a simulation testbed for a mih enabled system

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A Simulation Testbed for a MIH enabled system. Şerban Georgică Obreja, Octavian Fratu, Alexandru Vulpe. The Faculty of Electronics, Telecommunications and ...
A Simulation Testbed for a MIH enabled system Şerban Georgică Obreja, Octavian Fratu, Alexandru Vulpe The Faculty of Electronics, Telecommunications and Information Technology University POLITEHNICA of Bucharest Bucharest, Romania [email protected], [email protected], [email protected] Due to the relevance of interoperability between heterogeneous mobile networks there are several related work on this topic. European Union also funded some projects based on Media Independent Handover. The Ambient Networks project defined a novel trigger-based architecture for handover optimization [7]. The HURRICANE project targets to specify, design, implement and test innovative vertical handover mechanisms, providing seamless inter-technology mobility [8]. In [9], [10] and [11] mobility management solutions based on MIH framework are presented. In [9] presents novel handover procedures to address seamless mobility in heterogeneous environments. The proposed scheme is an enhanced version of the IEEE 802.21 MIH platform, called enhanced Media Independent Handover Framework (eMIHF). In [10], Media independent preauthentication (MPA) provision is suggested. MPA provides a significant reduction in handover delays for both network-layer and application-layer mobility management protocols.

Abstract— Interoperability between heterogeneous wireless access networks will help the operators to improve the quality of service offered to the users and the networks resource utilization. Media Independent Handover (MIH) standard is designed by IEEE to optimize the handover between heterogeneous networks. This paper presents a solution for mobility management in heterogeneous networks which is based on the MIH framework. It is presented the architecture and the simulation testbed used for system validation. QualNet simulator was chose to implement the proposed solution. Keywords: IEEE 802.21, MIH, vertical handover, simulation

I.

INTRODUCTION

The convergence of communication networks and services consist a great challenge for network engineers. While at the core level the convergence will lead to an all IP network, at the access level several technologies coexist offering great opportunities for services availability and quality. To take advantage of these opportunities a common mobility management framework is required. It should be able to provide service continuity, to optimally manage the network resources in order to improve the system performance and capacity, and implicitly the service quality offered to the users.

The paper is structured as follows. The following section summarizes the main features and functionalities described by the IEEE 802.21 standard. In the third Section the RIWCoS architecture for a mobility management system based on MIH standard is presented. Then, we discuss a testbed for implementing an architecture based on 802.21, and finally we draw conclusions and emphasize future work needed to implement this standard.

Much functionality required to provide session continuity depend on complex interactions that are specific to each particular technology. IEEE 802.21 standard provides a framework that allows higher levels to interact with lower layers to provide session continuity without dealing with the specifics of each technology. It provides the missing, technology-independent abstraction layer, thus hiding technology-specific primitives. This abstraction can be exploited by the IP stack (or any other upper layer) to better interact with the underlying technologies, ultimately leading to improved handover performance [1]. With networks supporting vertical handover (VHO), terminals can move between these networks without losing connectivity or interrupting active services. Not only this allows users to move freely but also does not bother them with the network selection or other related activities.

II.

A. 802.21 Objectives The purpose of this standard is to improve the user experience by providing MIH functionality that facilitates both mobile-initiated and network-initiated handovers. The standard[1] consists of the following three main elements:

In this paper a mobility management system for heterogeneous access network is presented. It defines a framework which provides a set of mechanisms for seamless handover based on the IEEE 802.21 standard. This system was proposed and is being implemented in the RIWCOS NATO project.

c 978-1-4244-6363-3/10/$26.00 2010 IEEE

OVERVIEW OF IEEE 802.21

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A framework that enables service continuity while a mobile node (MN) transitions between heterogeneous networks. It relies on the presence of a mobility management protocol stack within the network elements that support the handover.



