Context-Based Adaptation ofMob-le Phones Usilng Near-Field Communlat-ion

Sudha Krishnamurthy* Dipanjan Chakraborty, Sandeep Jindal, Sumit MittalDeutsche Telekom Laboratories, Berlin, Germany IBMIndia Research Lab, New Delhi, India

sudha.krishnamurthy@telekom.de {cdipanjan, sajindal, sumittall}in.ibm.com

Abstract 1.1. D'istract'ions Alrising from Mobile PhonesThe greater flexibility and accessibility provided by mo-

Smntextart extironmentusethat ca adtoaptiba ong thev c len bile phones has been a boon to the society to a large extent.condantextar sThexrem y usefulefr a sutmating enveonsimle However, in the case of person-to-person communication,mundace thasks. The ey c pe ofch a envhronmen this accessibility has resulted in an increase in the number

of interruptions. Several efforts have been made to study thethat can draw inferences by aggregating the context from impactlmatthat the interruptions caused by moblle phone usagedifferent sources, and a set ofpolicies that drive the adata- have had on the society [IO]. These studies reveal that mosttion. In this paper we describe a context-based adaptation people find the use of mobile phones in public places to besystem to alleviate the distraction caused by one ofthe mostYS ~~~~~~~~~~~~~~~annoying.The study conducted by Monk and othelrs [ 1L2] re-ubiquitous devices ofmodern day - the mobile phone. Our vealed that mobile phone conversations in public are moresystem makes use of sources, such as REID devices, that distracting than face-to-face conversations, because peopleemploy near-field communication technology to extract raw

p

contxt.Wedscrbe ow w adpt he rlesof hesedevces pay more attention to one-way conversationas. These inter-context. We describe how we adalpt the roles ofthese devices rutoshvbemeucanieglprtforlvs,htto etrac botenvronmntaland ersoal cntex. Tore- ruptions have become such an integralL par of our lLives, that

ducethex distractb vironmctause bynmolerhones wtex.he de- we tend to either overlook them or react by turning off theducelopediapol-asedmcnmoenbe ontex-ased phone or placing it in vibration mode, but only after the in-veloped a policy-balsed mechanilsm to enalble context-based

terpto ha'curd n,dmaebe oe nsmterrupotion has occu.rred. anld damage been d.one. In someadaptation of these devices. We have implemented a proto- cases, the abrupt ringing of a phone is not simply a distrac-type of our system and conducted some usage studies. We tion, but could also lead to disastrous consequences. Thisdescribe the details of our implementation andpresent the is especially true when a mobile phone rings in the midst oflessons learnedfrom the usability experiments, time-critical and safety-critical situations, such as when an

operation is being performed, in an operation theater.1. Introduction The social disturbance caused. by mobile phones can be

addressed in several ways. One approach is to introduceMobile devices have become an indispensable compo- legislation for the use of cell phone in public places. An-

nent of modern day living, because of their ability to pro- other approach is to constantly educate people by putting upvide access to people and, information, anytime and, any- signs, which serve as polite reminders. However, these ap-where. Among the different mobile devices that are cur- proaches ignore the personal preferences of the phone usersrently available in the market, mobile phones have in partic- themselves, and require the users to change the settingsular peirmeated the daily lives of people, regardless of their manually. A more aggressive approach is to use jamming.age and occupation, in developed and developing countries However, the problem with this approach is that phone jam-alike. As of year 2005, there are nearly 2 billion mobile mers are likely to affect wider areas and frequencies otherphone users and this number is only likely to increase fur- than those that they are intended, for, which can be disruptivether. The greater flexibility and accessibility provided by to critical services, such as operations ofemergency and, res-mobile phones has changed the way people expect to be cue workers. Thus, such a "one size fits all" approach mayconnected together. No longer does a callee have to wor not be useful in all environments.about missing calls or be confined to a single location in or-der to carry on a conversation. Callers expect that calling 1.2. Context-Based Adaptationthe mob:lLe pholne of a persoln w:lL: help iln connecting to thatperson immediately and tend to prefer that option. In many cases, the social problem arising from mobile

*palrt ofthe wrkdonwLhile being atIBM India Researh Lab Ne phone usage can be alleviated ifthe caller has some aware-Delhi, InLdia ness of the context of the calUlee and if users do not have to

1-4244-0499-1/106/$20.00 ©2006 IEEE

manually configure their phones to reduce the distraction. other instances of NFC as well. The use of NFC for theThe mechanism we propose in this paper makes context- purpose of capturing contextual data has several advantagesawareness part of the mobile phone device and. uses the over competing technologies. First, NFC does not requireawareness to enable personalized adaptations, because each line-of-sight. Second, since data is captured. in close prox-user may require a different kind, of adaptation under the imity, the data transfer can occur securely. So the possibilitysame context. By context we mean a combination of en- of eavesdropping and loss of privacy is minimized. Third,vironmental and personal information that should be used unlike long-range protocols, such as Bluetooth or wirelesswhile determining the adaptation required. The adaptation Ethernet, NFC poses no difficulty in selecting the correctneeds to consider the context of the callee and, to some de- device out of a multitude of devices in the range for datagree, that of the caller. capture and actuation. That is particularly useful for the ap-

