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Mobile Server: An Efficient Mobile Computing Platform Based on Mobile Agent

Wen-Bin Hu, Bo Meng

College of computer science and technology, Wuhan University, Wuhan 430070 china [email protected] [email protected]

Abstract A mobile agent computing platform based on

J2ME technology and Jini system architecture, Mobile Server was presented. The platform was established on extended Jini system architecture, and was embedded software kernel to support computing style of mobile agent. In order to overcome the shortage of traditional database access technology in mobile computing enviornment, a centralized database and a distributed heterogeneous database access technology based on mobile agent was proposed. Amied at the usable resource restraints in mobile computing environment, an enviornment apperceiving middleware was designed to allocate and manage the resources. The application results show that the effect in saving computing time by using this platform is notable. Keywords: mobile computing, mobile agent, middleware, J2ME, resource restraints

Ⅰ. INTRODUCTION

Mobile computing represented the inevitable direction of network development, which made it true that people used computer resources according to their wills [1]. Despite the exponential growth of CPU speed, modern computers cannot cope with the growing demand for computational resources that occur in areas such as bio-informatics [2][3]. Computer models are becoming more refined and often show an exponential time complexity. Moreover, the amount of data to be processed is growing rapidly. At the same time, there is a huge amount of unused computer power available on the desks of people, especially after office hours. The SETI@home project has demonstrated convincingly the scalability and feasibility of mobile computing with spare CPU cycles. At the same time Gnutella, KaZaa and Morpheus have generated ample interest in peer-to-peer (P2P) networks and have shown their utility. Combining these two approaches is an obvious step. Mobile agents seem the ideal tools for such unification, because (1) they can react flexibly on the availability of resources,

and (2) they allow for new computational tasks to be created without the need for installing new software on multiple hosts.

The characteristic of mobile computing environment is the ceaseless changing of resources, and changes in a limitation. So in the environment with restrictive resource, the usable resources should be correctly used, and when the quality of usable resources drops or the usable resources become to be unusable, the system should be fit for the changes. Moreover, mobile computing users maybe transfer from one network to another in the mobile process, which means to support to operation of network transferring. The characteristic of alterable bandwidth is very important to mobile computing users in order to resolve the influence of restrictively factor relative to dynamic network transferring, so the stronger adaptability of mobile computing system is the key technology to resolve mobile problems.

In another way, there are many data accessing problems in the mobile computing, the mobile computing environment is narrow communicating bandwidth and big delay. To desktop computer, mobile terminal is weakly computing ability and limited power, while the traditional data accessing style is aimed at desktop computer, which requires terminal with higher computing intelligent (equipment more relative software), larger bandwidth and lower delay, so it needs to find a new data accessing method to fit the mobile computing environment.

A mobile agent computing platform based on J2ME technology and Jini system architecture, Mobile Server was presented, aimed at the problems of limited resource and data accessing in mobile computing system. The platform was established on extended Jini system architecture, and was embedded software kernel to support computing style of mobile agent. In order to overcome the shortage of traditional database access technology in mobile computing enviornment, a centralized database and a distributed heterogeneous

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database access technology based on mobile agent was proposed. Aimed at the usable resource restraints in mobile computing environment, an enviornment apperceiving middleware was designed to allocate and manage the resources.

The remainder of this paper is organized as follows: Sect.2 outlines the system architecture of Mobile Server; Sect. 3 describes data transferring technology of our platform; Sect. 4 presents the designing of the middleware of our platform, Sect.5 presents an application. Finally, Sect.6 presents our conclusions,

Ⅱ. ARCHITECUTRE OF MOBILE

SERVER The architecture of Mobile Server is

showed in figure 1, which is combined by tow kinds of component, one is MS Engine and HM Engine that run on the mobile computing server; the other is Service Engine, at least exit one on the J2ME terminal equipment [4].

M S E ng ine

Service E ng ine

E nvironm ent A p perceiving M iddlew are

H M E ng ine

H um an Interface

Failu re M od ule

N av igation M odule

S ecurity M odule

C om m u nica tion M odule

Serv ice En gin e

Mob

ile A

gent

inte

grat

ive

data

base

acc

essi

ng

tech

nolo

gy

Fig.1. The architecture of Mobile Server

A HM Engine HM Engine is communicating interface

between users and J2ME terminal equipment. Users use local browser to configure J2ME terminal equipment, state watching and harmony controlling by HM Engine, which is realized by Applet and Servlet technologies.