The MIH function (MIHF), which is an entity consisting of a set of handover-enabling functions within the protocol stacks of the network elements



between Broadcast Networks (DVB-T, DVB-H), Cellular Mobile Telecommunication Networks (HSDPA, UMTS), and IP-based Wireless Networks (WLAN, WMAN).

Service access points (SAPs), which define both media-independent and media-specific interfaces. They offer both access for MIH Users to the MIH function and help for the MIHF to collect link information and control link behavior during handovers.



Service continuity. One of its main goals is to eliminate or avoid as much as possible the need to restart an application after a handover has taken place.



Quality of service (QoS)-aware handovers. 802.21 provides the necessary functions in order to make handover decisions based on QoS criteria







MIH User

MIHF

Network discovery. This feature allows MIH Users to be provided with information on candidate neighbor networks for a handover.





Network selection assistance. The 802.21 framework provides the necessary functions to assist making the handover decision based on several factors (e.g., QoS, throughput, billing etc.). Note that it does not make handover decisions, which are left to higher layers.

Resource Manager

MIH_SAP

MIH_SAP

Interoperability Manager

MIH_NET_SAP

Interoperability Manager

MIH_LINK_SAP

MIH_LINK_SAP

Interoperability Module

Interoperability Module 802.11

802.16

802.16

Figure 1: RIWCOS Architecture

RIWCoS project addresses terminal mobility, i.e., the action which allows a mobile node to move between IP subnets while continuing to be reachable for incoming requests and maintaining sessions across subnet changes. Other types of mobility include: session mobility, which allows a user to maintain a session even while changing terminals, personal mobility, which allows to address a single user located at different terminals by the same logical address and service mobility, which allows users to maintain access to their services even while moving or changing devices and network service providers.

Power management. The standard allows the MN to discover different types of wireless networks, avoiding powering-up of multiple radios and/or excessive scanning at the radios. Thus power consumption can be minimized.

It also monitors the parameters for the active link to detect when to trigger the handover. The handover could also be triggered by the MAC events. The IM has a MAC specific MIH_SAP

Media Independent Event Service (MIES): detects events and delivers triggers from both local and remote interfaces.

Mobility Manager

Media independent Command Service (MICS): provides a set of commands for the MIHUs to control handover relevant link states.

IM Engine

Media Independent Information Service (MIIS): provides the information model for query and response, thus enabling more effective handover decisions across heterogeneous networks. III.

Resource Manager

802.11

B. MIH function services IEEE 802.21 defines three services that facilitate handovers across heterogeneous networks. These are managed and configured by a fourth service which is called the management service. Through the service management primitives, the MIHF is capable of discovering other MIHF entities [2]. •

MIH PoA

MIH Mobile Node

Additionally, the standard defines a set of secondary goals. These are:

Net Res

Link Res

MIH Protocol MIH_NET_SAP

RIWCOS ARCHITECTURE

RIWCoS is a project that aims to integrate different wireless communications technologies into a common hybrid “easy to use” communication infrastructure.

MIH_LINK_SAP

Figure 2: Interoperability module

The main technological objective is to develop, implement and demonstrate an open, secure, fast-reconfigurable content delivery platform based on MIH framework, for high quality multimedia services (transport and distribution), through any type of wireless access networks to mobile and residential endusers. The project specific goal is to exploit the synergy

component, called Interoperability module, for each technology specific MAC. It is used to add MIH functionalities for each type of MAC layer. At the PoA the IM has the following functionalities: provision of information to mobile terminal

540

about the neighbor networks, provision of link state information, MIH messages handler.

two heterogeneous networks. A mobile node attached to an 802.11 access point detects that the link quality is degrading

The RM module deals with network selection and resource allocation [2] [4]. Based on the monitoring performed by the Interoperability Managers, the RM selects the destination PoA for the mobile node. The selection process takes into account the user profile, the network load, in a way which assures an optimal resource allocation while providing the desired service quality to the mobile user.

