MOBILITY MANAGEMENT FOR BEYOND 3G

RECONFIGURABLE SYSTEMS

Nancy Alonistioti

The University of Athens, Department of Informatics and Telecommunications, Athens, Greece

Alexandros Kaloxylos, Andreas Maras

The University of Peloponnese, Department of Telecommunications’ Science and Technology, Tripoli, Greece

Keywords: Reconfiguration Management Plane, session setup, handover.

Abstract: Reconfiguration is the action of modifying the operation or behaviour of a system, a network

node, or functional entity when specific events take place. This paper describes an integrated

control and management plane framework for end-to-end reconfiguration, and maps this model

to a Beyond 3G mobile network architecture. Emphasis is provided on the reconfiguration

actions that take place when a session setup or a handover are executed in a heterogeneous

mobile network.

1 INTRODUCTION

Evolution of 3G cellular mobile systems and

interworking with off-the-shelf products (e.g.,

WLAN cards and access points) in conjunction with

the progress on broadband wireless IP-based

networks (e.g., IEEE 802.16 series, IEEE 802.20)

and digital broadcasting (e.g., DVB-T, DAB) raises

new research challenges for the control and

management of such Composite Radio Access

Networks (RANs). On the other hand, the trend

towards All-IP mobile networks, with IP routing,

mobility, and Quality of Service (QoS) mechanisms

in addition to recently adopted bare IP transport,

necessitates further research on the efficient

application of IT temperament in evolving telecom

world networking (

3GPP TR 22.978, 2004).

Reconfiguration spans across end-user devices,

network equipment, software, and services. Target

reconfigurable elements include, in the mid-term,

the User Equipment (UE) and Base Stations or

Access Points. Signal-processing modules in the UE

as well as firmware enhancing the Hardware

Abstraction Layer (HAL) can be upgraded.

Operational and non-operational software can be

downloaded (

The Software Defined Radio Forum).

Service and content adaptation have already gained

attention in the mobile world, promising on-the-fly

playout adaptation via, for example, download of

upgraded codecs. In the long-term, interior network

nodes such as routers and switches or even (parts of)

the network itself could be reconfigured, especially

for large user groups requesting specialized

treatment.

In order to accomplish flexible service offering

and to cope with complex systems, the need for end-

to-end reconfigurable architectures, systems, and

functions raises. (

Dillinger 2003, IST Project E²R)

End-to-end reconfiguration dictates the design

and specification of an integrated control and

management plane for coordinating the interactions

between the involved entities, and for enabling the

decision-making and enforcement of mechanisms

supporting reconfiguration in a dynamic fashion. In

(

Alonistioti 2005), the Reconfiguration Management

Plane (RMP) was introduced, whose main task is to

provide layer abstractions to applications and

services on one hand, and to terminal equipment and

network devices on the other. Furthermore, the RMP

is responsible for the coordination of the

reconfiguration process and for the provision of the

required resources. In this paper, we augment the

identified plane management modules with layer

management functions. We also demonstrate a

possible operation of these functions during the

Alonistioti N., Kaloxylos A. and Maras A. (2005).

MOBILITY MANAGEMENT FOR BEYOND 3G RECONFIGURABLE SYSTEMS.

In Proceedings of the Second International Conference on e-Business and Telecommunication Networks, pages 5-12

DOI: 10.5220/0001410400050012

 SciTePress

execution of a session establishment or the execution

of a handover in a beyond 3G heterogeneous mobile

system.

The rest of the paper is organized as follows: the

design goals of modelling control and management

functions for end-to-end reconfiguration are

sketched in Section 2. The constituent RMP modules

and the mapping of the RMP logical model to

evolved physical configurations are described in

Section 3. The challenge for end-to-end

reconfiguration differentiation is elaborated in

Section 4. We conclude and describe future work on

accomplishing the differentiation of reconfiguration

services in Section 5.