Previous approaches have derived context by mapping plication we are considering in this paper, as it prevents thethe imprecise data gathered by general-purpose sensors to adaptation mechanism from switching off or turning downhigher-level context using complex inferencing techniques. the volume of the wrong mobile phone. Fourth, comparedThe effectiveness of the adaptation in this case depends on to long-range communication interfaces, it takes less time tothe precision of the sensory data and, the accuracy of in- capture data using NFC. Fifth, unlike sensor devices, whichferencing. Our use cases target mobile users whose context are self-powered and use their own power for data capturechanges quickly. Hence, our goal is to improve the accuracy and communication, NFC not only allows communicationand latency ofthe adaptation by gatheringprecise context at between self-powered devices (active mode), but also be-the outset and reduce the need, for complex inferencing. In tween a pair of devices, only one of which is powered (pas-addition, our goal is to leverage existing features on com- sive mode). This is useful for a battery-powered, device,mercial, off-the-shelfmobile phones, and make the context- since it does not have to expend, its own energy when it re-based adaptation seamless, without changing the interface sponds to an external initiator device, like an RFID reader.between the user and his mobile phone. Modifications, if Finally, mobile phone manufacturers have already begunany, will have to be simple and, incremental. A large number shipping mobile phones enabled with RFID reader/writer.of people that use mobile phones are not technically savvy. For example, the Nokia 5140 and 5140i phones with the in-Retaining the interface the users are already familiar with, tegrated Xpress-on RFID Reader shell and the NFC shellprovides better incentives for an average user to adopt our for Nokia 3220 allow users to launch services and accessapproach. phone functions such as dial or send messages by touching

an RFID tag [3, 4].

1.3. Near-Field Communication 1.4. Paper OrganizationIn order to realize the above goals, our approach uses The remainder of this paper is organized as follows. In

emerging technologies based on near-field, communication Section 2, we discuss related approaches that have been(NFC) and takes advantage of sma environments. NEC is a used to make mobile phones/devices context-aware. In Sec-short-range wireless connectivity standard that has evolved tion 3, we describe our solution based on near-field commu-from a combination of contactless, identification, and net- nication that enables the mobile phones to be context sensi-working technologies [2]. The NFC range extends to ap- tive and socially-aware, and illustrate the use ofthe solutionproximately 20 cm and it is complementary to existing in specific application scenarios. In Section 4, we describelonger range wireless technologies, such as bluetooth and our prototype implementation. In Section 5, we present re-Wi-Fi. NFC operates in the unregulated radio-frequency sults of our user survey based on our prototype and lessonsband of 13.56 MHz and is interoperable with existing con- learned from the experience. Finally, we present our con-tactless smartcard and RFID standards. A typical exchange clusions in Section 6.using NFC involves an initiator device that initiates andcontrols the exchange of data and a target device that an- 2. Related Workswers the request from the initiator. The data acquired isusually very precise and structured. The increased use of The use of context-aware adaptation in mobile phones tomobile services benefiting from synergies with NFC is be- provide a distraction-free environmentprimarily depends oncoming more apparent. For example, NFC-enabled devices the callee context and to some extent on the caller context.storing the access code or ticket can be presented near a Previous approaches that have used. context-aware adapta-reader for access control and ticketing applications. tion to alleviate the distraction caused by mobile devices

In tillspaper, we propose a novel use of NFC tO provid,e hlave prilmarily focused, on enhlancing mobile dLevices witcontext-based adaptation of molbile phones. Although we low-level physical sensors to gather context (e.g., Sensayprimarily focus on Radio EFrequency Id.entification (:REFID) [18], (T:EA)[16]). These approaches use cu.stomized sen-as a concrete instance of NEFC, our approach encompasses sors, some of whic:h are mounted. on the user's body, to pro-

vide situational awareness. A decision module then uses a communication channels (CDMA or GSM) for messaging.set of rules to analyze the sensor data and infers the current These phones are typically not programmable.context ofthe user, which is then used to perform automatic Category 2: NFC-enabled smartphones. NFC-enabledcontext-based adaptation on the mobile phone, taking into phones typically have in-built RFID readers that can be usedaccount the preferences in the user profile. to capture data from or store data onto external tags. These

The effectiveness of the adaptation in the Sensay and phones can also be used to capture data relevant to a context,TEA approaches depends on the precision of the data such as calendar events, from compatible NFC-enabled de-gathered by general-purpose sensors and the accuracy of vices and the captured data can be stored as data entriesthe inferencing techniques that map that data onto higher- in the phone. Some models of the NFC-enabled phoneslevel context. In contrast, our approach gathers precise also have in-built tags that can be used, to store informa-and higher-level context using technologies based, on NFC, tion, such as a phone number. These phones are typicallywhich reduces the need, for complex inferencing and, enables programmable and support regular cellular communication.quicker adaptation. In addition, our approach retains much Category 3: Mobile phones with long-distance commu-of the interface of commercial, off-the-shelfmobile phones, nication channels: Phones in this category support one orand does not require any customized sensors to be added. more long-distance wireless communication channels, like

Context-based adaptation has been well-studied in gen- Wi-Fi and Bluetooth, which can be used to communicateeral, for scenarios other than mobile phone usage (e.g., with the remote backend. infrastructure. Phones that support[8, 11, 17]). Our work is complimentary to this body of non-cellular, long-distance wireless communication may orwork and can essentially leverage it. may not have inherent support for NFC. For instance, T-

