No Wires Attached: Usability Challenges in the Connected World

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No wires attached:

Usability challengesin the connected

mobile world

by L. Gorlenko

R. Merrick

Mobile computing platforms combining small,lightweight, low-power devices with wirelessnetwork connectivity enable the performanceof familiar tasks in new environments andcreate opportunities for novel interactions.Since mobility imposes significant cognitiveand ergonomic constraints affecting deviceand application usability, ease of use iscentral to devices in the fully mobile wirelesslyconnected (FMWC) world. In this paper, weconsider mobility as an attribute both of the

computer and the user. We explain thedifferences between transportable and fullymobile devices, and we contrast applicationsthat are essentially FMWC applications, thosethat can be adapted to the FMWC context,and those that are unsuitable for it. Wediscuss the unique challenges to usability formobile users and devices and theirinteraction, and we point out the increasinglycritical role of usability in the mobileenvironment.

Mobile devices supported by wireless connectivitycan dramatically change the ways in which peopleinteract with computers. On the one hand, tasks thathave been traditionally undertaken in a fixed setting,such as an office, can be performed in arbitrary lo-cations (at least in theory.) On theother hand, manytypes of field work that had not been previously as-sisted by computers can benefit from instantly avail-able computational and informational resources.Furthermore, the connected mobile world opens upnumerous possibilities beyond the realm of workexpanding our leisure, entertainment, and informal

communication activities. The field of mobile wire-less computing is continuing to develop rapidly, notonly in the range of mobile devices (for example,per-sonal digital assistants [PDAs], mobile phones, andwearable computers), but also in the range of avail-able communication technologies (for example, theWireless Applications Protocol [WAP], Bluetooth**wireless technology, and IEEE 802.11 wireless stan-dards).

Attempts to understand the design and usability im-plications of the connected mobile world started

more than a decade ago. These included the con-struction of taxonomies of mobile computers1 aswellas identification of some broad issues in mobile userinterfaces.2 At first, the intrinsic constraints of mo-bile devices were identified with technological lim-itations, suchas poorcomputational resources (com-pared withstatic computers), limited energy sources,and less reliable network connections. 3 Later, var-ious aspects of human interaction with mobile com-puters came under scrutiny, including ergonomicconstraints,4 properties of ubiquitous access, 5 andcollaboration in mobile environments. 6 In the lastfewyears, particularly intensive debateshave focused

on the problems of input and output mechanismsfor mobile devices.

It is now clear that the goal of anytime, anywhere,anyhow access for anybody 7 presents more chal-

Copyright 2003 by International Business Machines Corpora-tion. Copying in printed form for private use is permitted with-outpayment of royalty provided that (1)each reproduction is donewithout alteration and (2) the Journal reference and IBM copy-right notice are included on the first page. The title and abstract,but no other portions, of this paper may be copied or distributedroyalty free without further permission by computer-based andother information-service systems. Permission to republish anyother portion of this paper must be obtained from the Editor.

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lenges to its inventors and designers than had been

originally anticipated. While many existing techno-logical restrictionsmay be only a fewstepsaway frombeing resolved, a large number of environmental con-straints and some limitations on the human side willremain. For a mobile solution to be successful, ev-eryone involved in the development of various com-ponents must focus on the total user experience ingeneral, and on usability in particular. This calls fortechnical specialists to attend meticulouslyto the im-pact of mobility on usability, andfor usabilityexpertsto be well informed about one of the fastest growingsegments of the human-computer-interaction (HCI)domain.

This paper presents a detailed analysis of the fieldof mobile wireless computing. Most contemporarymobile devices feature wireless connectivity. Typi-cally, mobile is used as an attribute of a computingdevice; it implies that a device can be easily trans-ported to a location where the user wants to inter-act with it. However, mobility in its usual sense con- veys nothing about the user and the type ofinteraction. In this paper, we consider mobility anattribute of both the user and the device; we classifyan interaction as mobile if both the user and the de-vice can relocate during the interaction. Only thosedevices that support mobile interactions are fully mo-

bile; devices that can be moved to a different loca-tion but require the user to remain stationary dur-ing the interaction are no more than transportable.To distinguish the specific case of fully mobile com-puting combined with wireless connectivity, we in-troduce the concept of fully mobile wirelessly con-nected (FMWC) computing, and apply it to devices,applications, and contexts of use. On the usabilityside, we see some critical differences between sta-tionary interactions, where user movement is re-strained, and mobile interactions, where various de-grees of body movement are allowed, particularly,walking. Placing the interaction into a freely mov-

ing context, we face a whole new world of environ-mental and cognitive challenges that affect usabilityof devices and applications. Within applications thatcan be considered for FMWC devices, we distinguishthree types: essentially FMWC applications, applica-tions adapted forthe FMWC context,and applicationsthat are unsuitable for it. We describe the salientcharacteristics of each type and their impact on ap-plication usability.

The paper is written for both the technical andbroadHCI communities. Both groups can benefit from theanalysis of the FMWC field (see the section Defin-

ing the space of mobile wireless computing) that

examines various classes of mobile devices and thethree types ofFMWC application. The section Con-texts and interactions in the FMWC world also tar-gets both reader audiences and describes two majortypes of mobile interaction context: the mobile of-fice context and the field context. The following sec-tion, on implications for technical and HCI commu-nities, emphasizes the importance of User-CenteredDesign (UCD) for creating easy-to-use FMWC prod-ucts. Essential usability implications of the FMWCworld that need particular attention from hardwareandsoftware engineers are then presented, followedby a discussion targeted for the HCI community fo-cusing on methodological issues ofUCD inthe FMWCenvironment.

Defining the space of mobile wirelesscomputing

The following section describes the spectrum ofFMWC devices and how these devices, the applica-tions that run on them, and interactions with themcan be characterized.