B MS Engine

MS Engine includes the below six modules: 1) Human Interface

It is used to watch, configure the Mobile Server interface.

2) Failure Module It is used to control and watch the terminal

equipment network, deal with network abnormity, equipment trouble and service declining and so on. 3) Navigation Module

It is used to assure the relative network location and realize the connection of communication. 4) Security Module

It is used to protect host, network resource, code object and mobile code object. 5) Communication Module

It is used to realize the communication among terminal equipments. 6) Harmony Module

It is used to harmony the resource among mobile computing equipments

C Service Engine

Service Engine is the center of mobile computing platform, which is used to analyze and find user service. Service Engine adopts Lookup service mechanism of Jini architecture to realize searching service, and support hiberarchy searching.

Ⅲ. A CENTRALIZED DATABASE ACCESSING TECHNOLOGY BASED ON

MOBILE AGENT In order to realize centralized database

accessing technology based on Mobile Agent in mobile computing, mobile terminal equipment (MH) needs to provide mobile Agent with database accessing function. Database server needs to provide running environment of Mobile Agent and database connection interface and driver program. But it doesn’t need to provide the support of Mobile Agent to finish Farther Agent (FA) and Home Agent (HA) of Mobile IP.

We extend and modify some classes of IBM Aglets, and realize three components: Accessing Create Interface (ACI); Accessing Mobile Agent (AMA) and Accessing Execute Environment. ACI provides a user interface of input database accessing request, which transfers the accessing request to AMA in bite code, and return the executing result to user. AMA is used by ACI to execute the database accessing request of ACI in the remote SQL database server, accepts results and return to

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ACI and AEE to run in the Tahiti Server Environment of SQL database server. Tahiti Server Environment assigns database source and driver program of local computer, assistants to connect database source, and execute database accessing request [5].

Return result (Block)

From one network to the other

SQL Server

Tahitiz+AEE

Internet

HA

MH

Return result FA

Return result

Database Application transfers ACI with SQLsentenceAMA with SQL sentence

Fig.2. Centralized database accessing technology based on

Mobile Agent

The accessing steps of centralize database in mobile computing environments are show in below (just as figure 2):

1) When user database applications on MH need to access remote database, the database-accessing request (that is SQL sentence) is input to ACI, ACI can contain one or more relative database-accessing requests.

2) ACI transfers one Mobile Agent (AMA), AMA transfers the database-accessing request to SQL database server according to a given route strategy.

3) AMA arrives SQL database server, Tahiti service program accept AEE and tell the usable driver program and connectable database source to SQL database source, AMA connects the database according to the appointed resource and with the help of AEE to execute the database-accessing requests.

4) After the database-accessing requests are executed, AMA sends the results to HA of MH, HA searches the location registration information of MH and gets the FA address of the network, and sends the results to FA from the door of HA and FA. FA returns the results to MH again.

5) After MH gets the results, the results is returned to ACI, and ACI returns the results to database application to finish the database accessing process.

In the above steps, database access and other tasks of MH asynchronous parallel executes, which means when the AMA executes the database-accessing request, MH can executes other tasks, includes transferring from one network to other network and not to wait the results returning. This centralized database accessing technology not only allows the transferring of database accessing function, but also the transferring of host (such as MH). MH doesn’t need to equipment database connecting driver program, which lets SQL database server to execute database connection and database accessing, and realizes the localization of database accessing. The AMA can be used several times, so the database accessing of MH becomes more flexible, convenient and efficient. The MH becomes more portable, so this database accessing technology fit the database accessing in mobile computing environment.

Ⅳ. DESIGN OF ENVIRONMENT APPERCEIVING MIDDLEWARE Environment apperceiving middleware

(EAM) manages and configures the mobile computing equipments and resources with Harmony Module of MS Engine. J2ME mobile equipment is registered by EAM, which is convenient to accept and manage information of high-level events. The high-level events include: original language events of operation system and events of user software. EAM inputs information to this original language to compose the three components of Mobile server before the high-level events transfers to application system. The three components are: Channel Manager (CM), Event Producing Manager (EPM) and Event Objects Manager (EOM) [6]. A CM

Channel is the key of event transferring structure, which bonds the event producer and customer, realizes event transferring strategy and save environment state information with a serial of events. Ordinarily, a channel connects a component of mobile environment.

