Umts chap5

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)
 interfaces with user and radio interface
 Radio Access Network (RAN, UMTS Terrestrial RAN =
UTRAN)
 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) HLR (Home Location Register)
b) MSC/VLR (Mobile Services Switching Centre/Visitor
Location Register)
c) GMSC (Gateway MSC)
d) SGSN (Serving GPRS (General Packet Radio Service)
Support Node)
e) 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
 connects UTRAN to CN
 Iur interface
 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 radio-
specific 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)
 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
 SS7的第二層為信號鏈路層(Signaling Link Level)
 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：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MAC-
c/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
1. Node B Communication Contexts for dedicated and
shared channels
 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
 defines the basic set of network elements and interface
protocols for the support of Release ’99 WCDMA radio
interface
 Enhancement of the Release’99 UTRAN
architecture
 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
 the transport technology used in the first release of
UTRAN
 IP transport
 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
 a bigger step in radio access evolution from GSM
networks
 UMTS core network
 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

Umts chap5

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