Mobile, pervasive, ubiquitous or wireless?Asinanynew area of technology, the terminology of mobilewireless computing is still unsettled. Every now and

then, the term mobile wireless computing is used inconjunction or interchangeably with ubiquitous or

pervasive computing. Ubiquitous computing, first in-troduced at Xerox PARC (Palo Alto Research Cen-ter) in 1988, is the method of enhancing computeruse by making many computers available through-out the physical environment, but making them ef-fectively invisible to the user. 8 Some attributes ofubiquitous computing, such as instant availability tothe user, may be similar to those of mobile comput-ing, but the two are not synonymous. While the no-tion of a computer being with the user at all timesis essential for mobile computing, ubiquitous com-

puting emphasizes the invisibility of the computingenvironment; that is, the notion of computers beingwidely available and inconspicuous. Pervasive com-puting aims to manage information and reducecomplexity for a mobile workforce and a mobile so-ciety. 9 Pervasive computing emphasizes the net-working capabilities of computers and, as IBMs Per-vasive Computing initiative definesthe term, is abouteverything [being] wireless, mobile, and voice. 9

Most often, however, computers that feature net-work connectivity on the move are described simplyas mobile or wireless computers (the term portable

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is also occasionally used.) Although common, each

definition captures only part of the meaning of mo-bile connectivity. Not all mobile devices are enabledas wireless, and not all wireless devices are mobile.Figure 1 gives a more accurate view of the mobileand wireless categories. As a generic term for mo-bile wireless computing, pervasive computing seemsmost appropriate. However, for the purpose of eval-uating usability of mobile wireless products, this def-inition is imprecise, as we shall see in the followingsections.

Device mobilityand modes of interaction. From theusability point of view, it is not the qualities of a com-puting device that are paramount, but the qualitiesof the interaction between the user and the device.A continuum of existing personal computers, of vary-ing degrees of mobility, is shown in Figure 2, andthis figure assists us in analyzing how the degree ofdevice mobility determines possible interactionmodes. Figure 2 presents the five major types of per-sonal computers in existence today, with degree ofdevice mobility increasing from left to right. This isan extension of a classification of personal comput-ers by portability introduced by Weiss. 10 We maycharacterize each device by two attributes: form fac-tor (including dimensions and weight), and surfacesupport requirements (whether or not the device

needs to be held against any fixed surface outsideof the users body, or if the users body is used tosupport the device).

Desktops. Desktop computers are large and heavyobjects that require a fairly constrained physical ar-rangement of their components. Their input and out-put mechanisms are placed on firm horizontal sur-faces for normal operation. In the mobility spectrum,we classify such computers as fixed. The only pos-sible mode of interaction with a desktop is for theuser to be glued to the devices location. We callsuch an interactionmode stationary, as both the user

and the device are stationary during the interaction.

Laptops. Laptop computers (including subnote-books) are much smaller and lighter than most desk-tops. Similar to desktops, they need to be supportedby a fairly firm, fairly horizontal surface while in op-eration (that is, a desk or the userslap).Duetotheirsmaller form factor, they can be moved to variouslocations and thus are classified as transportable inthe mobility spectrum. Despite the fact that laptopscan moved from place to place, in operation boththeuser andthe device must remain in one location.Consequently, the interaction mode is stationary.

Palmtops. The design of palmtop computers11

(sometimes known as clamshells) is similar to thatof laptops, but the former are significantly smallerand lighter, andcan often fit into a large pocket (suchas the Psion Revo** Plus or the Hewlett PackardJornada**). For very short interactions (no longerthan few minutes), palmtops can be held in the us-ers hand, but even small palmtops must be placedon a table or another flat surface for efficient pro-longed operation. Similar to laptops, in the mobilityspectrum, palmtops are classified as transportable.The prevalent mode of interaction is stationary, de-spite the occasional non-stationary usage.

Handhelds. Handheld devices such as PDAs, pagers,and mobile phones, are small and lightweight andare best operated while held in the users hand. Ac-cording to Weiss, 10 a computer must pass three teststo qualify as handheld: (1) it must be easily used whilein ones hands, not resting on a table; (2) it must op-erate without cables, except temporarily, while re-

charging or synchronizing; (3) it must either allowthe addition of new applications or support Inter-net connectivity. Similar to laptops and palmtops,handhelds can be easily relocated. Unlike palmtops,however, handhelds do not require surface supportoutside the users body nor does the user need toremain in one locationduring the interaction. There-fore, in the mobility spectrum we classify handheldsas fully mobile. Since both the user and the devicecan change location while the user interacts with thedevice, handhelds afford their users a mode of in-teraction fundamentally different from the station-ary mode. We call this mode mobile interaction.

Figure 1 Mobile and wireless devices

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Some ambiguity exists in categorizing tablet-typecomputers that do not have a keyboard and rely ona touch-sensitive input. While small tablets such asPDAs are a clear case of handheld computers, Weissdoes not include larger tablets such as Microsoft

TabletPC** or Stylistic** in the handheld category,simply because of [their] size. 10 In contrast, we doconsider larger tablets handheld computers becausetheir mode of interaction is closest to that of hand-helds.

Wearables. Wearable computing devices, or wear-ables, are essentially modular computers whose com-ponents are small and light enough to be worn ona users body for convenient operation. The inputand output components of wearables are worn closeto the users sensors (eyes and ears) and actuators(hands and mouth). By definition, wearables do not

need anysupport other than the users body, and thisclassifies them as fully mobile. Similar to handhelds,wearables enable mobile interaction. Incorporatinginput and output components and processing mod-ules into the typical users personal items (for ex-

ample, an inch-sized display projector that clips ontoa users glasses or a keyboard that wraps around theusers wrist) brings near invisibility to the wearablesand makes them both mobile and ubiquitous.

Table 1 lists the form factor, degree of mobility, in-teraction mode, and degree of modularity for thecontinuum of personal computer types.

