Ishiriya Wireless Technologies-3G Architecture, Networks, Protocols

3G

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M2M COMMUNICATIONS MOBILE APPLICATION DEVELOPMENT DIGITAL SIGNAL PROCESSING AND DATA ACQUISTION

WIRELESS APPLICATIONS WIRELESS TEST AND MEASUREMENT WIRELESS COMMUNICATION CHIPSETS AND MOBILE DEVICES

Contents
1. Introduction to UMTS ............................................................................................................................... 4
1.1 UMTS Network Architecture ............................................................................................................... 5
1.1.1 Basic Structure of UMTS Network ............................................................................................... 5
1.1.2 Architecture Overview ................................................................................................................ 6
1.1.3 User Equipment ........................................................................................................................... 7
1.1.4 UMTS Radio Access network........................................................................................................ 7
2. UMTS Core Network ............................................................................................................................... 13
2.1 Structure of UMTS Core Network ..................................................................................................... 13
2.2 IP Multimedia Sub-System ............................................................................................................... 15
2.3 Home PLMN ...................................................................................................................................... 18
2.4 Home Location Register .................................................................................................................... 18
2.5 Authentication Center (AuC)............................................................................................................. 19
2.6 Equipment Identity Register(EIR)...................................................................................................... 19
2.7 Mobile Switching Center ................................................................................................................... 20
2.8 Visitor Location Register(VLR) ........................................................................................................... 20
2.9 Gateway Mobile Switching center (GMSC) ....................................................................................... 20
3. UMTS N/w Transaction ........................................................................................................................... 21
3.1 Iub – Node B Setup ........................................................................................................................... 22
3.2 Message Flow.................................................................................................................................... 23
3.3 Iub – Iu – Loaction Update ................................................................................................................ 24
4. UMTS Protocols....................................................................................................................................... 25
4.1UMTS Related Signalling Protocols .................................................................................................... 25
4.1.1 Medium Access Control (MAC) protocol ....................................................................................... 26
4.1.2 Radio Link Controller protocol ....................................................................................................... 27
4.1.2.1 RLC Transparent Mode (TM) Entity ........................................................................................ 28
4.1.2.2 RLC Unacknowledged Mode Entity ......................................................................................... 29
4.1.2.3 RLC Acknowledged Mode Entity ............................................................................................. 31
4.1.3 Packet Data Convergence Protocol (PDCP).................................................................................... 32
4.1.4 Broadcast Multicast Control (BMC) ............................................................................................... 33
4.1.5 Radio resource Control (RRC) ........................................................................................................ 34

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4.1.6 RRC States and States Transition including GSM ........................................................................... 35
4.2 ATM and ATM Adaptation Layers ............................................................................................... 37
4.2.1 Asynchronous Transfer Mode (ATM) ........................................................................................ 37
4.2.2 ATM Protocol Architecture ........................................................................................................ 38
4.2.2.1 ATM Adaptation Layer ............................................................................................................ 39
5. Application layer Protocol....................................................................................................................... 42
5.1 Radio Access Network Application Part (RANAP) ............................................................................ 42
5.1.1 Introduction ............................................................................................................................... 42
5.1.2 Functions of RANAP ................................................................................................................... 43
6. UMTS Protocol Structure ........................................................................................................................ 45
6.1Transport Network Layer ................................................................................................................... 46
6.2 Radio Network layer ......................................................................................................................... 47
6.3 System Network layer ....................................................................................................................... 48
7. OSI Protocol Stack ................................................................................................................................... 49
8. Introduction to GSM .............................................................................................................................. 51
8.1 When Cell is Turned on ..................................................................................................................... 51
8.2 When Cell move from one cell site to another ................................................................................. 53
9. References .............................................................................................................................................. 54

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1. Introduction to UMTS

 3G is referred as Universal Mobile Telecommunication system in Europe which is one of the mobile
phone technology.

 UMTS is a Standardized by 3GPP and is European answer to the ITU IMT 2000 requirements.

 For 3G cellular Radio System UMTS is an evolution of GSM technology UMTS, the 3G successor to
GSM which utilizes the W – CDMA air interface and GSM infrastructure so it is called 3GSM.

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1.1 UMTS Network Architecture

1.1.1 Basic Structure of UMTS Network

User Equipment Access Network Core Network
To
(UE) (AN) (CN)
Other
Networks
(e.g.PSTN)

Uu Interaface Iu Interaface
Basic Structure of UMTS Network

User Equipment

 The User Equipment is used to access services provided by network.
 To connect to a network a UE interfaces with access network using WCDMA air interface which is
referred to as Uu interface.

Access Network

 Access Network performs functions specific to the radio access technique.
 Access Network has 2 entities – The Base transceiver station(BTS) that terminates the radio
connection with the UE and a Base Station Controller(BSC) that controls the resources of BTS.
BSC interfaces with CN over Iu interface.

Core Network

 Core Network performs the core functions of the network which includes mobility management, call
control, switching and routing.
 It also manages the subscription information of a subscriber and provides services based on the
information.

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1.1.2 Architecture Overview

UTRAN CN

CS Domain

Iub
MSC GMSC

Node B RNC
(Radio
Network
Contoller)

Iub
PSTN
Node B
HSS(Home
Subscriber
Iur Server)

PS
Domain
Iub

RNC
Node B (Radio IMS
SGSN GGSN
Network
Controller)

Iub

Node B
UE

Radio Iu
Uu

MSC : Mobile Switching Center SGSN : Serving GPRS support Node
GMSC : Gateway MSC GGSN :Serving GPRS Support Node
PSTN :Public Switched telephone Network IMS: IP Multimedia CN Subsystem

UMTS Architecture

• UMTS system consists of number of logical network elements connected through open
interfaces or access points.
• These elements are grouped into radio access network and the core network.
• UTRAN handles all radio related functionality, radio resource and mobility management.
• Core Network (CN) is responsible for switching and routing calls and data connections to
external n/w’s .

