as configuration and fault management

Main functions of Common NBAP






set-up of the first radio link of one UE, and selection
of the traffic termination point
cell configuration
handling of the RACH/FACH/CPCH and PCH
channels
initialization and reporting of Cell or Node B specific
measurement
Location Measurement Unit (LMU) control
fault management
5.5.2.2 DEDICATED NBAP

When the RNC requests the first radio link for
one UE via C-NBAP Radio Link Set-up procedure
Node B assigns a traffic termination point for the
handling of this UE context
 every subsequent signaling related to this mobile is
exchanged with dedicated NBAP (D-NBAP)
procedures across the dedicated control port of the
given Traffic Termination Point


Main functions of the Dedicated NBAP





addition, release and reconfiguration of radio links
for one UE context
handling of dedicated and shared channels
handling of softer combining
initialization and reporting of radio link specific
measurement
radio link fault management
5.6 UTRAN ENHANCEMENTS
AND EVOLUTION
5.6.1 IP Transport in UTRAN
5.6.2 Iu Flex
5.6.3 Stand Alone SMLC and Iupc Interface
5.6.4 Interworking between GERAN and UTRAN,
and the Iur-g Interface

Release’99 UTRAN architecture


Enhancement of the Release’99 UTRAN
architecture


defines the basic set of network elements and
interface protocols for the support of Release ’99
WCDMA radio interface
support new WCDMA radio interface features to
provide a more efficient, scalable and robust 3GPP
system architecture
Four most significant additions to the UTRAN
architecture introduced in Release 5 are
described in the subsequent sections
5.6.1 IP TRANSPORT IN UTRAN

ATM


IP transport


the transport technology used in the first release of
UTRAN
introduced in Release 5
In addition to the initially defined option of
AAL2/ATM, user plane FP frames can also be
conveyed
over UDP/IP protocols on Iur/Iub
 over RTP/UDP/IP protocols in Iu CS interface

5.6.2 IU FLEX



Release’99 architecture presented
in Figure 5.3
 only one MSC and one SGSN
connected to RNC
 i.e. only one Iu PS and Iu CS
interface in the RNC
Iu flex (flexible)
 allows one RNC to have more
than one Iu PS and Iu CS
interface instances with the
core
Main benefits of this feature
 possible load sharing between
core network nodes
5.6.3 STAND ALONE SMLC AND
IUPC INTERFACE
Location-based services
 expected to be a very important source of
revenue for mobile operators
 a number of different applications are expected
to be available and largely used
 UTRAN architecture includes a stand alone
Serving Mobile Location Centre (stand alone
SMLC, or, simply, SAS)
 a new network element for handling of
positioning measurements and calculation of
the mobile station position


SAS
connected to RNC via Iupc interface
 Positioning Calculation Application Part (PCAP) is
the L3 protocol used for RNC-SAS signaling
 SAS performs the following procedures

provides positioning (GPS related) data to
RNC
 performs the position calculation function for
UE assisted GPS

SAS and Iupc interface are optional elements
 Iupc

the first version, supported only Assisted GPS
 later versions, support for other positioning methods

5.6.4 INTERWORKING BETWEEN
GERAN AND UTRAN, AND THE IUR-G
INTERFACE

Iu interface
scheduled to be part of the GSM/EDGE Radio Access
Network (GERAN) in GERAN Release 5
 allows reusing 3G Core Network also for GSM/EDGE radio
interface (and frequency band), but also allows a more
optimized interworking between the two radio technologies


Effect
RNSAP basic mobility module is enhanced to allow
the mobility to and from GERAN cells in the target
and the source
 RNSAP global module is enhanced in order to allow
GERAN cells measurements to be exchanged
between controllers
 allows a Common Radio Resource Management
(CRRM) between UTRAN and GERAN radios


Iur-g interface

refer to the above-mentioned set of Iur functionalities
that are utilized also by GERAN
5.7 UMTS CORE NETWORK
ARCHITECTURE AND EVOLUTION
5.7.1 Release’99 Core Network Elements
5.7.2 Release 5 Core Network and IP Multimedia
Sub-system

UMTS radio interface, WCDMA


UMTS core network


a bigger step in radio access evolution from GSM
networks
did not experience major changes in 3GPP Release’99
specification
Release’99 structure was inherited from GSM
core network

both UTRAN and GERAN based radio access
network connect to the same core network
5.7.1 RELEASE ’99 CORE NETWORK
ELEMENTS

Two domains of Release’99 core network



Circuit Switched (CS) domain
Packet Switched (PS) domain
The division comes from the different
requirements for data

depending on whether it is real time (circuit switched)
or non-real time (packet data)

Figure 5.12
Release’99 core network
structure with both CS
and PS domains
 Registers
 HLR, VLR, EIR
 Service Control Point (SCP)
 the link for providing a
particular service to end
user


CS domain has the following elements
Mobile Switching Centre (MSC), including Visitor
Location Register (VLR)
 Gateway MSC (GMSC)


PS domain has the following
elements
 Serving GPRS Support
Node (SGSN)
 covers similar functions
as MSC for packet data,
including VLR type
functionality
 Gateway GPRS Support
Node (GGSN)
 connects PS core
network to other
networks, e.g. to the
Internet

In addition to the two domains, the network
needs various registers for proper operation
Home Location Register (HLR)
 Equipment Identity Register (EIR)

contains the information related to the
terminal equipment
 can be used to, e.g., prevent a specific terminal
from accessing the network

5.7.2 RELEASE 5 CORE NETWORK
AND IP MULTIMEDIA SUB-SYSTEM

Release 4 included the change in core network CS
domain
MSC was divided into MSC server and Media
Gateway (MGW)
 GMSC was divided into GMSC server and MGW


Release 5
contains the first phase of IP Multimedia Sub-system
(IMS)
 this will enable a standardized approach for IP-based
service provision via PS domain



Release 6
 enhance IMS to allow the
provision of services similar to CS
domain services from PS domain
Release 5 architecture is presented
in Figure 5.13
 Home Subscriber Server (HSS)
 shown as an independent item
 Session Initiation Protocol (SIP)
 the key protocol between
terminal and IMS
 the basis for IMS-related
signaling
MSC or GMSC server
 takes care of the control functionality as
MSC or GMSC, respectively
 user data goes via Media Gateway (MGW)
 one MSC/GMCS server can control multiple
MGWs
 this allows better scalability of the network
when data rates increase with new data
services
 in this case, only the number of MGWs
needs to be increased
 MGW performs actual switching for user data
and network interworking processing
 e.g., echo cancellation or speech decoding/
encoding


IMS includes the following key
elements
 Media Resource Function (MRF)
 controls media stream resources
or mixes different media
streams
 Call Session Control Function
(CSCF)
 the first contact point to
terminal in the IMS (as a proxy)
 handling of session states
 acting as a firewall towards
other operator’s networks

Media Gateway Control Function
(MGCF)
handle protocol conversions
 control a service coming via CS
domain and perform processing in
an MGW, e.g. for echo
cancellation