Within the group of devices classified as fully mo-bile, there are varying degrees of freedom of move-ment for the user. With handhelds, the freedom ofmovement is simply the ability of the user to walk

Figure 2 Device mobility continuum

Table 1 Characteristics of personal computing devices

DeviceType

FormFactor

Highest Degreeof Mobility

Mode of Interaction Modularity

Desktops Large Fixed Stationary only Fully modular input/outputmechanisms

Laptops Medium Transportable Stationary only Single unit device withoptional external outputmechanisms (audio)

Palmtops Small Transportable Stationary, with minorexceptions

Single unit device withoptional external outputmechanisms (audio)

Handhelds Medium tosmall

Fully mobile Mobile interaction enabled Single unit device withoptional externalinput/output mechanisms

Wearables Small Fully mobile Mobile interaction enabled Fully modular input/outputmechanisms



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about while using the device. Some handhelds, like

mobile phones, permit one-hand device operation.With some handhelds and wearables, freedom ofmovement extends to the whole body, includinghands-free interaction and, in some cases, eyes-freeinteraction. Eyes-free mode is the ultimate in free-dom of movement during interactions, as interac-tion requiring visual attention still constrains freebody movement.

The focus of the rest of the paper is on fully mobile,wirelessly connected (FMWC) devices, the applica-tions running on them, and their usage environments.The difference between stationary and mobile inter-

action modes has significant implications for usabil-ity ofFMWC computers in different usage contexts.Consideration of the effects of mobility should in-fluence not only the design ofFMWC hardware, butalso the choice of applications appropriate for a fullymobile environment. This consideration is discussedin detail in later sections.

Network connectivity continuum. Networks can beeither wired or wireless, and a network connectioncanbe either permanent or intermittent. Table 2 listsvarious types of personal computers according to theconnection configuration they support on the move,

if any.

Transportable and fully mobile communicating devices inevitably have to deal with circumstanceswhere communication is not available for a periodof time. These intermittently connected devices andtheir applications need to compensate for the lackof an available connection. In this case, some appli-cations will require that the information necessaryto perform a task beobtained in advance when a con-nection is available and retained for operation whendisconnected. Similarly, applications may need tostore information obtained when disconnected andtransmit it after a connection becomes available.

Classifying applications. Usability in a mobile envi-ronment is influenced both by the effects of mobileinteraction and by the nature of applications run-ning on FMWC devices. These may be communica-tion applications (for example, e-mail and Webbrowsing) or non-communication applications (forexample, word processors and spreadsheets). Dor-nan 12 provides a comprehensive guide to wirelesscommunication applications, describing in detail theunderlying technologies and emerging services.

Table 3 classifies applications (communication andnon-communication) based on how appropriate theyare for the FMWC hardware and environment. Wedistinguish the following types of applications:

Essentially FMWC applications, which must be bothmobile and wireless,

Adapted for FMWC applications, which may beenabled on a FMWC device, and

Unsuitable for FMWC applications, which are in-appropriate for the FMWC environment.

In Table 3, a cell is marked with No if a particularapplication cannot exist on a particular hardwaretype, with Yes if it does or can, and with Con-ditional if it exists conditionally (see the sectionApplications adaptedfor the FMWC context for fur-ther detail on conditional applications).

Essentially FMWC applications. EssentiallyFMWC ap-plications offer solutions that are unique to the wire-less connectivity environment and can be deliveredmainly through FMWC devices. On-the-spot commu-nication and context-aware mobile computing char-acterize the two branches of these applications. Manycurrent on-the-spot communicationapplications arevoice-based, such as mobile telephony; text-based,such as Short Message Service (SMS); or multimedia-based, such as Multimedia Messaging Service. In thefuture, on-the-spot communication applicationsmayexpand to include messaging through other human

senses, such as touch or smell.

Contextual awareness in mobile environments is of-ten perceived as critical for a successful FMWC ap-plication. There is a large body of research that hasbeen done recently in this area, the discussion ofwhich is outside the scope of this paper. However,one of the seminal projects in this area is worth men-tioning here. The Remembrance Agent13 is a pro-gram that augments human memory by displayinga list of documents relevant to the users current con-text. Augmentation of the user, through extendingboth memory and perception is often seen as thepath

Table 2 Network connectivity and device types

Wired Wireless

Permanent Desktops Desktops

Intermittent Laptops,palmtops

Laptops, palmtops,handhelds, wearables



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by which the next generation of devices (which aremostly wearables) will become one with the user.

In general, contextual awareness can be categorizedas follows:

Location awarenessUsed in location-based ser-vices, this is the ability to track users whereabouts

at each moment and provide them with the infor-mation relevant to the current location. This in-cludes, but is not limited to: offering maps and roadguidance, supplying details about specific objects andplaces close by (for example, retrieving extendedproduct descriptions while shopping), or flagging thepresence of other users in the area, according to theuser-specified buddy list. Location-based applica-tionsmay alsoprovide data management services ac-cording to user-defined preferences, for example,managing incoming personal and business calls de-pending on the present whereabouts of the user.

Environmental awarenessThe ability to read thespecifics of the interaction setting, such as a noisycrowd, a one-to-one conversation, or an enclosedspace.

Mobility awarenessThe ability to decode a usersmovements and body posture at each moment, forexample, knowing whether the user is currently sit-ting, standing, walking, or running.

Health awarenessThe ability to measure variousphysical conditions of the user, such as heart rate,body temperature, and blood pressure.

Activity awarenessThe ability to understand cur-rent high-level activities of the user, for example,reading, watching TV, or writing.

In the mobile environment, there are two possibleinterpretations of location thatare important to wire-less applications. We define them as the absolutecontext and the relative context. In the absolute

context, the users location consists of his or her geo-graphic or spatial coordinates at each moment intime. In the relative context, the users location islinked to another entity, moving or stationary, forexample, a car or a building. The absolute contextof the user in a moving car is changing, but the rel-ative context will stay the same until the user stepsout of the car. Different location contexts call for dif-ferent location-based applications; understandingthe difference between the contexts will help to de-liver usable wireless applications when they areneeded and in the way the user wants them.