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1.1.3 User Equipment

Universal
Subscriber MobileTermination
Identity (MT)
Module
(USIM)

Terminal
Universal
Equipment(TE)
Integrated
Circuit
Card(UICC)
Mobile Equipment(ME)

User Equipment(UE)

Structure of User Equipment

 The User Equipment (UE) is a device used by user to access services provided by a network.
 UE is divided into 2 parts – Mobile Equipment(ME) and Universal Integrated Circuit Card(UICC).
 UICC is a smart card that contains an application called USIM. USIM contains the logic required to
identify the user. USIM is user dependent part of UE.
 USIM interoperates with UMTS Terminal to provide mobile user access to the UMTS services.
 USIM Contains the permanent identity of user called IMSI(international Mobile Subscriber Identity),
The shared secret key(used for authentication), the user phone book and a host of other
information.
 ME is user independent part of UE. It contains a slot to hold UICC which is required to access UMTS
network.
 ME is further divided into 2 parts – Mobile Termination(MT) and Terminal Equipment(TE).
 MT is a part of ME that performs a functions like radio transmission termination, authentication and
mobility management.
 TE component of ME manages the Hardware and end user applications. TE interact with ME via
Terminal adaptation (TA) function.

1.1.4 UMTS Radio Access network
 UTRAN is subdivided into individual Radio N/w System(RNSs),where each one is controlled by radio
network controller(RNC).
 Within RNS, the RNC is connected to a set of Node B Elements, each of which can serve one or
several cells.
 UTRAN is located between two new open interface Uu and Iu.
 The Uu interface is a WCDMA radio interface through which UE accesses the fixed part of the
system.

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 Uu Interface – Uu Interface is a WCDMA radio interface between mobile and Radio access n/w.
User Plane Control Plane

CS Domain PS Domain BC Domain

L3
RRC

PDCP BMC

L2

RLC

MAC

Physical Layer
L1
FDD Mode TDD Mode

Uu Interface

 The protocol stack has 2 planes – the user plane carries data streams of interest to the user, while
control plane carries the n/w’s signaling msgs.
 The User plane is divided futher, to distinguish data streams to and from circuit switched, packet
switched and broadcast control domains.
 The protocol are as follows
 Radio Resource Control (RRC) – This is the main signaling protocol in the Uu interface. It defines
signaling messages that are exchanged between mobile and radio access n/w.
 Broadcast Multicast Control (BMC) – This is an extra interface to the cell broadcast service. It
distributes cell Broadcast messages from the n/w and collects them at the mobile.
 Packet data convergence protocol (PDCP) –This is an extra interface for packet data. It carries out
functions such as header compression of IP packets.
 Radio Link control (RLC) – This manages the radio link between mobile and n/w, for example by
optionally retransmitting data packets that have not e received correctly.
 Medium access control (MAC) – This carries out low level manipulation and control of the physical
layer, for example it prioritises the transmission of different data streams from mobile or Node B to
ensure that each one has an appropriate data rate.
 Physical layer – This carries out the low – level transmission and reception. It has 2 modes of
operation, FDD and TDD.

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 Iu Interface – Iu interface connects the UTRAN to the CN. The Packet switched data is transmitted
through Iu-Ps interface and circuit switched data is transmitted over Iu-cs interface.

Control Plane
Transport n/w Control Plane User Plane

CS Domain BC Domain

Radio
n/w Layer

RANAP Frame Protocols SABP

Signalling Transport Transport n/w signalling Data Transport
Transport
n/w layer

Physical layer

Iu Interface

 Its protocol stack is divided into 2 layers
 All UMTS related issues are in the radio n/w layer, while the transport n/w layer contains standard
technology used for the underlying transport.
 Stack is divided into 3 planes
 User Plane handles data streams that eventually reach UE, control plane handles Iu signaling
messages and transport n/w control plane manages the underlying transport.
 RANAP – Defines the signaling messages exchanged over Iu Interface.
 SABP – Defines the data streams used by the cell broadcast service, and the frame protocols define
the CS and PS data streams.

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 Iur Interface – Iur Interface is the Logical interface enables handling of RRM and eliminates the
burden from CN.

Control Plane

Radio
n/w Layer
Frame Protocols
RNSAP - Common Channels
- Dedicated Channels

Transport n/w signalling
- Common Channels Data Transport
Signalling Transport - Dedicated channels - Common Channels
- Dedicated Channels Transport
n/w layer

Physical layer

Iur Interface

 Its Protocol Stack is divided into 2 layers
 All UMTS related issues are in the radio n/w layer, while the transport n/w layer contains standard
technology used for underlying transport.
 User plane handles data streams that eventually reach UE, control plane handles Iur signaling
messages and transport n/w control plane messages the underlying transport .
 RNSAP – Defines the signaling messages exchanged over Iur Interface and frame protocols define
data streams.

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 Iub Interface – Iub Interface is the Interface between RNC and Base station. The Main task of UTRAN
is to create and maintain Radio access bearers for communication between UE and CN.

Control Plane

Radio
n/w Layer
Frame Protocols
NBAP - Common Channels
- Dedicated Channels

Transport n/w signalling
- Common Channels Data Transport
Signalling Transport - Dedicated channels - Common Channels
- Dedicated Channels Transport
n/w layer

Physical layer

Iub Interface

 Its protocol stack is divided into 2 layers
 All UMTS related issues are in the radio n/w layer, while transport n/w layer contains standard
technology used for the underlying transport.
 User plane handles data streams that eventually reach UE, control plane handles Iub signaling
messages and transport n/w control plane messages the underlying transport.
 Node B Application Part (NBAP) – Defines the signaling messages exchanged over Iub interface and
Frame protocols defines data streams.

