Research Areas - Mobile and Pervasive Computing Research in the Computer Science Department at Carnegie Mellon

CSD faculty: David Garlan, David O’Hallaron, Adrian Perrig (ECE), Mike Reiter, M. Satyanarayanan, Bradley Schmerl, Srini Seshan, Dan Siewiorek, Peter Steenkiste

Mobile computing and pervasive computing represent major evolutionary steps in a line of research dating back to the mid-1970s. Figure 1 illustrates this evolution from a systems-centric viewpoint. New problems are encountered as one moves from left to right in this figure. In addition, the solutions of many previously-encountered problems become more complex — as the modulation symbols suggest, this increase in complexity is multiplicative rather than additive. It is much more difficult to design and implement a mobile computing system than a distributed system of comparable robustness and maturity; a pervasive computing system is even more challenging. As Figure 1 indicates, the conceptual framework and algorithmic base of distributed systems provides a solid foundation for mobile and pervasive computing.

Mobile computing was born in the early 1990’s with the advent of full-function laptop computers and wireless LANs. Although many basic principles of distributed system design continued to apply, four key constraints of mobility forced the development of specialized techniques. These constraints are: (a) unpredictable variation in network quality; (b) lowered trust and robustness of mobile elements; (c) limitations on local resources imposed by weight and size constraints; (d) concern for battery power consumption. Mobile computing is still a very active and evolving field of research, whose body of knowledge awaits codification. The results achieved so far can be grouped into the following broad topics:

• mobile networking, including Mobile IP, ad hoc protocols, and techniques for improving

Figure 1: Evolution of Mobile and Pervasive Computing from Distributed Systems TCP performance in wireless networks.

• mobile information access, including disconnected operation, bandwidth-adaptive file access, and selective control of data consistency.
• support for adaptative applications, including transcoding by proxies and adaptive resource management.
• system-level energy saving techniques, such as energy-aware adaptation, variable-speed processor scheduling, energy-fair ad hoc networking, and energy-sensitive task and memory management.
• location sensitivity, including location sensing and location-aware system behavior.

By 2000, mobile computing research began to touch upon issues that we now identify as the purview of pervasive computing. The founding manifesto of pervasive computing, also known as ubiquitous computing, was a seminal 1991 paper entitled “The Computer for the 21st Century” by Mark Weiser of Xerox PARC. He observed that “The most profound technologies are those that disappear. They weave themselves into the fabric of everyday life until they are indistinguishable from it.” Thus, the essence of pervasive computing is the creation of environments saturated with computing and communication, yet gracefully integrated with human users. When articulated in the early 1990s, this was a vision too far ahead of its time — the hardware technology needed to achieve it simply did not exist. It is only now, nearly 15 years later, that the computing and wireless communications technologies needed for its realization are becoming easily available. Carnegie Mellon is at the forefront of institutions pursuing this vision.

As Figure 1 shows, pervasive computing shares many research themes in common with mobile computing. In addition, it addresses four key issues:

• Smart Spaces: embedding computing infrastructure in building infrastructure brings together two worlds that have been disjoint until now. The fusion of these worlds enables mutual sensing and control of these worlds.
• Invisibility: the ideal expressed by Weiser is complete disappearance of pervasive computing technology from a user’s conciousness. In practice, a reasonable approximation to this ideal is minimal user distraction. If a pervasive computing environment continuously meets user expectations and rarely presents him with surprises, it allows him to interact almost at a subconcious level.
• Localized Scalability: as smart spaces grow in sophistication, the intensity of interactions between a user’s personal computing space and its surroundings increases. This has severe bandwidth, energy and distraction implications for a wireless mobile user. Scalability, in the broadest sense, is thus a critical problem in pervasive computing. Like the inverse square laws of nature, good system design has to achieve scalability by severely reducing interactions between distant entities. This directly contradicts the current ethos of the Internet, which many believe heralds the “death of distance.”
• Masking Uneven Conditioning: Uniform penetration of pervasive computing technology into the infrastructure is many decades away. In the interim, there will persist huge differences in the “smartness” of different environments. This large dynamic range of “smartness” can be jarring to a user, detracting from the goal of making pervasive computing technology invisible. One way to reduce the amount of variation seen by a user is to have his personal computing space compensate for “dumb” environments. As a trivial example, a system that is capable of disconnected operation is able to mask the absence of wireless coverage in its environment.