Applications adapted for the FMWC context. In con-trast, applications adapted for the FMWC context areexclusive neither to the wireless connectivity nor tothe mobile environment, andexist in a different formelsewhere.Examples include most office applicationsthat originally existed on desktop computers andwere later enabled first on transportable and thenon fully mobile devices, as lighterversions of the orig-inal application. These include e-mail programs, cal-endars, Web browsers, word-processing programs,spreadsheets, and similar applications. Most of theseadapted applications exist on all three types of hard-ware: fixed, transportable, and fully mobile. Some,

Table 3 Classification of FMWC applications

Type ofApplication

Hardware Mobility Sample Applications

Fixed Transportable Fully mobile

Essentially FMWC No No Yes On-the-spot product guide, voicecommunication, field engineeringapplications

Adapted for FMWC Conditional Yes Yes Field data logging

Adapted for FMWC Yes Yes Yes Web browsing, spreadsheets, calendar,simple drawing

Adapted for FMWC Yes Yes Conditional E-mail, word processing

Unsuitable for

FMWC

Yes Conditional No Complex design and image processing

applications, for example,AutoCAD** or Photoshop**



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such as field-data-logging applications used by med-

ics, field engineers, or surveyors, have been devel-oped to automate tasks that were not performed oncomputers previously. Although these applicationscan exist on desktop computers as well, they are pri-marily used on mobile and transportable comput-ers.

Within this group of applications, most afford mo-bile interaction with an FMWC device through eithertext-based or natural language input. These appli-cations are mainly based on interaction styles involv-ing direct manipulation, menu selection, and the useof forms. 14 Certain applications (marked Condi-tional in Table 3) afford mobile interactionpredom-inantly through natural language interfaces. Theseare applicationsthat typically presume a sizeable textinput. In most cases when text needs to be enteredby hand, the interaction becomes stationary, as ei-ther both hands are engaged with a typical keyboard,or text is entered more slowly with one hand, via astylus or a chord keyboard. For these applications,an FMWC device acts as a de facto transportable de-vice.

Applications unsuitable for the FMWC context. Theseapplications are inappropriate for FMWC devices be-cause they cannot overcome the challenges posed

by the mobile environment. Although these appli-cations normally require substantial memory, pro-cessing power, andlarge screen size, it is not thetech-nology that makes them unsuitable for the mobileworld. What prevents these applications from beingported to FMWC devices is the complexity of theFMWC environment, not the complexity of the ap-plications themselves. Applicationsunsuitable for theFMWC environment demand intense concentration,extremely high visual attention and, often, very ac-curate manual input. All these requirements are im-possible to meet during mobile interaction, since itassumes relatively short interaction time; high-de-

gree of attention sharingbetweenthe interactionandbackground activities; and lower concentration oneach activity that is going on in parallel (see moredetail about mobile contexts in the section Mobilework contexts). Thus, most computer-aided design(CAD) applications, complex modeling tools, and im-age processing applications are unsuitable for FMWCdevices. We classified this type of application as con-ditionally suitable in Table 3, evenfor transportables;this is because certain parameters of the environ-ments in which transportables may be used comeclose to those of the mobile settings, particularly forpalmtops.

Contexts and interactions in the FMWC

worldUser experiences in the FMWC world are dramati-cally different from those in the traditional comput-ing environment and present a number of technical,environmental, and social challenges15 in the usabil-ity ofFMWC devices and applications. Some techni-cal challenges relate to network connectivity, suchas dealing with an evolving infrastructure, coverageand feedback concerns, security hazards, and com-plex integration issues for a wide variety of devices.For example, the intermittent nature of wirelesscon-nectivity and changing connection speeds affect theoverall usability of many applications because these

applications fail to respond to the user as expected.Other technical challenges are posed by device de-sign constraints which are imposed by trade-offs be-tween size and functionality, or between weight andbattery life.

A fully mobile computer is prone to enormous vari-ations in the environment and work contextsin whichit operates. Environmental variations pose the larg-est and most diverse group of usability challenges inthe FWMC context. They include: fluctuation of tem-perature and lighting conditions, varying levels ofnoise and distractions, mobility of the user, compe-

tition for attention in multitask mobile settings, andthe need to manipulate other physical objects dur-ing interaction. While most of the resulting techno-logical challenges will be dealt with in the comingyears, the burden of environmental constraints can-not be reduced significantly. Many of them are in-herent in mobile interaction, such as the work con-text, weather conditions, physiological limitations ofthe human body, and cognitive restrictions; all ofthese will continue to put the usability ofFMWC de-vices or applications to a serious test.

Social challenges of mobile experiences include per-

sonalization,16

comfort, acceptance and adoption is-sues, and privacy concerns, especially for location-based applications. The ability to monitor a userswhereabouts creates an opportunity for a great num-ber of convenient context-aware services and is par-ticularly valuable in emergency situations. At thesame time, some users will consider revealing theirlocation a serious infringement of their privacy. Thismay adversely influence the overall user satisfactionwith a location-based application, especially if em-ployees are required to run such applications on theirFMWC devices; some users may even perceive this asa disadvantage of the device itself.



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Mobile work contexts. The FMWC world broadens

the space of traditional computing settings and al-lows office workers to become more mobile, con-nected and, as a result, flexible. It also brings com-puting power to areas and occupations where it hasbeen rarely, if ever, applied before. The more ad-vanced FMWC devices and wireless technology be-come, themore areaswill exploit andrely on theben-efits of FMWC computing. We distinguish betweentwo types of FMWC environments, with fundamen-tal differences between them: the mobile office con-text, in which traditional office-type computing ismade mobile, and the field context, to which tradi-tional computing has not been applied, and whereFMWC devices are the only computing devices used.

Understanding the differences between the two con-texts is of great consequence to both technical andusability specialists, as each context requires a spe-cific approach to the design of FMWC devices, ap-plications and interactions.

Mobile office context. In the mobile office context,FMWC devices are used similarlyto desktops andlap-tops in a traditional office-based computing environ-ment, with most tasks and applications aiming to du-plicate those enabled on stationarycomputers.In thiscontext,the assumption is that, while interacting with

an FMWC device, the user performs familiar work incircumstances which are less familiar for that typeof work. For a considerable time, stationary com-puters are expected to remain the primary platformfor most office applications, with FMWC devices act-ing as auxiliary devices.

