A Summary of Ubiquitous, Mobile, and Wearable Computing (1/22/03)

Not for citation

Ubiquitous computing, wearable computing, mobile computing and augmented reality are all up-and-coming fields, and have considerable overlap. This report gives a brief summary of the fields, current big players, and problems that are getting focus.

Please note: This is a high-level overview I wrote as a tutorial for my coworkers, and it is by no means complete. If I left out your favorite project, lab or research area I apologize. Please do not cite, and if you see any glaring errors or omissions feel free to send them to rhodes@bradleyrhodes.com.

Some definitions

Ubiquitous Computing (Ubicomp), Pervasive Computing, Things That Think
Xerox Wireless PARC Tab, circ. 1993
The term ubiquitous computing was coined by Mark Weiser of Xerox PARC in 1988. His 1993 Communications of the ACM paper entitled "Some computer science issues in ubiquitous computing" describes a world where wirelessly networked computers are distributed throughout the environment, largely invisible until needed. PARC's early experiments dealt primarily with three different sizes of device: tabs (about the size of a post-it note or small PDA), tablets and full boards hung on the wall. Pervasive computing is a synonym for Ubicomp.

In the mid 1990's the MIT Media Lab started the Things That Think consortium. Closely related to ubicomp, the Things That Think project is based on the idea that everyday objects such as coffee cups, frying pans and toys should use computers to enhance their normal usage. The main distinguishing feature between TTT and Ubicomp is TTT focuses specifically on integrating computers into a particular physical object to help with that object's function.

Wearable Computing
Thad Starner wearing the MicroOptical display
The fuzzy definition of a wearable computer is that it's a computer that is always with you, is comfortable and easy to keep and use, and is as unobtrusive as clothing. My personal definition is that wearable computers have many of the following characteristics:

An overall design philosophy for wearables can be implied from these characteristics. Wearable computers are by their nature highly portable, but their main distinguishing feature is they are designed to be usable at any time with the minimum cost or distraction from the wearer's primary task. A wearable computer user's primary task is not using the computer, it is dealing with his physical environment. The computer will be in a secondary or support role. That's not to say you couldn't use a wearable to edit spreadsheets, but such a focused task tends to be better accomplished with laptop or desktop machines. Wearables make many sacrifices in the name of conserving user attention. Those sacrifices are wasted when the wearable is the user's primary focus, as is often the case in desktop situations.

Augmented Reality, Mixed Reality
A view from the AR Toolkit
Augmented reality is a merging of virtual, graphical objects with the real world. For example, you might look at a wall and "see" graphical overlays on the wall indicating where electrical wiring is located. There are also AR systems for fusing live medical sensor data (ultrasound, X-ray, etc) for a surgeon while performing an operation.

Augmented reality tends to use one of two methods. Overlay-based AR uses a transparent head-up display, or a non-transparent display over one eye while the other eye is unoccluded, to project graphics with the correct position and size to fit naturally into the physical environment. Video-based AR places cameras near the user's eyes and sends the video from those cameras to VR goggles in real-time. The video can then be augmented in software to add graphics effects.

Mixed reality also combines real and virtual images in a physical space, but often goes beyond head-up displays to accomplish it. For example, many mixed-reality systems use a "magic mirror" metaphor where you see yourself as if in a large wall-sized mirror, but also in the mirror-image are graphical elements not in the real world. There is much overlap between AR and MR, and often the words are used synonymously.

Conferences and Journals

Because the work is inherently interdisciplinary, papers in ubiquitous, mobile and wearable computing fields are also to appear in conferences such the ACM Computer-Human Interface conference (SigCHI) and the IEEE International Conference on Image Processing (ICIP).

Some Labs Working on Ubicomp, Wearables or Augmented Reality

Research areas within these domains

Infrastructure and hardware

Resource discovery.

You enter a room, building or city with your mobile computer. Various resources have been made available, and more are being added all the time. On a small scale, your laptop may want to find the local printers. On a larger scale, your car computer may want to know about all traffic-cameras along I-280 between Palo Alto and San Francisco.

The main questions are how:

Some examples

The INS/Twine system is a scalable peer-to-peer network of query resolvers. It uses hashes of keywords, so an ontology can be created and extended on-the-fly. Code is available (though it's not clear under what license).

