8/8/2019 4g_issues

1/6

Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made ordistributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post onservers or to redistribute to lists, requires prior specific permission and/or a fee.

InterSense '06. Proceedings of the First International Conference on Integrated Internet Ad hoc and Sensor Networks, May 30-May 31 2006, Nice, France2006 ACM 1-59593-427-8/06/05...$5.00

Mobility Management Challenges and Issues in 4G Heterogeneous NetworksSadia Hussain, Zara Hamid and Naveed S. Khattak

Department of Computer Sciences, MCS, NUST, Pakistan

{sadia_swe, xarahamid}@yahoo.com

khattakn-mcs@nust.edu.pk

Abstract

Mobility is one of the most invigorating features,

having an enormous impact on how communication is

evolving into the future. Mobility in 4G networks

requires new level of mobility support as compared to

traditional mobility. There is plenty of related research

on mobility in next generation networks, which

promises support for emerging ambient and ubiquitous

communications. This paper aims to identify and

explore the different issues and challenges related tomobility management in 4G heterogeneous networks.

A review of the existing solutions and ongoing projects

related to these mobility management issues is

presented; which can help in discovering a unified

approach to seamless mobility in future generation

networks.

Keywords: 4G heterogeneous networks, ambient,

ubiquitous, mobility management, mobility

architecture.

1. Motivation

Mobile communications and wireless networks are

developing at an astounding speed, with evidences ofsignificant growth in the areas of mobile subscribers

and terminals, mobile and wireless access networks,

and mobile services and applications. The present time

is just right to start the research of 4G mobile

communications because of the limitations of 3G [1]:

Necessity: according to 3G goals, 3G is necessary

but not sufficient to the mobile communication

strategy, in which many problems are only partly

solved and there are still many problems left to be

solved in the next generation, i.e. 4G.

Difficulty in continuously increasing bandwidth and

high data rate to meet multimedia services

requirements, together with the coexistence of

different services needing different QoS. Limitation of spectrum and its allocation.

Difficult to roam across distinct service environment

in different frequency bands.

Lack of end-to-end seamless transport mechanism

spanning a mobile sub-network and a fixed one.

A new level of mobility support is required by the

networks supporting emerging ambient and ubiquitous

communication needs. Mobility exposes users to

heterogeneity and dynamics on different levels, e.g.

access technologies, trust domains, device capabilities

and user contexts. As a result, the clear distinction

between network and terminal is increasingly

breaking down, as is the distinction between user

and operator with laypersons turning into operators

of small personal area or vehicular area networks [2].

The 4G mobility management includes additionalmobility related features, absent in previous generation

networks, such as; Moving Networks, Seamless

Roaming and Vertical Handover.

Our aim is to explore the above mentioned and

other such mobility management issues, and review the

available solutions. The rest of the organization of this

paper is as follows: In the Second section we are going

to discuss the architecture of 4G networks from

mobility point of view. The Third section deals

specifically with mobility challenges in 4G. In section

Four we will be reviewing the present and upcoming

solutions and projects.

2. 4G Heterogeneous Networks GeneralArchitecture

For 4G networks a Full IP model is proposed. The

major idea is to have one common internet core for all

different access networks. This architecture looks very

simple and is optimal. Services are provided partly by

mobiles themselves and the Service Domain while the

Network Domain is responsible about the bit pipe

management. But there are also huge challenges in this

paradigm since otherwise this solution would have

been implemented a long time ago. Some concern has

to still dedicate for the Quality of Service (QoS),

Security and Mobility Management (MM) support.

Distributed architecture, where control and user planesare separated, may also lead to performance and

network management challenges. But, it can be

assumed that, sooner or later the future architecture

will resemble this one [3].The 4G Mobile

communications will be based on the Open Wireless

Architecture (OWA) [4] to ensure that the single

8/8/2019 4g_issues

2/6

terminal can seamlessly and automatically connect to

the local high-speed wireless access systems when the

users are in the offices, homes, airports or shopping

centers where the wireless access networks (i.e.