Mobile's MDA III phone supports GPRS and Bluetooth, in

3. Solutilon Descr'ipt'ion addition to GSM [5], but it is not NFC-enabled.

In order to build a context-based adaptation framework 3.2. Context Discovefor minimizing distractions in mobile phones, our solution Context is a description of the current situation at an ab-needs to address the issue of context acquisition in mobile stract level. There has been considerable previous work onphones, context synthesis, and policies for adaptation based defining different kinds of context (e.g., [7, 15, 17, 19]). Weon the context. The key components that we have used for can minimize the distractions resulting from mobile phones,enabling context-awareness in mobile phones using NFC in- if the mobile phones have some awareness of the context ofclude the mobile phones, the NFC (RFID) infrastructure, a the callee and the caller. The caller context identifies thecontext synthesizer, and the communication channel. The caller, urgency, and time of the call The callee context isNFC elements, which may be an integral part of or exter- determined by who the callee is with, the activities that thenal to the mobile phones, gather contextual information and callee is engaged in, and the environment the callee is inpass it to the context synthesizer. The synthesizer combines when he receives the call. Thus, the adaptation is basedthis information to determine how the mobile phone con- on synthesizing the context of the callee and caller, alongfiguration of the user must be adapted in the current envi- with the environmental context of the callee. We now de-ronment. The adaptation directive is then sent to the mo- scribe how we apply NFC technology for each of the abovebile phone, resulting in an appropriate reconfiguration of mobile phone categories, in order to discover personal and,the phone. Depending on the capabilities of the phone and environmental context.the environment concerned, NFC plays an important role in In the case of phones with no inherent NFC capability,each of those processes. The remainder of this section de- we explicitly affix RFID tags to the phones. We call thesescribes those roles in more detail. tags that are affixed to cell phones, cellular tags (or c-tags).

C-tags store personal context. Some examples of personal3.1. Categories of Mobile Phones context are phone number, schedule for the day, and, pro-

files. User profiles may specify preferences, such as: blockFor the purpose of this paper, we broadly classify the my calls when I am inside an operation theater. The amount

mobile phones that are currently available commercially, of information that can be stored in the tags depends on thealong two dimensions. This classification of mobile phones storage capacity of the tags. For example, Phillips offersis based on: a) inherent support for NFC in the phones in or- NFC compatible MiFare cards that have 1KB of EEPROM.der to capture contextual informration, b) support for long- The personal context stored in the c-tags is read by the RFIDdistance, non-celUlLulLar communication channels to enforce readers in the environ4-ment and used as the basis for adapta-the adaptatioln. tion, as explLained lLater.

Categolry 1: Rlegularz phzones: Wve classify regular In thle case of NEC-enabled, phlones, whichl we consid,erpXhones to 'be those mobile pXhones that do not have inher- to 'be programmable, the personal context is stored withinent NE capabili However, they have the basic cellular the pholne. Ifthe personal contlext, such as calendar entries,

are stored in another NFC-enabled device, then the informa- hospitals), the usage policies gathered from the e-tags takestion can be conveniently transferred by simply bringing the precedence over individual user preferences stored in thetwo NFC-enabled devices in close proximity to each other. c-tags. Such precedence rules help resolve conflicts. SinceSimilarly, the personal context stored in the phone can be the context information gathered from NFC sources is fairlytransferred to external RFID tags with the help of the REFID precise and high-level, the aggregation and inference logicreader/writer in the phone. is not complex. Hence, in our framework, the context syn-

The above explanation describes the use of RFID tags thesizer is a thin entity and may even be optional in somefor discovering personal context. In addition, we use RFID cases.tags to gather the environmental context. We call these tags We now discuss the placement ofthe context synthesizerenvironnmental tags (or e-tags). We consider environments module for each of the phone categories we listed earlier.where e-tags are affixed as smart environments and use the In the case of regular mobile phones, the context synthe-in-built RFID readers in NFC-enabled phones to capture the sizer resides at a remote backend server or is part of thecontext from e-tags. Examples of environmental context in- mobile service provider's system, because we do not con-formation include the type of the environment (such as op- sider this class of phones to be programmable. In this case,eration theater), and activities scheduled to take place there the RFID readers in the neighboring environment gatheron a day (e.g., list of operations and surgeons participating the callee context from the c-tags on the phone and sendin the operation). that along with the environmental context directly to the re-

In summary, the use ofNFC technology allows a mobile mote context synthesizer using RS232, wired LAN, or otherphone to play different roles in discovering context. When long-distance wireless communication interface. Alterna-a tag that is either in-built into an NFC-enabled phone or tively, if the mobile phone supports non-cellular commu-explicitly attached, supplies the context, then the mobile nication interfaces (e.g., phones belonging to Category 3),phone acts as the context source. On the other hand, if then the RFID readers can forward the context they havethe mobile phone is equipped with an RFID reader, then gathered to the back-end or mobile service provider's server,the phone serves as a sensor that is capable of gathering using the long-distance messaging channels available on thecontext from the tags in the smart environments. The role- phone. In the case of NFC-enabled phones, which we con-based abstraction ofthe tags into e-tags and c-tags is primar- sider to be programmable, the context synthesizer residesily based on the different context information they provide. on the phone. The context synthesizer module can directlyHowever, physically both these tags are passive tags that access the environmental context gathered by the in-builtare compliant with NFC standards and are therefore, inter- RFID readers and the callee and caller context stored in thechangeable. If the space available on a tag is insufficient, phone. So in the case of NFC-enabled phones, the aggre-then we can store a pointer to the actual information (e.g., gation and adaptation can be done internally by the mobilea link to the user profile). The context synthesizer receives phones, obviating the need for long-distance communica-this link from the RFID reader and then accesses the link tion.over long-distance communication channels to retrieve the 3.4. Policies for Context-Aware Adaptation incontext information.

