Application of Radio Frequency Identification for Museum Environment

Transcription

1 2013 Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises Application of Radio Frequency Identification for Museum Environment Romeo Giuliano, Franco Mazzenga, Marco Petracca, Francesco Vatalaro University of Rome Tor Vergata, Department of Enterprise Engineering, Rome, Italy Contact author: Abstract Recently, Information and Communication Technologies provided a significant support to the communication activities of cultural heritage centers. In particular, Radio Frequency Identification (RFID) is a promising solution to improve both object inventory and visitor guide applications in museums. However, due to the indoor propagation environment, it is necessary to properly characterize the RFID system behavior to ensure the correct functioning of RFID applications. In this paper, we evaluate the performance of a RFID system for cultural heritage applications. We consider that museum visitors are endowed with RFID Readers able to detect RFID Tags storing the appropriate artwork description. We carry out various tests aimed at assessing the capability of the system to support visitors in real environmental conditions. The obtained results can be useful for system dimensioning and deployment. Keywords RFID; proximity based interaction; measurements I. INTRODUCTION In recent years, the field of Information and Communication Technology (ICT) has provided a major boost to the communication activities of cultural heritage centers, such as archaeological sites, historical buildings, art galleries and museums. Multiple technological solutions allow to improve the level and quality of the interaction with visitors: thanks to the wide variety of communication media through which to convey the information flows, they can enjoy advanced services within cultural sites during the process of direct content fruition. In this context, Radio Frequency Identification (RFID) is one of the most successful technologies [1]. Indeed, the benefits deriving from the application of RFID technology to museum and art gallery environments are numerous. Such applications can be grouped in two main categories: Collection Management System (CMS) and visitors interaction. The first one includes the enhanced artwork and archive management, that can be achieved easily and in a cost-effective way. For example, long term management and preservation of collections can be improved by reducing unnecessary handling required to open crates and packaging to read labels and by gaining insights into the actual amount of movements objects and artworks are being subjected to. It can be also possible to continuously update object or artwork s whereabouts and audit trails detailing who moved which object(s) and when. Moreover, staff time spent either looking for misplaced objects and/or updating information into CMSs can be significantly reduced. Finally, RFID can be used as assist system for theft prevention. The second category is represented by the so-called proximity based interaction applications, which envisage that the interaction between people and objects is simply based on their vicinity. According to this paradigm, each visitor endowed with a smart device (e.g. smartphone and tablet equipped of or connected to a RFID reader) can automatically enjoy advanced multimedia applications by approaching the considered object. In order to ensure the correct functioning of the museum applications (especially related to the visitor interaction), it is necessary to properly characterize the RFID system behavior. Indeed, it should be considered that indoor environments are generally more complex than outdoors in terms of radio propagation conditions. There are different obstacles, such as walls, equipment, people, etc., which can affect the propagation of electromagnetic waves, leading to multi-path effects and high attenuation. In addition, noise and other interference sources such as wireless and wired networks can cause performance degradation. Finally, the structure of the building, the mobility of people and the critical environmental conditions (e.g. high temperature and high pressure) have an impact on the identification system [2]. In this paper, we characterize the behaviour of a RFID system for cultural heritage applications. The considered system uses RFID Tags deployed in the museum environment, each one storing data on the corresponding artwork. The visitor is equipped of a RFID Reader able to detect Tag messages that provide the appropriate object description. Thanks to the limited RFID range, visitors can enjoy the information related to museum rooms, paintings, sculptures, etc. We evaluate the performance of the RFID system by carrying out various tests aimed at assessing its capability to support museum visitors in real environmental conditions. The obtained results can be useful for system dimensioning. The paper is organized as follows. The considered scenario is described in Section II. In Section III we detail the experimental setup used to characterize the behavior of the RFID system. In Section IV we provide the test description. We report test results in Section V. Finally conclusions are drawn. II. SCENARIO We considered the reference scenario depicted in Figure 1 for system characterization. A visitor or in general a museum assistant is equipped of a RFID Reader, while Tags are deployed inside the museum. RFID Tags are positioned in a strategic place (e.g. close to a famous painting or to the emergency exit door). When the RFID Reader is in close proximity of a specific Tag (e.g. about a couple of meters) the Tag interrogation succeeds and it receives the Tag ID close /13 $ IEEE DOI /WETICE