2 DESIGN GOALS

End-to-end reconfigurability necessitates an

integrated framework to address all management

aspects related to composite reconfigurable

environments. The ITU FCAPS topics, i.e., Faults,

Configuration, Accounting, Performance, and

Security, comprise traditional management areas,

along with resource management and access and

security management. The 3GPP has introduced

additional management areas tailored to the

management domains and areas of a 3G PLMN,

including roaming management, fraud management,

software management, User Equipment

Management (UEM), QoS Management,

Subscription Management, and Subscriber and

Equipment Trace Management (

3GPP TS 32.101,

2004).

The Reconfiguration Management Plane

comprises a network-agnostic protocol-independent

model for specifying operations and notifications.

The RMP comprises a logical model, i.e., an

expression of an abstract view of a network element

or subnet by means of functional entities

incorporating specific functionality to realize

physical implementation independent control and

management tasks. The Reconfiguration

Management Plane can be considered either as

extension to existing control and management planes

or as a new intermediary plane between legacy

control and management planes for dedicated

reconfiguration-related tasks, such as context

management, policy and profile definition and

provision, service management, and native

reconfiguration and download management. In

addition, the RMP incorporates layer management

functions tailored to the O&M needs of

reconfigurable network elements and subnets (e.g.,

Composite RANs). The above design considerations

are fulfilled by the RMP modules described in the

following section.

The proposal of physical configurations based on

concrete network architectures is achieved by

mapping the RMP model to a horizontal, two-tier

organization of reconfiguration managers within a

single administrative domain. These managers are

hereafter called the ReConfiguration Manager

(RCM) and the Radio Reconfiguration Support

Function (R-RSF). This pair of network elements is

capable of interworking with systems not offering all

areas of traditional management and control, such as

Wi-Fi islands. This design decision is further

elaborated in the following section, which sketches

the network support architecture for end-to-end

reconfiguration.

3 THE RECONFIGURATION

MANAGEMENT PLANE

The Reconfiguration Management Plane

accommodates the following plane management and

layer management modules (Fig. 1).

A. Plane Management Modules

The RMP plane management consists of the

Context Management, Policy Provision,

Performance Management, Access and Security

Management, Reconfiguration Management,

Software Download Management, Service

Provision, and Billing and Accounting Management

modules.

The Context Management Module (CMM)

monitors, retrieves, processes, and transforms

contextual information. Contextual information

affects the service provision phase, and provides

input to policy decisions and reconfiguration

strategies. Contextual information includes profile

information as well as resource-specific information.

Profile composition and provision is handled by the

CMM Profile Management Module (PrMM), which

manages and combines the different profiles. Profile

information originates from different parts of the

system, and includes user profile, network profile,

application/service/content profile, terminal profile

(the so-called Reconfigurability Classmark),

charging profile, and security profile. The CMM

ReSource Management Module (RSMM) handles

resource-specific data regarding the reconfiguration

progress, such as the operational mode, state

information, and congestion indication. In addition,

ICETE 2005 - WIRELESS COMMUNICATION SYSTEMS AND NETWORKS

the CMM Reconfigurability ClassMarking Module

(RCMM) assigns and retrieves the Reconfigurability

Classmark, which characterizes any mobile terminal

and specifies the level of dynamism regarding

reconfiguration, as well as the capabilities of the

terminal (e.g., enhanced MExE/WAP classmark).

The calculated value of the classmark depends on

the type of reconfiguration requested and negotiated,

on the type of software to be downloaded, on

business incentives, and on individual or operational

chains of stakeholders involved in the

reconfiguration process.

The Policy Provision Module (PPM) is the main

decision-making entity for reconfiguration, by

comprising the entry point for reconfiguration-

related system policies. Furthermore, it exploits

contextual information and redefines policy rules

and reconfiguration strategies. This module

produces an up-to-date decision about the feasibility

of a reconfiguration as well as respective actions to

be triggered. In addition, the PPM caters for inter-

domain issues, interacts with Policy Enforcement

Points (e.g., in the GGSN), and facilitates the

mechanics for the differentiation of end-to-end

reconfiguration services.

The Mobility and Performance Management

Module (MPMM) is responsible for mobility

management, triggering and controlling inter/intra

system handovers and also collects performance

measures, usage data, and traffic data, and estimates

performance and cost constraints, which can be

exploited for network-initiated element

reconfiguration.