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Node B

 Node B is a physical unit for radio transmission reception in cells. Node B connects with UE Via the
WCDMA Uu radio interface and with RNC via the Iub asynchronous transfer mode(ATM) Based
interface. RNC is where Radio resources are managed

Radio Network Controller

 Radio Network Controller is the switching and controlling element of the UTRAN located between
Iub and Iu interface. It also has a third interface called Iur for inter RNS connections the RNC
interfaces the CN for both packet-switched and circuit-switched services domain and also
terminates the RRC protocol that defines the messages and procedures between mobile and
UTRAN.

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2. UMTS Core Network

2.1 Structure of UMTS Core Network

Core
Network
PS Domain

To Packet
SGSN GGSN
Network

To
Access
Network AuC HLR EIR

HLR/AuC

MSC/VLR GMSC To PSTN
Network

CS Domain

SGSN: Serving GPRS Support Node GGSN : Gateway GPRS Support Node
HLR : Home Location Register AuC : Authentication Center
EIR : Equipment Identity Register VLR: Visitor Location Register
MSC : Mobile Switching Center GMSC : Gateway Mobile Switching Center

Structure of Core Network

 Core Network Consists of entities that provide support for various network features and services
and performs functions like mobility management, call control, switching, session management,
routing, authentication and equipment identification.
 The UMTS Core Network is divided into 2 domains : the Circuit switched (CS) domain and Packet
Switched(PS) domain.

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 The CS domain provides services related to voice transfer, the PS domain to those related to data
transfer.

Circuit Switched CN

 CS Domain refers to set of all CN entities offering a “CS type connection” the entities specific.
To CS domain are
 MSC – Mobile Switching Center Switch serves ME at its current location for circuit switch services.
 MGW – Media Gateway performs actual switching for user data.
 GMSC – Gateway MSC serves UMTS where it is connected to ext CS network.

Packet Switched CN

 PS domain transports the user information using autonomous concatenation of bits called
Packet CN PS domain in UMTS has 2 basic n/w elements.
 SGSN – Serving GPRS support node serves ME for packet data.
 GGSN – Gateway serving GPRS support node connects to packet switch n/w to internet.

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2.2 IP Multimedia Sub-System
IP Multimedia n/w’s

Legacy mobile
PSTN Signalling N/w’s

PSTN Mm
Mb PSTN
Mb
BGCF CSCF
C, D
Gc,Gr
Mk
Mk
Mw

BGCF

Mj Mi
Mn Mg
Cx
IMS-
MGCF CSCF
MGW HSS

Mp Mw Gm
Mr
MRFP MRFP P-CSCF UE

Mb Mb
Mb Go IM Subsystem

 The IP Multimedia CN sub-system (IMS) includes the collection of signaling and bearer related
network elements.
 The IMS introduces three main logical network elements to the existing infrastructure: the Call
Session Control Function (CSCF), the Media Gateway Control Function (MGCF) and the Media
Gateway (MGW). The Home Subscriber Server (HSS) is also introduced providing user profile
information.
 Call Session Control Function
o The Call Session Control Function (CSCF) is a SIP server that provides/controls multimedia
services for packet-switched IP terminals, both mobile and fixed.
o It can act as Proxy CSCF (P-CSCF), Serving CSCF(S-CSCF), Interrogating CSCF (I-CSCF),
Breakout Gateway CF (BGCF) or Multimedia Resource Function (MRF).
 Proxy-CSCF
o The Proxy-CSCF (P-CSCF) is the first contact point for the UE within the IM CN subsystem
thus always located in the network where the UE resides.
o Its address is discovered after or as a part of a successful PDP context activation.
o The P-CSCF forwards SIP messages from UE to the specific I-CSCF or to the SIP server (S-
CSCF) acting as a SIP proxy.

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 Serving-CSCF
o The Serving-CSCF(S-CSCF) is always assigned in the home network.
o It acts as a registrar making information available through the location server (HSS) and
subsequently performs the session control services.
o As P-CSCF, the S-CSCF can also act as a SIP proxy server.
 Interrogating-CSCF
o The Interrogating-CSCF (I-CSCF) is mainly the contact point within an operator’s network for
all IMS connections destined to a subscriber of that network operator, or a roaming
subscriber currently located within that network operator’s service area.
o As the contact point, it accesses the HSS to resolve the SIP server addresses involved in the
session (ICSCF, BGCF or S-CSCF).
o It obtains the S-CSCF linked with the user in the registration procedure and the S-CSCF of the
terminating counterpart in the session establishment.
 Breakout Gateway Control Function
o The Breakout Gateway Control Function (BGCF) selects the network in which PSTN/CS
Domain breakout is to occur forwarding the session signaling to another BGCF if it is a
different one.
o Once in the network in which the inter-working with PSTN/CS domain is to occur, it selects a
MGCF which is responsible for such inter-working.
o Therefore this logical entity acts as a signaling entity for call/session control.
 Multimedia Resource Function
o The Multimedia Resource Function (MRF) is split into Multimedia Resource Function
Controller (MRFC) and Multimedia Resource Function Processor (MRFP).
o MRFP controls the bearer on the Mb reference point and provides media stream resources
to be controlled by the MRFC.
 Media Gateway
o The Media Gateway (MGW) terminates bearer channels from a circuit switched network
and media streams from a packet network.
 Media Gateway Control Function
o The Media Gateway Control Function (MGCF) entity controls the MGW and performs
translation at the call control signaling level between ISUP signaling, used in PSTN, and SIP
signaling, used in the UMTS multimedia domain.