Mobille Phones3.3. Context Synthesis Having gathered and aggregated the callee's personal and

Context synthesis is an intermediate step in determining environmental context, as well as the caller context, the nextthe type of adaptation required by the mobile phone. The step is to trigger the appropriate adaptation that minimizesenvironmental context gathered from e-tags has to be ag- the distraction due to mobile phones in that context. Exam-gregated with personal context gathered from c-tags, in or- ples of common adaptations include controlling the volumeder to draw higher-level inferences. In addition to the callee of the ring tone (e.g., high, low, vibration); switching to thecontext, the context synthesis takes into account the avail- appropriate messaging mode (e.g., voice call, text messag-ab,le caller context. The context synthesizer prioritizes and ing, MMS, instant messaging); adapting the voice messagefilters information from different sources and resolves con- on the phone to indicate availability of user; and turningflicts, in order to determine the appropriate adaptation. For the phone off/on. We have used a rule engine to trigger theexample, in an office environment, sometimes meetings are adaptation based on the context. In order to decide the ap-held in an impromptu manner. Hence, the calendar entries propriate adaptation, the rules also need to consider whethermay be obsolete or incorrect. If an REID reader detects the callee is entering a context, located within a context, orthe presence of an employee in a conference room using exiting the context. Wherever possible, this informIation isthe c-tag attached to his mrobile phone, then since this lLoca- alLso gathered by the NFC elelments and sent as inputs totion informlation is captured in real-time, it takes precedence the rule engine. HIowever, in some cases, the informationover the employee's calendar entries. Similarly in environ- about ent and exit may have to bededucedby the con-ments where policies have to be enforced mandatorily (e.g., text synthesizer. We now illustrate how the conatext-based

adaptation that we propose using NFC can be used in spe- staff(L)) - action(turn-off(phone(Z, Y)) and voice-mnessage(Zcific real-world scenarios to achieve an environment that has unavailable until" + end-time(T, event(surgery))))minimal disruptions due to mobile phones. The above rule specifies that ifthe environmental context

1) Safety-critical environments: A hospital is a good determines that a user Y is entering or is within an opera-example of an environment in which the distraction caused tion theater in a hospital and Y is a member of the staff per-by mobile phones can have different impact in different con- forming the surgery, then Y's phone (indicated by the phonetexts. For example, the use of mobile phones in intensive- number Z) has to be turned off and, its voice message turnedcare units and, coronary units, where patients are moni- on to indicate the user's unavailability until the surgery istored and pacemakers are present, may have serious conse- completed. In this example, the location X, duration T ofquences [ 13]. Hence, when patients and medical staff enter the surgical event, and the staff list L, are part of the en-those areas, they should, remember to turn. off their mobile vironmental context obtained from the RFID devices in thephones. Similarly, if the mobile phone of a surgeon rings hospital premises, while the user identity Y and his phonewhen a surgery is in progress, it not only distracts the sur- number Z are part ofthe personal context obtained from thegeon, but also the rest of the team in the operation theater. c-tag on the phone. The example illustrates how the use ofThe loss of concentration could result in unintended med- NFC technology allows us to capture high-level informationical errors, costing the hospital millions of dollars in law about the environment and the user, in order to determine asuits. The ringing of mobile phones when a consultation suitable adaptation. An additional benefit of using such ais in progress or near an in-patient ward, especially during system is that it can detect the entry of an unauthorized userthe night, may not result in disastrous consequences, but is who is neither the patient nor a part ofthe surgical team and,nevertheless, a disturbance for the staff and patients. In con- notify the appropriate authorities immediately.trast, the use ofmobile phones poses minimal disturbance or Rule 2: Turn on the phone when surgery is completedrisk in an out-patient ward, cafeterias, lobbies, offices, and location-context(exit, X is(X operation-theater)) and nmem-other non-clinical areas. ber(Y surgery-staff(L)) -c action(turn-on(phone(Z, Y)) and voice-

Thus, as medical staff and patients traverse through dif- message(Z, "))ferent areas in a hospital, they should remember to recon- Rule 2 specifies that if the environmental context indi-figure their mobile phones appropriately, in order to prevent cates that a user Y is exiting a location X, which is identi-distractions. Such manual reconfiguration is hard to achieve fied as an operation theater, after participating in a surgicalon a daily basis. Thus, hospital environments would greatly event, then Y's phone (indicated by the phone number Z)benefit by deploying the NFC-enabled adaptation mecha- has to be turned on and its voice message has to be turned.nisms we have proposed, with the added advantage that the off. The context information is obtained, as explained in theoperating frequencies ofNFC technologies do not interfere previous example. In environments where the entrance andwith the hospital environment. The deployment would. re- exit points of the operation theater are distinct, we can havequire passive RFID tags at the entrance of operation the- different RFID readers at each point. In such a case, theaters that can store information about whether an opera- entry and exit events can be easily distinguished from eachtion is in progress and how long the procedure is likely other based on the context information gathered by the NFCto last. Such dynamic, high-level context information is elements. However, in environments where this distinctionhard to gather using general-purpose physical sensors (for cannot be made based on the raw contextual data gatherede.g., motion sensors that monitor movement in the opera- by the NFC elements, the context synthesizer or a highertion theater). Besides, some basic context information (e.g., level module has to infer this information, based on exter-whether an operation is in progress or not) is small enough nal correlations. For example, if there is only a single RFIDto be stored in the e-tags. Medical staff can be provided with reader in the operation theater, then the first reading fromNFC-enabled mobile phones and as they enter the operation the reader, reporting the presence of a user on a particulartheater, the mobile phones can be turned off or switched day, is regarded as the entry event for that user and the nextto an appropriate messaging mode, according to the user's reading for the same user is regarded as an exit event. Inpreferences. Additionally, the voice mails on the mobile such a case, an appropriate module in our software frame-phones can be automatically adapted to inform the callers work has to store some state information, which is feasibleabout the phone owner's current context and availability. in environments like an operation theater, where the num-This allows the callers to retry their calls later at an appro- ber of users entering or exiting the environment is limited.priate time. The following rules illustrate the policies for This stored state may also be used to support more advancedcontext_-beandiaptation In ahslpital environment, actions such as restoring the mobile phone to its previous