Wireless LAN, Broadband Wireless Access, WirelessLocal Loop, HomeRF, Wireless ATM, etc) are

available. When the users move to the mobile zone, the

same terminal can automatically switch to the wireless

mobile networks (i.e. GPRS, W- CDMA, cdma2000,

TD-SCDMA,etc.).This converged wireless

communication can provide the following advantages

[4]:

Greatly increase the spectrum efficiency

Mostly ensure the highest data-rate to the wireless

Best share the network resources and channel

terminal utilization

Optimally manage the service quality and

multimedia applications

The modules within the architectural framework

should be able to incorporate the following high-level

mobility issues:

Users: This focuses on the movement of user, and

allows user access to his/her home network while on

the move [5][6], which involve the provision of

personal communication.

Terminals: This allows the provision of services at

any time and anywhere. Terminal mobility allows

mobile clients to roam across geographic boundaries

of wireless networks. The greatest challenge in

providing terminal mobility within a 4G

Infrastructure is to locate and update the locations of

the terminals in various systems.

Networks: Network mobility is the ability of the

network to support roaming of an entire subnetwork,

structured or ad hoc.

Figure 2.1: Mobility Dimensions [11]

Applications: Mobile application should refer to a

users profile so that it can be delivered in a way

most preferred by the subscriber, such as context-

based personalized services [1].

The incorporation of new functions into existing

mobility protocols and mechanisms does not

appropriately solve the demands of future

communication scenarios. Therefore a new Mobility

Architecture needs to be defined, based on the

following principles: Diversity, Harmonization among

layers, Legacy Awareness, Concept of mobile entities

and Naming and name management

3. Mobility Management Issues

According to the mobility scenarios [8] for future,

referred to in many ongoing researches and projects;

many requirements have been identified on the basis of

which the following mobility management issues can

be highlighted and are discussed as follows:

3.1. Connectivity

3.1.1. Triggering. Different kinds of events:

traditional radio link specific conditions, context-

dependent, security-related, upper-layer requirements

and other system, application or user-dependent events

within a pervasive environment can trigger mobility

management actions. These triggers are internal to the

network, and the triggering functional area has to

coordinate and develop mechanisms to compile

triggers that could be relevant to the HO decision

process. A general framework is required to resolve

conflicting triggers generated simultaneously by

different components, on the basis of predefined

policies and rules. The functionality of the triggering

processing component could be thought of containing

the following functions [13]:

Collecting and identifying various events, which

may trigger mobility management actions.

o for Handover Process

o for Routing Group Management

The handover decision engine that determines the

necessity of handovers and the applicable handover

mobility dimension based on production rules.

Decision contention resolution that might occur

among the mobility management decisions.

3.1.2. Handover. In the emerging 4G networks which

are both multi-domain and multi-technology, handover

requests could be based on a number of different needs

or policies such as cost reduction criteria, network

resource optimization, service related requirements,etc. Various handover solutions have been devised to

provide seamless transfer of services across

heterogeneous boundaries.

IP-Based: Many researchers agree that Mobile IP will

be the key for providing efficient interworking

8/8/2019 4g_issues

3/6

between different technologies. [9]Provides a solution

to a soft-handover management at the IP layer. The IP

Soft handover approach is based on four main

processes: the registration process, the duplication

process, the merging process and the handoverprocess. They allow duplication and merging of IP

flows without the need to synchronize duplicated-flow

transmission.

IDMP-Based[10]:IDMP protocol is designed to

provide intra domain mobility and does not use MIP

for global mobility management. IDMP uses two

dynamically auto configured care-of addresses (CoAs)

for routing the packets destined to mobile nodes. The

global care-of address (GCoA) is relatively stable and

identifies the mobile nodes attachment to the current

domain, while the local care-of address (LCoA)

changes every time the mobile changes subnets and

identifies the mobiles attachment to the subnet level

granularity. This handoff minimizes the intra-domain

update delay & completely eliminates the Link-layerestablishment delay providing a fast handoff

mechanism.

Agent-Based: are being widely explored to provide

seamless roaming within heterogeneous networks. [6]

Presents an architecture where the basic structural

elements are software agents that either represents

users, network providers or the MAP. The

architectures focus is on the initiation and decision

phases of the handover mechanism. Handover target is

selected among wireless networks on the basis of user,

terminal and application constraints. The adoption of

the agent oriented approach simplifies

conceptualization and modeling of the system.