The Access and Security Management Module

(ASMM) participates in the mutual authentication of

the user / reconfigurable terminal, verifies the

authorization to download, and determines the

security control mechanisms (e.g., agreement on

security keys) prior to download transfer.

The Reconfiguration Management Module

(RMM) initiates network-originated and coordinates

device-initiated configuration commands, by

communicating with Reconfiguration Support

Functions at the User Equipment (U-RSF), as well

as at interior network nodes (e.g., the R-RSF

handling a Composite RAN). In order to accomplish

the supervision of end-to-end reconfiguration, the

RMM incorporates the signaling logic, including

negotiation and capability exchange services. In the

case of scheduled software download, the

Reconfiguration Management Module hands-over

the control of the residual reconfiguration steps to

the Software Download Management Module.

Finally, the RMM undertakes the necessary session

management and Mobility Management (MM)

context transfer and translation in cases of inter-

domain handover, e.g., from a 3GPP System to a

WLAN/Wi-Fi access network.

The Software Download Management Module

(SDMM) is responsible for identifying, locating, and

triggering the suitable protocol or software for

download, as well as for controlling the steps during,

and after download.

The Service Provision Module (SPM) is

responsible for the interaction between the RMP and

the application/service. This entity accepts and

processes service improvement requests from the

service providers. In addition, the SPM can initiate a

reconfiguration command on behalf of the

application. For example, it can initiate network

configuration changes or selection of different

settings by the users, or it can launch mobility-

induced events. In addition, the Service Provision

Module may trigger service adaptation actions based

on network or device capability modifications, or

based on updated policy conditions. Finally,

roaming issues for service provisioning are also

tackled by the SPM.

Finally, the Billing and Accounting Management

Module (BAMM) collects charging records from the

additional network elements supporting

reconfiguration (i.e., the R-RSFs), processes these

records, and apportions the reconfiguration-induced

revenues to the involved business players.

B. Layer Management Functions

Layer management functions handle Operation

and Maintenance (O&M) tasks per protocol layer.

The number and scope of these layers depends on

Figure 1: The reconfiguration management plance.

RMP Layer

Management

RMP Plane Management

O&M Functions

ASCU

centric

O&M

specific

O&M

RAT

centric

O&M

Device

specific

O&M

Network

centric

O&M

Context Management

SW Download Management

Service Provision

Reconfiguration Management

Profile

Management

Reconfigurabilit

Classmarking

Resource

Managemen

Access & Security

Management

Mobility and

Performance

Management

Billing/Accounting

Management

Policy Provision

MOBILITY MANAGEMENT FOR BEYOND 3G RECONFIGURABLE SYSTEMS

the managed environment. In environments

supporting end-to-end reconfiguration, layer

management functions can be introduced in order to

support the service provision stage, and should be

adapted based on input related to the definition and

enforcement of reconfiguration policies. End-to-end

differentiation of reconfiguration services should

also take into account the outcome of

reconfiguration functions for O&M, such as

monitoring reports and capabilities of network

elements.

Reconfiguration-oriented O&M functions can be

classified to five categories: Application-, Service-,

Content- and User-centric (ASCU) functions;

Operating-System-specific; Network-centric; RAT-

centric; and Device-specific.

Provision of customer care information is a

typical example of ASCU-centric O&M function.

Logging is an important feature, offering the history

of reconfiguration actions (e.g., recent over-the-air

upgrades), statistical information on the latest faults

and alarms reported to the user, etc.

OS-specific O&Μ functions should coordinate

the auditing, testing, and validation procedures at the

reconfigurable terminal. Network-centric O&M

functions estimate the impact of mobility and QoS

on the software download process. In addition,

dynamic network planning and its impact on traffic

split comprise important O&M functions for

reconfigurable network elements.