fRule 11: Tulrn off the phone when surgelry is in configuration, when the user exits the operation theater. Inprogress Section 5, we discuss such enhancements and the anomalies

locatian-cantext(enter, X~is(X~aperaltionz-theater)) or localtionz- resulting f:romr failLure to detect events.cantext(in Y, is(X opel ation-theater))) alnd men ber(Y, surgery- 2) Silent environments: The ringing of a mobiLle pholne

often violates the etiquette in certain public places where Callers have little information about the current situationpeople are required to maintain silence (e.g., religious insti- of the person they are calling and expect quick responsive-tutions, libraries, examination rooms, and funerals). Class- ness when they call or leave a voice message on a mobilerooms and concert halls belong to another class of silent phone. If the response is not forthcoming, the callers keepenvironments, in which the activity takes place for a cer- retrying their calls, which in turn aggravates the distrac-tain fixed period of time and the abrupt ringing of a phone tion for the colleagues with offices nearby. This problemcauses distraction. The adaptation that we have proposed can again be alleviated with the help of the context-basedusing NFC provides a more effective way to prevent distrac- adaptation mechanism that we have proposed. Many orga-tion in such settings, than putting up signs. The following nizations these days require their employees to wear RFID-rule illustrates how the personal and environmental context enabled access control tags that identifies the employee.gathered by the NFC elements are used for context-based The RFID reader in an NFC-enabled mobile phone can beadaptation in a silent environment. programmed to infer the absence of the owner in the neigh-

Rule 3: Switch the messaging mode of a mobile phone borhood, when it fails to detect the access-control tag of theto a user-specific mode in a library owner in the vicinity. When there is an incoming call, this

location-context(in 47 is(X librai-y)) and desired-mode("text- can then automatically trigger a reduction in the volume ofmode", X phone(Z, Y)) and allowed-mode ("text-mode ", X) and the ringtone and if required, a notification can be sent to thenot("text-mode mode(AM, phone(Z, Y))) -c action(switch("text- caller indicating the current context of the callee. The fol-mode" mode(M, phone(Z, Y)))) lowing is an example of a policy that is relevant in an officeA library environment is less critical than a hospital envi- environment.

ronment. Hence, in such environments, the user preferencestored in the phone or on the c-tag affixed to the phone is Rule 4: Reduce the volume to vibration level when aretrieved to deternnine the adaptation policy. Rule 3 spec- meeting is in progressifies that if the RFID readers in a premise determine thata user Y is in a library X, and that the user profile stored location-context(in, 4 is(X meeting)) and social-in the c-tag indicates that the user wants his mobile phone context(includes, manager (Y)) -- action(volume-level(vibration,(indicated by the phone number Z) to be in text messaging phone(Z, Y)))mode in a library location, then the phone has to be switchedto text mode. To prevent users from switching their phones Rule 4 specifies that if the RFID readers in an officeto disruptive modes, we verify that the user-specific mode premise detect that a user Y's location is in a meeting roomis one of the allowed modes in the library. The allowed in which his manager is present then Y's phone (indicatedmodes are obtained from the environmental context. If the by the phone number Z) has to be switched to vibrationuser-specific mode is not one ofthe allowed modes, then the mode, so that he can decide to accept the call without dis-phone is switched to a mode that is dictated by the default tracting the other attendees. The social context indicatesenvironmental policy. Moreover, a library may have RFID who Y is with and that can be determined with the helpreaders in multiple places. This redundancy ensures that if of the RFID readers that keep track of the people enteringthe reader at the entrance fails to capture an entry event, then the meeting room by reading the c-tags on their phones orother readers within the library can enforce the adaptation. their RFID-based access control tags. Alternatively, if allHowever, the redundancy may result in duplicate actions, the users own NFC-enabled phones, then the in-built readerwhich we avoid by ensuring that the phone is switched to in each user's phone can read the context information fromthe text mode, only if it is not currently in the appropriate the other NFC-enabled phones in the vicinity to deduce themode. social context of the user.