2 to it. Moreover, the RFID Reader is endowed with Bluetooth connectivity to transmit received information on detected tags to an User Device, like smartphone or tablet (note that other connectivity strategies can be adopted, eventually considering energy consumption constraints [3] [4]). Based on this strategy, it is possible to provide many ap- position in the museum or within the storeroom at low-cost. Moreover, it is not difficult for the museum manager to update information for visitors related to some artworks. It just needs to associate the Tag ID to another content avoiding problems with paper labels on the wall. Finally this scenario can be extended out of the museum buildings by connecting the museum objects to Internet. Visitors can access the museum artworks directly by their home and can pre-define their preferred tour or share comments on visited artworks/museums with their friends/contacts through social networks. With the RFID diffusion it is not untimely to envisage that each artwork can be uniquely identifiable moving the cultural heritage towards the Internet of Things (IoT). III. EXPERIMENTAL SETUP Extensive measurements have been carried out to characterize the behavior of the RFID system. In Figure 2 we show the generic test bed considered in our tests. The main parameters that describe the system are the distance d between the Reader and the Tag and the azimuth and elevation angles for both devices, referred to as θ and ϕ, respectively. According to Fig. 1. Operational scenario for museum environment. plication in the museum environment. The visitor is able to exploit the proximity-based interaction through the User Device. He/she needs just to approach to an artwork and the communication between the Reader and the related Tag univocally identifies the close artwork. Then, through the User Device the visitor can automatically receive information on it pre-stored on the device or retrieved from the remote Management & Control Centre (M&C2) through a wireless connection to the Access Point (see Figure 1) 1. This system is able to provide also position-based services. As an example, the visitor can find a particular artwork since he/she is able to know him/her position thanks to received RFID tag IDs. The User Device can display the position on the download museum map and provides the best or shortest route to the selected artwork. Moreover the M&C2 can collect data on the visitors behaviour in terms of observation time for certain artworks, internal museum paths or preferred artworks. The museum staff can accommodate properly the artworks in large rooms according to visitors behaviour to avoid crowding. It is worthwhile to note that the User Device can exploit the available embedded chipset to calculate its outdoor position (through A-GPS) as well as to integrate the indoor localization procedure (through Accelerometer Sensors, Digital Compass, etc.). This approach is out of the scope of this work and can be investigated in further studies. Furthermore, the RFID system simplifies the artwork collection enabling the museum staff to quickly know the artwork 1 The wireless connection between the User Device and the Access Point can be local and in this case Wi-Fi technology or femtocells can be adopted [5] [6]. But in the most general case connectivity can be provided by 2G/3G/4G wireless networks, e.g. GSM [7] and WiMAX [8] [9], or Professional Mobile Radio (PMR) systems, like TETRA [10]. In the latter case the M&C2 can manage data of more than one museum but can be shared at city or regional level. The algorithms for efficient service management in the museum area [11]- [14] are not discussed in this work. Fig. 2. Generic test-bed. the functioning of the RFID system, the Reader transmits an interrogation. If the Tag receives enough power through the interrogation message, it re-transmits its code stored in its internal memory. Finally, the Reader can receive the Tag code if sufficient power is detected by its antenna. In such a case, the communication between the Reader and that Tag of the RFID system is successfully performed. To fully understand the behavior of both the devices, it is necessary to characterize their antenna radiation patterns. The experimental setup is depicted in Figure 3. We utilize UHF passive Omni-ID Ultra Long Range RFID Tags [15]. They operate in the MHz frequency band and in the temperature range C. As for the memory banks, these Tags have 96 bits of Electronic Product Code (EPC) and 512 bits for the User Memory. The RFID CAEN A528 OEM UHF multiregional compact Reader [16] has a maximum transmission power of 500 mw on the MHz frequency range, with temperature comprised between -20 C and +60 C. According to the reference scenario, this reader is endowed with Bluetooth connectivity. Possible interferences due to transmission in ISM band are assumed negligible since they can be properly avoided with specific algorithms [17] [18] or they are not harmful [19] [20]. The software package utilized to collect data and evaluate the performance of the RFID-based system is the CAEN RFID EASY2READ EASY CONTROLLER [21], which allows to 191