INS/Twine is designed to handle city-wide discovery of particular resources out of a pool of potentially millions, so scalability is a large focus of the project.

Jini is Sun's java-based distributed application infrastructure. The infrastructure uses Java types for a syntactic ontology (e.g. "is this a color printer") and includes a Lookup Attribute system for a more semantic ontology. Jini is mainly meant for local resource negotiations, like automatically downloading drivers for local printers to your laptop. It has been around for several years, and while it hasn't taken off it is in commercial products. Jini is primarily designed for discovering resources within a floor or building.

Rendezvous is Apple's open-architecture system for discovering other resources on the local-link. For example, OS-X uses Rendezvous to find printers, print servers, shared disks, iChat clients and Airport wireless base stations. The system is based on Multicast DNS. See the Rendezvous tech brief and Multicasat DNS Internet draft. Source code available from Apple (open source). Rendezvous is currently being integrated into printers from Brother, Epson, HP, Xerox and Lexmark, as well as non-printer third-party developers including TiVo.

Toolkits and architectures

Research groups with a more software engineering bent often spend a great deal of time designing toolkits with just the right set of features to make ubicomp, wearable and augmented reality applications easy to write.

A few examples of note

Context Toolkit (Anind Dey, now at Intel Berkeley)
A toolkit that provides support for distributed sensors and processing of those sensors. Completed as Anind's PhD thesis in the Future Computing Environment Group at Georgia Tech (Gregory Abowd's group).

Tiny OS (UC Berkeley)
TinyOS is a component-based runtime environment designed to support concurrent programs running on minimal hardware. The OS is a part of the Wireless Embedded Systems project at UC Berkeley, which includes the Smart Dust / Motes systems.

iRoom Event Heap (Stanford University)
The iRoom Event Heap is an architecture for multi-device communication being used in the Interactive Workspaces Project at Stanford University. The architecture focuses on real-time communication between devices in a smart room or office.

AR Toolkit (University of Washington HIT Lab)
The AR toolkit is a library for producing augmented reality applications using fiducials. It is free for non-commercial use.

Hardware Improvements

Many research papers are along the lines of "Here is a new design for an even smaller, lighter, lower-power computer." While this is important research it is well outside of my field. Suffice to say that Moore's Law continues to function, and it is often useful to see what tools are becoming available to the researcher who needs the next generation of hardware. These papers are becoming less frequent now that handheld and embedded computation is becoming increasingly commercial, and the latest and greatest hardware is available from small start-ups or powerhouses like IBM and Intel rather than a universities or industry labs.

Mobile Ad-hoc Networking (MANET)

A "mobile ad hoc network" (MANET) is an autonomous system of mobile routers (and associated hosts) connected by wireless links--the union of which form an arbitrary graph. The routers are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. Such a network may operate in a standalone fashion, or may be connected to the larger Internet. Main issues include routing algorithms, fault tolerance, scalability and minimizing power consumption.

There are numerous industry, academic and government programs interested in MANETs. Some good starting places for more information are the National Institute of Standards and Technology and the MANET IETF Working Group.

Sensor Networks & Distributed Computation

Berkeley Mote
Sensor Nets are combinations of small sensor devices that combine their data to produce large-scale sensor readings. Usually sensor nets are based on a mobile ad-hoc networking infrastructure, though it isn't strictly necessary.

The prototypical sensor-net application is the ability to throw thousands of dime-sized sensors onto a field, have them organize into an ad-hoc network and broadcast soldier movements in the area. Other applications include detecting vibrations in bridges and buildings, environmental monitoring and wearable sensor networks for detecting gesture and context. As with MANET there are many players in this field, with UC Berkeley and Intel Berkeley as strong local examples.

Distributed computation is the study of algorithms that can be run across multiple distributed CPUs. For example, the Pushpin project at the MIT Media Lab experiments with using CPUs in each of the small sensors to compute the shape of light projected on a group of push pins. Theoretical examinations of these algorithms include the Paintable Computing project at the MIT Media Lab and the Amorphous Computing project at the MIT AI Lab.

Wireless Personal Area Networks

A personal area network is designed for extremely short-ranged communications, usually between different objects on the body or the immediate surrounding area. Bluetooth is one PAN technology, designed primarily for wireless cellphone headsets. The IEEE 802.15 Working Group for WPAN is looking at several technologies that trade off data rate for power consumption. Companies like Symbol, Federal Express, Motorola and BBN have all been interested in these standards.