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 Home Subscriber Server
o The Home Subscriber Server (HSS) is the master database for 3G/UMTS Rel5/6 IP users.
o It contains the subscription-related information to support the network entities handling the
IP session.
o This entity also integrates the Home Location Register (HLR) functionality for both packet
and circuit domain, which is there on considered as a HSS Subset.

HSS(HLR/UMS)

Subscription Location
Information Information

Gr Cx
Gc
(MAP-Based) (IP based Interface)
(MAP- Mh
Based)

SGSN GGSN R-SGW CSCF

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2.3 Home PLMN
 In UMTS the highest level of hierarchy is a public land mobile network (PLMN).
 A PLMN is defined as a telecommunications network providing mobile cellular services.
 A PLMN is uniquely identified by its PLMN identifier.
PLMN identifier

MCC MNC
(3 digits) (2/3 digits)

MCC: Mobile Country Code MNC: Mobile Network Code
PLMN: Public Land Mobile Network

Structure of PLMN identifier

 The PLMN identifier comprises of Mobile Country Code(MCC) and Mobile Network Code(MNC).
 The MCC is of 3 digits identifies the country to which the PLMN belongs.
 The MNC of 2 or 3 digits identifies a particular PLMN within a country.

2.4 Home Location Register
 Home location Register is a large database that permanently stores the data about subscribers.
 The HLR maintains subscriber- specific information such as MSISDN, IMSI, current location of the
Mobile station, roaming restrictions and subscriber supplement features.
 There is a logically only one HLR in any given n/w, but generally speaking each n/w has multiple
physical HLRs spread out across its n/w.

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2.5 Authentication Center (AuC)
MSC
EIR

VLR

HLR

AuC
Authentication Center(AuC)

 Authentication Center holds Authentication Information .
 This information is used for authentication and security related functions.
 It is often depicted as a part of HLR.
 Thus the term AuC/HLR is used to represent the entity that performs the functions of HLR and AuC.
 The Interface between HLR and AuC is called H interface.

2.6 Equipment Identity Register(EIR)
MSC
F Interface EIR

VLR

HLR
MSC
VLR
D Interface
B Interface

Equipment Identity Register(EIR)

 Equipment Identity Register(EIR) is a database that keeps tracks of handsets on the n/w using
International Mobile Equipment Identity(IMEI).
 The IMEI is used for identifying a user equipment.
 There is only one EIR per n/w. It is composed of 3 lists.

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 Black List – Is a list if IMEIs that are to be denied service by the n/w for some reason.
Reasons include IMEI if handset is malfunctioning or doesn’t have the technical capabilities to
operate on n/w.
 Grey List – Is a list of IMEIs that are to be monitored for suspicious activity.
This could include handsets that are behaving oddly or not performing as the n/w expects it to.
 White List – Is an Unpopulated list. That means if an IMEI is not on the black list or on the grey list
then it is considered good and is “on the white list”.

2.7 Mobile Switching Center
 Mobile Switching Center is a heart of a network.
 It handles call routing, call setup, and basic switching functions.
 MSC is a node that interfaces between the Access network and the Core network.
 It performs all functions necessary to handle the circuit switched services.

2.8 Visitor Location Register(VLR)
 Visitor Location Register is a database that contains a subset of information located on HLR.
 It contains a similar information as HLR, but only for subscribers currently in its location area.
 There is VLR for every location area.
 The VLR reduces the overall number of queries to HLR and thus reduces n/w traffic.
 VLRs are often identified by location Area Code(LAC) for area they service.

2.9 Gateway Mobile Switching center (GMSC)
 The Gateway MSC functions as a gateway between two n/w’s.
 If a mobile subscriber wants to place a call to a regular land line, then call would have to go through
a Gs GMSC order to switch to (PSTN).
 It also provides the means for an incoming call to be delivered to the MSC where the MS is
registered.
 Eg – If a subscriber in a circular n/w wants to call a subscriber on T – mobile n/w, the call would have
to go through GMSC.

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3. UMTS N/w Transaction

Node B RNC MSC SGSN

RRC Connection Setup

Iub Bearer Establishment

Transaction Reasoning

Authentication Security Control

Iu-CS/ PS Bearer Establishment
Radio Bearer Establishment

End – to – End Connection

Iu -CS/PS Bearer Release

Iub Bearer Release

Clearing of RRC Connection

The procedures running between UE, Node B and RNC will exchange Access – Stratum messages

Whereas procedures going through to the CN, MSC,SGSN will exchange NON Access Stratum messages

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3.1 Iub – Node B Setup
ATM Virtual Path
Node B RNC
(VPI =x)

RACH
a b a b
Common
FACH Transport
Channels c d c d
PCH

PCH:
ATM STM - 1 Line Before Node CID =8
B setup FACH:
CID =9
After Node B setup RACH :
CID =10
ATM
Virtual
Chann
els
VCI =a->NBAP
VCI =b->ALCAP
VCI =c,d->Reserved for AAL2

Node B setup against a RNC

Step 1 – The Node B requests to be audited by the RNC. During the audit, Node B informs the RNC of

How many cells belongs to Node B and which local cell identifiers they have.

Step 2 – For each cell, the RNC performs a cell setup. During cell setup, the physical(radio interface)

Channels are parameterized. These channels are mandatory in case of a UE initial access. In other words

If there channels are not available it is impossible for UE after it is switched on to get access to the n/w

Via the radio interface.