3 distance between devices such that the system efficiency is not null (i.e., η > 0) or above a predefined threshold (i.e., η η thr ). The system is also characterized in terms of radiation pattern of both Reader and Tag antennas. To this aim, tests are carried out by measuring the system efficiency obtained by varying the azimuth or the elevation angles of the RFID devices. As an example, to depict the azimuth radiation pattern of the Tag antenna, we measure η obtained for various azimuth angles of the Tag antenna (while maintaining 0 elevation) in respect to the Reader positioned at increasing distances from the Tag. We also evaluate the system performance under dynamic Fig. 3. Experimental setup. explore the main CAEN RFID readers capabilities. Thanks to a friendly user interface, the user can read and inventory tags. In particular, this software is able to collect data related to the following parameters: a = Tags/s, i.e., the average number of tag detections per second; b = Acquisitions/s, i.e., the average number of reader queries per second, included the unsuccessful acquisitions; η = a/b, i.e., the efficiency of the RFID system; RSSI, i.e., the average value of the proportional received signal strength indicator; count, i.e., the number of tag detections over the duration time of the test. The EasyController application for Android devices is also available, allowing smartphone and tablets to directly communicate with the RFID Reader and perform data acquisition, in accordance with the envisaged scenario. IV. TEST DESCRIPTION In this section we describe the test planning adopted to evaluate the system performance. We firstly characterize the proposed system in ideal conditions, i.e., LOS transmissions between RFID Tag and reader, regular environmental setting (e.g., temperature, humidity, etc.), RFID reader set on a RFtransparent pole, etc. Then we prove the feasibility of a RFID system supporting the interaction between visitors and artworks by means of a demonstration carried out in a typical museum environment. Fig. 4. Setup configuration for the system characterization. conditions, i.e. by considering the RFID Reader set on the body of a visitor moving around the museum environment. Two configurations are assumed for the Reader positioning, i.e. visitor s shoulder and chest. As shown in Figure 5, we consider three different movement trajectories of the visitor with respect to the Tag: radial, tangent, secant. In addition, for each trajectory we carry out tests in two directions: towards and away from the Tag. Moreover, in order to simulate different operative conditions, we repeat each test by varying the speed of the movement. In particular, we assume two speed levels: amble, equal to about 0.75 m/s, and fast, about 1.5 m/s. Since the aim is to assess the capability of the RFID system to support visitor interaction with objects and artworks within the museum, all these tests are carried out by measuring the count parameter. Indeed, the number of tag detections during the movement time of each test is directly related to the delivery of information flows to the visitors. A. System characterization Many tests are performed to characterize the system performance under ideal conditions according to the setup configuration shown in Figure 4. These tests are aimed at obtaining the reference case results. We firstly evaluate the operative distance of the RFID system. This test is carried out by measuring the system efficiency η as a function of the distance between Tag and Reader, considering the optimum pointing between the two antennas. In such a way, the maximum operative distance could be defined as the Fig. 5. Movement trajectories considered for the system characterization. 192

4 V. R ESULTS We carried out several tests to evaluate the performance of the RFID system in the considered scenario. In order to collect mean values of the interest parameters, every static test is averaged by collecting data for 60 seconds, while each dynamic test is repeated 5 times. In Figure 7 we show the trend of the system efficiency as a function of the distance between Reader and Tag. Since sometimes the object/artwork position can impose constraints on the space available for Tag installation, we considered both vertical and horizontal Tag orientation. The typical on-off behavior of the RFID system is observed. In particular, based on the considered test environment we obtain the maximum system efficiency for distances ranging from about 3 to 4 meters. For slightly greater distances, the efficiency rapidly decreases up to reach the complete inefficiency of the system. As regards the tests to characterize the radiation pattern of both the Reader and the Tag antennas, results show that the system efficiency rapidly decreases when the distance between RFID devices as well as their elevation angles increase. As an example, we derive that for an elevation angle equal to 30 the distance must be decreased from 2.7 m to about 1.2 m in order to keep η = 1. In Figure 8 and Figure 9 the system efficiency is reported as a function of the azimuth angle of the Tag and the Reader, respectively. As for the Tag, we can observe that for distances between RFID devices below 1.2 meters, we always measured η = 1 even for θ = 0 /180. The angle of maximum system efficiency decreases with the increase of the distance, up to reach about 40 for d=3 m. A similar trend is experimented for the azimuth radiation pattern of the Reader antenna, which results a little bit larger than the Tag one for greater distances. In Table I, we show results of dynamic tests considering radial Fig. 7. System efficiency vs operative distance for different Tag orientations. B. Demonstration This test is carried out to assess the capability of the RFID system to support interactions between visitors and artworks in a typical museum environment. In particular, we aim at verifying the limits of the system when NLOS conditions occur due various types of obstructions, such as walls, doors, tables, human bodies, etc. The floor plan of the indoor museum-like environment is reported in Figure 6, where the visitor path (blu line) and the Tag positions and orientations (red color) are also depicted. As shown, the demonstration is properly planned to stress the capability of the system to avoid ambiguous detection of the visitors within a room or a narrow corridor, wheres he/she is inside an adjacent room. Moreover, the visitor path inside the building is designed to evaluate the effects on the system performance due to the presence of metal objects. Indeed, reflective objects like metal desks and cabinets can cause missed identifications or ambiguous detections, like localization of the visitor in rooms adjacent to the real one. In accordance with the described operative scenario, during the demonstration we measure the count parameter, which is closely connected to the capacity of the RFID system to provide visitors with the description of the corresponding artwork. Fig. 8. Polar representation of the system efficiency as a function of the azimuth angle of the RFID Tag for different distances between Tag and Reader. Fig. 6. trajectories for different visitor speeds and Reader positions on the body of the visitors. We consider the movement direction towards the Tag and we carried out measurements for both the incident angles described in Figure 5. The chest positioning provides slightly better performance than the shoulder case for an incident angle of 0, while the count values are almost Floor plan of the considered indoor museum-like environment. 193

