Location Based Services for Mobile Devices – a Practical Evaluation
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LOCATION BASED SERVICES FOR MOBILE DEVICES – A PRACTICAL EVALUATION Thomas Krahmer1, Andreas Lang1, Jana Dittmann1, Christian Krätzer1, Claus Vielhauer1,2 1Otto-von-Guericke University of Magdeburg 2Brandenburg University of Applied Sciences ITI Research Group, Multimedia and Security Department of Informatics and Media Postfach 4120 PSF 2132 39016 Magdeburg 14737 Brandenburg / Havel Germany Germany ABSTRACT different guide systems available for museums or We reach an age where mobile devices are affordable for exhibitions can be divided into the four main categories nearly everyone. The technology used within these small [6]: devices with a keyboard, PDAs, mobile phones and devices is evolving with every new generation of the devices for specific application scenarios. devices and allows us, for example, to gain information The devices with a keyboard are similar to a classical about the place we are presently. In the example of phone, where the user enters, for example, the object location based services in museums the common way to number of an exhibit in a museum to get information provide information to a visitor is to equip him with a about the object. An automatic identification of the object device bought and maintained by the museum. The idea number is uncommon in this class [7, 8]. For PDA’s a from [6, 22] using the user’s mobile device, which he similar principle is used to identify an object number already knows is further developed in this paper from the within a museum by entering this number via touch software setup procedure. Today’s mobile devices offer screen [9]. Current audio guides, who use the mobile different techniques and protocols of transmitting text and phone of the visitor, offer a phone number which the user multimedia data between their users which allows us to can call to get the requested information [10, 11]. Using bring the guide software directly to the visitors mobile such a system, customer’s accounting for the service is device. In this paper, we discuss and compare different done via the user’s phone bill. There is also a system possibilities to offer location based services to the user by available, which offers the requested information via short using different existing transmission techniques message service (SMS) to the user’s mobile phone. The (Bluetooth [1], GPRS [2] and UMTS [2]) with their last category of audio guides for specific application protocols (OBEX [3], MMS [4] and WAP [5]) in focus of scenarios are for example the guidePort or pickup-user a location based service like for example for a museum. guide [12, 13]. The provider of a location based service Thereby, their pros and cons of transmitting a specific for mobile devices has the choice between either application or requested information to the users mobile distributing dedicated hardware for the service (like in the phone are compared and discussed. The main goal of this case of the devices with a keyboard) or employing the paper is to describe how to transmit and install software users mobile devices for the execution of the service. for audio guides and to evaluate the interoperability of In the first case a positive fact can be seen in the different devices regarding to the technology, which is homogeneous hardware being provided. The software can needed for an audio guided tour with these devices. The be used on every mobile device provided by this vendor practical work is based on the examination of three and there is no need of modification. As a downside the selected mobile devices from different vendors (Nokia, financial fact plays a big role. The soft- and hardware Samsung and Sony Ericsson). must be bought, maintained and supplied to the visitor which requires additional effort in the institution. KEY WORDS In the second possible case, the employment of the user’s Mobile multimedia, transport protocols devices for the service is expensive for the user at the moment, but the idea is, to install a museum specific 1. Introduction software on the users mobile device, which guides him In the past, there were posters or signs to provide within the museum. To control the software, on one hand, orientation and flyers to give additional information about the keyboard could be used as known from [7, 8] or the an exhibition. Today, a lot of museums and exhibitions microphone of the mobile device records the background provide the information about exhibitions or navigation noise or music, retrieves a digital watermark, which is information to their visitors digitally. Different vendors used to identify the position of the user [22]. offering specific electronic solutions for guide systems Motivated from this fact, in this paper we introduce and share a market for a more comfortable and more flexible discuss an audio guide system, which uses the museum way to provide access to larger amounts of data. The visitor’s own mobile device (here the user’s cellular phone is considered) combined with a location based o C++ can be used for programming software on service offered by the museum to reduce the amount of mobile phones for SymbianOS [14] and also for costs. The aim is to introduce this audio guide system in phones with Microsoft Windows mobile. There form of especially developed software provided locally to is a wide range of mobile phones based on the visitor. SymbianOS including phones of vendors like The Software needed for an audio guide must be able to Nokia, Samsung, Sony Ericsson or Panasonic. provide: Recent discussions raised doubts about the - visual information (text and images) security of Symbian based software. Security - user interaction risks concerning the confidentiality, authenticity, - audio playing techniques integrity and non-repudiation of services and The increasing spectrum of technology embedded into data (i.e. modify/delete content on the file mobile devices results in a new approach for distributing system, doing disallowed calls, sending SMS) of information. In nearly every recent mobile device found S y m b i a n b a s e d m o b i l e p h o n e s on the market we are able to run software from third were published. In regard to the intention of parties. In view to a guide for a museum or exhibition this transmitting software to a user’s mobile phone, means, we just need to provide the software to the visitor an evaluation of the security aspects is necessary and use the hardware he provides in the form of the users to protect the user. own mobile phone. In that way we achieve a cost o Java programs can be written for a lot of new minimization for the information providing institutions mobile phones and are not restricted to certain and ensure a priori that the user is familiar to the operating systems. The common platform for hardware. java programs is J2ME [15]. Using mobile devices for guided tours bring also some J2ME’s concept is based on configurations and restrictions with it. As mentioned before, supplying the profiles. While a configuration provides some user with homogeneous hardware implicates no need of libraries and a virtual machine (CLDC [16]), a modification for the software, but if the hardware is profile is the API, existing for that configuration brought along by the user, the software has to be adapted (MIDP [17]). Java programs based on J2ME to the different kinds of these mobile devices. Limitations come with extension “jad” and “jar” and are given for the mobile devices are for example: limited called Midlets. storage capacity, different supported executable formats, Within this document tests are presented for transmitting different operational systems and virtual machines, a J2ME-based java program over different transport different supported audio formats (for audio guides). The protocols to the mobile phones with the intention of problems which arise from the inhomogeneity of the installing the program. devices are described in this paper in detail for mobile phones as an example of mobile devices. 3. Transport Services and Protocols for After the specification how to transmit and install the Mobile Phones specific audio guide software, we want to replace In this section the common transport techniques and common techniques of event driven information gaining protocols available for mobile phones are described and by controlling the user’s mobile phone via digital advantages as well as disadvantages in regard to location watermarks for example embedded in background music based services are discussed. The examination of IrDA of the museum. [3] (Infrared data association) for transmitting data to a The paper is structures as follows. In section 2, the two mobile phone is excluded because the actual generations major and supported programming languages for mobile of mobile phones do not support IrDA anymore. phones are described briefly. Transport services and The following 5 protocols for transmitting data are protocols used by the mobile phones are in section 3 supported by nearly every modern mobile phone found on introduced and discussed. In section 4, our test goals and the market. test scenarios are presented, whereby in section 5 our test results are introduced and discussed. The paper closes in The first protocol, Bluetooth, can be used for short range section 6 with a summary and future work. transmission over a distance of up to 100 meters. Related to the mobile phone based audio guide in museums or exhibitions this transmission range is sufficient. An 2. Supported Programming Languages on advantage of using Bluetooth is the fact that data Mobile Phones transmission over this protocol is free of charge. A Currently there are two different major programming computer installed in the area can provide the whole languages supported by today’s mobile phones for third service over Bluetooth, which means direct connection to party programs.