Step 3 – The common transport channel paging channel PCH, forward Access Channel and Random

access channel are setup and optionally parameterized in each cell of new Node B. On the Iub interface

There common transport channels are carried by AAL2 connections on ATM lines. ATM/AAL2 header

Values (VPI/VCI/CID) are important because without knowing them it is impossible to monitoring

Signaling and data transport on PCH,RACH and FACH. If there channels are monitored some of the most

Important message for call setup and mobility management procedures, such as paging messages and

RRC connection setup will be missed call traces. Once the AAL2 connection for a communication

Transport is installed during Node B setup it will not be released until Node B is taken Out of service.

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3.2 Message Flow

Node B RNC

NBAP UL initiating Message Id- audit required

NBAP DL initiating Message Id- audit start of audit

NBAP UL Successful Outcome id – audit, end of audit sequence”(Local cell -ids)

Opt. FP up – and Downlink Node sync(PCH between Node B and RNC)

NBAP DL initiating message id -cell setup (Cell-id, primary scrambling code, common
physical channel IDs

NBAP UL successful Outcome id – cell setup

NBAP DL initiating Msg id – system information update(SiBs)

NBAP DL initiating Msg id – common transport channel setup
Cell-Id,ctrch -id+PCH TFS)

NBAP UL successful outcome id – common Transport channel setup(cTrcH-ID,
bind ID =h)

ALCAP DL ERQ(Path-ID, Ch-ID, SUGR=h)

ALCAP UL ECF

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3.3 Iub – Iu – Loaction Update

1) Setup DCCH/RRC Connection

2) DCCH/RRC Connection 3) SCCP/RANAP connection
SCCP CR(RANAP IM
LUREC LUREQ)
LUACC or LUREJ RNC LUACC or LUREJ MSC

4) SCCP/RANAP Release
5) DCCH/RCC Release

Step 1 – Set up the dedicated control channel (DCCH) for the RRC connection on the Iub interface.

Step 2 – MM/CC/SM(Mobility Management/ Call Control/Session Management) msgs are

transparently forwarded to the RNC on behalf of RRC direct transfer msgs in this case the location

Update request (LUREQ) msg.

Step 3 – The reception of the LUREQ message triggers the setup of a SCCP/RANAP connection

on the Iu-CS interface towards MSC/VLR. The LUREQ is embedded in a SCCP connection Request

The answer can be either location update accept (LUACC) or location update reject(LUREJ).

Step 4 – After tending the answer msg, the SCCP/RANAP connection on Iu-CS is released.

Step 5 – Triggered by the release messages from the Iu – CS the RRC connection and its DCCH

are also released.

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4. UMTS Protocols

4.1UMTS Related Signalling Protocols

Access Stratum and Non Access Stratum protocols

Control Plane

CC SM SS SMS
User Plane Protocols
(eg.IP)
Non – Access
Stratum
MM/GMM

RRC
Access Stratum
Control PDCP
BMC

RLC

MAC

Physical Layer

Structure of Access Stratum and Non access Stratum

 Access Stratum are the protocols used on the radio interface between UE and UTRAN.
 These protocols are used for the transfer of user and control data between UE and UTRAN.
 The Access stratum protocols of UE are implemented in Radio termination (RT) component of
Mobile Termination (MT).
 These protocols include the following

 Physical Layer – The Physical Layer is the lower-most layer of the UMTS radio interface stack.
It is the layer that is responsible for actual transmission of higher layer data over the Physical.

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4.1.1 Medium Access Control (MAC) protocol
 Medium Access Control (MAC) protocol - Medium Access Control (MAC) Layer is the lowest sub –
layer of layer 2 of the protocol stack.
The MAC communicates with the physical layer using the transport channels.
The Main functionality of MAC layer is to map higher layer data on to appropriate transport
channels of the physical layer.
BCCH PCCH BCCH CCCH CTCH DCCH DTCH Logical
MAC-
Channels
Control

MAC - d

MAC-b
MAC – c/sh

Transport
Channels
BCH PCH FACH RACH CPCH DSCH DCH DCH
MAC Layer Logical Architecture

 MAC –b – This controls access to the Broadcast channel (BCH).
 MAC –c/sh – It controls access to the common and shared channels.
 MAC – d – The MAC –d control access to the Dedicated Channel (DCH).

MAC PDU Format

MAC Header MAC SDU

TCTF UE -Id UE-Id C/T MAC - SDU
Type

MAC PDU

 MAC Header Consists of
 Target Channel Type Field (TCTF) – a flag that provides identification of logical channel class on
FACH and RACH transport channels.

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 C/T field – provides identification of the logicalk channels instance when multiple logical channels
are carried on the same transport channels.
 UE – id field – provides an identifier of UE on common transport channels.
 UTRAN Radio N/w Temporary identity(U-RNTI) may be used in MAC header of DCCH when mapped
onto common transport channels in downlink directions the U-RNTI is never used in uplink
directions.
 Cell Radio N/w Temporary Identity(C-RNTI) is used on DTCH and DCCCH in uplink, and may be used
in DCCH in downlink and is used on DTCH in downlink when mapped onto common transport
channels.
 UE-Id to be used by MAC is configured through MAC control SAP.
 UE-Id type field –is needed to ensure correct decoding of UE-Id field in MAC headers.

4.1.2 Radio Link Controller protocol
Tr - SAP AM - SAP UM - SAP

RLC Control

Transmitting Receiving Acknowledged Transmitting Receiving
Transparent Transparent Mode Unacknowledged Unacknowledged
Entity Entitiy Entity Entity Entity

BCCH/PCCH/CCCH/DCCH/DTCH DTCH/DCCH CCCH/CTCH/DTCH/DCCH

RLC Logical Architecture

 Provides Segmentation/reassembly(payload units,PU) and retransmission service for both users and
control data.
 Transparent Mode (Tr) : no overhead is added to higher layer data.
 Unacknowledged Mode (UM) : no retransmission protocol is used and data delivery is not
guaranteed.
 Acknowledged Mode (AM) – Automatic Repeat request (ARQ) m echanism is used for error
correction.

