By means of the interaction technique touching the user can select a real world object by touching it with a mobile device. According to the taxonomy described in subsection 2.3.2 touching is an absolute and direct interaction technique. For using touching the user must be first of all aware of the augmentation of the object. In the next step the user has to touch the object which is only possible when she is nearby to the object. Through this the mobile device knows exactly with which object the user wants to interact and presents related services.
This interaction technique is very natural because it conforms to one of our everyday physical interactions. We often touch objects with our hand or fingers while we speak about them to support the fact that we talk about this object and its attributes. One disadvantage when using this physical mobile interaction technique is that the user must be aware of the augmentation of the object and the provided services. Touching is convenient when the user is nearby the object and does not have to take a long walk to it. Sometimes it is even impossible to go nearby to an object, e.g. when it is on the other side of the motorway. Furthermore, sanitation might be a problem for some users because they have to touch a potentially dirty object with their mobile device.
[Want et al. 1999] were one of the first who presented a prototype for the interaction technique touching which incorporates Radio Frequency Identification (RFID) tags and an RFID reader connected to a mobile device, in this case a tablet computer. They used this prototype for instance to interact with augmented books, documents and business cards to establish links to corresponding services like ordering a book or picking up an email address. In [Tuomisto et al. 2005, Välkkynen et al. 2003] this interaction technique is called TouchMe which they realized via proximity sensors that sense the distance between the augmented object and the mobile device.
Typical technologies for implementing this interaction technique are short range RFID and Near Field Communication (NFC). When talking about the usage of RFID as an implementation of touching in the remainder of this thesis then always short range RFID is meant. When using RFID or NFC the objects do not have to be directly touched and depending on the used technology a distance of approximately 0-5 centimetres is sufficient for the selection. As described in [Falke 2005a] the needed dexterity can be also a problem for inexperienced users when they for instance do not know where the tag reader in the device is located and how they have to touch the object or, more precisely, the tag. A typical RFID system consists of an RFID tag or transponder and an RFID reader or writer [Finkenzeller 2003]. RFID tags can be very small and are inexpensive through which it is easily possible to tag objects. NFC is a short range data communication technology using the frequency band of 13.56 MHz. It is a combination of RFID contactless communication technology and wireless networking technology. NFC is a standardized through the Near Field Communication Interface and Protocol NFCIP 1/2 (ECMA-340, ECMA-352, ISO/IEC 18092) and is compatible to MIFARE (ISO/IEC 14443A), FeliCa (complies with ISO/IEC 18092) and ISO/IEC 15693.
The following Figure 4 illustrates the several interaction styles provided by NFC. The first one illustrates that the NFC chip can read information from and can write information to a tag. This is the functionality which is also provided by conventional RFID chips in mobile phones. The second one shows that the NFC chip can emulate an NFC tag, which is read by a reader of an interaction point like e.g. a turnstile in a train station. The last one
2 Related Work and Classification
illustrates that NFC also supports bidirectional communication between two devices which is comparable with very short range Bluetooth communication.
NFC Device NFC Device NFC Device NFC Chip NFC Chip NFC Chip Tag Information Interaction Point Reader NFC Device NFC Chip
Figure 4: NFC interaction styles.
There are a lot of standards and proprietary solutions in the field of RFID and NFC based contactless short range communication. In the following, just the most important or innovate ones are mentioned.
MIFARE from Philips Semiconductors is a standard for contactless and dual interface smart cards which is fully compliant with ISO 14443A [@Mifare]. These tags were particularly designed for using them as electronic tickets in public transport and have memory capacities of up to 72 kilobytes. According to Philips there were 400 million cards issued and 2 million installed readers in 2003. FeliCa from Sony is a contactless IC card technology certified by ISO/IEC 18092 which is used for electronic ticketing, electronic wallets, identification, access control or e-Commerce [@SonyFelica]. Texas Instruments as another tag vendor offers among others 13.56 MHz and 134.2kHz RFID tags based on ISO/IEC 15693 and ISO/IEC 18000-3 [@TexasInstruments].