Intheoffice context, most tasks performed while in-teracting with a computer are internal to the oper-ation of the computer, that is, the task itself takesplace in thecomputer, such as creatinga spreadsheetor a Word** document, sending e-mail or browsingthe Internet. In the mobile office context, the inter-

nal computing tasks are likely to dominate duringthe interaction with a FMWC device, with the taskstaking place outside the computer (for example,walking or manipulating other physical objects) be-ing secondary.

Field context. In the field context, FMWC devices areusedin a non-traditional computing environment fortasks unrelated to the stationary use of computers.The field context is much more diverse than that ofthe mobile office, and we believe that in the near fu-ture the number of FMWC devices in the field con-text will largely outgrow the number of FMWC de-

vices in the mobile office context. The field context

covers a broad range of tasks and occupations, suchas service engineering, law enforcement, medicine,social work, and surveying. It also includes nonpro-fessional activities for which computers have notbeen previously used, for example, store shoppingand travel. Often in the field context, tasks that arecurrently enabled on FMWC computers have beenpreviously facilitated by a different medium, for ex-ample, pen and paper or telephone. In some cases,present field activities had no equivalent in thenon-FMWC world, such as on-the-spot communica-tion. In the field context, the user remains in famil-iar circumstances but applies a less traditional toolto facilitate the work.

Kristoffersen and Ljungberg17 point out four impor-tant features of mobile interaction that they iden-tified for telecommunication service engineers andmaritime consulting staff. We believe that the samefeatures apply to most field contexts:

Task hierarchyWhile interacting with an FMWC de-vice, tasks external to operating the device (for ex-ample, fixing wires or examining a patient) are cen-tral; the tasks taking place in the computer (forexample, reporting status) are supplementary.

Visual attentionVisual attention of the user islargely directed to events occurring outside the com-puter, to avoid danger or to monitor the progress ofthe primary task.

Hand manipulationsDuring the interaction, the us-ers hands are commonly engaged with a variety ofphysical objects unrelated to the interaction with theFMWC device (for example, other equipment).

MobilityDirected by the nature of the dominanttask outside the computer, some users may be re-quired to remain highly mobile during the task.

Consider, for example, an aircraft service engineerwho typically installs, tests, or repairs aircraft equip-ment and wiring. In addition to a toolkit, a torch,and some spare materials, the engineer may carryan FMWC device to substitute for such traditionalcompanions of aircraft engineers as aircraft schemat-ics, a notebook, and a pencil. The FMWC device mayprovide new functionality, previously not availableduring inspections, such as the capability of check-ing stock and placing spare part orders.

A closerlook at the engineers working environmentpoints out factors such as the small spaces inside an



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aircraft among which the engineer moves during the

inspection, inferior lighting conditions, and littleroom for body maneuvering within each space. Dur-ing most of the inspection, both hands of the engi-neerare occupied withmeasuring equipment,cables,repairing tools, and other objects.

Recently, handhelds with touch screens, keyboards,and additional stylus input have been promoted forfield use (for example, the customizable PanasonicToughbook** wireless handhelds). With touch-screen handhelds, direct manipulation remains theleading interaction style, supported by menu selec-tion and the use of forms.

For the engineer, there are two ways to approachoperating his FMWC device: he may make place 17

for interacting with the device, that is, interrupt themain task of inspection, log the data or read themoff the device, and then resume the main task; or hemay try to arrange for the interaction to take place,that is, to operate the FMWC device while executingthe main task. In the make place case, the inter-action with an FMWC device is not significantly dif-ferent from interactionwith a paper notebook. It caneven be less efficient since the engineer has to per-form some extra actions, such as locating and savingfiles or navigating through menus. Attempting the

take place interaction, the engineer faces a num-ber of problems at once: where to place the device,how to operate it with both hands busy, and how tokeep visual attention focused on the main task whilefollowing on-screen instructions.

It is highly unlikely that the take place interactioncan happen in the aircraft engineers case if he usesa handheld. Handhelds afforda very particular modeof interactionthe engineer has to focus on the de-vice when reading or entering data. However, takeplace FMWC interactions are desirable in all fieldcontexts, and essential in some, for example, in the

area of public and emergency services. Recently, po-lice departments started introducing FMWC devicesaspart ofofficers toolkits to allow the officers to ex-change information with control rooms and head-quarters quickly and efficiently. For instance, offic-ers can see emergency calls on their FMWC devicesalong with the map of the area and operators com-ments,18 or match fingerprintsof an offender againstthe police database.19A huge demand for FMWC de-vices and applications is predicted for other serviceprofessionals, such as firefighters and paramedics.20

With FMWC devices, an emergency crew would beable to transmit the patients data to the hospital,

where the doctors could monitor the patients con-

dition, advise the crew, and prepare to begin the cor-rect treatment immediately after the patient arrivesat the hospital. With 3.1 million emergency journeysreported in England alone last year, of which abouta third were life-threatening, 21 the benefits of suchservices will be massive. It is also clear that in noneof the above examples, can the FMWC users affordto make place for the interaction; the FMWC activ-ities should instantly and effortlessly take place inthe situation at hand.

Comparative characteristics of stationary and mo-bile interactions.As described in the preceding dis-cussion, mobile interactions are not homogenous.Within the mobile interaction type, we can now dis-tinguish between (1) mobile interaction in the mo-bile office context and (2) mobile interaction in thefield context.Table 4 contrasts andcompares thefea-tures of the two types of mobile interactions and sta-tionary interaction. For mobile interaction, the val-ues of certain parameters, such as the environment,device size, time of interaction, and user mobility,are the samefor the mobile office and field contexts.The values of other parameters, such as competitionfor attention, task hierarchy, parallel manipulationof other physical objects, and interaction style, varynot only between stationary and mobile interactions,

but also between mobile-office and field contexts.