1 Research Thrusts

From the earliest days of mobile computing, Carnegie Mellon has been a major contributor of fundamental ideas, systems, and experimental validations. For example, the Wireless Andrew project transformed Carnegie Mellon into the world’s first campus with complete wireless coverage. The Coda file system pioneered the concepts of disconnected and weakly-connected operation, and the Odyssey project introduced the concept of application-aware adaptation. Carnegie Mellon created the term “wearable computing” which employs user-centered design methodologies to seamlessly integrate into current end-user work flows while dramatically improving user productivity. The entire February 1996 issue of IEEE Personal Communications was devoted to mobile computing at Carnegie Mellon. This early momentum continues unabated. In fact, it has accelerated with the broadening of the research agenda to pervasive computing.

Distraction-free Pervasive Computing A number of CSD faculty (Garlan, Satyanarayanan, Schmerl, Siewiorek, Steenkiste) are exploring the use of proactivity and self-tuning as unifying mechanisms for reducing user distraction in pervasive computing. Proactivity refers to the ability of a system layer to anticipate requests from a higher layer. Self-tuning refers to the ability of system layers to observe the demands made on them and adjusting their performance and resource usage characteristics accordingly. These issues are being explored in the context of Project Aura.

Two of Aura’s most important capabilities are supporting user mobility and shielding users from variations in resource availability. When a user moves from one environment to another, Aura attempts to reconfigure the new environment so that the user can continue working on tasks started elsewhere. As resources in an environment change (such as wireless bandwidth), Aura attempts to adapt ongoing tasks to accommodate the change, possibly reconfiguring certain services or replacing one service with another. In a major departure from existing systems, Aura introduces a new layer of system abstraction: a task layer called Prism. This layer sits above individual applications and services but below the user. By explicitly representing user intent, Prism makes available a powerful system-wide basis on which to adapt or anticipate user needs.

The Chroma component of Aura supports cyber foraging, which refers to the transient and opportunistic use of compute servers by mobile devices. Through remote execution, even a lightweight wearable or handheld mobile device with limited memory and processing capacity can execute resource-intensive applications such as speech recognition, natural language processing, image processing, augmented reality, planning and decision-making. Such applications can augment the cognitive abilities of mobile users.

Aura supports a contextual information service that appears as a virtual database to applications. Unlike previous efforts in context awareness, this service provides applications with a consistent, lightweight and powerful mechanism for obtaining contextual information, and includes explicit support for on-demand computation of contextual information. This allows applications to merge contextual information from several sources in order to provide users users with behavior most appropriate to the environment in which they reside.

A number of experimental applications to support on-campus collaboration are being developed on Aura infrastructure. Two examples are the Portable Help Desk (PHD) and Idealink. PHD is a context-aware application built on two fundamental services: spatial awareness and temporal awareness. Idealink is a virtual collaboration environment that facilitates planned and ad-hoc collaboration among mobile users. Its goal is to provide easy access to information needed to initiate and conduct collaborative design meetings using mobile hardware.

Seamless Mobility on Pervasive Hardware In close collaboration with the Intel, a number of faculty (Farber, O’Hallaron, Perrig, Satyanarayanan) are exploring a concept called Internet Suspend/Resume (ISR). ISR enables a hands-free approach to mobile computing that appears well suited to future pervasive computing environments in which commodity hardware may be widely deployed for transient use. The key insight of ISR is to recognize that the suspend/resume metaphor supported by mobile hardware today can be extended to situations where a user carries no hardware. In other words, one can logically suspend a machine at one Internet site, travel to some other site and then seamlessly resume work there on another machine.

ISR is implemented by combining two off-the-shelf technologies: virtual machine (VM) technology and distributed file system technology. Each VM encapsulates distinct execution and user customization state. The distributed file system transports that state across space (from suspend site to resume site) and time (from suspend instant to resume instant). The ISR concept has spawned many new research problems. Examples include: efficient handling of huge VM state, preserving the privacy of VM state on servers, dynamically varying client thickness to track network bandwidth and latency, enhancing safety through remote inspection of VM state by trusted agents, empirical data on ISR usage, and clean separation of policy and mechanism regarding saved VM state.

