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. The choice of the programming language the mobile phone without the usage of its principal is influenced by the addressed runtime environment; protocol GSM (Global System for Mobile therefore these two programming languages are briefly Communications). In the case of a Bluetooth transmission introduced in the following: there is besides the storage size of the mobile phone no constraint for the data size to be transmitted. examined. In the near future UMTS flatrates might A second possibility for offering a location based service become more and more attractive, too. With GPRS or is the usage of MMS (Multimedia Messaging Service) UMTS it would also be possible to distribute the software over the WAP protocol. WAP is based on the packet by email. A problem for the usage of this protocol is the oriented GPRS protocol. Over GPRS a mobile phone still very low spread of UMTS capable devices. opens a permanent connection to the remote station but only if data packets are sent the user has to pay for the 4. Test Scenarios and Test Goals service. In respect of the usability of the system, sending In this section, our test scenarios and test goals are MMS to the user’s phone is quite simple. The mobile presented. phone needs to be set up to allow receiving and sending of MMS. Receiving an MMS would be free of charge for 4.1 Test Environment the user but has to be paid by the location based service In the test environment we used a server (IBM Z60m with provider for every message sent. Another disadvantage is Bluetooth and LAN/WAN) running Debian Linux to the limitation of the message size which can be sent provide data to the mobile phones. This server is called within an MMS (dependent on the bearer; MMSC). This LBCP (LocationBasedContentProvider) in this paper. In would not be a problem in an environment where just a the practical tests the three different mobile phones Nokia small program needs to be provided, but in audio guides 6230, Sony Ericsson P900 and Samsung SDA are used the transmitted data size would exceed the limit in most with the intention to provide audio guides for a museum cases. or exhibition on them. The software to be installed on the phones is based on the Browsing over WAP (Wireless Application Protocol) is J2ME framework with minimum requirement of CLDC another way to transmit software to a mobile phone. Like 1.0 and MIDP 2.0. We decided to use this framework due MMS, WAP can also be transmitted over GPRS. The to the platform independency of the java programming process can be compared with normal browser requests language and the wide support on mobile phones. The from a computer over HTTP [18]. Special WAP sites software is called GuideIT which is a J2ME Midlet provide similar content like normal HTML [19] based developed for Meisterhäuser Dessau (Germany, [21]), websites but are optimized for mobile phones with their providing text and audio based information about the display, storage and bandwidth limitations. The used several points of interest. description language is called WML [20] (wireless mark- up language) which is xml based and can be distributed 4.2 Transmission over conventional web servers. Regarding usability the Different ways for software transmission from the LBCP user is the main actor in this scenario and has to be more to the mobile phones are evaluated, in detail: Bluetooth, familiar with his mobile phone than in other scenarios. To MMS, WAP, GPRS and UMTS. The aim is to find out assist the user in getting the software it is possible to send which of these services is the most useful in case of him a WAP push SMS which includes a WAP address museums or exhibitions location based services. Figure 1 nested in the SMS. The user receives the message and if shows our test scenario for the evaluation of the WAP is supported, the nested WAP address is called. transmission via Bluetooth. This could be the address to the software to be provided to the user. The downside of the usage of this protocol is Bluetooth the occurrence of relatively high costs (compared to the other introduced approaches) for the user.