3) Office environments: Office environments also serveas another fertile setting for frequent mobile phone distrac- The above examples illustrate the use of an innovativetions. This problem is especially conspicuous in environ- mechanism to employ NEC devices in different roles, in or-ments where cubicles are densely packed next to each other. der to minimize the disruptions arising from mobile phoneUnlike hospital environments, the distractions in office en- usage. The use of NFC technology allows us to determinevironments do not have disastrous consequences. Unlike context that is both precise and detailed compared to relatedlibraries, office environments do not require people to re- mechanisms that use low-level physical sensors for context-main silent. Furthermore, unlike theaters and class rooms, based adaptation [16, 18]. In some cases, the tags attachedthe context of the employee changes in an ad-hoc manner to the mobile phones supply the user context required toand may not always adhere to fixed time schedules. trigger the adaptation. In other cases, the REID readers em-Acommon problem in anoffice environmentisthatsome bedded in the mobile phones gther the environmenta and

employees leave their mobile pXhones behind without turn- sociafl context, and combine it with the user's personafl con-ing down the volume, when they are away from their desk. text to trigger the appropriate adaptation.

3.5. Enforcilng the Pol.ic1ies are read/write tags and have a maximum storage capacityAfter the rule engine determines the action to be taken of 112 bytes. The reader can detect tags that are within

* 1 ~~~~~~~~~~~~afew celntimeters and caln forward the ilnformation that itunder different contexts, the next step is to execute the ac-tions that will result in the context-based adaptation. The reads to the backenda through a serial link. Our protoypemanner in which the adaptation is enforced by the rule en- currently assumes all phones to be regular phones (Cate-gine varies for the different mobile phone pes listed ear- gory 1). As mentioned in Section 3.1, these phones have

-er, because the phones have different capabilities. no in-built RFID readers or tags and do not have any long-As mentioned earlier, the context synthesizer and rule distance wireless communication channels, other than the

engine for the regular phone category reside at a backend regular cellular messaging channels. We chose this categoryl. ~of phones, becau.se they are representative of the phonesserver or at the mobile service provider (MSP). In this case,

the rule engine determines the action based. on the rule-set owned by the users that participated in our survey. Users af-

and enforces the adaptation either directly through the MSP fix a passive RFID tag on their phones, which serves as the: - . .< . ~~~~~c-tag and supplLies the user context. We currentlL store theor by sending an SMS to the user. For example, if the c-tag g y

on the mobile phone identifies the user as a surgeon and an <user phone number, user profile URI> in each c-tag. TheREFID reader in a hospital premises detects that the surgeon user profile URI points to the personal rules of the user. C-

is entering an operation theater, then the rule-set (e.g., Rule tags are read by the RFID readers installed at the entrances

1 in the examples above) would determine that all incom- of the conference and meeting rooms.

ing calls to the surgeon's phone need, to be blocked, until thesurgeon leaves the operation theater. If the MSP has the ap- 4.2. Specification of Rules and Profilespropriate support, the incoming calls to the surgeon's phonecan be buffered for a limited period of time. Otherwise, Each environment (for example, meeting room and, con-the rule engine can remotely enforce the action to be taken ference room) has environment rules associated, with it. En-(for example, turn off the phone) through a long-distance vironment rules specify the desired behavior with respectcommunication channel (if the phone has this capability). to usage of mobile phones in that environment. Moreover,In the absence of a long-distance communication channel, users can also indicate their own personal adaptation logican SMS is sent to the user indicating the appropriate action through personal rules. Both environment rules and per-to be taken, and the user has to then manually perform the sonal rules are specified with the help of an administrationadaptation. console, as shown in Figure 1(a). An admin console en-

In the case of NFC-enabled smart phones, the mobile ables users to add, update, and delete rules from anywherephone can be programmed with the context synthesizer and in the building, and access is secured by passwords. Therule-engine modules. As a result, the rule engine can au- rules are represented in XML format and are read and inter-tomatically enforce the adaptation, without any manual in- preted with the help of a rule interpreter capable ofprocess-tervention. In enterprise environments that support a SIP- ing XML. For ease of acceptance and adoption, we chosebased, infrastructure and where all of the users have SIP- the commonly used event-condition-action paradigm [6] toenabled mobile phones, the context-based adaptation can be represent rules. In our initial prototype, we have provided aenforced by taking advantage of the SIP infrastructure [ 14]. simple user interface for specifying the rules, which is pre-In this case, the user and environmental context information dominantly a manual process. However, we can easily ex-gathered by the RFID readers can be sent to a SIP/Presence tend this to support more convenient alternatives to a point-server The notifications received from the presence server and-click interface, such as the ability to create rules fromcan then be used to influence the way an incoming call to a existing rule files or templates. One of our future goals is tomobile phone is handled. leverage related, work (e.g., [9]) to automate the process of

profile specification. In NFC-enabled, devices, the rules and,4. Prototype Implementat'ion profiles can be copied between devices by bringing them

close to each other. After the environment and personal pro-To demonstrate and test our ideas, we have implemented files are created, they can be stored in the e-tags and c-tags

a prototype of our solution for office environments. We have respectively, by programming the tags over the air.also deployed it in our research lab in select conference andmeeting rooms. 4,3, Software Framework

4.1. NFC Infrastructure Figure -(c) shows the components of the solution wehave deployed. The essential co:mponents of this syste:m

Our NFC infrastructure consists of an REID reader fro:m are the REID event handler, event interpreter, and the con-fEscor M:emor Systems (EXMS) and Phillips VMIiEare pas- text synthesizer. We now describe each component in moresive REFI:D tags that operate at 113.56 VM:Hz. These tags detail,

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an event, the next step is to determine the adaptation d.;- proposed. for eliminating di;stractionls arising from mobile