3.2. Location Management

Location management involves two operations;

location registration and call delivery. Location

registration involves the mobile terminal periodically

updating the network about its new location (access

point).This allows the network to keep a track of the

mobile terminal. In the second operation the network is

queried for the user location profile and the current

position of the mobile host is retrieved.

Current techniques for location management

involve database architecture design and the

transmission of signaling messages between various

components of a signaling network [11]. Since locationmanagement deals with database and signaling issues,

many of the issues are not protocol dependent and can

be applied to various networks such as PLMN-based

networks, the PSTN, ISDN, IP, Frame Relay, X.25, or

ATM networks, depending on the requirements.

3.3. Routing Group Formation (Moving

Networks)

Moving networks (persons with a few devices,

entire trains) are a prominent component of futurenetworking scenarios. a typical example can be of

moving users with several terminals forming

temporary moving clusters and network hierarchies

while travelling on a train. A common characteristic

for this kind of scenarios is that some mobile entities

that are close by move together, forming a cluster,

these devices will often, but not necessarily, be joined

together into a unified network. The formation of this

unified network will be highly dynamic, and some

kind of hierarchy will be needed in order to integrate

them into encapsulating moving networks. These

requirements bring about the necessity of new ways of

communication between devices as well as protocols to

recognize, set-up, and maintain these cluster-triggered

Networks which usually share many commonalities

with traditional ad-hoc networks [2].

3.4. Seamless Mobility

Seamless mobility must be a set of solutions that

will provide easy, uninterrupted access to information,

entertainment, communication, monitoring and control

when, where and how we want, regardless of the

device, service, network or location. Instead of

experiencing a disconnect as movement occurs

between different devices, environments and networks,

seamless mobility will deliver experiences that span

the home, vehicle, office and beyond. Such

architecture [12] incorporates a continuum of wide

area networks, including existing networks such as

CDMA, GSM9 and 3G, cable, fiber and DSL, and

emerging 4G networks and 802.16 wireless OFDM

based broadband networks such as WiMAX. It also

encompasses shorter range networks such as 802.11,

Bluetooth and Ultra-Wide Band (UWB) wireless that

may be deployed in homes, vehicles and public places.

All are connected to a common IP core network

through gateways.

3.5. Mobility Context Management

It is assumed that the future terminals, applications

and networks will be able to provide a versatile set ofinformation about themselves, their surroundings and

the situation where they are used. Already SIP[24]

protocol provides means for the end user to express a

number of alternative contact means. The user and the

application context information, that could be either

8/8/2019 4g_issues

4/6

static or dynamic, should be structured for efficient

mobility management.

The mobility management component needs

access to the Context Information Base, CIB, within

the network that is responsible for maintaining userpolicy and context information, and that is updated by

mobility triggers from the mobility events. The

mobility management component could act proactively

or on demand basis depending on the decision logic

and the state of the context information. Based on this

and other supplemental information, such as terminal

capacity, type and number of interfaces, network

topology and availability, the mobility context

management guides the handover process decision

process. The use of mobility context management to

implement inter-address space mobility, inter-trust-

domain mobility and aggregation of mobility are areas

of further research [13].

3.6. Paging

Current paging solutions are dependent on the

link layer technology and network structure. The 4G

Network requires the facility to be able to page across

heterogeneous network technologies. For instance, a

multi-interface terminal may switch its wide-area

interface into a power saving mode, but keep its

shortrange Bluetooth-interface active. Thus, the device

may be paged over the wide-area interface, or

incoming calls would be always routed through the

active short-range radio interface [10]. IDMPs IP-

layer paging solution provides a flexible and radio-

technology-independent solution to this important

problem and helps minimize the power wasted by anMN in unnecessary mobility related signaling. Since

limited broadcast of solicitations is really the central

feature of paging, the idea of multicast groups can be

extended to provide paging support [13].

3.7. Network composition

Composition, as a new architectural element, can

enable new type of dynamic networks where new

business models and roles evolve: anyone can become

a network/service operator. In this view, everything is

a network and a terminal is a network itself [8].