Usability implications of FMWCcomplexities for technical and HCIcommunities

Designing for the world of connected mobility is ahuge challenge for a wide range of experts, fromhardware engineers to software developers and HCIspecialists. More than any other area of computing,the FMWC world in its complexity and diversity callsfor a thorough understanding of its users, rigorous-ness of the design process, and meticulous attention

to the usability of both devices and applications.

The importance of User-Centered Design (UCD)forcreating easy-to-use products and systems is arguedfor in this issue 22 and elsewhere. 23,24 Unlike otherdesign methods that focus on the product itself, UCDfocuses on the product in use and the total user expe-rience; this requires more rigor in the design pro-cess than other approaches. The FMWC world is stillin its infancy, and it is natural that attention is oftenpaid to the feasibility of an idea or technology morethan to anything else. This frequently makes design-ers and developers adopt the trial-and-error ap-



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proach, where bringing the product to life quicklyis seen as more beneficial than bringing the productto life carefully. As the field matures, the viabilityofFMWC technologies will become more importantthan their feasibility. In these circumstances, UCD isno longer simply a highly desirable design approach,but a vital mechanism for ensuring that the FMWCproducts are capable of being useful and usable.

Usability implications for designers and develop-ers of FMWC applications. There are several usabil-ity implications ofFMWC complexities that are par-

ticularly important to application designers anddevelopers. These include understanding the natureof and differences among applications that are suit-able for the FWMC context and those that are not.Clearly, porting FWMC-unsuitable applications ontoFMWC hardware is unlikely to succeed. Difficult en-vironmental conditions, as well as the intrinsic hu-man constraints of mobile interaction, will preventmost users from effective use of this type of appli-cation in mobile settings.

There are very few or no benchmarks for applica-tions which are essentially FMWC applications, or al-

ternatives to them; users, therefore, are likely to betolerant of their imperfections. In contrast, the vastmajority of FMWC users have experienced applica-tions adapted for FMWC outside the FMWC environ-ment, in traditional computing settings. In these cir-cumstances, the users have benchmarks forapplication performance in their minds and will bemore critical of the FMWC implementations.

Most applications used in the mobile office contextare those which have been adapted for FMWC. Be-cause the majority of users continue to use appli-

cations in both mobile andtraditional office contexts,these adapted applications should aim to preserveas much of the look and feel of the original appli-cations as possible. If the same application differssignificantly in the two contexts, the user-perceivedusability and satisfaction with the FMWC version ofthe application may suffer. Mastering a new versionwhile using the old one would be more difficult thanmastering a new version while unlearning the pre-vious one.

The nature of the field context in most cases insiststhat the interaction take place as the user cannot sus-

Table 4 Comparative characteristics of stationary and mobile interactions

Interaction Parameters Stationary Interaction Mobile Interaction

Mobile Office Context Field Context

Environment Largely indoors, fewfluctuations in theenvironment

Indoors and outdoors,with frequentfluctuations

Indoors and outdoors,with frequentfluctuations

Device Size Medium to large Small Small

Time of Interaction Medium to long Short to medium Short to medium

User Mobility Fixed, mainly sittingposition, restricted bodymaneuver

Any position, variousdegrees of free bodymovement allowed

Any position, variousdegrees of free bodymovement allowed

Competition for Attention Little Some Significant

Task Hierarchy As a rule, interaction-relatedtasks are the primaryactivity

Interaction-related tasksmay be a secondaryactivity

Interaction-related tasksare mainly asecondary activity

Parallel Manipulation ofPhysical Objects outsideInteraction

Rare Occasional Frequent

Interaction Styles High dependence on directmanipulation; other stylesare complementary

Greater reliance onforms and menuselection, supportedby directmanipulation andnatural language

Natural language is ofprime importance,supplemented bymenu selection andforms



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pend his or her primary task. Because direct-manip-

ulation interaction style suggests the make place in-teraction, relying on direct manipulation in the fieldcontext can be a dangerous option. Instead, the ap-plication should aim to support other interactionstyles as well, particularly, natural language. In thefieldcontext, the user should be able to choosewhichinteraction style is appropriate for the situation athand. A robust well-thought-out field applicationwould support both visual and audio output modal-ities, as well as natural language and manual input.

Implicationsfor designersand developers of FMWChardware. FMWC hardware should account for mo-

bility of both computers and their users. Not all de-vices usually classified as mobile enable mobile in-teractions. As argued in the section Defining thespace of mobile wireless computing, full mobilityis determined by both the form factor of the deviceand by its surface support requirements. Most cur-rent FMWC hardware has been designed primarilywith mobile office applications in mind and is notappropriate for the field context. Most single-unithandheld devices, both with touch screens and key-boards, suggest that the user will make place for theinteraction and keep visual attention on the screenor have both hands free of other physical objects.

Because in the field context the take place interac-tion is the natural and often the only option, the ul-timate goal of hardware designers should be mak-ing field FMWC devices both mobile and ubiquitous.We believe that modular hardware that consists ofvarious devices and input/output components wouldwork best in the field context. The user should beable to pick and mix components for his personaldevice network, similar to the way he can pick andmix blocks from a construction kit. Single-unit mul-tifunctional devices are useful because of their gen-erality, but are rarely the best option for any par-ticular function.

Field contexts are complex andoften hazardous, andinteraction with a FMWC device is predominantly asecondary task. Therefore, efficiency requirementsin the field are higher than anywhere else. For thepersonal device network, all components should befully compatible and able to communicate with eachother.

UCD challenges in the FMWC world. The complex-ity of the FMWC world presents serious challengesnot only in the design process, but equally, in thedesign methodology. We strongly believe that UCD

isthemost efficient designapproach for FMWC prod-

ucts. It is also clear, however, that UCD itself will needto undergo certain transformations and findnewso-lutions to become an effective and efficient FMWCdesign method. We do not have these solutions atthe moment; they do not exist, to our best knowl-edge. In this last section, our goal is to highlight thecritical points in the UCD process that need partic-ular attention and adjustment. We invite both HCIexperts and technology specialists interested in UCDto join us in discussing and developing the compre-hensive UCD methodology for the FMWC world.

