IEEE 802.21 based Multihoming approach to vertical ... - IEEE Xplore

IEEE REGION 8 SIBIRCON 2008

449

IEEE 802.21 based Multihoming approach to vertical handover in Heterogeneous Networks Faiza Iqbal*, Muhammad Younus Javed† and Ghalib Asadullah Shah† * Dept. of Computer Science, College of Telecommunications † Dept. of Computer Engg, College of Electrical and Mechanical Engg National University of Sciences and Technology, Rawalpindi, Pakistan. * [email protected], †(myjaved, ghalib)@ceme.edu.pk Abstract— Seamless vertical handover is in great focus in contemporary world of research. Multi-interfaced mobile devices are introduced in the market to enable heterogeneous access. The main problem is how to efficiently use these multi-interfaced devices to achieve best data throughput, reduced packet loss and optimized handover. In this paper, the advantages of multihoming approach have been combined with IEEE 802.21 Media Independent Handover (MIH) to achieve simultaneous access at available networks. The MIH services are used to achieve link layer information earlier than the handover execution. The simultaneous binding option of multihoming is used to achieve soft handover so that multiple interfaces can be efficiently used.

Internet

WiMAX

Cellular

802.3/802.11

Seamless Handover while nomadic

I. INTRODUCTION As the number of mobile devices and access technologies are increasing, the competition between network companies and internet service providers has also increased. They are aiming to provide improved service and seamless mobility to their customers. Interoperability and seamless roaming between heterogeneous access networks, such as WiFi, WiMAX, wired and cellular networks, requires considerable efforts in order to achieve session and service continuity, location and handoff management, bandwidth and QoS provisioning, and cost and power management. In addition, the development of dual mode, multi-interfaced mobile terminals has increased the need for inter-working between these networks [1]. The emerging IEEE 802.21 [2] standard is endeavoring to provide interoperability and seamless mobility between heterogeneous networks. The standard is aiming to develop Media Independent Handover (MIH) function which will enable vertical handover between 802 technologies and cellular networks. Currently, the selection of network from the list of available networks is done on signal strength or from the priority based static list. It is not an efficient scheme to satisfy the user demands in multi-access environments [3]. Therefore, the initial thinking behind IEEE 802.21 working group was to define layer 2 (L2) triggers to improve handover decision. Fig. 1 shows a general architecture for MIH enabled Mobile Node (MN). The framework of IEEE 802.21 MIH function consists of three services namely Event Service, Command Service and Information Service. The MIH function defines effi-

978-1-4244-2134-3/08/$25.00 ©2008 IEEE

Multi-Interfaced MN Fig. 1. Architecture of MIH enabled MN

cent framework for network detection and selection. Different implementation of this framework on multiinterfaced mobile terminals may result in diverse performance. Multihoming in mobile IP can be used to enhance the performance of MN and make efficient use of multiinterfaces [4]. Multihoming is a technique used to enable multi-interfaced devices to have multiple IP addresses to enable simultaneous connections. In this paper, a multihoming approach based on IEEE 802.21 MIH function has been proposed to enable soft handover in dual-mode mobile terminals. The effectiveness of the proposed technique has been analyzed and an algorithm is presented to describe the approach. The rest of the paper is organized as follows. In section 2, the related work is discussed. The framework of IEEE 802.21 and MIH function is described in section 3. Mobile IPv6 for multiple interfaces and overview of multihoming in mobile nodes is described in section 4. The proposed scheme, its analysis and algorithm are presented in section 5 and section 6 concludes the paper. II. RELATED WORK Enabling vertical handover and accessing heterogeneous networks using multi-interfaced mobile terminals are the focused research areas now-a-days. A large number of study groups and projects are established to address this problem area. Unlicensed Mobile Access (UMA) [5] was a standard originally developed by group of operators and vendor