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ing the adaptation directive. Users also agreed that it would restore the mobile phone to its original settings or reconfig-be useful to implement context-based voice messaging as ure the phone according to the user's preferences for hispart of the adaptation for certain users (e.g., system admin- office environment. In cases where the exit event is not de-istrators). However, their opinion was that detailed context tected and, in addition, no other event corresponding to theinformation about the callee has to be conveyed, only to cer- user is detected for a certain period oftime, the context syn-tain callers that the callee should be able to select and the thesizer can use a timer value, the user's calendar, or humanother callers should just receive a default voice message. behavioral pattern to decide when to automatically restoreWe now highlight some of the practical challenges that the mobile phone to its original state. For example, if the

we had to deal with when using NFC devices to capture con- reader detected. the exit event for most of the participants attext in an office environment and use the lessons we learned a meeting, the context synthesizer can use that to infer theto discuss some of issues we would need to address when absence of the exit event for the remaining participants anddeploying our solution in other real-world environments. accordingly restore the state of their mobile devices. The

Missed Events: While the short range of NFC devices ability ofNFC elements to capture higher level, social con-minimizes the possibility of eavesdropping, it may result text is particularly amenable to deriving such correlations.in a higher likelihood of false negatives, when the tags are Duplicate Events: If the RFID reader is set to operatenot within the read range of the readers. We found that in a continuous mode and a user persists in the vicinity ofif the mobile phone affixed with c-tags is not sufficiently the reader after his tag has been read, then the reader mayclose to the reader as the user walks in and out of a room, read his tag multiple times. If not handled correctly, thethe entrance or exit event of the user misses being detected. context synthesizer may interpret this as distinct events in-Hence, sometimes the users have to manually position their stead of interpreting them as duplicate instances ofthe samephones in a way that the reader can detect the c-tags. Thus, event. This results in incorrect adaptations, especially in theone of the challenges is to prevent such misses, while at case where we interpret each distinct read as an entry or exitthe same time read the tags conveniently, without manual event for a user. We currently handle such duplicate eventsintervention. One way to address this issue is by having by filtering them at the event handler based on a timer inter-walk-through readers with multiple antennas to improve the val, before passing the event to the event interpreter. Baseddetection. Since these readers are more expensive, they may on our experiments, we found that a timer threshold of 5be more suitable in public places, where more users need to seconds was appropriate for filtering duplicate read eventsbe detected simultaneously. This also allows the cost to be in our prototype. If the same tag is read by a reader multipleamortized over a larger number of mobile phone users. times within this interval, then the event handler filters the

In the case of entry events, detection can be ensured duplicate read events.by combining the use ofNFC for mobile phone adaptation Security and Privacy: A well-known problem thatwith access control. Several organizations require users to arises when using NFC devices is that unauthorized read-present their RFID-enabled badges to the readers, in order to ers may eavesdrop and capture sensitive information, suchgain admission into a conference room or office. Instead, if as credit card numbers, from tags. Moreover, some tagsthe c-tag on the mobile phone stores the appropriate creden- may be counterfeit. Our prototype currently does not fo-tials, then the user can present that to the readers at the en- cus on these issues, because in order to reconfigure the set-trance. The context synthesizer logic can be programmed to tings on the phone, the tags need, not store very sensitiveuse the input from the RFID reader to provide access to the information. Although in some cases, the tags may storeuser as well as enforce the adaptation on his mobile phone. identity information, in most of the cases it is the user's

It is also important not to miss the detection of exit contextual information and preferences that are more im-events, especially if the phone has to be reconfigured to the portant for triggering the adaptation. In our prototype, weoriginal settings. For example, in the hospital scenario dis- have primarily targeted use cases where users are mobilecussed in Rule 2 in Section 3.4, if the NFC reader fails to and change context frequently. Hence, using high-level con-detect a surgeon exiting the operation theater, the surgeon's text to effect quick adaptation was a more important consid-phone will continue to be turned off. We propose to address eration. Wherever security and privacy concerns are impor-this problem by deploying readers in multiple places. This tant, it is possible to encrypt portions of information storedredundancy helps the system to self-stabilize, even if one on the RFID tag. Also, there are RFID readers that use chal-of the readers misses an event. For example, in the case of lenge/response or other forms of authentication in order toan office environment, we can deploy RFID readers in the detect counterfeit tags. While our solution can be deployedconference roo:ms, as well as in offices or at other vantage with such devices, reading encrypted information or per-points, such as entrances to elLevators. If a user leaves a con- formling authentication prior to reading information fromrference room and his exit event iS undLetected, bJut he enters eachl tag iS llikely to result in some delay in triggering thlehis office where the RFID reader detects his presence, then adaptation. Our current system communicates the adapta-the context synthesizer can use the latest read, event to either tioln drective immediatley after the tag iLS read, so it would,

be interesting to measure the delay incurred when it is used other related approaches, we have not modified the inter-in conjunction with the above mechanisms. face between the user and the mobile phone. Hence, our

Cost-benefit Tradeoffs: We have shown that our solu- approach is convenient to adopt in a variety of settings.tion can work even with cheaper models of mobile phonesthat do not have any enhanced, features, thereby making our Referencesapproach easy to adopt. However, the c-tags that are explic-itly attached on the phones may be lost or swapped. More-over, since these phones are not programmable, the adap- 31]IBM Websphere RFID Premises Server. bttp://www-tationcano be efrewihumaalntvnio. We 306.ibm.com/software/pervasive/wsrrfdpremises server/.