RAT-centric O&M functions manage RAT-

specific issues for a single Radio Access Technology

or guarantee efficient collaboration of multiple

RATs. The Composite Radio Environment

Management function handles stability, conflict

resolution, and certification issues, and ensures

proper collaboration between network infrastructure

manufacturers and terminal providers. The Radio

Element Management function cooperates with the

RMP Performance Management Module. Analysis

of RAT-specific performance data is an example of

performance management, which may in turn affect

real-time reconfiguration. The Function Partitioning

and Reallocation entity coordinates coupling issues

as well as distribution of functional entities for

multi-RAT environments owned by a single

administrative authority. Finally, the Interworking

function verifies the correct operation of control

plane functionality between radio elements owned

by different operators, as well as network sharing

scenarios. RMP RAT-centric O&M functions

communicate with the R-RSF for efficient

management of composite multi-RAN

environments.

Device-specific O&M functions include, for

example, functions for User Equipment

Management. Remote equipment diagnosis assists in

the remote identification of equipment faults, taking

into account security threats. Finally, coordination

with Hardware Abstraction Layer configuration

modules can also be accomplished through device-

specific RMP O&M functions.

C. The RMP in a Beyond 3G Mobile Network

The provision of end-to-end reconfiguration

services and management in Composite RAN

environments, coupled with scenarios of evolved

core network architectures (

S. Uskela, 2003), should

be accommodated via a two-tier control and

management architecture depicted in Fig. 2. From a

high-level perspective, the architecture consists of

two managers, i.e., the ReConfiguration Manager

and the Radio Reconfiguration Support Function.

The RCM is a realization of the RMP logical

model to the heterogeneous network architecture. To

cope with complex scenarios, the RCM is located at

the highest network hierarchy, i.e., either in the core

network domain (e.g., attached to the Gi and/or the

Gp interface in a 3GPP System) or in a trusted third

party domain. Alternatively, the RCM would be

distributed in the core network, with its functionality

apportioned to the SGSN and GGSN. The first

option facilitates future architectural scenarios. For

example, apart from intra-domain connection of

RAN nodes to multiple CN nodes currently

supported in a 3GPP Release 6 System, inter-domain

connection as well as network sharing scenarios

dictate the presence of the RCM as a separate

network element beyond the GGSN in the network

hierarchy. This decision also facilitates independent

evolution paths for future all-IP core networks, i.e.,

with IP routing and IP mobility except IP transport

[1]. The second option is more efficient for mobility

management purposes; when a User Equipment

abruptly de-attaches from a 3GPP System and

attaches to a WLAN or Wi-Fi hot-spot, the RCM

Reconfiguration Management Module should

manage the necessary Mobility Management (MM)

context to capture the movement from UMTS to

WLAN and vice versa.

The R-RSF manages a single or a Composite

RAN, thus, being responsible for functions such as

Joint or Common Radio Resource Management,

Network Planning, and Spectrum Management [7].

The R-RRSF function in UMTS is placed in the

RNC and cooperates closely with RNC’s RRC to

execute handovers and session establishments.

ICETE 2005 - WIRELESS COMMUNICATION SYSTEMS AND NETWORKS

Fig. 2, also depicts a collection of repositories in

the form of four integrated systems. The collection

of profile repositories should be viewed as a

composite Profile Provision System (PPS). The PPS

should apply to an n-tier system capable of

disseminating profile management policies into an

n-layered architecture. Such multi-tier architecture

can be constructed based on topological

considerations and/or on semantic aspects.

Segmentation and distribution of profile data

representation via profile staging, should offer

performance and flexibility benefits.

Accordingly, the download servers are organized

into a Software Provision System, whilst the Policy

Provision System holds reconfiguration policies and

strategies. Finally, the Billing and Accounting

System calculates the revenues induced by

reconfiguration operations, both due to signaling and

user traffic.

4 SESSION SETUP AND

HANDOVER EXECUTION

As a case study we consider a network topology

similarly to the one of Figure 2 where a UMTS

network is integrated with a WLAN. We consider a

tight integration between the two systems in order to

achieve a satisfactory performance for the execution

of mobility management procedures.

To understand in depth the proposed

functionality of RCM and R-RSF we consider the

establishment of a session setup and the execution of

an vertical handover from UMTS to WLAN. In both

cases we make the following assumptions:

1) Both the UMTS and the WLAN infrastructure

belong to the same operator.

2) There is global UMTS coverage but WiFi

islands also exist.

