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.
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
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).
In Proceedings of the Second International Conference on e-Business and Telecommunication Networks, pages 5-12
DOI: 10.5220/0001410400050012
execution of a session establishment or the execution
of a handover in a beyond 3G heterogeneous mobile
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.
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,
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
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
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,
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
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
RMP Plane Management
O&M Functions
Context Management
SW Download Management
Service Provision
Reconfiguration Management
Access & Security
Mobility and
Policy Provision
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
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
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.
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.
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
O&M Functions
Device O&M
Network O&M
Device O&M
Network O&M
Intranet/IP backbone
Software Provision
Policy Provision
Profile Provision
BTS/Node B
BTS/Node B
Composite RAN
2/3G CN
IP backbone
4G Access
(Native IP)
WLAN / Wi-Fi
Access Network
Access Network
Access Network
consider multi-mode terminals (i.e., they can be
concurrently attached to two different RATs).
4.1 Connection setup through a
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
enhanced with the appropriate parameters and their
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
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.
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
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
3GPP TR 22.978, 2004. All-IP Network (AIPN)
Feasibility Study (Release 7), V1.0.0.
The Software Defined Radio (SDR) Forum,
M. Dillinger, K. Madami, and N. Alonistioti (Editors),
2003. Software Defined Radio: Architectures, Systems and
Functions, John Wiley & Sons Ltd.
IST-2003-507995 Project E²R (End-to-End
N. Alonistioti, Z. Boufidis, A. Kaloxylos, and M.
Dillinger, 2004. Integrated Management Plane for Policy-
based End-to-End Reconfiguration Services. In 13
Mobile and Wireless Communications Summit, France.
3GPP TS 32.101, 2004. Telecommunication
management; Principles and high-level requirements.
S. Uskela, 2003, Key concepts for evolution toward
Beyond 3G Networks. In IEEE Wireless Communications,
vol. 10, no. 1.
Alexandros Kaloxylos, George Lampropoulos and
Nikos Passas, 2005. A Flexible Mechanism for Service
Continuity in 4G Environments". In Elsevier Computer
Communications Journal, special issue on “End-to-end
QoS Provision Advances” (accepted for publication).