Second International Conference on Computer and Network Technology
Mobility Management in Heterogeneous Wireless Access Network with IEEE 802.21 Services
Shaifizat Mansor
Tat-Chee Wan
Faculty of Computer and Mathematical Sciences Universiti Teknologi MARA 08400 Merbok KEDAH
[email protected]
School of Computer Science Universiti Sains Malaysia 11800 Penang, Malaysia
[email protected] mobility management is a major issue for Future Generation Wireless Network.
Abstract— Roaming across different access technologies permit people to access Internet via heterogeneous wireless networks such as WLAN, WiMAX, GPRS, 3G and Beyond 3G networks. The convergence of heterogeneous wireless access networks with handoff support enable mobile nodes to freely move in and out of any available networks without breaking the connection to the Internet. In this paper, an Adaptive Cross Layer handoff Management for Future Generation Wireless Networks is presented and an efficient approach in optimizing the handoff decision procedure between WLAN and WiMAX networks utilizing IEEE 802.21 media independent handover functions (MIHFs) is proposed. This is expected to support seamless mobility while reducing handoff latency and call dropping probability for optimal user experience.
There are two possible scenarios in FGWN: horizontal handoffs (intra-system handoff) and vertical handoffs (intersystem handoff). The horizontal handoff process involves movement between two access points using the same access technology, whereas vertical handoff involve transferring of the connection between two access points belonging to two different systems. For vertical handoff between WLAN and WWAN, the process of link layer switching will require “break before make” handoff where the existing connection must be detached before the new link can be engaged [2]. When a mobile node switches from one network to another, QoS for the serving may decrease below a predefined threshold level. In addition, MIPv6 has become a primary solution for supporting mobility between various IP-based access networks. However, long handoff latency in MIPv6 degrades the QoS level of the mobile user. To overcome this issue, Fast handoff for MIPv6 (FMIPv6) was proposed to reduce packet loss by establishing a new fast connectivity link to the targeted network [3]. Nevertheless, no considerations of other critical issues such as radio access discovery or candidate access discovery were discussed, which also affect handoff performance.
Keywords-component; Handoff, Mobility Management, MIH 802.21, Heterogeneous Wireless Access Network
I.
INTRODUCTION
Higher data rate services and enhanced multimedia applications impose stringent Quality of Service (QoS) demands on next generation wireless networks. Rather than developing totally networks to fulfill the needs for transferring large amount of data with QoS support, the Future Generation Wireless Network (FGWN) strive to seamlessly integrate existing heterogeneous networks by adapting different types of access technologies to a common signaling interface via IEEE 802.21 Media Independent Handover (MIH) [1]. The different features of each network component such as bandwidth, Received Signal Strength Indicator (RSSI) and data rates provide users with optimal bandwidth and QoS based on existing network condition.
The MIH standard was developed to enable interoperability between wireless access networks. IEEE 802.21 defines a generic interface between the different link layer technologies and upper layers. However, the existing MIH primitive is very limited for optimizing the handoff latency. In this paper, an enhanced handoff mechanism is proposed s to introduce new MIH primitives and parameters for supporting better prediction target network selection in consideration of competition among different users.
Relevant factors such as monetary cost, network conditions, number of mobile nodes (MN), user preferences and cell coverage must be considered. The various characteristics of network such as General Packet Radio Service (GPRS), Wireless LAN, Third Generation (3G) and World Wide Interoperability for Microwave Access (WiMAX) limits the ability of a user to move from one network to other network automatically. Therefore, the
978-0-7695-4042-9/10 $26.00 © 2010 IEEE DOI 10.1109/ICCNT.2010.91
The rest of this paper is organized as follows: Section II discusses the theoretical background of mobility management, Game Theory for handoff management, MIPv6 handoff and media independent handover services. 110
Section III presents the proposed solution using ACLM. Finally, Section IV summarizes the work. II.
Movement Detection Router Solicitation/advertisement message delivery
THEORETICAL BACKGROUND
Channel scanning
A. Mobility Management Mobility management is a key component in performing handoff for FGWN. Mobility management can be defined as an ability of mobile node to travel from one wireless access network to another type of wireless network seamlessly without experiencing any severe service degradation. One approach for handling horizontal and vertical handoff was described in [2], where cooperation between Layer 2 and Layer 3 handoff significantly enhanced the performance of both intra and inter-system handoffs, since measuring a single metric like RSSI itself is insufficient and resulted in an increased probability of handoff failure.