3) The MT has always a UMTS signaling

connection through which it initiates all procedures.

It can however choose to pass a number of its new or

established data connections through a WLAN for

reasons of cost and bandwidth availability.

4) The session establishment and the execution

the handover are executed in two phases. Initially,

the MT gathers dynamic network information (e.g.,

SNR status) and combines this information with

static information such as the user profile (e.g.,

preferences in execution efficiency and cost,

subscription status), the terminal capabilities, the

service profile and builds a prioritized target list of

RAT to be used. This list is send to the network

where the operator will enforce its policy based on

the current traffic load of the targeted RATs and the

subscription class of the requested user.

5) The overall system guarantees seamless

service continuity (Kaloxylos, 2005) and we

Figure 1. The RMP in a Beyond 3G mobile network architecture.

Control/Management Functions

CMM

RSMMPrMM

RCMM

PPM BAMM

PeMM

RMM

SDMM

ASMM

SPM

O&M Functions

ASCU O&M

OS O&M

RAT O&M

Device O&M

Network O&M

ASCU O&M

OS O&M

RAT O&M

Device O&M

Network O&M

Billing/Accounting

System

RCM

Intranet/IP backbone

Software Provision

System

Policy Provision

System

Profile Provision

System

GERAN/UTRAN

BTS/Node B

U-RSF

UEUE

U-RSF

Composite RAN

2/3G CN

IP backbone

BSC/RNCBSC/RNC

4G-BSC

2/3G-SGSN2/3G-SGSN

3G-GGSN3G-GGSN

3G CN

3G-SGSN3G-SGSN

3G-GGSN3G-GGSN

R-RSFR-RSF

2/3G-SGSN2/3G-SGSN

BSC/RNCBSC/RNC

4G Access

Network

4G CN

(Native IP)

WAG/PDGWAG/PDG

WLAN / Wi-Fi

Access Network

4G-BS

APC

WiMAX

Access Network

DxB

Access Network

APCAPC

R-RSFR-RSF

MOBILITY MANAGEMENT FOR BEYOND 3G RECONFIGURABLE SYSTEMS

consider multi-mode terminals (i.e., they can be

concurrently attached to two different RATs).

4.1 Connection setup through a

WLAN

Figure 3 illustrates the signalling message exchange

when a data connection is configured to pass

through a WLAN access network. Before any

service is executed, the MT needs to attach to the

network and initiate an RRC signalling connection.

Then, the MT scans the signal strength of the

neighbouring Node Bs and APs. When a service is

to be executed, it decides that a PDP connection is

required, and issues an Activate PDP Context

Request Message towards the SGSN.

The SGSN-RCM checks the user’s subscription,

selects the Access Point Name (APN) and performs

the host configuration. It then sends a Create PDP

Context Request to the target GGSN. The GGSN

creates an entry to its context table to enable the

packet routing with the external packet data

networks and returns a confirmation message to the

SGSN (Create PDP Context Response).

Figure 3. Outgoing connection setup through WLAN

After receiving the RAB assignment request and

before activating the Radio Access Bearer, the

RNC’s RRC asks for the current measurements from

the MT. The U-RSF entity replies with the MT’s

prioritized list of target access networks based on the

reachable APs or Node Bs, the service requirements,

the user preferences and the terminal profile. The

RNC’s R-RSF will process this list and will decide,

based on the traffic load and the policy of the

operator, whether this connection should be served

by a WLAN or the UMTS.

In our scenario we assume that WLAN is

preferred and thus the RNC a) notifies the MT with

an Inter RAT Handover from UTRAN message to

associate with the WLAN and b) notifies SGSN-

RCM (RAB Assignment Response) that resources

should be allocated in the WLAN for the specific

PDP context. The first message may also contain

information or protocols that the MT will need in

case this is the first time it will connect to a WLAN.

Right after the receipt of Inter RAT Handover

from UTRAN message, the MT will be reconfigured

to send all session related packets through the

WLAN interface. U-RSF is the responsible entity to

accomplish the reconfiguration. When the 802.11

association and the reconfiguration are completed

then the AP’s R-RSF is notified. This entity in its

turn will notify the SGSN-RCM entity.