Research in the area seems to have moved on to other topics as the standards committees grind away, although there is still some work being done in using the electrical skin effect to transmit data (and possibly even power) through a person's skin to other devices on the body or in contact with the body (e.g. a doorknob or another person).

Power Harvesting

MIT Media Lab Power-harvesting shoe
Power harvesting is the capture of power from the environment to charge devices or batteries. Solar power is still the main technology in this area of course, but other technologies are also being developed. The energy collected is usually quite small, but is still enough to run RF-ID tags and small sensor-net nodes. Technologies include piezo-electric shoe inserts and AM radio harvesting. Joe Paradiso at the MIT Media Lab is one of the main researchers in this area. As might be expected, DARPA also has an interest in this area.

Fabric Circuitry

The Burton Amp MP3 Jacket
One of the more interesting fusions in wearable computing is between textiles and electrical engineering. For the past decade researchers have been working on ways to create circuitry that feels like cloth, is washable, and that can be integrated into clothing using standard weaving and automatic embroidery techniques. One of the more interesting projects is the Sensate Liner, a t-shirt that can detect injuries sustained by soldiers and automatically report them to medical personnel. More commercially, this research recently lead to an MP3 jacket for snowboarders that is being marketed by Apple.

Machine Perception

Thad Starner ASL translator wearable
Machine perception is the processing of data from physical sensors into more abstract classifications. The area spans several fields, including machine vision, speech and sound recognition and general pattern recognition.

Research can generally be divided two different ways, by the kind of sensors used and the kind of classifications desired. Sensors include cameras, microphones, infra-red beacons, radio-frequency beacons, GPS, biometric sensors (e.g. Galvanic Skin Response), accelerometers, and using existing infrastructure such as cell-phone emissions. The current trend is to combine several kinds of sensors in one system. The data people are trying to get from these systems include location, face/speaker recognition, gesture recognition (both unconscious and explicit), general activity (walking, sitting, running), social situations (in conversation, meeting someone, in a meeting), mood or cognitive load, and most recently "activity that might be suspicious or a security risk."

The key thing to remember about machine perception is that these systems are developed with a particular application in mind (stated or unstated). Whether a machine truly understands what is happening in a particular situation is a philosophical question that does not need to be answered. All that needs to be answered is whether the machine can make the classifications necessary for the application at hand, with the required accuracy. Often, constraining the scope of an application or careful user interface design can make up for otherwise unsolvable perception problems.

Machine perception is a large field well beyond wearable and ubiquitous computing. A few players that are especially active within the wearable/ubicomp field are:


There are three major issues of interface design in ubiquitous, mobile and wearable computing:
  1. Messy environment. The environment for these applications is less controllable than the desktop environment. This means the interfaces need to accommodate more unexpected situations. People using wearable, mobile and ubiquitous computing devices are also more distracted by the environment, and so these interfaces need to require fewer perceptual and cognitive resources to operate.
  2. Large amounts of captured data. These kinds of devices are very good at automatically capturing large amounts of data. How can this data be organized such that it is useful without being overwhelming?
  3. New interface paradigms. Human-computer interaction has been mired in the WIMP (Windows, Icons, Menus and Pointers) paradigm for over two decades. Ubicomp, mobicomp and wearables all bring out new interface possibilities that need to be explored.

Augmented Reality

Augmented Reality systems have special machine-perception needs. In particular, AR systems need to recognize particular locations, angles and sometimes occlusion in a video stream so that graphics can be added, all in real-time and with good frame-rate. Three methods are used for this:

Some major players in the space (not complete):

Ubicomp generalizable interfaces

When a person enters a new office or building there may be many different resources available, including communication, information and object-control services. Each of these services have different interface requirements. Some are absolute, e.g. a voice communicator requires a microphone. Others are more fuzzy, such as a map interface that requires some way to scroll but could use either buttons or sliders as appropriate.

This research area looks at how to create interfaces on-the-fly for different resources, based on whatever hardware is available. For example, a directory service may provide an interface that uses audio commands for a cellphone interface and touchscreen buttons for a PDA.

The Pebbles project at CMU is especially working on this problem, as is the Project Oxygen at the MIT Lab for Computer Science.