CoA Configuration (CoA Creation)
Binding Update (to CN and HA)
Authentication Association
t
L2 Handoff (100 ~ 300ms) L3 Handoff (2000 ~ 3000ms)
Figure 1. MIPv6 handover procedure [3]
Once the MN detects its movement to the new network, it needs to send a binding update (BU) to register its new location. Later, MN is able to communicate with the Internet by using its home address after receiving binding acknowledge (BA) from Home Agent (HA). However, long handoff delays in MIPv6 that degrades the QoS may cause the MN to suffer from packet loss and service disruptions.
An intelligent approach was proposed for a seamless vertical handoff in next generation wireless networks that assess the adjacent network performance based on RSSI, access cost and network performance and network bandwidth [4] . A cross layer handoff management protocol (CHMP) was developed to reduce the cost of false handoff initiation lowering the false handoff initiation probability [1]. An initial preparation for the handoff process can be made to eliminate packet loss and reduce handoff latency.
D. Media Independent Handover (MIH) IEEE 802.21, also known as the Media Independent Handover (MIH) framework is an intermediate layer for assisting in the vertical handoff process to coordinate the exchange of information and commands between different devices. Although the main objectives of IEEE 802.21 is to enable interoperability between wireless access networks, more specific goals include [4]:
B. Game Theory for Handoff Management Game theory can be applied to solve the radio resource management problem in wireless access network. In [5], a radio resource management framework was designed to support seamless handoffs between a cellular network and a WLAN, whereas in [6], an admission control scheme for vertical handoff was proposed, in which call blocking probability, throughput and packet delay performance issues were addressed. However, there is no consideration on competition among users.
Service continuity during and after the handoff procedure. Handoff-aware and QoS-aware applications. Provide information on the candidate neighbor network for handoff and perform network selection assistance. Minimizing power consumption if MN receives information such as network coverage maps, optimal link parameters, or sleep or idle mode of the network.
C. MIPv6 handoff
Three primary components in IEEE 802.21 include Media Independent Event Services (MIES), Media Independent Command Services (MICS) and Media Independent Information Services (MIIS). Firstly, MIES is responsible for facilitating handoff by providing services to the upper layers and reporting events both locally and remotely. Secondly, MICS offers command to the upper layer to allow them to coordinate the functions of the lower layers by using a set of primitives and commands. And thirdly, MIIS provides a framework for neighboring access network information, network topology and available services offered by an available adjacent networks.
MIPv6 supports handoff to maintain existing network connections moving to a new IPv6 subnet. The basic handoff procedures involve two components, L2 handoff and L3 handoff. L2 handoff supports for roaming at the link layer while L3 handoff occurs at the network layer level. There are three phases involved in the MIPv6 handoff procedure as depicted in Figure 1 [3]. Movement detection is a prerequisite procedure for the L2 handoff operation. After L2 handoff occurs, router discovery is achieved via router advertisement (RA) from the new Access Router (nAR). The IPv6 address must be configured for use on the new network using the Care of Address (CoA) update procedure to get the mobile node’s new CoA (nCoA).
Seamless handoff mechanism with negligible handoff delays are required to maintain active connections during roaming across these networks [7-9]. Figure 2 demonstrates 111
During the initiation phase, both information request and response via neighboring access networks are performed respectively. In the second phase, network selection will be made whereby the decision on the targeted network is chosen. The next phase occurs when the link layer connection from both entities has been established, by releasing unneeded resources from the MN or targeted networks. Though IEEE 802.21 support seamless mobility, the standard lacks mechanisms to facilitate seamless handover provision reduce handoff latency [10].
the service interaction in 802.21 with upper layers and lower layers of the protocol stack.
SIP
MIPv4
MIH Events
MIPv6
HIP
L3MP
Information Service
MIH Commands
MIH Function
Information Service
Link Commands
Link Events
802.3
802.11
802.16
3GPP
III.
3GPP2
A. FGWN Design Approach There exist many wireless technologies that compliment each other. Thus the integration of these technologies and a unified FGWN would offer the best features of every individual network to users. This research proposes an Adaptive Cross Layer handoff Management model (ACLM) to ensure seamless mobility and session continuity in a heterogeneous network with minimal handoff latency. It is very important to support seamless mobility where mobile node will select the best connected network and move from one network to another network based on their service needs as illustrated in Figure 4. The focus of ACLM is on the mobility between WLAN such as WiFi and WiMAX networks.