450


companies but later was integrated into 3GPP standards and was renamed as Generic Access Network (GAN). UMA enabled dual-mode handsets can seamlessly roam between cellular and WiFi networks. It can be said as a mobile-centric version of IEEE 802.21. Issues and advantages of using multiple interfaces in mobile nodes and mobile networks have been discussed [6]. The authors have analyzed Mobile IP version 6 (MIPv6) and Network Mobility (NEMO) basic support as L3 mobility protocols and presented a tunnel re-establishment technique to utilize robustness of multiple access interfaces. The optimized support of multiple wireless interfaces in IPv6 enable mobile terminal has also been described [7]. The paper presented the architecture of IPv6 end terminal called Multiple Interfaces Management Protocol (MIMP). Dynamic adaptation techniques are described for real-time applications in order to optimize the resource usage by multiple interfaces. It discusses the multi-interfaced mobile terminals architecture but does not specify any technique for interface selection. A multi-interface proposal for IEEE 802.21 MIH has been presented by Mo Li et al. [8]. The presented schemes make alternative use of multiple interfaces of mobile terminal to enable hard handover in accessing heterogeneous networks. The scheme is expected to work with standard TCP and Mobile IPv4 agent routers. Simulation results of multiple interfaced based implementation of MIH are compared with that of single interface. But the simulation is done only by using 802.11 interfaces. MIH framework has been discussed [9] to enable seamless handover across heterogeneous networks. The experimental implementation of 802.21 based mobility management is done. The results show the reduction in packet loss and disconnection time during handover. Researchers have presented a multi-homing approach to enable low latency handoff in heterogeneous networks [10]. In the proposed scheme, multi-homing is exploited to reduce network selection delay and to enable fast initiation of MIP handover.

work (L3) layer through media independent Service Access Point (SAP). MIHF interacts and obtains information from link layer (L2) access technologies through technology dependent SAPs. SAP is an interface point in the protocol stack where services of lower layers are available to higher layers. MIHF provides three different services: Media Independent Event Service (MIES), Media Independent Command Service (MICS) and Media Independent Information Service (MIIS). Fig. 2 illustrates the architecture with MIHF services. A. MIHF Services MIES is used to provide event notification of link changes to MIHF which then propagates them to upper layers. MIES deals with local and remote events. Local events are generated from L2 of local stack whereas remote events are received from MIHF of remote network entity. Upper layer may register themselves to different events of interest and thus are notified by MIHF only when those types of events occur. The types of events include state change (link up, link down, link detected), link parameters, link transmission and link handover synchronous. When upper layers get notified about the event occurred, they make use of MICS to control the behavior of link layer for making handover decision. Link commands from the upper layers are sent to MIH which then propagate them to lower layer. MIH commands are sent to MIHF of remote network entity. The commands include MIH Configure, MIH Poll, and Link Configure etc. MIIS provides information of available neighboring networks to MIHF, which can use this information to make intelligent decisions to optimize handover between heterogeneous networks. Mobility Management Protocols like MIPv4/v6, F-MIP, HIP, SIP etc Upper Layers (L3 and above)

III. IEEE 802.21 ARCHITECTURE

The IEEE 802.21 architecture [12] enables service continuity as the MN roams between different link-layer access technologies. The central unit of the 802.21 framework is MIH Function (MIHF) which is added between network layer and link layer. It provides services to Net-

MIH_SAP MIH Commands

MIH Events

Information service

MIH Function Link Events

Information service

The IEEE 802.21 MIH [11] standard is being developed to optimize handover between heterogeneous networks by providing link layer network related information to network and upper layers. The heterogeneous media may include wired and wireless media of 802 standard and cellular media. The standard is aiming to provide network discovery and selection. This is done by gathering network information from neighborhood network. This information includes link type and ID, link status and link quality of available networks in vicinity. This information when provided to mobile devices helps them to connect to most appropriate network depending on user preferences.