Composition of networks will be possible,

independently from the technologies of composingnetworks: the networks will be available anywhere,

realizing the always best connected vision for the

user. These new networks will be made of specific

network types integrated: sensor networks, personal

area networks, vehicular networks, ad-hoc networks.

There are two possible approaches to composition,

centralized and decentralized [8] .The first step is to

perform network and discovery services. Once a

network has been found in the neighborhood,

authentication and authorization takes place to build atrust relationship between the ambient networks

involved. Following this, the networks will negotiate

and create composition agreement. Two Networks can

compose in three different ways, referred to as network

integration, control sharing and network interworking.

It would allow composition of different networks

either dynamically or statically, to provide a control

space that enables sharing of information, resources

and service components.

3.8. Migration

Backward compatibility and migration is one of

the basic requirements in the evolution and deployment

of heterogeneous networks. Although migration from

current technologies and compatibility is different,

similar approaches that address both these issues exist.

Backward compatibility enables smooth migration. So

such a design should be aimed that includes existing

technology in the following ways:

Encapsulation of existing functionality to be used to

hide it and use it in a different context with potentially

different interfaces.

Enhance functionality to make it compatible and

interoperable with new networking functionality.

Interoperate with existing technologies using their

original interfaces. This means to extend the new

technology by additional interface [8].

Migration strategies [8] for mobility management needto distinguish between local and global mobility

management solutions.

4. Research Scenarios and Discussions

There is considerable research being done on

mobility management within heterogeneous networks,

out of which some popular and current projects would

be discussed in this section. Mobility solutions can be

found by either developing improvements within the

current architecture, or by revising the architecture to

reflect the changing environment and to comply with

the new requirements. Each discussed solution is

unique and focuses on mobility management from aparticular point of view e.g. connectivity, location

management, network management etc. The solutions

propose different addressing and packet forwarding

schemes. Almost all of them are IP based solutions,

which allow interoperability and easy integration with

8/8/2019 4g_issues

5/6

the existing architectures. Within each of the solutions

the relevance to mobility and their strengths and

limitations, are discussed very briefly.

The Internet Indirection Infrastructure (i3) [15],

is a scalable, self-organizing scheme which easilyintegrates with legacy systems. It proposes an

architecture that offers a communication abstraction

based on rendezvous points in an overlay network.

When a host wants to send a packet, it forwards the

packet to one of the servers it knows. A packet

keeps traversing the network till the target server is

reached; this leads to delay in route discovery and

packet forwarding.

FARA (Forwarding directive, Association, and

Rendezvous Architecture) [16] is an ongoing

project whose main purpose is to provide mobility

by separating location from identity. One advantage

is that neither an entirely new namespace nor a

globally unique one is required for the entities. It

allows several different forwarding mechanisms to

co-exist in the network, resulting in variability in

characteristics like mobility, identity, and

anonymity. However, FARA model fails to take into

consideration many packet forwarding issues like

performance of network nodes, or the balance of

anonymity vs. identity for communicating end-

nodes. It does not accommodate for security either.

Recent work on HIP (Host Identity Payload) [17]

provides another way of breaking the binding

between identities and topological locations of

network nodes. HIP introduces new cryptographic

identities that can be dynamically mapped to IP

addresses. However, HIP Host Identity (HI), being a

public key, is not practical in all actions; it issomewhat long, it needs to be hashed before being

used in IPv6 applications. While providing support

for mobility and multi-homing with a major

architectural change in the addressing concept, the

solution requires only small changes in current host

implementations.

IST MIND [20] develops the concepts and protocols

generated in BRAIN [19] by enabling hosts to co-

operate with self-organizing wireless ad-hoc

networks. It provides independent, interoperable

solutions for local/micro-mobility from global

mobility.

DRiVE [21] specifies a multi-access architecture

allowing for seamless intersystem- handover. Theconcept of a host-controlled flow control was

developed to enable parallel usage of different

access systems. The architecture is based on

Hierarchical Mobile IP, extended by an AAA

(Authentication, Authorization and Accounting)

component. OverDRiVE [22] extends the scenario

with moving networks (e.g. vehicles, trains, etc.) in a

multiradio/multi-access environment, defines a

Mobile IP-based solution, and focuses on multicast

support. The project has strong influence on theongoing work within the IETF NEMO [22]

(NEtwork MObility) group.

