Elsevier

Computer Networks

Volume 55, Issue 12, 25 August 2011, Pages 2675-2688
Computer Networks

OPNET-based modeling and simulation study on handoffs in Internet-based infrastructure wireless mesh networks

https://doi.org/10.1016/j.comnet.2011.04.013Get rights and content

Abstract

Wireless mesh networks (WMNs) have recently emerged to be a cost-effective solution to support large-scale wireless Internet access. Handoff management plays an important role in WMNs in delivering Quality of Service to mobile users. Hence, the analysis of handoff performance in WMNs is in a critical need for network researchers and engineers. Recently, OPNET simulation platform becomes a leading provider of solutions for evaluating network designs and applications. However, there is no formal approach or methodology as to how OPNET can be used to assess the support and readiness of an Internet-based WMN in supporting handoffs incurred by various roaming types. In this paper, we propose detailed simulation models for network topology and elements necessary to construct an Internet-based infrastructure WMN using OPNET, along with the modeling and implementation of two handoff designs considering the special design challenges in WMNs. Sequential handoff steps involved in multilayer handoffs are analyzed thoroughly via the OPNET debug tool. Moreover, the paper discusses many design and engineering issues pertaining to the deployment of handoff management in Internet-based infrastructure WMNs. The implemented simulation module provides handoff performance results for both intra- and inter-gateway roaming scenarios and can be an effective evaluation tool for handoff management designs in Internet-based infrastructure WMNs.

Introduction

Wireless mesh networks (WMNs) are being deployed in many cities in order to provide a cost-effective solution for ubiquitous Internet access [1], [2]. An infrastructure WMN is composed of static mesh routers and mobile mesh nodes. Mesh routers form a wireless multihop backbone network. Some mesh routers function as the gateways and are connected via wired links to the Internet. Mesh routers are dedicated nodes for routing wireless traffic either from mesh nodes to the wired Internet or between mesh nodes. Mesh nodes access the network via a mesh router which serves as the access point (AP). Since WMNs are primarily used for Internet-based applications [3], [4], [5] and handoff management is one of the key issues in mobility management dedicated to provide seamless end-to-end services to roaming users [6], [7], [8], [9], the analysis of handoff management performance in an Internet-based infrastructure WMN (IiWMN) is crucial in designing optimized handoff schemes for supporting seamless roaming with certain service level agreement.

An effective performance analysis of handoff management in IiWMNs must be based on the understanding of two factors: the characteristics of IiWMNs and the possible handoff scenarios that will occur in such networks. For instance, in an inter-subnet roaming scenario, when the movement of an MN causes its attachment point change in the Internet domain, i.e., the MN accesses the Internet in a different subnet, not only the link-layer (L2) handoff (which takes care of the switch of the communication channel) is necessary, but also the network-layer (L3) handoff (which takes care of the change of the IP address and/or routing path) and application-layer (L5) handoff (which takes care of the change of multimedia communication sessions) have an important impact on the quality of service. Hence, the analysis of the impacts of the handoffs involved in multiple layers on the performance of application-level services is in a critical need. In addition, the analysis of the deficiencies reflected by the performance results can be utilized to reconfigure the network architecture design and develop new protocols to improve handoff performance.

One way to evaluate networking architecture and protocols is using simulations. As one of the leading simulators for network research and development, OPNET [10] provides powerful simulation capability for the study of network architectures and protocols. It is widely used in both industry and academia. Compared to another well-known simulator NS-2 [11], OPNET has a well-engineered user-interface using mainstream software and operating system which are attractive to network operators. Another reason to choose OPNET is the fact that it contains a vast amount of models for commercially available network elements and has various real-life network configuration capabilities, which makes the simulation of real-life networks close to reality. OPNET is built on top of a discrete-event system which simulates the system behavior by modeling each event happening in the system and processes it by user-defined processes. It uses a hierarchical strategy to organize all the models to build a whole network. Other features of OPNET include GUI interface, comprehensive library of network protocols and models, source code for all models, graphical results and statistics, etc.

However, the current OPNET simulator does not provide build-in models for analyzing the handoff performance in IiWMNs because it lacks the following supports: (1) no existing architecture models for an IiWMN, and (2) no existing models for multilayer handoffs involved in an inter-gateway roaming scenario. Only partial independent handoff mechanisms are supported (e.g., IEEE 802.11b handoff on the link-layer and Mobile IP on the network-layer). In addition, there are many simplifications in the implemented models of networking layers for handoffs in OPNET. To the best of our knowledge, no existing literature has addressed how to model and analyze multilayer handoffs in IiWMNs in OPNET.