Channel saves the current state of mobile environment by saving log file of an Event Object. It saves the latest state of Event Object until the new Event Object arrives. When the first Handle registers the channel the first time, the Event Object will transfer the latest state of current environment of channel to Handles.

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The common interface of channel and strategy classes is illustrate in figure 3 as below: Class Channel{ Class Strategy {

Strategy strategy; Handler * List; Event * State MAX} void Deliver (Event *) Channel (char * name); virtual void Reset(); Channel (char * name, Strategy * s); NextHandler ();

…….} virtural void AddHandler() ……}

Fig.3. The structural of Channel and Strategy classes B EPM

Events are checked by EPM, EPM is corresponding to entity Producer. One Producer is a software module (relative to mobile environment). In this EAM, it engenders Event Objects by extending information, which means when it checks an event, Producer will pack the relative information into Event Object. This Event Object will be transferred to one Channel and transferred to the relative EAM application system. The Producer and Handler classes are illustrated in figure 4 as below.

Class Producer{ Channel * channel; Producer (char * channel); Void PostEvents (Event *); …….}

Class Handler{ Channel * channel; Handler (char* channelname); Void Body(); ……}

Fig.4. The structural of Producer and Handler classes C EOM

Though different events are relative to different information. A kind of information is public to one or more events. The organization of Event Object may to be an extend type arrangement. We define the basic event object, which is aimed to the given event demands and function. Each Event Object is the child class of root class.

The typical events in the mobile computing application include: Connections Event, Services Event and so on. The typical information of Connections Event includes: 1) network gate ID; 2) connection is UP or DOWN. The package information of Service Event is the usable of network service, includes such as printer, SMTP and NUTP. The common interface of EOM is showed in figure 5.

Class Event { Event(); Virtural size_tMarshal (void *, size_t); Virtural Event * UnMarshal (void * size t); Virtural void Handle(); ………}

Fig.5. The structural of Event class

Ⅴ. EXPERIMENTS

The experiments conducted on WebitAgent [4] platform and Mobile Server platform. The running time of a task is showed in table 1.

Tab.1. Time used for two platforms Time used (s) Time gain (%) Number

WebitAgent MobileServer 20,000,000 152 155 -0.65 40,000,000 410 405 1.46 60,000,000 731 655 10.52 80,000,000 1103 870 21.48

100,000,000 1518 1215 19.96

From the above table, the effect of time saving is obvious to Mobile Server, because of the new database accessing technology and the design of environment apperceiving middleware.

Ⅵ. CONCLUSIONS The Mobile Server model presented in this

paper connected the J2ME equipment with Internet, which made the equipment on the network be watched and controlled at any time and anywhere by any authorized person. Mobile Server was established at extended JINI technology, so the network embedded J2ME equipment was not only flexible and dynamic, but also the equipment has initiative ability with the help of Mobile Agent. In another way, this paper presented a centralized database accessing technology and EAM to support mobile computing platform. The experiment show the project is viable and the effective of saving computing time is remarkable.

REFERENCES

[1] Dong Won Jeong and Doo-Kwon Baik, “ AMC: An Adaptive Mobile Computing Model for Dynamic Resource Management in Distributed Computing Environments remarkable”, Springer-Verlag Berlin Heidelberg, LNCS 2344, pp. 671-678, 2002

[2] Sung-Hoon Park. “AN Efficient Election Protocol in Mobile Computing Environment”, Springer-Verlag, Berlin Heidelberg, LNCS 2657, pp. 387-396, 2003

[3] Xi Wang, Xu Liu, Xiaoge Wang and Yu Chen. “ A Middleware Based Mobile Scientific Computing System- MobileLab” , Springer-Verlag Berlin Heidelberg, LNCS 3251, pp. 1013-1016, 2004.

[4] Wang Jiyong. “An Embedded Mobile Computing platform:WebitAgent System Model”. Journal of Northeastern University (Natural science), Vol 23, No.5, pp. 421-424.2002.

[5] Xiong Yan. “Database Access Technologies Based on Mobile Agents in Mobile Computing Environments”, MINI-MICRO SYSTEM, Vol.23 No.10, pp.1165-1168, 2002.

[6] Li Dong. “Research of Application’s Solution Using Middleware Technology in Mobile Computing”, MINI-MICOR SYTEM, Vol.21 No.11, pp.1201-1204, 2000.

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