At the same time, when the SGSN-RCM is

notified by RNC’s RRC, it sends to the AP’s R-

RSF a RAB Assignment Request message. Upon

receipt of this message the AP’s R-RSF reserves

resources and it will notify the SGSN about the

completion of all radio resource management

procedures and the MT’s reconfiguration. Finally,

SGSN-RCM receives the RAB assignment Response

and it will notify the MT that the connection is

active and communication can begin (Activate PDP

context accept).

Handover from UMTS to WLAN

The execution of handover from UTRAN to

WLAN is illustrated in Figure 4. A MT with active

connections monitors periodically for events that can

trigger a vertical handover (e.g., the signal received

by neighboring APs and Node Bs, battery level,

etc.), either for a specific PDP context or for all PDP

contexts. In case a MT moves from the coverage

area of one RNC to another, then any active PDP

context will be switched either to a target RNC or a

target AP. In this section, the single PDP-context

transfer case to a target AP is discussed.

When a handover initiation criterion is met, the

U-RSF checks the different profiles (i.e., service,

user, terminal) and builds a prioritized list for the

service that needs to be handed over to a different

radio access technology. This list is sent with the

message Measurement Report to the RNC’s

RRC. This message is the standard RRC message

ICETE 2005 - WIRELESS COMMUNICATION SYSTEMS AND NETWORKS

enhanced with the appropriate parameters and their

semantics.

Based on the policy of the operator and the

traffic load measurements, the received list is

processed by the R-RSF based on the operator’s

policy for the current traffic load and the user’s

subscription status.

In our example the target AP is selected and the

RNC’s RRC is notified (RAT Selection). In its turn

the RRC will notify the SGSN’s RCM that the PDP

Context will be relocated to the AP. In the next step

the MS’s RRC will be notified (Inter RAT handover

from UTRAN).

The RNC’s RRC will also notify AP’s R-RSF to

start receiving packets from the serving RNC

(Relocation Commit). The MT, upon reception of the

Inter RAT Handover from UTRAN, it reconfigures

the protocol stack to exchange all session related

packets through the WLAN interface. It also

establishes an 802.11 association with the AP.

The AP’s R-RSF notifies the SGSN that a

handover is under execution (Relocation Detect).

Upon reception of this message, the SGSN

configures the GTP-U protocol to switch the flow of

the specific PDP Context towards the AP.

When the MT finishes the WLAN association, it

communicates with the AP (Inter RAT Handover

From UTRAN Indication). In case reservation of

resources is needed at the WLAN, this is done at this

point using standard IP-based QoS provision

methods, such as RSVP. This clearly requires proper

mapping of UMTS QoS parameters to IP-based QoS

parameters at the MT and ERNC. After that, the

SGSN is notified (Relocation Complete) to release

resources (Iu Release Request/Complete) in the

UMTS.

In case there are no resources to serve the

connection, then the relocation process fails. The AP

notifies the SGSN to try the next candidate in the list

of target RATs, if there is one left.

5 CONCLUSIONS

We presented an integrated plane management and

layer management framework for the support of end-

to-end reconfiguration, and elaborated on the

constituent modules for control and management

operations. The introduced Reconfiguration

Management Plane comprises a network-agnostic

protocol-independent model for specifying

operations and notifications, viewed as extension to

existing control and management planes or as a new

intermediary plane for dedicated reconfiguration-

induced tasks.

Envisaging the major challenges for end-to-end

reconfiguration differentiation, we identified the

requirement of communication between

reconfiguration-aware and unaware nodes, and the

necessity to offer transparent reconfiguration

services.

To prove the feasibility of our proposal we

demonstrate how the overall architecture would

operate in the case of session establishment and

handover execution in tightly coupled UMTS-

WLAN network. The proposed procedures are based

on existing protocols and mechanisms which we

enhance to support the required reconfigurable

functionality. The result is a network that can

support advanced services which are future proof

since they are easily modified and extended.

Figure 4: Handing over a connection from UMTS to

WLAN

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MOBILITY MANAGEMENT FOR BEYOND 3G RECONFIGURABLE SYSTEMS

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