[Type text]


4.1.2.1 RLC Transparent Mode (TM) Entity
Radio Interface
(Uu)
UE/UTRAN UTRAN/UE

TM-SAP TM-SAP

Transmission
Reassembly
buffer
Recei
Transmitti
ving
ng
TM-
TM-RLC
RLC
Entity
Entity

Segmentation Reception Buffer

CCCH/DCCH/DTCH/SHCCH – UE CCCH/DCCH/DTCH/SHCCH – UTRAN
BCCH/PCCH/DCCH/DTCH - UTRAN BCCH/PCCH/DCCH/DTCH - UE

RLC Transparent Mode Entity

Receiving TM-RLC Entity
 The Receiving TM-RLC entity receives TMD PDUs through the configured logical channels from the
lower layer.
 If segmentation is configured by upper layer all TMD PDUs received within 1 TTI are reassembled to
form the RLC SDU.
 If segmentation is not configured by upper layers, each TMD PDUs is treated as a RLC SDU.
 The receiving TM RLC entity delivers RLC SDUs to upper layers through the TM-SAP.

Transmitting TM –RLC Entity
 Transmitting TM-RLC entity receives RLC SDUs from upper layers through the TM – SAP.
 All received RLC SDUs must be of a length that is multiple of one of the valid TMD PDUs lengths.
 If segmentation has been configured by upper layers and a RLC SDU is larger than the TMD PDU size
used by the lower layer for that TTI, the transmitting TM RLC entity segments RLC SDus to fit the
TMD PDUs size without adding RLC headers.All the TMD PDUs carrying one RLC SDU are sent in the
same TTI, and no segment from another RLC SDU are sent in this TTI.
 If segmentation has not been configured by upper layers then more than one RLC SDU can be sent in
one TTI by placing one RLC SDU in one TMD PDU . All TMD PDUs in one TTI must be of equal length.
 When the processing of a RLC SDU is complete the resulting one or more TMD PDUs are is
submitted to the lower layer through either a BCCH, DCCH, PCCH, CCCH, SHCCH or a DTCH logical
channels.

[Type text]


4.1.2.2 RLC Unacknowledged Mode Entity

Radio Interface
(Uu)
UE/UTRAN UTRAN/UE

UM-SAP UM-SAP

Transmission
Reassembly
buffer
Recei
Transmitti
ving
ng
UM-
UM-RLC
RLC
Entity
Entity

Segmentation &
Removal RLC Header
Concatenation

Add RLC Header Reception Buffer

Ciphering Deciphering

CCH/DTCH – UE DCCH/DTCH – UTRAN
CCH/SHCCH/DCCH/DTCH/CTCH - UTRAN CCCH/SHCCH/DCCH/DTCH/CTCH - UE

RLC Unacknowledged Mode Entity

[Type text]


Receiving UM-RLC entity
 The Receiving UM-RLC entity receives UMD PDUs through the configured logical channels from
lower layer.
 The Receiving UM RLC entity deciphers(if ciphering is configured and started) the received UMD
PDUs. It removes RLC headers from received UMD PDUs and reassembles RLC SDUs.
 RLC SDUs are delivered by the receiving UM RLC entity to the upper layers through the UM-SAP.

Transmitting UM-RLC entity
 Transmitting UM-RLC entity RLC SDUs from upper layers through the UM-SAP.
 The transmitting UM-RLC entity segments the RLC SDU into UMD PDUs of appropriate size if the RLC
SDU is larger than the length of available space in the UMD PDU. The UMD PDU may contain
segmented and/or concatenated RLC SDUs. UMD PDU may also contain padding to ensure that it is
of a valid length. Length Indicators are used to define boundaries between RLC SDUs within UMD
PDUs length indicators are also used to define whether padding is included in the UMD PDU.
 If Ciphering is configured and started an UMD PDU is ciphered before it is submitted to the lower
layer.
 The transmitted UM-RLC entity submits UMD PDUs to the lower layer through either a
CCCH,SHCCH,DCCH,CTCH or a DTCH logical channel.

[Type text]


4.1.2.3 RLC Acknowledged Mode Entity
RRC/BMC/
PDCP/..

AM entity
Segmentation and concatenation
RLC Control Unit

Add RLC Header Reassembly

Piggy Backed status
Retx. Buffer and management
Remove RLC Header and extract piggybacked
info
Acks

RLC
MUX
Acks
Reception buffer and management

Transmission Buffer

De-Ciphering
Set fields in PDU header (eg set poll bits) and piggybacked
STATUS PDU

Ciphering Demux/Routing

MAC
RLC Acknowledged Mode Entity

 The Receiving side of the AM-RLC entity receives AMD and control PDUs through the configured
logical channels from the lower layer.
 AMD PDUs are routed to the deciphering unit and then delivered to the reception buffer.
 The AMD PDUs are placed in the reception buffer until a complete RLC SDU has been received. The
receiver acknowledges successful reception or requests retransmission of the missing AMD PDUs by
sending one or more STATUS PDUs to the AM RLC peer entity through its transmitting side.
 The associated AMD PDUs are reassembled by the reassembly unit and delivered to the upper layers
through the AM-SAP.
 RESET and RESET ACK PDUs are delivered to the RLC control unit for processing. If a response to the
peer AM RLC entity is needed an appropriate control PDU is delivered by the RLC control unit to the
transmitting side of the AM RLC entity.