In this paper, we focus on the architecture modeling and performance study of handoffs in IiWMNs. We use a simulation approach based on OPNET Modeler v14.5 [10]. In our paper, the IiWMN is deployed based on IEEE 802.11b standard on the link-layer and IPv6 protocol suite on the network-layer. Various handoff scenarios involved in multilayer handoffs are analyzed and new OPNET models are developed to enable different handoff detection mechanisms on the network-layer, which leads to different handoff scenarios. Debug-based simulation is utilized to examine and analyze each sequential handoff component involved in multiple layers in an inter-gateway roaming scenario. In addition, a comprehensive parametric-based study on handoff performance is conducted to investigate important factors affecting the handoff performance. Hence, the results and conclusions obtained from this research can provide great insights in designing and implementing handoff management in IiWMNs.

The rest of the paper is organized as follows. Section 2 presents the detailed network planning and deploying for an IiWMN architecture in OPNET. Section 3 describes a detailed study of both intra- and inter-gateway handoff scenarios in IiWMNs along with the implementations in OPNET. Section 4 shows the detailed analysis of sequential handoffs involved in multiple layers under the OPNET debug environment and various handoff performance results obtained under the parametric-based study. Finally, Section 5 concludes the study and identifies future work.

Section snippets

WMN handoff architecture in OPNET

In this section, we first describe the key factors of deploying a WMN network in OPNET. Then, we introduce the components for setting up an IiWMN architecture in OPNET.

Handoff implementations in OPNET

In this section, we propose two multilayer handoff designs for both intra- and inter-gateway roaming scenarios in an IiWMN and their implementations in OPNET Modeler.

Handoff performance analysis in OPNET

In this section, we first introduce the assumptions in our OPNET simulation. Then, we analyze the handoff performance of the two multilayer handoff designs proposed in Section 3 in an inter-gateway roaming scenario via the OPNET debug tool. Finally, parametric-based studies are conducted to examine the impact of important factors on the handoff performance in IiWMNs.

Conclusion and future work

The analysis of handoff performance in WMNs is in a critical need for network researchers and engineers as it helps to analyze what quality of service can be guaranteed to mobile users, especially for Internet-based end-to-end services. This paper presented a performance study of handoffs in Internet-based infrastructure WMNs based on OPNET simulations. The OPNET simulator makes it easy for network designers and planners to assess network readiness in IiWMNs. However, OPNET Modeler does not

Weiyi Zhao received his B.S. degree in Information Engineering from Nanjing University of Information Science and Technology, China, in 2004 and his M.S. degree in Control Theory and Control Engineering from Jiangnan University, China, in 2007. Currently, he is working towards his Ph.D. degree in Electrical Engineering from the University of North Carolina at Charlotte. His research interests are mobility management and Quality-of-Service in multihop wireless networks. He is a student member of

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  • Cited by (0)

    Weiyi Zhao received his B.S. degree in Information Engineering from Nanjing University of Information Science and Technology, China, in 2004 and his M.S. degree in Control Theory and Control Engineering from Jiangnan University, China, in 2007. Currently, he is working towards his Ph.D. degree in Electrical Engineering from the University of North Carolina at Charlotte. His research interests are mobility management and Quality-of-Service in multihop wireless networks. He is a student member of the IEEE Communications Society.

    Jiang Xie received her B.E. degree from Tsinghua University, Beijing, China, in 1997, M.Phil. degree from Hong Kong University of Science and Technology in 1999, and M.S. and Ph.D. degrees from Georgia Institute of Technology in 2002 and 2004, respectively, all in electrical and computer engineering. She joined the Department of Electrical and Computer Engineering at the University of North Carolina at Charlotte as an Assistant Professor in August 2004. Currently, she is an Associate Professor. Her current research interests include resource and mobility management of wireless networks, QoS provisioning, and next-generation Internet. She is on the Editorial Boards of IEEE Communications Surveys & Tutorial, Computer Networks (Elsevier), Journal of Network and Computer Applications (Elsevier), and Journal of Communications (Academy Publisher). She has served as a Symposium Co-Chair for the Wireless Networking Symposium of IEEE GLOBECOM 2009 and 2010 conference.

    She received an NSF Faculty Early Career Development (CAREER) Award in 2010, a Best Paper Award from IEEE/WIC/ACM International Conference on Intelligent Agent Technology (IAT 2010), an Outstanding Leadership Award from IEEE GLOBECOM 2010, a Best Symposium Co-Chair Award from IEEE GLOBECOM 2009, and a Lee College of Engineering Graduate Teaching Excellence Award from UNC-Charlotte in 2007. She is a senior member of IEEE and a member of ACM.

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