[2] NFC Forum. http://www.nfc-forum.org/aboutnfc/.need to look into enlisting the support of a mobile service [3] Nokia Mobile RFID Kit.provider to see if simple directives like "switching a phone http://europe.nokia.com/nokia/0,,76310,00.html.to silent mode" can be effected over-the-air by the service [4] Nokia NFC Shell.provider. The above shortcomings can also be addressed http://europe.nokia.com/nokia/0,,76314,00.html.

[5 T-Mobile MDA III Manual.by using NFC-enabled. phones. While such phones with in- http://www.manuals.t-mobile.co.uk/start.asp?manual=844.built REID read.ers are more expenlsive thanl conventionlal [6] J. Bailey, A. Poulovassilis, and P. Wood. Anmobile phones, they are less expensive than a standalone Event-Condition-Action Language for XML. In Proc. oftheRFID reader. Moreover, these phones are already being World Wide Web Conference, Hfonolulu, Hawaii, 2002.used for other purposes, such as self-checkout and payment [7] G. Chen and D. Kotz. A Survey of Context-Aware Mobileat point-of-sales. Hence, we believe that their cost is likely Computing Research. Technical Report TR2000-381,to be driven down in the future by the sales volume. Dartmouth College, 2000.[8] H. Chen, T. Finin, A. Joshi, F. Perich, D. Chakraborty, and

L. Kagal. Intelligent Agents Meet the Semantic Web in6. Conclusions Smart Spaces. In IEEE Internet Computing, volume 8,

2004.

We have presented a mechanism to convert mobile [9] M. Cherniack M. J. Franklin and S. Zdonik. ExpressingUser Profiles for Data lRecharging. IEEE Personall

phones from a passive messaging device to a context- C omints Augusta 21.IP ~~~~~~~~~~~~~~~~~~Comminicaltions, August 20011.sensitive, socially-aware device, with the goal of minimiz- [10] A. Khalil and K. Connelly. Context-Aware Configuration:ing the distractions caused by mobile phones. To realize A Study on Improving Cell Phone Awareness. In Proc. ofthis goal, we make use of the emerging near-field commu- Context 2005, pages 197-209, July 2005.nication technology. One of the novelties in our approach [11] H. Lei D. M. Sow J. S. Davis G. Banavar, and M. R.is the use of role-based, abstraction of RFID technology. Ebling. The Design and Applications of a Context Service.

Mobile Computing and Comm inications Review (MC2R)We use the same technology for gathering higher level con-text wheher t isrelaed t th envronmnt o to he uer.6(4):45-55., October 2002.text, whether It ils related to the environment or to the u.ser. [12] A. Monk, J. Carroll, S. Parker, and M. Blythe. Why are

While in the typical case, RFID readers are stationary and Mobile Phones Annoying? Behaviour and Informationtags are mobile, in this work we have also proposed the use Technology, 23(l):33-41, 2004.of readers that are integrated, into mobile devices and, tags [13] S. G. Myerson and A. Mitchell. Mobile Phones inthat are stationary. Tags associated, with the mobile phone Hospitals. BMJ, 326(460), 2003.store user context, while tags affixed. in smart environments [14] J. Rosenberg, H. Schulzrinne G. Camarillo A. Johnston

J. Peterson R. Sparks M[. SHandlLey and E. Schooler.store environmental context. The use of RFID allows us S.terson,I .Spation P . IeTF RE326 oJue2.

to uiquly istiguih btwen enitis o th sam kn. Session Initiation Protocol. IETF fRFC 3261L, June 2002.to uniquely distinguish between entities of the same kind. [15] W. N. Schilit, N. I. Adams, and R. Want. Context-AwareOn the other hand, previous approaches use disparate tech- Computing Applications. In Proc. ofthe Workshop onnologies, such as calendars and address books, for gathering Mobile Computing Systems and Applications, pages 85-90,high-level context, while using sensors to gather low-level 1994.physical context. [16] A. Schmidt, K. Aidoo, A. Takaluoma, U. Tuomela,

rThe use o rf?NFC allows us to gather context thatispre-K. Laerhoven and W. Velde. Advanced Interaction inThe se o NEallws u togathr cotex tha is re-Context. In Proc. ofintl. Symposium on Haudheld andcise and to adapt quickly before the distraction occurs. Such Ubiquitous omputin 1999.

proativeadatatin isim rtan in nvionmets, her Ubiquitous Comwputinlg, 1999.proactive adaptation iS imporant in environments, where [17] A. Schmidt, M. Beigl, and H. W. Gellersen. There is Morepeople are highly mobile and context changes are rapid. to Context than Location. In Proc. of Workshop onWhile our current prototype uses a simple rule engine, we Interactive Applications ofMobile Computing, 1998.are considering the use ofthe IBM Websphere RFID frame- [18] D. Siewiorek et al. Sensay: A Context-Aware Mobilework r1] to impllLement our rules and event corelations, in Phone. In Proc. ofIntl. Symposium on Wearable Computersorder to provide a more robust imp'lementation in the fu- 2003.[119] A. Smailagic, D. P. Siewiorek J. Anhalt and F. Gemperle.ture.~~~~~~~~~~~~~~~~Th-otx-aedpainw aepooe n Towards Context Aware ComLputing: Experiences andcompasses di1fferenat tpes of commercial mobile phones,LsosInPc.fWrkhpnfteatieAlctos:ranging from simple phlones to NECl-enabledL sma tphones, ofobl Computin 1998.and those with multiple communication interfaces. Un'li'ke