Link Commands

LINK_SAP

LLC_SAP

CS_SAP

3GLINK_ SAP

3GLINK_ SAP

802.3

802.11

802.16

3GPP

3GPP2

Lower Layers (L2 and below) Figure 2: MIH framework and services

FAIZA IQBAL, MUHAMMAD YOUNUS JAVED AND GHALIB A. SHAH: IEEE 802.21 BASED MULTIHOMING

IV. MOBILE IPV6 FOR MULTIPLE INTERFACES Mobile IPv6 [13] is the mobility management protocol which enables the MN to roam around the internet. Each MN is assigned a global Home Address (HoA) from its home network. When MN visits a foreign network a Care of Address (CoA) is assigned to it by Foreign Agent (FA). MN registers that address with its Home Agent (HA). HA, then, establishes a tunnel with FA and redirects all flows to FA which were received to it from some Correspondent Node (CN). FA forwards those to CoA of MN. To enable vertical handover, mobile IPv6 must support multiple interfaces in mobile nodes. Fig. 3 shows a scenario where a dual mode MN is attached to different networks through multiple interfaces. Each interface must be assigned an IPv6 address so that MN could be reached through these interfaces. MobileIPv6 should be used in those interfaces so that mobility and vertical handover could be achieved. Mobile IPv6 for Multiple Interface (MMI) [14] is an extension to MIPv6 so that MN can reliably use its multiple interfaces and can redirect or distribute flows between these available interfaces. There are many ways through which MN can use its multiple interfaces. It can keep other interface as backup to use it in case of failure to current interface or can use both interfaces simultaneously to distribute flows and optimize data throughput. In heterogeneous networks, MN can use multiple interfaces to achieve soft handover. Soft handover is the procedure in which MN can be connected to different Access Networks (AN) simultaneously. V. 802.21 BASED MULTIHOMING APPROACH Seamless vertical handover can be achieved with efficient use of multiple interfaces in MN. It requires optimization in L2 and L3. The optimization at L2 demands that all available networks should be detected. Then among those detected networks, the most optimal network should be selected and then handover should be performed using available interface of that network. The optimization at L3 can be achieved through optimized use of mobile IP for address management of multiple interfaces and tunnel

451

establishment with foreign networks. Once the optimization at these two layers is achieved, the optimized vertical handover would be possible. The proposed scheme uses IEEE 802.21 framework [2] to optimized handover at L2. A MIH layer would be added in the mobility management protocol stack. The 802.21 MIH defined services will be used for network detection and selection. Information will be gathered from different networks through available interfaces and optimized L2 handover decision will be taken. To achieve L3 optimization, mobile IP would be incorporated with multi-homing approach. Mobile IP with multihoming will be capable of holding multiple HoA-to-CoA bindings for MN. The proposed scheme would optimize handover delay by reducing network selection time and optimizing MIP handover. The concept of soft handover would be used by carrying out simultaneous connections through available network interfaces. Using MIH, available networks will be detected. Before actual handover takes place at L2, binding with the target network can be achieved. With the concept of simultaneous binding in multihoming approach, a list of all available FA will be maintained. This will allow MN to connect to most appropriate FA when L3 handover occurs. Fig. 4 illustrates the proposed architecture of 802.21 MIH based multihoming approach. The architecture is based on WiFi/WiMAX and 3GPP/3GPP2 enabled MN. MIH function is used as a middle layer between L2 and L3. MIH services are used to achieve link information. Link events are propagated to L3 by MIHF. MIH commands are generated after necessary processing and the decision about L2 handover is taken. Using multihoming approach, a simultaneous binding with the new network is created. This is done to achieve soft handover. After some time when the new network is fully connected, all the flows are shifted to new interface and the connection with the old network is disconnected.