The most obvious challenge is dealing with the re-

quirement for mobility itself. In the FMWC context,not only does the user influence the method of in-teraction with the device, but the context itself of-ten defines the interaction. Users may interact withthe device differently, depending on the situation athand. Context-aware applications may significantlyalter the user experience. In order to fully under-stand how a user interacts with the FMWC device, itis not sufficient to simply examine the users directinteraction with the devicethe evaluator must alsobe aware of the external context in which the inter-action takes place, that is, the evaluator must per-ceive the context the wayusers perceive it themselves.

One of the first attempts to design a general reus-able tool that would aid the researcher in studyinginteractions with mobile (particularly, wearable)computers in the field environment is presented inReference 25.

On the methodological side, the anytime, any-where attribute of mobile interaction lets the envi-ronment variability genie out of the bottle,andmakessome UCD stages extremely difficult and significantlydifferent from current procedures. The affectedstages are taskanalysis, prototyping, and design eval-uation and validation.

Task analysis. Task analysis for a mobile product issignificantly more complex than such analysis for anon-mobile product. The first challenge of task anal-ysis is accounting for all possible usages of the prod-uct. The mobility paradox is that the more conve-nient the FMWC device in a particular setting, thebigger the chance that the user will try to use it ina completely different setting as well. We doubt thatthe designer of the first laptop seriously thought ofusing it on the beach, but the laptops did find theirway there eventually. With fully mobile devices, thenumber of previously unthought-of usages jumps.



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Obviously, if an FMWC device or application has not

been designed with the new task or context in mind,the product may be difficult to use there. However,for the user it is natural to quickly get used to thepower of the product in one context and assume thatproduct should cope with another context with equalsuccess.

Consider, for example, the case of mobile phones.The primary usage (at least as it had been believedfor a long time) is for voice-based communication.When SMS was introduced in the past decade, it wasseen as a minorapplication, andfewdesigners wouldhave considered conducting task analysis for SMS in

the design of a new phone. Nowadays, with 45 mil-lion short messages sent in the U.K. alone every day,26

a mobile phone that has theeasiest interface forvoicecommunication is likely to fail the user satisfactiontest if it does not provide a reasonably good SMS in-terface. PDAs are another example of this. Originallydesigned with office-type applications in mind, theyare now considered almost universal FMWC devices,although they are definitely not universally usable.

The second challenge of task analysis also comesfrom the variability of the usage environments andaffects the course of task analysis in specific settings.

Consider the difficulties of observing the details ofhow a worker in the field context tackles a task. Thismaybe as simple as followinga delivery driveraroundor as complex as observing how an aircraft serviceengineer goes about maintenance of components in-side a jet engine. In some cases, task analysis maybe performed in a simulated environment of a jetengine, for example, but a realistic simulation is dif-ficult for the case of the delivery driver, where en-vironmental conditions of the operating environmentare very important. The nature of the environmentmay vary over the span of a single task, but it mayalso vary based on other considerations, for exam-

ple, the time of year or weather conditions that willaffect light levels and temperatures in the operatingenvironment.

The third challenge of task analysis stems from themultitasking nature of mobile interaction. In mostcases, especially in the field context, FMWC applica-tions require the user to interact with them whilesimultaneously undertaking other tasks. These par-allel tasks may be as simple as following directionswhile walking or as complex as operating in a haz-ardous environment and applying the appropriatelevel of attention to both the FMWC-based part of

the task and whatever work it supports. Task anal-

ysis, therefore, should carefully consider the wholevariety of parallel activities.

Prototyping. UCD includes prototyping at variousstages. Prototypes for FMWC products will need tohaveahighdegreeoffidelity and exhibit thekey char-acteristics of the finished product for some of theevaluations, for example, size and weight constraintsor robustness, as in the aircraft service engineer ex-ample. Because operation of the product is typicallysecondary to the main task, successful testing of aprototype canonly be performedin conjunction witha realistic simulation of the primary task. This may

significantly increase the cost of prototyping. Sim-ilarly, the limited capabilities of the FMWC device mayconstrain the ability to instrument the device andhence make monitoring more difficult.

Design evaluation and validation. Design evaluationand validation will share most of the same difficul-ties that were encountered during task analysis. Inparticular, designers need to evaluate the FMWCproduct in a realistic environment, where the real-ism may include different periods during a day, dif-ferent lighting andnoise levels, or even different sea-sons. Evaluating an FMWC device for a deliverydriver

on a perfect summer daytells us little about the ease-of-use characteristics of the device on a frosty Jan-uary morning, where the driver may wear gloves orthe device maynot function properly due to weatherconditions. More than any other environment, theFMWC world calls for sustained evaluation to assessthe viable lifespanof the product. Mobility, however,makes sustainable observation of an FMWC producteven more difficult than that of a non-FMWC prod-uct because it introduces far more factors to recordand evaluate.

Finally, the connected nature ofFMWC products and

the flexibility of the users in theFMWC

environmentintensely stimulate collaborative work. Significant ef-forts of application designers have been dedicatedto developing a wide variety of mobile collaborativeapplications. UCD is difficult enough for non-mobilecollaborative applications, and it will certainly be-come more difficult for mobile collaboration.

Conclusion

Living in a mobile connected world opens up numer-ous opportunities for both work and leisure activ-ities and makes our daily conduct both more effi-



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cient and more exciting. These opportunities,

however, pose challenges to the technical and HCIcommunities. Although mobility has been one of thehottest topics of the last decade, mobility is most of-ten considered an attribute of a computing deviceor a user in general, not as an attribute of a user anda device during the interaction. In this paper, we fo-cused precisely on the latter and showed that thereare a number of critical differences between inter-acting with a mobile computing device and interact-ing with a computing device that can be taken to anarbitrary location and used there in a stationarymode.