Wearable Computing Carnegie Mellon has been a pioneer in the creation and use of wearable computing systems. Dan Siewiorek, in collaboration with Asim Smailagic of the Institute for Complex Engineered Systems (ICES), has led this effort since 1990. Nearly two dozen wearable computers have been designed, implemented and stressed in live usage environments such as military and industrial contexts. Much of this research activity is centered in the HCI Institute and ICES.

Current research in this area explores how wearable computing can be effective in pervasive computing environments such as Aura. This poses a number of research challenges: developing social and cognitive models of applications; integrating input from multiple sensors and mapping them to social and cognitive user states; anticipating user needs; and interacting with users. These challenges are being explored in the development of a Virtual Coach, that represents a wearable augmented cognition platform.

Secure Key Setup Between Ubiquitous Devices The proliferation of camera-equipped mobile phones presents a powerful platform that can be leveraged to conveniently provide strong authentication between devices that share no prior context, without the assistance of a trusted authority. Adrian Perrig and Mike Reiter are exploring applications for Seeing-is-Believing (SiB), a system that utilizes machine vision on camera-phones to achieve security properties formerly unattainable in a non-intrusive way. This research leverages the human-verifiable visible channel to transfer legitimate public keys to remote devices.

Overlap with Other Research Figure 1 represents a focused perspective on the research ancestory of mobile and pervasive computing. Looking ahead, Figure 2 presents a broader perspective of the research challenges we face in this area. As this figure shows, mobile and pervasive computing share many research topics with other areas discussed in this briefing book. For example, a research project that sits at the intersection of Security and Mobile Computing is Grey. Grey seek to develop a secure and fiexible framework for access control to both physical and virtual resources. In this framework, a user exercises and delegates her authority using her smartphone.

Figure 2: How Mobile and Pervasive Computing Relate to Other Areas

2 Education

A graduate course that focuses on recent developments in mobile and pervasive computing has been developed by M. Satyanarayanan and Dan Siewiorek. The course is cross-listed both by the School of Computer Science (15-821) and by the Department of Electrical and Computer Engineering (18-843). Originally entitled “Mobile Computing Systems and Applications,” the course is now called “Mobile and Pervasive Computing” to refiect the broadening of its scope over time. It has been offered once a year since Fall 2000, and has proved very popular with computer science and electrical engineering students. In addition to extensive readings, the course involves a substantial hands-on project. Each student is also required to write one of two documents based on an idea in mobile and pervasive computing: a research proposal summary (similar in spirit to an NSF proposal), or a short business plan for a commercial opportunity.

• Transient authentication
• Location privacy
• Low-energy encryption
• Biometric authentication

Another relevant course, developed by Dan Siewiorek and Asim Smailagic in the HCI Institute and cross-listed by the Computer Science Department, is entitled “Rapid Prototyping of Computer Systems.” (15-540/05-540). It is offered every spring, and draws students from Computer Science, Electrical and Computer Engineering, Design, Human-Computer Interaction, and Mechanical Engineering. Students work in interdisciplinary teams of up to three dozen students to develop a functional prototype system for an industrial application.

Last spring, Peter Steenkiste offered a new course in Wireless Networking that focuses on topics at the physical and link layers, with light treatment of higher layers. The format of the course loosely follows that of the mobile and pervasive computing course describe above (15-821/18-843), and complements its content. It is likely that this course will be offered again, possibly on a regular basis.

3 Research Community Leadership

In keeping with their pioneering role in mobile and pervasive computing, Carnegie Mellon faculty have consistently played a leadership role in shaping the research community. Papers on mobile and pervasive computing topics by Carnegie Mellon authors are widely used in the reading lists of graduate courses worldwide. Dan Siewiorek was the founding general chair of the MobiSys series of conferences on mobile computing systems, services and applications. He was instrumental in founding the International Symposium on Wearable Computing, and was the founding chair of the IEEE Technical Committee on Wearable Information Systems. He was also a founding editorial board member of IEEE Pervasive Computing. Satyanarayanan was the founding program chair of the IEEE Workshop on Mobile Computing Systems and Applications, the oldest research forum in mobile computing. He was also the founding Editor-in-Chief of IEEE Pervasive Computing, the founding Area Editor for Mobile and Pervasive Computing in the Synthesis lecture series by Morgan and Claypool, and the program chair for the 2006 Mobisys conference.