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Advancing technology in wireless communication offers users anytime, anywhere access to information and network resources without restricting them to the fixed network infrastructure. Mobile computing represents a shift in the distributed systems paradigm. The potential of decoupled and disconnected operation, location-dependent computation and communication and powerful portable computing devices gives rise to opportunities for new patterns of distributed computation that require a revised view of distributed systems. Mobile environment brings different challenges to users and service providers when compared to fixed, wired networks. Mobility brings uncertainties, as well as opportunities to provide new services and supplementary information to users in the locations where they find themselves. A mobile user is one who, on occasion, disconnects from his/her home network to change location and then reconnects, possibly using a different access technology. A necessary feature of mobility management is the ability to continue to provide system and network services to mobile users seamlessly, regardless of their location and the form of their connection. In general, most application software, operating systems and network infrastructures are intended for more conventional environments and so the mobile user has great difficulty in exploiting the computational infrastructure as fully as he/she might. The Internet Roaming solution for corporate wireless data users integrates mobile networking across private wireless local area networks (WLANs), public WLANs and cellular data networks. In this study we have developed an infrastructure using mobile agent for integrating the Wireless LAN and cellular data called Internet Roaming System (IRS). It is implemented on PMADE mobile agent system developed at IIT Roorkee.
Key words: Wireless LAN, mobile agent, MCMA, SGMA
Wireless local area networks (WLANs) and cellular data networks are complementary technologies. WLANs have several advantages over cellular networks, including higher speed and lower operating and equipment costs. However, their coverage is typically limited to corporate buildings, residences and certain public hotspots. Cellular data networks, on the other hand, provide wide-area coverage but at lower speeds and a much higher cost [1,2]). Naturally, integrating WLAN and cellular data networks to serve users who need both high-speed wireless access as well as anytime anywhere mobile connectivity is the best of both worlds.
Mobile agent technology offers a new computing paradigm in which an autonomous program called mobile agents (MAs) can migrate under its own or host control from one node to another in a heterogeneous network. In other words, the program running at a host can suspend its execution at an arbitrary point, transfer itself to another host (or request the host to transfer it to its next destination) and resume execution from the point of suspension ). There are two main areas in which MAs offer considerable advantages, namely: systems and distributed management and information retrieval. Other areas where mobile agents are seen as offering potential advantages, are disconnected computing, also known as wireless or mobile computing, dynamic deployment of code, thin clients or resource-limited devices, personal assistants and mobile agent-based parallel processing [4-6]).
Currently, most WLAN-cellular network integration solutions are operator-oriented, the objective being to bundle hotspot public WLAN service with the data service offered by cellular operators [7,8]). In such a setup, the public WLAN service reuses the cellular network's infrastructure and resources, giving users benefits such as a single bill ). However, operator oriented solutions are not entirely hassle-free, especially for corporate users. After getting a wireless connection to the Internet via a cellular network or a public WLAN, for example, a corporate user must run a virtual private network (VPN) program to create a secure connection to the corporate intranet. Typically, if the user switches the wireless connection--by moving into or out of a public WLAN's range, for instance--the secure connection breaks, forcing the user to re-launch the VPN program to reconnect. Moreover, operator-oriented integrated solutions only cover public WLANs in hotspots, not private WLANs such as office and residential-telecommuting WLANs (which could require different connection and security configurations of the WLAN adaptor on the user's system). Corporate users roaming between these environments need to frequently change their WLAN configurations--a burdensome and error-prone task ). Mobile agents can replace VPN programs. In our model agent submitter (AS) [3,11] perform this task and is fully platform/network independent.
Our prototype WLAN-cellular network integration solution, called Internet Roaming System (IRS) lets corporate users create a secure connection using a single sign-on authentication interface, regardless of which wireless network their system is connected to. Once the secure connection is created, the system produces a computing environment that doesn't change, even if the user moves from one wireless network to another. In addition, we designed IRS to use existing technologies as much as possible, including mobile agents [3-5], Mobile IP , the IP security protocol (IPsec)  and various wireless access methods. IRS is implemented on PMADE mobile agent system developed at IIT Roorkee ). We have also done comparison performance of some existing router.
Overview of PMADE: Figure 1 shows the basic block diagram of PMADE. Each node of the network has an Agent Host (AH), which is responsible for accepting and executing incoming autonomous Java agents and an Agent Submitter (AS) , which submits the MA on behalf of the user to the AH.
[FIGURE 1 OMITTED]
A user, who wants to perform a task, submits the MA designed to perform that task, to the AS on the user system. The …