Address Management List of available FA Multiple HoACoA binding

Multihoming and Mobile IP MIH_SAP MIH Events

MIH Commands

Information

MIH Function AN (WiMAX) Home Network CN

MN

AN (WiFi)

AN (Cellular) Tunnel

Foreign Network

Fig. 3. Dual-mode MN with multiple Access Networks (AN)

Link Layer info (Signal Strength, Link ID, and Link Parameters)

Link Events

Link Commands

CS_SAP

3GL_SAP

WiFi/ WiMAX

3GPP/ 3GPP2

Fig. 4. Architecture of proposed scheme

Link Information

452


TABLE I. ALGORITHM OF THE PROPOSED SCHEME

L2 Handover Process Continuously monitor for new ANs If (Link Event=new AN found) then Check for Link parameters of new AN Check the state of current AN If (signal strength of current AN decreasing) Bind the available NIC with new AN Continue traffic on both interfaces L3 Handover Process Manage the list of available FAs Check the movement patterns of MN Establish tunnel with the available FA on the path If L2 and L3 handover successful Transfer all traffic flows to new ANs interface Release all resources at old AN Due to ‘make-before-break’ strategy, packet loss will be greatly reduced during handover. It will also improve data throughput and handover latency. The upper layers (transport and application) are made transparent for the multihoming operations. Table 1 describes an algorithm of the proposed approach. VI. CONCLUSIONS AND FUTURE WORK In this paper, 802.21 MIH based multihoming approach is adopted to enable seamless vertical handover in heterogeneous networks. L2 optimization is achieved by using MIHF and its services. Link-layer information is used to make efficient decision of handover. L3 optimization is obtained by using multihoming at IP layer. Multihoming is incorporated with mobile IP to achieve simultaneous connection on multiple interfaces. This is done to enable soft handover. This approach will reduce packet loss during handover process. Data throughput and handover latency will also be improved. Authors are planning to simulate this approach to analyze the results and compare them with that of existing approaches.

REFERENCES [1] http://www.umatoday.com/mobileHandsets.php [2] IEEE 802.21, "IEEE 802.21 Media Independent Handover," vol. 2006: IEEE 802.21, pp. http://www.ieee802.org/21/ [3] Jani Puttonen and Gabor Fekete, “Interface selection for Multi-homed Mobile Hosts,” inProceedings of the 17th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 2006 [4] N. Montavont, R. Wakikawa, T. Ernst, C. Ng, K. Kuladinithi, “Analysis of Multihoming in Mobile IPv6,” draftietf-monami6-mipv6-analysis-04.txt (work in progress) [5] http://www.umatoday.com/ [6] Chan-Wah Ng, Thierry Ernst, “Multiple access interfaces for mobile nodes and networks,” IEEE 2004. [7] F. Andre, J.-M. Bonnin, B. Deniand, K Guillouard, N Montavont, T Noel, L Suciu, “Optimized support of Multiple Wireless Inetrfaces within an IPv6 End-Terminal,” presented at Smart Objects conference (SOC’2003), France, May 2003 [8] Mo Li, K. Sandrasegaran, and T. Tung, “A Multi-Interface Proposal for IEEE 802.21 Media Independent Handover,” presented in 6th International Conference on the Mangement of Mobile Business (ICMB 07), IEEE 2007. [9] A. Dutta, S. Das, D. Famolari, Y. Ohba, K. Taniuchi, T. Kodama, H. Schulzrinne, “Seamless Handover across Heterogeneous Networks – An IEEE 802.21 Centric Approach,” WPMC 2005. [10] V. S. Kaulgud, S. A. Mondal, “Exploiting Multihoming for Low Latency Handoff in Heterogeneous Networks,” presented in 8th International Conference on telecommunications-ConTEL, 2005 [11] Jared Stein, “Survey of IEEE802.21 Media Independent Handover Services”, available online at http://www.cs.wustl.edu/~jain/cse57406/ftp/handover/index.html [12] IEEE 802.21 DCN 21-05-0271-00-0000One_Proposal_Draft_Text.doc, May 2005 [13] D. Johnson, C. Perkins and J. Arkko, “Mobility Support in IPv6,” IETF RFC 3775, June 2004 [14] N. Montavont, T. Noel, M. K-Lahlou, “Mobile IPv6 for multiple interfaces (MMI),” draft-montavont-mip6-mmi02.txt (work in progress)