The architectural principles of Ambient Networks

[2] [7] [8] require the integration of a multitude of

different communication environments, rather than

suffer from heterogeneity. The approach is to use

network composition as the principle: Instead of

terminals, networks as such can form the basic

building block of the communication architecture.

Network composition is a more powerful concept

than the simple internetworking as enabled by the

Internet Protocol. The current Internet assumes

homogeneity in the environment in which to provide

control. Ambient Networks have the potential to

solve this issue of fragmented control.

Developing Standards for Seamless & Secure

Mobility [14]: Several industry consortia and

standard development organizations such as the

IEEE 802 LAN/MAN Standards Committee and the

Internet Engineering Task Force (IETF) are

expending considerable efforts to develop a common

framework and extend existing mobility protocols in

order to facilitate and optimize handover

performance. Various activities are currently under

way, including extensions to Mobile IP at the IETF,

and the formation of the Media Independent

Handover (MIH) working group in IEEE 802, in

addition to several task groups within IEEE 802.11

in order to deal with roaming (IEEE 802.11r) andinterfacing to external networks (IEEE 802.11u).

The best solution among the current and ongoing

projects will be the one that successfully addresses all

the present related challenges as well as allows

scalability for future possibilities. In our point of view,

out of all the above stated schemes, Ambient

Networks provides an optimum solution for all the

mobility management issues discussed. It not only

provides network composition as an additional feature,

but also takes into account the possible future

scenarios as well. A few open issues, however, need to

be addressed in most of the existing projects; i.e.

synchronization of the entire network and sound QoS.

5. Conclusion

The intention of the paper is to focus on the

different aspects significant to realize mobility within

4G heterogeneous networks. WWI projects; E2R, and

8/8/2019 4g_issues

6/6

Ambient Networks are leading the research, in

mobility within heterogeneous networks. MOBY

DICK, BRAIN, MIND and DRiVE are examples of

some ongoing research work committed towards

achieving seamless mobility within 4G networks. Thispaper reviews the developments within this area,

highlights the prominent issues to be focused upon;

and suggests possible ways of dealing with such

issues. Integration of different technologies, seamless

mobility and interworking, composition of networks

and connectivity, are some of the most crucial issues

that need to be addressed in order to accomplish

complete and seamless mobility within a ubiquitous

infrastructure. The progress towards uninterrupted

mobility will, certainly, pave the way for successfully

deploying next generation heterogeneous networks.

Providing mobility architecture for 4G networks

is a very challenging task for the wireless research

community. There are many issues involved in

seamless mobility within a heterogeneousenvironment, which are yet to be dealt with, the most

critical being security, End-to-End Reconfigurability,

providing QOS and interoperability between different

standards and synchronization of the networks

globally. Further issues like mobile multimedia,

handoff delay, adaptability and scalability and most

importantly providing connectivity at vehicular speeds

will play an important role in the design of efficient

mobility architecture.

6. References

[1] Jun-Zhao Sun, Jaakko Sauvola, and Douglas Howie,

Features in Future: 4G Visions from a TechnicalPerspective.In IEEE Global Telecommunications

Conference, GLOBECOM '01.

[2] Ville Typp, Jochen Eisl, Jan Hller, Ramn Agero

Calvo, and Holger Karl, Research Challenges in Mobility

and Moving Networks: An Ambient Networks View. In

Workshop on Challenges of Mobility in conjunction with

IFIP World Computing Congress , 2004.

[3] Y Raivio, 4G - Hype or Reality. In IEE 3G Mobile

Communication Technologies, Conference Publication, Mar.

2001, No 477, pp. 346-350.

[4] Janny Hu,Willie W. Lu ,Open Wireless Architecture -

The Core to 4G Mobile Communications. In Proceedings of

ICCT, 2003.