Figure 2.Service interaction between MIH components [5]
In addition, the main goal of providing the 802.21 service is to enable handoff between heterogeneous technologies, more detailed aims of 802.21 include allowing service continuity during network transitions where renewal of session after the handoff process is not required. This standard also allows handoff-aware and QoS-aware applications to minimize service disruptions and to perform handoff decisions based on various QoS criteria respectively. As shown in Figure 3, the MIH framework consists of MIH Discovery, MIH Selection, Mobility Management and MIH Completion. MN MIH
Serving MIHF
Neighboring MIHFs
ADAPTIVE CROSS LAYER HANDOFF MANAGEMENT
IS
MIH Selection
MIH Discovery
MIH_Get_Information_Request MIH_Get_Information_Response MIH_MN_HO_Candid ate_Query_Request
MIH_MN_HO_Can didate_Query_Reso urce_Response
Target Network Decision MIH_MN_HO_ Commit_Request
Access Point (AP)
MIH_N2N_HO_Ca ndidate_Resource_ Request
Base Station (BS)
MIH_N2N_HO_Ca ndidate_Query_Res ource_Response
Mobile Node S(MN)
MIH_N2N_HO_ Commit_Request MIH_N2N_HO_ Commit_Response
WiFi Network
MIH_MN_HO_ Commit_Response
Figure 4. Vertical handoff scenario
Mobility Management Protocol HO Execution
MIH Completion
WiMAX Network
MIH_MN_HO_ Complete_Request
In describing a vertical handoff scenario, the mobile node is considered to be moving in an overlapping area covered by a set of different wireless networks managed by the same network operator. The WiMAX network covers the entire mobility area, while WiFi network provide a limited coverage area. We assume that the WiMAX network provides a relatively low data transfer rate as compared to the WiFi network that provides a higher data transfer rate.
MIH_N2N_HO_ Complete_Request MIH_N2N_HO_ Complete_Response MIH_MN_HO_ Complete_Response
Figure 3. Mobile initiated message diagram in 802.21 MIH Services [4]
112
The collected parameters are used to decide the appropriate time to initiate and execute handoff procedure using Game Theory approach on Dynamic Network Selection mechanism adapted from [11]. Within this approach dynamic network selection is modeled by defining game between heterogeneous access networks. Mobile nodes make service requests which can be handled by either of the two networks. To model the game, network will represent the players trying to maximize payoff which is the parameters from both Layer 2 and Layer 3. The best available strategy is chosen to satisfy the request that best fits their characteristics.
In order to provide QoS support to the MN, the vertical handoff decision should be made together with admission control for a new call. Admission control schemes are the decision making part of network to provide users with guaranteed QoS in order to reduce network congestion and dropping probability. Whenever a new connection is rejected by the current network, WLAN for example, MN should be transferred to the WiMAX network using vertical handoff procedure. Thus an efficient admission control algorithm should be proposed to ensure service continuity in FGWN. B. Handoff Management Using Game Theory Approach This research proposes an Adaptive Cross Layer Handoff Management module to initiate a handoff procedure by integrating link layer (Layer 2) and network layer (Layer 3) parameters. As illustrated in Figure 5, the module collects information from link layer and network layer for handoff management to decide the appropriate time to initiate and execute the handoff procedure by utilizing IEEE 802.21 MIHF. Link layer parameters Received Signal Strength
MN’s Velocity
Finally, Handoff Manager Unit makes handoff decision based on the result from dynamic network selection mechanism. Hence, by estimating the handoff initiation time, the proposed ACLM is significantly enhances the performance of both intra-system and inter-system handoffs while reducing handoff latency. C. Integration with the IEEE 802.21 MIH function (MIHF) IEEE 802.21’s target is to enable inter-technology handoff by reducing handoff latency to improve user’s satisfaction while using mobile terminal. In this paper, a newly defined handoff framework is proposed specifically at the network discovery and network selection phases as illustrated in Figure 6 within the highlighted messages.
Network layer parameters Neighbor Discovery Unit
Handoff Signaling Delay Unit
Game Theory Approach Approach on on Dynamic Network Network Selection Selection Mechanism
Intrasystem and Intersystem Handoff Registration
Network Discovery Initiation
Handoff Manager Unit
Serving MIHF
MIH_MN_ Report
Network Selection
MN MIH
Target Network Decision
MIIS
MIES
MICS
MIPv6
Neighboring MIHFs
IS
MIH_Get_Info_Req MIH_Get_Info_Resp
MIH_MN_HO_ Consign_Req
MIH_N2N_HO_Can d_Resource_Req MIH_N2N_HO_Cand_ Query_Resource_ Resp
MIH_N2N_HO_ Commit_Req
MIH_MN_HO_ Consign_Resp
MIH_N2N_HO_ Commit_Resp
Figure 5. Adaptive Cross layer Handoff Management Process Flow
MIIS
MIES
802.11
MICS
MIH FUNCTIONS
The proposed ACLM initiates handoff by using MN’s velocity and received signal strength unit as input from link layer. Whereas neighbor discovery unit and signaling handoff delays unit are gathered as parameters from network layer. Neighbor discovery unit assists the MN to learn neighboring Base Station (BS) while handoff signaling delay unit estimates the delay within intra-system and intersystem handoff.