The transmitting side of the AM-RLC entity receives RLC SDUs from upper layers through the AM-
SAP.
 RLC SDUs are segmented and/or concatenated into AMD PDUs of a fixed length.
o The segmentation is performed if the received RLC SDU is larger than the length of available
space in the AMD PDU.
o The PDU size is set during AM-RLC establishment.
o The packets could be segmented, concatenated, padded.
o Boundaries between the packets are indicated by a length indicator.
 After segmentation and/or concatenation are performed the AMD PDUs are placed in the
retransmission buffer at the MUX.
 AMD PDUs buffered in the retransmission buffer are deleted or retransmitted.

[Type text]


 The MUX multiplexes AMD PDUs from the Retransmission buffer that need to be retransmitted and
the newly generated AMD PDUs delivered from the segmentation/concatenation function.
 The PDUs are delivered to the function that completes the AMD PDU header and potentially
replaces padding with piggybacked status information . A Piggy backed STATUS PDUs can be of
variable size in order to match the amount of free space in the AMD PDU.
 The ciphering (if configured) is then applied to the AMD PDUs.
o The AMD PDU header is not ciphered.
o Control PDUs(i.e STATUS PDU, RESET PDU and RESET ACK PDU) are not ciphered.

4.1.3 Packet Data Convergence Protocol (PDCP)
 The Packet Data Convergence protocol (PDCP) layer is used to carry user plane information for the
PS domain.
 PDCP carries data protocols like IP and PPP.
Radio Bearers
(User Plane Information)

PDCP SAPs

Control PDCP
(RRC)

UM AM TM

RLC

PDCP Layer Architecture

 PCDP Architecture provides means to transfer user plane information using one of the modes of RLC
layer (TM, UM or AM).
 The RRC layer controls the behaviour of the PDCP layer.

[Type text]


4.1.4 Broadcast Multicast Control (BMC)
BMC SAP

BMC - Control

BMC Entity

RLC SAPs

UM - SAP
BMC Layer Architecture

 The Broadcast Multicast Control (BMC) layer is used to carry user plane information in the downlink
direction.
 Storage of cell broadcast messages.
 Traffic volume monitoring and radio resource request for CBS.
 Scheduling of BMC messages.
 Transmission of BMC messages to UE.
 Delivery of cell broadcast messages to upper layer.

[Type text]


4.1.5 Radio resource Control (RRC)
 Used for setting up, reconfigured and reestablish radio bearers.

Message Routing
BMC-
Control
SAP

PDCP-
Control
SAP PNFE BCFE
DCFE
RLC-
Control
SAP

MAC-
Control
SAP
I1-
Control
SAP
RLC SAPs

AM-SAP AM-SAP AM-SAP UM-SAP Tr-SAP
RLC Logical Structure

 Dedicated Control Functional Entity (DCFE) – Handler functions and signaling specific to UE one DCFE
entity for each UE.
 Paging and Notification control functional Entity (PNFE) – Paging of idle mode UE. At least one PNFE
in the RNC for each cell.
 Broadcasting Control functional Entity (BCFE) – Handles the Broadcasting of system information.
There is at least one BCFE for each cell in the RNC.

[Type text]


4.1.6 RRC States and States Transition including GSM

UTRA RRC Connected Mode

URA_PCH CELL_PCH

Out of Out of In GSM
In UTRA Inter – GSM Connected Mode
Servic servic Servic Handover
service RAT Handover
e e e

CELL_FACH
Out of In
GPRS Packet Transfer
CELL_DCH Servic servic
Mode
e e

Call Release RR Establish RR
Resele Connection Connection
ction
Release of Initiation of
temporary temporary
block flow block flow
Release RRC Establish RRC Release RRC Establish RRC
Connection Connection Connection Connection

GPRS Packet Idle Mode
Camping on a UTRAN cell
Camping on a GSM/GPRS Cell

Idle Mode

RRC States and States Transitions Including GSM

 Idle Mode –
o After UE in Switched on it will camp in a suitable cell. After Camping.
o User is able to send and receive system and cell broadcasting information.
o In the idle mode until it transmits request to establish RRC connection.
 Cell_DCH
o Entered from Idle Mode or by establishing a DCH from the cell_FACH state.
o DPCH and physical downlink shared channel(PDSCH) is allowed to UE.
o UE is in this mode until explicit signalling for Cell_FACH.
 Cell_FACH
o No dedicated channel allocated. Data transmitted through RACH and FACH.
o UE listens BCH.
o Cell reselection is performed (RNC is informed).

[Type text]


 Cell_PCH
o UE known at a cell level but can be reached via PCH.
o Usel listens BCH, some terminals also BMC.
o In case of Cell reselection automatically moved to Cell_FACH state.
 URA_PCH
o UE executes the cell update procedure only if the UTRAN Registration Area is changed.
o DCCH cannot be used in this state, all the activities initiated by the network through the
PCCH or RACH.

[Type text]


4.2 ATM and ATM Adaptation Layers

4.2.1 Asynchronous Transfer Mode (ATM)

 Asynchronous transfer Mode (ATM) is defined as a transfer mode in which the information is
organized into cells.
 Transfer Mode –
o Transfer Mode is used to transmit, switch and multiplex information. Transfer mode is
means of packaging, sending and receiving information on the n/w.
o Circuit switching and packet switching describe the two extremities of transfer mode.
o In circuit switching it is sent in bit streams, while in packet switching the information is sent
as large frames.
 Asynchronous Name –
o ATM is Asynchronous in the sense that the recurrence of cells containing information is not
periodic.
o The terms Synchronous and Asynchronous refer to the way the data is transmitted.
o In the synchronous mode, the transmitter and receiver clocks are synchronized and frames
are sent/received periodically.
o In asynchronous mode, timing information is derived from the data itself and the
transmitter is not compelled to send data periodically.
 Cell –based transfer –
o The Information in ATM is ‘organized into cells’, which means that lowest unit of
information in ATM is a cell.
o A cell is fixed size frame of 53 bytes, with 5 bytes of header and 48 bytes of payload.
o The header carries the information which is required to switch cells, while payload contains
the actual information to be exchanged.