5 Fig. 9. Polar representation of the system efficiency as a function of the azimuth angle of the RFID Reader for different distances between Tag and Reader. the same when 45 radial trajectories are considered. It is worthwhile to note that, in respect to an amble movement, a very sligth reduction of the count is measured when a fast speed is assumed, thus highlighting the system robustness. In Tables II we show the count values obtained from tests Reader position Speed 0 45 Chest amble fast Shoulder amble fast TABLE I. Count VALUES OF DYNAMIC TESTS CONSIDERING RADIAL TRAJECTORIES FOR DIFFERENT VISITOR SPEEDS AND READER POSITIONS. performed under dynamic conditions for secant and tangent movement trajectories towards the Tag. We considered different distances and speed levels and the Reader positioned on the visitor s chest. Obtained outcomes show that the count is not null even for distances above 4 meters. We measured a quite regular trend of the count with respect to the distance increase, except for the case of 2.5 meters for the tangent trajectory, where a performance reduction is registered, probably due to multi-path effects. In order to evaluate the capability of the RFID system to Speed d [m] Secant Tangent Amble Fast TABLE II. Count VALUES OF DYNAMIC TESTS CONSIDERING SECANT AND TANGENT TRAJECTORIES FOR DIFFERENT VISITOR SPEEDS AND DISTANCES BETWEEN TAG AND READER. support visitor interactions with the objects and artworks inside the museum, we performed the demonstration test described in Section IV. A typical art exhibition is simulated by installing a total of 8 Tags in the rooms or along the corridor of the indoor environment shown in Figure 6. The Tag deployment accounts for the results of the system characterization in terms of both operative distance and radiation pattern, thus obtaining an accurate system dimensioning. For example, based on the Tag position (room or corridor), we considered the most appropriate downtilt, by setting the value of the Tag inclination angle ranging from 0 up to 30. Tags are installed at a height of 2.3 meters, while the Reader is positioned on the chest of the visitor moving at low speed (amble) around the museumlike environment according to the path shown in Figure 6. In Figure 10 we report the count parameter measured for each detected Tag as a function of the duration time of the demonstration. As shown, when the Reader starts to identify a Tag, the count increases until the visitor is inside the coverage of the RFID system, i.e. the distance is less than the maximum operative range. So the final count value represents the total times the Reader receives the information message from the Tag during the test duration. It should be observed that the slope of the curves shown in Figure 10 are different for each Tag. It depends on the variability of the b parameter, that means that the average number of Reader acquisitions per second is not constant with time due to the indoor propagation effects. Moreover, this variability can be slow or fast: in the first case, the slope of the count increase does not significantly change in a short time period (i.e., few seconds); in the second case, the b parameter can strongly fluctuate even within brief time intervals due to the presence of obstacles or other causes that suddenly affect the radio propagation conditions. This latter case is clearly observed for Tag 2, due to the visitor path inside the room and the presence of obstacles therein. Anyway, from obtained results we can argue that the RFID system can properly support visitors in typical museum environments, in accordance with the reference scenario. It is worthwhile to note that, based on the considered Fig. 10. Count for each Tag deployed in the indoor test environment. environment, light walls (wooden or light brick) can cause high error probability of the visitor positions within building 194

6 areas (rooms, corridors, etc.). Indeed, such wall material does not significantly attenuate the signal propagation and therefore the Reader may identify a Tag positioned in adjacent rooms. On the contrary, we experimented that other types of wall do not allow the signal crossing, thus ensuring the absence of errors caused by ambiguous detections. VI. CONCLUSIONS RFID technology can enhance object inventory and visitor guide applications in museums. A typical scenario envisages that museum visitors endowed with RFID Readers can enjoy artwork descriptions stored into RFID Tags. Due to the indoor radio propagation environment, an appropriate system characterization is needed to ensure the correct functioning of RFID applications. In this work, we experimentally characterized a RFID system aimed at supporting the interaction between museum visitors and artworks. We designed an experimental setup and we carried out many tests to evaluate the system performance in different operative conditions. We show that in typical museum environments the proposed RFID system is able to automatically provide visitors with the information related to museum collections. The obtained results can be also useful for system dimensioning and deployment. ACKNOWLEDGEMENT This work has been partially performed within the research project REference implementation of interoperable indoor location & communication systems for FIrst REsponders (RE- FIRE) co-funded by the European Commission. REFERENCES [1] Mazzenga, F., Simonetta, A., Giuliano, R., Vari, M., Applications of smart tagged RFID tapes for localization services in historical and cultural heritage environments, Workshop on Enabling Technologies: Infrastructure for Collaborative Enterprises, WETICE 2010, pp [2] J. A. M. Ladd, K. E. Bekris, A. P. Rudys, D. S. Wallach, and L. E. 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