At first it was only possible to visit WAP pages with a mobile phone, but by enhancing the capabilities of modern mobile phones it became possible to visit regular web pages using GPRS. According to the scenario of a museum it is possible to embed the software with the provided service directly on the website, which means there is no need to support WAP services. Most museums and exhibitions have a website and therefore there would Figure 1: Test Scenario for Bluetooth Transmission be no additional costs for service providing. The costs regarding to the user are the same like in the WAP Our second test scenario, where we use the WAP and scenario. GPRS/UMTS protocols to stream the required data or to transmit MMS is shown in Figure 2. An even faster solution than GPRS is UMTS which provides an up to seven time’s higher bandwidth. The high bandwidth is the major advantage of UMTS because in the user guide scenario audio or video streaming becomes an interesting possibility which has to be INTERNET LBCP. For users who are not familiar to their phones, the steps have to be described in detail for every phone. The LBCP provides a web server and using a browser an WAP-Gateway operator can select the mobile phone from a list of recognized devices. After selecting the mobile phone and confirming to the transmission, the LBPC tries to connect to the given mobile phone. On each mobile phone the connection from the LBCP has to be accepted. After this procedure of generating mutual acceptance, the LBCP connects to the mobile phone and transmits the software. This transmission was successful for all three tested phones. Providing adapted software for different mobile phones Figure 2: Test Scenario for Transmission via WAP requires knowledge of the mobiles phone type. One possible way to determine the device type is by sending For both test scenarios, the following characteristics are AT-commands to the phone over Bluetooth. If the phone examined: the cost effectiveness for both provider and supports AT-commands we can send a type request as user, the ease of installation to provide the transmission follows in Table 1. service, the possibility of device specific software support and the support for the services on the different mobile Table 1: AT-Commands for device information phones. AT-Command Description AT+GMI Request Manufacturer Identification 4.3 Installation Process AT+GMM Request Model Identification The next step of the practical work is to examine the AT+GMR Request Revision Identification installation process. In consideration of the usability the software installation on the mobile phone is examined. To This was tested on the Nokia 6230 and the results for the do this, the J2ME Midlet is transmitted over one of the transmitted AT-Commands are shown in Table 2. previously described protocols and an examination of the steps used for the software installation procedure is Table 2: AT-Command result for Nokia6230 performed. AT-Command Result for Nokia 6230 AT+GMI Nokia 4.4 Audio Support and Storage AT+GMM Nokia 6230 With the intention to provide audio guides as location V 04.28 based services, an evaluation of the mobile phones 24-06-04 according to their support for different audio codec’s and AT+GMR RH-12 audio playing features becomes necessary. If a mobile GSM P1.1 phone includes an embedded player for audio files (c) NMP. supporting different codec’s like MP3, WAV, AMR or others, this does not imply that software from third parties An interesting information is also the MIDP and CLDC can provide the same support. Also the storage space and version of the J2RE embedded in the mobile phone for the possibility of streaming the audio data play a role in distributing hardware-specific software, but this the evaluation of different phones. In practice the support information could not be gained via AT-commands. of several audio codec’s on the different mobile phones is In practise disadvantages for the usage of Bluetooth were evaluated. found in the usage of different Bluetooth stacks. The evaluated mobile phones could be connected with our service providing host LBPC, but while analyzing 5. Test Results Bluetooth for transmitting data we realized that there are In this section the test results regarding to the different often problems with the different stacks available. For our transmission possibilities with their installation strategies transmission we used OBEX (OBject EXchange) protocol for a specific application to the mobile phones are which originally comes from IrDA. presented. Another disadvantage is the installation of the submitted program were i.e. the tested Nokia 6230 could not 5.1 Bluetooth – Setup, Transmission and Installation recognize the transmitted file type and an installation was Process only possible by using a proprietary software suite At first the transmission of GuideIT via Bluetooth to the provided by Nokia on the LBPC. In case of the SDA, the three chosen mobile phones is examined. During