[Type text]


4.2.2 ATM Protocol Architecture

Management Plane

Control plane User plane

Plane Management
Layer Management
Higher layers Higher Layers
(ALCAP and SAAL) (e.g. TCP/IP)

ATM Adaptation Layer

ATM Layer

Physical Layer

ATM Protocol Architecture

 It is a 3 – dimensional model
 User Plane –
o The User Plane is concerned with the transfer of user information.
o At transmitting side the plane is responsible for packing user information into cells and
transmitting cells using underlying physical medium.
o At receiving side, it performs reverse operation and derives the higher layer information.
 Control Plane –
o The control plane is responsible for establishing and releasing connection between a given
source and destination.
o When a new connection is established, the control plane establishes a mapping at the
intermediate switches between incoming VPI/VCI and outgoing VPI/VCI.
o When a same connection is released, the control plane removes the mapping stored within
the intermediate nodes.
 Management Plane –
o It is responsible for mapping the individual layers in the protocol stack and providing
coordination between the layers.
o It is divided into layer management and plane management.
o Layer Management – Layer management is responsible for managing each of the layers,
including their administration, management and configuration.
o Plane Management – Plane Management is responsible for coordination among different
planes.

[Type text]


4.2.2.1 ATM Adaptation Layer
 ATM Adaptation Layer (AAL) allows existing n/w’s to connect to ATM facilities.
 ATM Adaptation Layer resides over the ATM Layer.
 It is responsible for handling different types of data and mapping the requirements of the
applications to the services provided by the lower layer.
 The AAL2 and AAL5 is used in UTRAN.

ATM Adaptation Layer (AAL2)
 AAL2 resides over ATM layer.

Upper
Layers

Service Specific Convergence Sublayer (SSCS)
(May be Null)

AAL 2

Common Part Sublayer

Lower
Layers
Structure of AAL2

 AAL 2 Layer architecture is divided into 2 parts Common Part Sublayer (CPS) and Service Specific
Convergence Sublayer (SSCS).
 CPS provides the basic functionality of AAL2 which includes the packaging the variable payload into
cells and providing error correction.
 SSCS sublayer directly interacts with the user. This Layer is used to enhance the services provided by
CPS.

[Type text]


 Segmentation and reassembly functions of service specific convergence sublayer is divided into 3
parts.
 Service Specific Segmentation and Reassembly Sublayerv(SSSAR) –This is the Basic function of SAR
SSCS. It includes data transfer of SSSAR – SDUs of up to 65568 octets.
 Service Specific Transmission Error Detection Sublayer (SSTED) - The Role of SSTED is to detect
corrupted SSTED – SDUs.
 Service Specific Assured Data Transfer Sublayer (SSADT) – To provide support for retransmission,
the SSADT function may be used over and above the SSSAR and SSTED function.

ATM Adaptation layer 5 (AAL5)

Upper
Layers

Service Specific Convergence Sublayer (SSCS)
(May be Null)
Convergence
Sublayer

AAL5

Common Part Convergence Sublayer (CPCS)

Common
Part

Segmentation and Reassembly (SAR)

ATM

Structure of AAL5

 The AAL5 Layer is divided into 2 Sublayers convergence Sublayer (CS) and the Segmentation and
Reassembly Sublayer (SAR).
 The CS itself is divided into 2 parts Common part Convergence Sublayer (CPCS) and Service Specific
Convergence Sublayer (SSCS).
 Segmentation and Reassembly (SAR) –
o The segmentation and reassembly sublayer in AAL5 is very simple.
o This layer does not add any header or trailer to the SAR – SDU.
o It just breaks down the SAR – SDU into 48 bytes SAR –PDUs, which in turn form payload of
the cells.
 Common Part Convergence Sublayer (CPCS) –
o The CPCS of AAL5 provides 2 modes of data transfer, namely message mode and the
streaming mode.

[Type text]


o In message mode of data transfer an entire CPCS – SDU is received from the upper layer and
only then transferred to the SAR Sublayer.
o In streaming mode allows the CPCS to start transferring data before it has received the
complete CPCS – SDU from upper layer.

[Type text]


5. Application layer Protocol
5.1 Radio Access Network Application Part (RANAP)
5.1.1 Introduction
 The Iu Interface connects RAN to core n/w.
 The Radio Access n/w application part (RANAP) protocol is used over the Iu interface.
 RANAP carries Non Access Stratum (NAS) messages, which are relayed between CN nodes and the
Ues.
 Iu interface is divided into 2 instances
o The Iu Circuit switched (CS) to connect RAN to the MSC server.
o The Iu Packet Switched (PS) to connect to the SGSN.
 The Iu Interface is divided into
o A Control plane
o A User plane

Radio Resource Management (RRM)

RRC RANAP
RRC RANAP
Messages Messages

Radio
Iu transport
Interface
(Signalling Bearers)
protocols

To To Core
MS Network
RNC

Uu
Iu
Interface
Interface
Layer Architecture for RANAP

[Type text]


Ishiriya Wireless Technologies-3G Architecture, Networks, Protocols

Ishiriya Wireless Technologies-3G Architecture, Networks, Protocols

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