The following Table 3 shows some concrete examples of the mentioned RFID standards in combination with some technical details such as operating frequency and storage capacity.
Name MIFARE Standard
contactless Smart Card [@Mifare]
Felica Contactless IC card RC-S833 [@SonyFelica]
Texas Instruments RI-I11- 112A-03 RFID tag, [@TexasInstruments] Standards ISO/IEC 14443A ISO/IEC 18092 ISO/IEC 15693 and
ISO/IEC 18000-3 Facts 13.56 MHz, 1 Kbyte 13.56 MHz, 2 Kbyte 13.56 MHz, 2 Kbyte
2 Related Work and Classification
The following Table 4 shows some examples of the usage of these standards within mobile devices. In principle it is possible that the RFID and NFC capabilities are provided by the mobile device itself or by an external device.
The Cathexis IDBlue pen [@IDBlue] is a typical example for the latter. It can be connected via Bluetooth to a mobile device through which a corresponding application can read and write tags. Beside this there exist several integrated solutions.
Nokia offers within its Field Force Solution product line the Nokia Mobile RFID Kit for the Nokia 5140/5140i and the Nokia NFC shell for the Nokia 3220 [@NokiaFieldForce]. From Benq-Siemens, there exists a similar prototype based on the Siemens CX70 Emoty [@SiemensNFC].
i-mode Felica is a service which is provided by NTT DoCoMo in Japan [@i-modeFelica, Boyd 2005]. Here mobile phones like the NTT DoCoMo SH506iC include a FeliCa chip to emulate Felica tags. The i-mode Felica service is already widespread in Japan and is currently used for transportation, ticket, membership card, key/ID and shopping applications.
Name Cathexis IDBlue
Bluetooth RFID pen [@IDBlue] Nokia 3220 with Nokia NFC Shell [@NokiaNFCShell] Benq-Siemens RFID / NFC Prototype [@SiemensNFC] NTT DoCoMo SH506iC [@i- modeFelica] Supported tag standards ISO 15693-2, -3, Tag-it HF/HFI, Philips I-Code SLI Philips MIFARE ( Ultralight, Standard 1k / 4k) Philips MIFARE Standard 1k Sony Felica
Table 4: Mobile RFID or NFC devices.
The following Table 5 shows beside the advantages and disadvantages also the different properties of RFID and NFC. The different attributes are partly based on a classification discussed in [Ailisto et al. 2003].
As already mentioned the aim of this subsection was, beside the explanations regarding the interaction technique itself, the provision of a compact overview of techniques for the realisation of it. A comprehensive and detailed overview of short-range RFID and NFC, their usage in mobile applications and their differences, advantages and disadvantages can be found in [Falke 2005a, Falke et al. 2006b].
2 Related Work and Classification
RFID NFC
Unobtrusive tagging, simple, robustness, inexpensive, disposable, can be easily sensed Advantages
NFC device can emulate tags and supports the communication between two NFC devices
No visual awareness, additional visual marker like the NFC logo is needed. Proposals for solving this problem can be found in [Riekki et al. 2006].
Disadvantages
No emulation of tags possible Data transfer Bidirectional (read / write)
Data rate 212 kbps [@SonyFelica] 106, 212 or 424 kbits/s (ECMA-340, ISO/IEC 18092 )
Latency Ca. 1s [@IDBlue] Ca. 1s [@NokiaNFCShell]
Operating Range
0 - 5 cm [@IDBlue] 0 - 3 cm [@NokiaNFCShell] Data Storage
Type Fixed (read only tags), Dynamic (writeable tags) Most tags currently have a capacity of up to 5 Kbyte. Data Storage
Capacity
E.g. 2 Kbyte (Texas Instruments RI-I11- 112A-03 RFID [@TexasInstruments])
E.g. 512 bit to 4 kbyte [@Mifare] Unit costs Depends heavily on the number of ordered tags and the standard of the tag. Examples:
Expected 0,05 $ [Sarma 2001], 0,20 $ [Want et al. 1999], 1,75 € (order of 200 Philips MIFARE Standard 1k tags in 05/2006 from identmarket.de)
Table 5: Comparison of RFID and NFC.