Fusion of multiple capture devices

Several labs have smart meeting rooms and classrooms that capture information in various forms (whiteboard, video, audio, notes, etc.) and allow people to view the captured information later in a variety of forms. Most research focuses on ways to visualize different information streams, and especially visualizing different information streams that are linked together because the occurred at the same time. Some projects also focus on fusing notes taken by multiple people, thus providing a group-wide view of an event.

Related references

Tangible interfaces

Sony Augmented Surfaces System
Bill Buxton had an interesting talk at SIGCHI-98 where he had a picture of a monitor, keyboard and mouse with the title "What decade was this picture taken?" It was a picture of the Xerox Star taken 20 years ago. His point, of course, was "what have we been doing the last 20 years?"

Tangible interfaces is one drive to move away from the WIMP (Windows, Icons, Menus, Pointers) interface. Tangible interfaces are physical, graspable objects that rely more on tactile feedback than traditional interfaces. Physical icons known as phicons can be used to give a physical handle to virtual data. For example, a physical model of the Eiffel Tower might represent that geographic location on a Paris map. Physically moving the tower on a graphics table would scroll the map. Moving a physical model of the Louvre at the same time would provide a two-handed interface for scaling and rotating the map.

Major players in the area:

Ambient Interfaces / Calm Technology

Hirishi Ishii's Pinwheels showing wind speed in Tokyo
As was said earlier, interfaces in these areas need to minimize cognitive and perceptual load. One attempt is to use ambient interfaces to quietly deliver small amounts of information through background environment like light-level or ambient sounds. For example, one ambient display shows the number of people communicating in a virtual office space by projecting shadows on a translucent wall. Another represents network traffic as the sound of raindrops falling. The idea is to make an interface that is not distracting, but which:

Major players in the area:

Communityware, Tracking Social Interactions, and Smart Mobs

Many research groups are looking at how these technologies can improve social interactions and our understanding of those interactions. Howard Rheingold's book Smart Mobs gives a nice overview of how mobile communication is changing social structures by allowing real-time bottom-up organization of groups of people. The Wearable Communities work at the University of Oregon is looking at similar effects from a wearable computing perspective.

Many others are using smart badges and small mobile devices to help our understanding of community. Rick Borovoy's Folk Computing (Paper) project helps teach schoolchildren about how information flows through a society. Tanzeem Choudhury, a PhD candidate at the MIT Media Lab, is completing her thesis on "Sensing and Modeling Human Networks." Her methods use ubiquitous and wearable computers to track interactions, and then analyzes those interactions using pattern-recognition techniques.

Application-Driven Research

Many researchers come to these fields because they have a specific problem they want to solve. While the technologies and outcomes may be similar to the more basic research projects, their methodology is quite different. To quote one researcher working with the mentally disabled, "If I can help my patients best by using Post-It Notes, I'll use Post-It Notes." People working on real-world problems tend to take a very broad "whole system" view of their solutions, and very quickly find that ubiquitous, mobile and wearable solutions must integrate with the entire environment if they are to succeed in the real world.

Currently most application-based research is in three areas: aid for the disabled, military and industrial jobs. All three areas involve unpredictable environments where there is a serious need for information or command-and-control in the physical world.

Helping the Disabled

Several groups are using wearables and ubiquitous computing to help the disabled and elderly. These groups don't focus on the technology, but rather on understanding the particular needs of their users.

Some players

Industry and Military Case Studies

Symbol wearable designed for UPS
It is often difficult to integrate these technologies into real-world applications, and some of the most interesting research results are case-studies from these attempts. For example, Symbol technologies has published a detailed case study of the deployment of their wearable barcode-scanning ring and bracelet for the UPS packing center. Many issues arose, including the fact that wearables need to be sized to fit individuals, ruggedization was harder than expected, and it was easier to get buy-in from people who knew how hard the old way was without the wearable than from fresh recruits. ("Development of a Commercially Successful Wearable Data Collection System", R. Stein, S. Ferrero, M. Hetfield, A. Quinn, M. Krichever, ISWC '98.)

Companies especially interested in wearable and ubiquitous computing applications (as opposed to the technology itself) are Symbol Technologies, Federal Express, and especially DARPA. Industries looking at or using the technology include warehouses, medical (especially surgical), military, environmental and educational fields.