**Trademark or registered trademark of Bluetooth SIG Incor-

porated, Palm Incorporated, Psion PLC, Hewlett-Packard Com-pany, Microsoft Corporation, Fujitsu PC Corporation, AutodeskIncorporated, Adobe Systems Incorporated, or Matsushita Elec-tric Corporation of America.

Cited references and notes

1. D. Duchamp, Issues in Wireless Mobile Computing, Pro-ceedingsof the Third Workshop on Workstation Operating Sys-tems, KeyBiscayne, FL,IEEE Computer SocietyPress(1992),pp. 210.

2. J. A. Landay and T. R. Kaufmann, User Interface Issues inMobile Computing, Proceedings of the Fourth Workshop onWorkstation Operating Systems, Napa, CA, IEEE ComputerSociety Press (1993), pp. 4047.

3. M. Satyanarayanan, Fundamental challengesin mobile com-puting,Proceedings of Fifteenth Annual ACM Symposium on

Principles of Distributed Computing, Philadelphia, PA, ACMPress (1996).

4. C. Baber, J. Knight, D. Haniff, and L. Cooper, Ergonomicsof wearable computers, Mobile Networks and Applications4, No. 1, 1521 (1999).

5. M. Perry, Dealing with mobility: Understanding access any-time, anywhere,ACMTransactions on Human-Computer In-teractions 8, No. 4, 323347 (2001).

6. P. Luff and C. Heath, Mobility in Collaboration, Proceed-ings of ACM Conference on Computer Supported CooperativeWork, ACM Press (1998), pp. 305314.

7. Device Independence ActivityStatement, W3C(World WideWeb Consortium), http://www.w3.org/2001/di/Activity

8. M. Weiser, Some Computer Science Problems in Ubiqui-tous Computing, Communications of the ACM36, No. 7,7584 (July 1993).

9. See www.ibm.com/pvc10. S. Weiss, Handheld Usability, John Wiley & Sons, Hoboken,

NJ (2002).11. It is important not to confuse palmtop devices as a type of

personal computer with Palm product family that typicallybelong to the group of handhelds.

12. A. Dornan, The Essential Guide to Wireless CommunicationsApplications (2nd ed.), Prentice Hall PTR, Upper SaddleRiver, NJ (2002).

13. B. J. Rhodes, TheRemembrance Agent,Proceedings of theFirst International Conference on the Practical Application of Intelligent Agents and Multi-Agent Technology (PAAM96),487495 (1996).

14. B. Shneiderman, Designing the User Interface (3 rd ed.), Ad-dison-Wesley, Reading, MA, pp. 7173 (1998).

15. Architecting the Mobile UserExperience, ArcStream Solutions,http://www.arcstreamsolutions.com/resources/whitepapers.asp

16. A. Marcusand E. Chen, Designing thePDA of theFuture,Interactions, ACM Press 9, No. 1, 3444 (JanuaryFebruary2002).

17. S. Kristoffersen and F. Ljungberg, Making Place to MakeIT Work: Empirical Explorationsof HCIfor Mobile CSCW,

Proceedingsof the International ACMSIGGROUP Conference on Supporting Group Work, ACM Press, 276285 (1999).

18. IBM e-business Case Studies: Bullhead City Police Depart-ment, http://www.ibm.com/e-business/doc/content/casestudy/47405.html

19. Wireless Tools andLong Arms of theLaw,USA Today (No-vember30,2001),http://www.usatoday.com/life/cyber/wireless/2001-07-30-wireless-policing.htm

20. MESA (Mobile Broadband for Emergency and Safety Ap-

plications) project, www.projectmesa.org21. UK Office for National Statistics, http://www.statistics.gov.uk.22. K. Vredenburg, Building Ease of Use into the IBM User

Experience, IBM Systems Journal 42, No. 4, 517531 (2003,this issue).

23. K. Vredenburg, Designing the Total User Experience atIBM: An Examination of Case Studies, Research Findings,and Advanced Methods, Special Issue, International Journal

of Human-Computer Interaction 14, No. 3/4, 275278 (2002).24. K. Vredenburg, S. Isensee, and C. Righi, User-Centered De-

sign: An Integrated Approach, Prentice Hall, Upper SaddleRiver, NJ (2002).

25. K. Lyons andT. Starner, MobileCapture forWearableCom-puter Usability Testing, Proceedings of IEEE InternationalSymposium on Wearable Computing (ISWC01), Zurich, Swit-zerland, 133135 (October 2001).

26. Mobile Data Association, http://www.mda-mobiledata.org/

Accepted for publication June 1, 2003.

Lada Gorlenko IBM United Kingdom PO Box 31, BirminghamRoad, Warwick, CV345JL ([email protected]).Ms. Gorlenkois a cognitive scientist and a usability consultant at the IBM Easeof Use Group in Warwick, UK. She specializes in the usabilityof pervasive computing, particularly in multimodal interfaces andmobile and wireless products, and is involved in both researchand consultancy in the area. Prior to joining IBM, Ms. Gorlenkoworked at BTexact Technologies, where shedesignedand devel-oped interfaces that enable lifelike senses of vision and touch invirtual reality; she also studied user-perceived quality of servicein IP network transmission of vision and touch.

Roland Merrick IBM United Kingdom PO Box 31, Birmingham Road, Warwick, CV345JL ([email protected]). Mr.Merrick is a member of IBMs Ease of Use Strategy team andhasresponsibility for determining how emerging technologiescanenable new solutions in making the computer users experiencesimpler, more productive, and less error prone. His responsibil-ities include working with key projects in IBM to help solve spe-cific ease-of-use objectives. Since 1998, his work has focused onenabling multi-deviceaccess to theInternetbasedon XMLtech-nology for describing an abstract representation of a users in-teraction with a system. He also represents IBM on the W3C(World Wide Web Consortium) workgroup defining XForms, areplacement for HTML forms, and the W3C Workgroup on De-vice Independence.


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No Wires Attached: Usability Challenges in the Connected World

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