802.16
Figure 6. Proposed message diagram in 802.21 MIH Services
113
The initial phase will provide a user’s handoff policy and neighboring network information to the serving MN. The information flows via message MIH_MN_Report provide the user’s handoff policies and make a decision to the targeted network without additional request to the serving MIHF. Thus the MIH_MN_HO_Consign_Req message is defined in network discovery phase while MIH_MN_HO_Consign_Resp message is utilized at network selection phase. In contrast, the existing IEEE 802.21 that includes more messages during network discovery phase will result in a longer time taken to process neighbor network information within the MN MIHF.
[6]
[7]
[8]
[9]
A new link layer connection is established while the mobility management protocol is carried out between the MN and target network. A complete request message is sent by the MN to the prior serving network to release resources which were allocated to the MN. After the resources are successfully released, the new current network may send a complete response to the MN. Thus, the elimination of the message flow between the user and serving MIHF will result in reduction of handoff latency as compared with the existing approach. IV.
[10]
[11]
CONCLUSION
This paper described the current vertical handover approaches in heterogeneous wireless networks based on IEEE 802.21 Media Independent Handover. The integration of heterogeneous networks seems to be an optimal approach to achieve the FGWN “always best connected” vision. A new handoff framework is proposed to reduce of handoff latency using Adaptive Cross Layer Management approach. The next step is to investigate the optimal network selection algorithm and analyze its effect on handoff latencies. ACKNOWLEDGMENT This research was supported by a grant USM-RU-PRGS from the Universiti Sains Malaysia. REFERENCES [1]
[2]
[3] [4]
[5]
M. A. Abdelatif, G. K. Kalebaila, and H. A. Chan, "A CrossLayer Mobility Management Framework based on IEEE802.21," IEEE 18th International Symposium on Personal, Indoor and Mobile Radio Communications, 2007, pp. 1-6. A. Pontes, D. dos Passos Silva, J. Jailton, O. Rodrigues, and K. L. Dias, "Handover management in integrated WLAN and mobile WiMAX networks," IEEE Wireless Communications, vol. 15, pp. 86-95, 2008. D. Johnson, C. Perkins, and J. Arkko, "Mobility Support in IPv6," in RFC 3775, 2004, pp. 1-165. K. I. Itoh, S. Watanabe, J. S. Shih, and T. Sato, "Performance of handoff algorithm based on distance and RSSI measurements," IEEE Transactions on Vehicular Technology, vol. 51, pp. 14601468, 2002. G. T. Karetsos, S. A. Kyriazakos, E. Groustiotis, F. Di Giandomenico, and I. Mura, "A hierarchical radio resource
114
management framework for integrating WLANs in cellular networking environments," IEEE Wireless Communications, vol. 12, pp. 11-17, 2005. Y. Fei and V. Krishnamurthy, "Optimal Joint Session Admission Control in Integrated WLAN and CDMA Cellular Networks with Vertical Handoff," IEEE Transactions on Mobile Computing, vol. 6, pp. 126-139, 2007. A. De La Oliva, A. Banchs, I. Soto, T. Melia, and A. Vidal, "An overview of IEEE 802.21: media-independent handover services," IEEE Wireless Communications, vol. 15, pp. 96-103, 2008. L. Eastwood, S. Migaldi, X. Qiaobing, and V. Gupta, "Mobility using IEEE 802.21 in a heterogeneous IEEE 802.16/802.11based, IMT-advanced (4g) network," IEEE Wireless Communications, , vol. 15, pp. 26-34, 2008. E. Stevens-Navarro and V. W.S Wong, "Comparison between Vertical Handoff Decision Algorithms for Heterogeneous Wireless Networks," in Proceeding of 63rd Vehicular Technology Conf. (VTC ’06-Spring),, 2006, pp. 947 - 951. Z.-q. Huang, S.-n. Bai, and J. Jaeil, "A MIH Services Based Application-Driven Vertical Handoff Scheme for Wireless Networks," Fifth International Joint Conference on INC, IMS and IDC 2009, pp. 1428-1431. D. Niyato and E. Hossain, "Dynamics of Network Selection in Heterogeneous Wireless Networks: An Evolutionary Game Approach," IEEE Transactions on Vehicular Technology, vol. 58, pp. 2008-2017, 2009.