setup, on installation process can also not be considered user every phone the activation of Bluetooth is required and friendly, because after transmission of the GuideIT the thereby the device needs to become visible to other installation process is not intuitive and has to be described Bluetooth devices in order to connect to it from the in detail for end users. Besides the mentioned disadvantages providing location The costs for a user depend on the traffic generated, based services via Bluetooth is free of charge for the user because WAP is charged by traffic volume. The user has and cost-effective for the provider, because only a server to be informed that he possibly has to pay for the with Bluetooth hardware is required. transmitted data which might be expensive in case of audio guides. The service provider needs to maintain a 5.2 MMS – Setup, Transmission and Installation WAP supporting web server. To receive a MM (Multimedia Message) on a mobile phone the setup of the MMSC on this phone is required; 5.4 GPRS/UMTS – Setup, Transmission and otherwise no software could be retrieved. For the three Installation tested phones exist services of their vendors or of the Connecting the phones to a normal web service can be Mobile Provider, which can be used to transmit the MMS compared with the WAP-scenario described before but settings to the mobile phone by entering the mobile without the need of supporting special WAP content types number on their website. by the LBPC’s. The user also has to setup his mobile On the LBPC a GPRS modem has to be installed which is phone to be able to connect to the Internet via able to send MM’s to the phones after the user registered GPRS/UMTS and there are also services provided from his mobile phone on the LBPC’s website. The scenario the different vendors which help with the configuration of was simulated in the tests performed by sending the these protocols. software between two mobile phones. The tested phones The tested phones only support GPRS which has a lower were all able to retrieve MMS with nested software and bandwidth than UMTS. The installation process was as the installation finished without problems. Considering easy as in the WAP scenario which means the software the user and provider costs, the service is free for the user was easy to install after the download finished. Like for and the provider pays the given fee of his mobile provider WAP, the traffic over GPRS/UMTS is charged by for every MM sent which may be expensive for a large volume. number of visitors. 5.5 Tested Audio support 5.3 WAP – Setup, Transmission and Installation In order to provide an audio guide like GuideIT to the All three mobile phones tested support WAP for sending different mobile phones, we examined the supported data to and receive data from the Internet. The LBCP codec’s for the three tested phones. An overview can be therefore was connected to the Internet and provides the seen in Table 4. software over a web server. The web server must have support for WAP specific content types like WML Table 4: Supported content types on the tested phones (Wireless Markup Language), the software is then Nokia Supported Content Types SE P900 SDA provided over the WAP-page. The transmission over 6230 WAP was successful on all phones and the installation audio/x-tone-seq X X X after transmission is considered very user friendly (it audio/wav X started after well described installation steps). Another audio/basic X X advantage of using WAP is the possibility to identify the audio/x-wav X X phone which is connected to the WAP-web service. This audio/rmf X allows providing adapted software for specific device audio/mp3 X types. For identification of different mobile phone types audio/x-mp3 X the User Agent can be used, which is sent from a WAP audio/x-imelody X browser to the web service while requesting information. audio/iMelody X audio/midi X X X The following device specific information could be audio/sp-midi X gained in our test scenario: Table 4 shows that there are only two audio codec’s Table 3: User Agent sent by a WAP browser (marked with light gray) which are supported by all 3 Handytyp User-Agent SonyEricssonP900/R102 Profile/MIDP-2.0 phones, but these two codes are not practicable for human SE P900 Configuration/CLDC-1.0 speech. Considering also other phones this means that the Nokia6230/2.0 (04.28) Profile/MIDP-2.0 content provider has to provide different audio files for Nokia 6230 Configuration/CLDC-1.1 different phones based on their capabilities. In case of the Mozilla/4.0 (compatible; MSIE 4.01; Windows Nokia 6230 there is no audio codec supported which SDA CE; Smartphone; SDA/1.0 Profile/MIDP-2.0 allows us to play an audio file containing human speech Configuration/CLDC-1.1) with the installed J2ME based GuideIT. While in the first part of the audio tests the audio files As shown in Table 3 the browser also transmits the were nested in the submitted software, the storage size supported CLDC and MIDP of the J2ME of the phone. exceeded in case of one phone the available capacities. A The information can be used to provide extra services to a possible solution which therefore had to be examined, mobile phone which supports newer versions of the was the ability to stream audio files over GPRS/UMTS. profiles and configurations. For this case the phones had to be examined for their [2] 3GPP Specifications Home Page, HTTP-connection support which can be seen in Table 5. http://www.3gpp.org/specs/specs.htm, 06.12.2007