Qualnet simulated network

Socket communication WIMAX MIH

802.16e BS

The modes in which the RM can operate are: Emergency Mode, BatteryLowMode and Normal Mode. In the Normal Mode, the Decision block does simple switching of the user demands to what is available as a resource in the repository, selecting the resources that best fit with the user’s demand in terms of QoS. In the BatteryLowMode the Decision block selects the technology that best fits the battery saving, thus reducing QoS (the selected technology may not be best fitted for the QoS of the application). In the Emergency mode (started when LinkDown trigger from IM is received), the RM module uses specially designed algorithm implemented in user and network RM modules for sorting applications and serves them as sorted. IV.

Resource Manager

Gateway

MIIS

WiFi MIH

802.11 AP

Real network

MIH MN

Figure 3: RIWCoS simulated testbed

and sends a Link_Going_Down.indication primitive to its Interoperability Manager (IM). The IM forwards this indication to the Resource Manager (RM) located within a node inside the network. In order to find out the link parameters of the potential candidate points of attachment, the RM initiates a procedure for collecting the link parameters for the potential candidate networks, in this case a WiMAX network.

THE RIWCOS TESTBED

To find the potential candidates the RM uses the MIH Information Server. After it gets the link parameters for the candidate networks it applies the selection algorithm and selects the optimal network. After the network was selected the handover is initiated.

Because MIH enabled equipments are not available on the market yet it was decided to use a simulation environment for the RIWCoS system validation. The simulation environment used is Qualnet. The RM module was developed as a separate application so, in order to integrate the system, a link between RM and the simulated testbed was realized via socket interface (figure 3). This will lead to an undesired increase in the handover delay. Since the RM is mainly focused on the user side, the external RM application is logically linked with the Qualnet simulated MIH enabled mobile node.

First the procedure of establishing a layer 2 connection with WiMAX base station is initiated. If the connection is successfully established then the user data is forwarded from the WiFi AP to the WiMAX base station. After the transfer is completed the WiFI link is released by the mobile node. V.

The communication between the IM and RM modules is done via the MIH SAP interface. Because the modules will run on different virtual machines and they will be connected via socket interface, a mapping of the MIH SAP functions in socket messages was done. Only the relevant parameters are carried via socket, the other ones are added at the message reception. In this way the message dimension is reduced fastening the communication speed via the socket interface.

CONCLUSIONS AND FUTURE WORK

In this paper a simulated testbed for a mobility management system for heterogeneous networks, proposed in the RIWCoS project, was presented. The testbed is based on the QualNet simulator. The system implementation is not completed yet, only the mobility framework was done, which includes the Interoperability Manager, the MIH protocol and some basic functionality for the Link Interoperability Modules.

QualNet uses a layered architecture similar to that of the TCP/IP network protocol stack, within which data moves between adjacent layers. The QualNet protocol stack consists of the following layers (from top to bottom): Application, Transport, Network, Data Link (MAC) and Physical Layers [5]. The Interoperability Manager components were integrated in the layer 2 and layer 3 in the QualNet stack: The interoperability module, which is technology dependent, was integrated at the MAC level of the different technologies. The Interoperability manager was integrated at leyer 3 because it contains the MIH protocol which uses IP to communicate between different PoA.

For the near future we intend to finish the system implementation in the QualNet environment. It will permit us to evaluate the system’s performances such as the handover delay, the packets lost, etc. Also a Qualnet implementation for the RM module is considered in order to evaluate the improvement in the handover delay while comparing with the actual implementation with socket interface between RM and the simulated testbed. Another improvement that is intended for the next phase is to add support for IP mobility. This will be done by integrating support for the MIP protocol.