[5] Juuso Pesola, Sami Pnknen,Location-aided Handover

in Heterogeneous Wireless Networks. In Wireless Personal

Communications ,Volume 30 , Issue 2-4 ,September 2004[6] Vassilis E. Zafeiris, Emmanuel A. Giakoumakis , An

Agent-based Architecture for Handover Initiation &

Decision in 4G Networks. In Proceedings of the Sixth IEEE

International Symposium on a World of Wireless Mobile and

Multimedia Networks,2005.

[7]Ambient Networking: Concepts and Architecture, G.

Selander (ed.), IST2002-507134-AN/, December 2004.

[8]C. Kappler, Ed., Scenarios, Requirements and

Concepts, Ambient Network WP3 deliverable 3-1,July

2004.

[9] Farouk Belghoul, Yan Moret, Christian Bonnet, IP-Based Handover Management over Heterogeneous Wireless

Networks. In Proceedings of the 28th Annual IEEE

International Conference on Local Computer Networks ,2003

[10] Archan Misra , Subir Das, Ashutish Dutta, Anthony

McAuley and Sajal K. Das,IDMP-Based Fast Handoffs and

Paging in IP-Based 4G Mobile Networks. In IEEE

Communications Magazine, March 2002., pp. 138-145.

[11] Ian F. Akyildiz, Janise McNair, Joseph S.M. Ho,

Hseyin Uzunalioglu,Wenye Wang,Mobility Management

in Next Generation Wireless Systems, Tutorial at IEEE

NOMS, Florence, Italy, April 15, 2002.

[12]Seamless Mobility:A Continuity of Experiences Across

Domains, Devices and Networks; motorolla

[13] Hannu Flinck, Eleanor Hepworth , Jochen Eisl, Shintaro

Uno, Issues of advanced mobility management in Ambient

Networks, Wireless World Research Forum WWRF #12Toronto, Canada,Nov.2004

[14] Nada Golmie , Seamless and Secure Mobility.9th

DOD Annual Information Assurance Workshop in

Philadelphia, PA, 7-10, February, 2005

[15]I. Stoica, D. Adkins, S. Zhuang, S. Shenker and

S.Surana,Internet Indirection Infrastructure, IEEE/ACM

Transactions on networking, Vol. 12, No. 2, April 2004.

[16] D. Clark, R. Braden, A. Falk, and V. Pingali, FARA:

Reorganizing the Addressing Architecture. In Proc. ACM

SIGCOMM FDNA Workshop, August 2003.

[17]R. Moskowitz, and P. Nikander, Host Identity Protocol

Architecture, Internet Draft draftmoskowitz- hip-arch-05.txt

(work in progress), September 2003.

[18]P. Nikander, J. Ylitalo, & J. Wall, Integrating Security,

Mobility, and Multi-homing in a HIP Way. In Proc.

Network and Distributed Systems Security. Symposium

(NDSS '03), pp. 87-99.

[19] J. Urban, D. Wisely, E. Bolinth, G. Neureiter, M.

Liljeberg, T. Robles, BRAIN -an architecture for a

broadband radio access network of next

generation,Wireless Commns & MobileComputing,2001.

[20] P. Eardley, J. Eisl, R. Hancock, D. Higgins, J. Manner,

and P. Ruiz, Evolving Beyond UMTS - The MIND

Research Project. In Proceedings of IEE 3rd Intl. Conf. on

Mobile Commn Technologies, 2002, pp.449-454.

[21]T. Paila, S. Alladin, M. Frank, T. Goransson, W.

Hansmann, T. Lohmar, R. Toenjes, and L. Xu, Flexible

Network Architecture for Future Hybrid Wireless Systems.

InIST Mobile Summit, Barcelona, September 2001.

[22] M. Ronai, A. Petrescu, R. Tnjes, and M. Wolf,

Mobility Issues in OverDRiVE Mobile Networks, IST

Mobile Summit 2003.

[23]A.C. Snoeren, H. Balakrishnan, and M.F. Kaashoek,

Reconsidering Internet Mobility. In Proc. of the 8th

Workshop on Hot Topics in Operating Systems, 2001.

[24] J. Rosenberg , The Session Initiation Protocol,

RFC3261 (IETF, 2002).