Table 5: Supported protocols of tested phones [3] Welcome to IrDA, http://www.irda.org, 06.12.2007 Supported Nokia [4] 3GPP specification: 23.140, SE P900 SDA Protocols 6230 http://www.3gpp.org/ftp/Specs/html-info/23140.htm, file X 06.12.2007 https X [5] WAP Forum Specifications, http X X X http://www.wapforum.org/what/technical.htm, 06.12.2007 It can be seen in Table 5 that all three tested phones have [6] Sandra Gebbensleben, Jana Dittmann, Claus support for opening a HTTP connection but after detailed Vielhauer, Sicherheitsaspekte eines mobilen tests only the SDA and the P900 were able to stream Multimedia-User-Guides, D-A-CH Security 2006: audio files with GuideIT which is a result of the limited Bestandsaufnahme, Konzepte, Anwendungen, audio support of the Nokia phone. Perspektiven; syssec, Patrick Horster, pp. 445-457, ISBN 3-00-071866-0, 2006 6. Conclusion and Further Work [7] MEG – Museum Exhibit Guide, In this paper we describe the problems of existing http://www.absoluterealtime.com/resume/meg.html, technologies for providing audio guides in museums or 23.10.2007 exhibitions. The major disadvantages of existing audio [8] Antenna Audio, “X-plorer”, guides are identified and a possible solution is presented http://www.antennaaudio.com/xp.shtml, 06.12.2007 by distributing audio guide software to visitors mobile [9] cool IT GmbH, coolMuseum, http://www.coolit.ch, phones. The different possibilities of transmitting the 23.10.2007 example audio guide software GuideIT are discussed in [10] BeyondGuide - Your personal audio guide on your terms of feasibility, usability and cost effects for the mobile phone, http://tinyurl.com/2ehc8s, last visitors and the providers. requested 23.10.2007 The future work is to find a standardized way to transmit [11] Rocky Mountain Audio Guide, LLC, and install audio guide software to mobile phones and http://www.rmaguides.com/, 23.10.2007 increase the support of audio codec’s. [12] Sennheiser, guidePORT – Exhibits come to life, It can be summarized that Bluetooth is the most attractive http://www.guideport.de/, 23.10.2005 way to provide software for audio guides in a museum or [13] dataton, PICKUP-UserGuideVer1.2, exhibition, because it is a cost effective way to transmit http://www.dataton.com/pickup, 08.09.2005 data for both, visitor and service provider. The [14] Symbian OS: the open mobile operating system, transmission range fulfills the requirements of a location http://www.symbian.com/, 06.12.2007 based service. The only disadvantage is the usability due [15] Java Platform 2, Micro Edition, to the installation process, but we expect that there will be http://java.sun.com/javame/index.jsp, 06.12.2007 a standardized way of combined transmission and [16] Connected Limited Device Configuration (CLDC), installation process for software from third parties in the http://java.sun.com/products/cldc/, 06.12.2007 future. It is conceivable to combine Bluetooth with other [17] Mobile Information Device Profile (MIDP), mentioned transmission protocols to increase the http://java.sun.com/products/midp/, 06.12.2007 interoperability for different mobile phones. [18] RFC 1945 Hypertext Transfer Protocol -- HTTP/1.0, The future work of this project will be the examination of http://tools.ietf.org/html/rfc1945, 06.12.2007 how to provide specific information of a point of interest [19] Hypertext Markup Language - 2.0, in a museum by using digital watermarks embedded in http://www.w3.org/TR/WD-html2/, 06.12.2007 background playing audio data. [20] Wireless Markup Language Version 2.0,http://www.openmobilealliance.org/tech/affiliates Acknowledgement /wap/wap-238-wml-20010911-a.pdf, Version 11- Sep-2001 The work in this paper has been supported in part by the [21] Meisterhäuser/Masters' Houses in Dessau , European Commission through the IST Programme under http://www.meisterhaeuser.de/, 2008 Contract IST-2002-507932 ECRYPT. The information in [22] Sandra Gebbensleben, Jana Dittmann, Claus this document is provided as is, and no guarantee or Vielhauer, Multimodal Audio Guide for Museums warranty is given or implied that the information is fit for and Exhibitions, Proceedings of SPIE Electronic any particular purpose. The user thereof uses the Imaging - Multimedia on Mobile Devices II, vol information at its sole risk and liability. 6074, 2006 References [1] Bluetooth.com | The Official Bluetooth Technology Info Site, http://www.bluetooth.com/, 06.12.2007