The message sequence chart depicted in figure 4 illustrates the MIH signaling involved in triggering the handover between

541

MS RM

MIHF

WIMAX

WIFI

AP WiFI MIHF

RM

WIMAX

RM

BS WiMAX WIMAX MIHF

Link_Detected.ind MIH_Link_Detected.ind

Link_Going_Down.ind

Local Link Events

MIH_Link_Going_Down.ind Get Parameters procedure for the candidate networks – initiated by RM

Establish a new L2 connection - WIAMX

MIH_MN_HO_Commit.request (target PoA) Link_Action.req()

RNG_REG & SBC_REQ ®_REQ RNG_RSP & SBC_RSP & REG_RSP

Link_Action.rsp MIH_MN_HO_Commit.response MIH_Link_Action.req(DATA_FWD_REQ) Link_Action.req(DATA_FWD_REQ)

Forward data from WiFI to WiMAX Link_Action.rsp() MIH_Link_Action.rsp MIH_Link_Action.req(LINK_DISCONNECT) Link_Action.req(LINK_DISCONNECT) Link_Action.rsp MIH_Link_Action.rsp

Release old connection - WiFi Deregistration& Disassociation req Deregistration& Disassociation resp

Figure 4: The MSC for a vertical handover between WiFI and WiMAX [4]

E.C. Popovici, V. Atanasovski, RIWCoS SfP-982469 Architecture v1.3. November 2008. [5] L. Gavrilovska, V. Atanasovski,”Reconfigurable Interoperability towards Seamless Communications”, 10th International Symposium on Wireless Personal Multimedia Communications (WPMC 2007), Jaipur, India, December 03-06, 2007. [6] O. Fratu, A.C. Boucouvalas, L. Gavrilovska, R. Prasad. Reconfigurable Interoperability of Wireless Communications Systems (RIWCoS) Final Proposal, RIWCoS SfP-982469. 14 December 2006. [7] K. Pentikousis et al., The Ambient Networks Heterogeneous Access Selection Architecture, in Proc, First Ambient Networks Workshop on Mobility, Multiaccess, and Network Management (M2NM), Sydney,Australia, Oct. 2007, pp. 49-54. [8] Á. Gomes, N. Carapeto, P. Neves et al., HURRICANE: D2.1: Handover reference scenarios, requirements specification and performance metrics. [9] P. Neves, F. Fontes, S. Sargento, M. Melo, and K. Pentikousis, “Enhanced Media Independent Handover Framework”, Proc. IEEE 69th Vehicular Technology Conference (VTC2009-Spring), Barcelona, Spain, April 2009. [10] L. Eastwood et al., “Mobility Using IEEE 802.21 in a Heterogeneous IEEE 802.16/802.11-Based, IMT-Advanced (4G) Network”, IEEE Wireless Communications Magazine, pp. 26-34, April 2008. [11] G. Lampropoulos et al., “Media Independent Handover for Seamless Service Provision in Heterogeneous Networks”, IEEE Communications Magazine, pp. 64-71, Jan. 2008.

ACKNOWLEDGMENT This work is sponsored by NATO's Public Diplomacy Division in the framework of “Science for Peace” through the SfP-982469 "Reconfigurable Interoperability of Wireless Communications Systems (RIWCoS)" project and by Romanian Authority of Scientific Research in the framework of PNCDI 2 “Partnership” through the 12-126/2008 “Hybrid wireless access system with unique addressing (SAWHAU)” project. VI. [1]

[2]

[3]

REFERENCES

IEEE802.21-2008, Standard for Local and Metropolitan Area Networks - Part 21: Media Independent Handover Services. s.l. IEEE Computer Society, January 2009. O. Ognenoski, V. Rakovic, M. Bogatinovski, V. Atanasovski and L. Gavrilovska, “User perception of QoS and economics for a WiMAX network in a backup scenario”, 1st International Conference on Wireless Communications, Vehicular Technology, Information Theory and Aerospace & Electronic Systems Technology (Wireless VITAE 2009), Aalborg, Denmark, May 2009. A. de la Oliva, A. Banchs, I. Soto. “An overview of IEEE 802.21: Media Independent Handover Services”. IEEE Communications Magazine. August 2008, pg. 96-103.

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