Eight Billion Embedded Microprocessors1 Are Produced Each Year

PERVASIVE COMPUTING

B.SANJEEVIRAMAN

II MCA

GURUNANAK COLLEGE

PERVASIVE COMPUTING

B.SANJEEVIRMAN

II MCA

GURUNANAK COLLEGE OF ARTS AND SCIENCE

ABSTRACT

This article discusses the challenges in computer systems research posed by the emerging field of pervasive computing. It first examines the relationship of this new field to its predecessors: distributed systems and mobile computing. It then identifies four new research thrusts: effective use of smart spaces, invisibility, localized scalability, and masking uneven conditioning. Next, it sketches a couple of hypothetical

pervasive computing scenarios, and uses them to identify key capabilities missing from today’s systems. The article closes with a discussion

SUMMARY

Pervasive computing is a rapidly developing area of Information and ommunications Technology (ICT). The term refers to the increasing integration of ICT into people’s lives and environments, made possible by the growing vailability of microprocessors with inbuilt communications facilities. Pervasive computing has many potential applications, from health and home care

to environmental monitoring and intelligent transport systems. This briefing provides an overview of pervasive computing and discusses the growing debate over privacy, safety and environmental implications.

Eight billion embedded microprocessors1 are produced each year. This number is expected to rise dramaticallyover the next decade, making electronic devices ever more pervasive. These devices will range from a few millimetres in size (small sensors) to several metres (displays and surfaces). They may be interconnected via wired and wireless technologies into broader, more capable, networks. Pervasive computing systems (PCS) and services may lead to a greater degree of user knowledge of, or control over, the surrounding environment, whether at home, or in an office or car. They may also show a form of ‘intelligence’. For instance, a ‘smart’ electrical appliance could detect its own impending failure and notify its owner as well as a maintenance company, to arrange a repair.

Pervasive computing has been in development for almost 15 years (see Box 1) but still remains some way from becoming a fully operational reality. Some core technologies have already emerged, although the development of battery technologies and user interfaces pose particular challenges. It may be another 5-10 years before complete PCS become widely available. This depends on market forces, industry, public perceptions and the effects of any policy/regulatory frameworks. There have been calls for more widespread debate on the implications of pervasive computing while it is still at an early stage of development.

The goal of this article is to help us understand the challenges in computer systems esearch posed by pervasive computing. We begin by examining its relationship to the

closely related fields of distributed systems and mobile computing.

Pervasive computing history

Pervasive computing is the third wave of computing technologies to emerge since computers first appeared:

• First Wave - Mainframe computing era: one computer shared by many people, via workstations.

• Second Wave - Personal computing era: one computer used by one person, requiring a conscious interaction. Users largely bound to desktop.

•Third Wave – Pervasive (initially called ubiquitous) computing era: one person, many computers. Millions of computers embedded in the environment, allowing technology to recede into the background.

Related Fields

Pervasive computing represents a major evolutionary step in a line of work dating back to the mid-1970s. Two distinct earlier steps in this evolution are distributed systems and mobile computing. Some of the technical problems in pervasive computing

correspond to problems already identified and studied earlier in the evolution. In some of those cases, existing solutions apply directly; in other cases, the demands of ervasive computing are sufficiently different that new solutions have to be sought. There are also new problems introduced by pervasive computing that have no obvious mapping to problems studied earlier. In the rest of this section we try to sort out this complex intellectual relationship and to develop a taxonomy of issues characterizing each phase of the evolution.

Distributed Systems

The field of distributed systems arose at the intersection of personal computers and local area networks. The research that followed from the mid-1970s through the early 1990s created a conceptual framework and algorithmic base that has proven to be of enduring value in all work involving two or more computers connected by a network — whether mobile or static, wired or wireless, sparse or pervasive. This body of knowledge spans many areas that are foundational to pervasive computing and is now well codified in textbooks [2–4]:

• Remote communication, including protocol layering, remote procedure call [5], the use of timeouts, and the use of endto- end arguments in placement of functionality [6]

• Fault tolerance, including atomic transactions, distributed and nested transactions, and two-phase commit [7]

• High availability, including optimistic and pessimistic replica control [8], mirrored execution [9], and optimistic recovery [10]

• Remote information access, including caching, function shipping, distributed file systems, and distributed databases [11]

• Security, including encryption-based mutual authentication

Mobile Computing

The appearance of full-function laptop computers and wireless LANs in the early 1990s led researchers to confront the problems that arise in building a distributed system with

mobile clients. The field of mobile computing was thus born. Although many basic principles of distributed system design continued to apply, four key constraints of mobility forced the development of specialized techniques: unpredictable variation in network quality, lowered trust and robustness of mobile elements, limitations on local resources imposed by weight and size constraints, and concern for battery power consumption

Mobile computing is still a very active and evolving field of research, whose body of knowledge awaits codification in textbooks. The results achieved so far can be grouped into the following broad areas:

• Mobile networking, including Mobile IP ad hoc protocols and techniques for improving 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 . and energy-sensitive memory management

• Location sensitivity, including location sensing and location-aware system behavior .

Pervasive Computing

Earlier in this article, we characterized a pervasive computing environment as one saturated with computing and communication capability, yet so gracefully integrated with users that it becomes a “technology that disappears.” Since motion is an integral part of everyday life, such a technology must support mobility; otherwise, a user will be acutely aware of the technology by its absence when he moves. Hence, the research

agenda of pervasive computing subsumes that of mobile computing, but goes much further. Specifically, pervasive computing incorporates four additional research thrusts into its agenda..

Effective Use of Smart Spaces

The first research thrust is

Effective use of smart spaces. A space may be an enclosed area such as a meeting room or corridor, or a well-defined open area such as a courtyard or quadrangle. By embedding computing infrastructure in building infrastructure, a smart space brings together two worlds that have been disjoint until now .The fusion of these worlds enables sensing and control of one world by the other. A simple example of this is the

automatic adjustment of heating, cooling, and lighting levels in a room based on an occupant’s electronic profile. Influence in the other direction is also possible: software on a user’s computer may behave differently depending on where the user is currently located. Smartness may also extend to individual objects, whether located in a smart space or not.

Invisibility — The second thrust is invisibility. The ideal expressed by Weiser is complete disappearance of pervasive computing technology from a user’s consciousness. 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 subconscious level At the same time, a modicum of anticipation may be essential to avoiding a large unpleasant surprise later, much as pain alerts a person to a potentially serious future problem in a normally unnoticed body part.

Localized Scalability — The third research thrust is localized scalability. As smart spaces grow in sophistication, the intensity of interactions between a user’s personal computing space and his/her surroundings increases. This has severe band width, energy, and distraction implications for a wireless mobile user. The presence of multiple users will further complicate this problem. Scalability, in the broadest sense, is thus a critical problem in pervasive computing. Previous work on scalability has typically ignored physical distance — a Web server or file server should handle as many clients as possible, regardless of whether they are located next door or across the country. The situation is very different in pervasive computing. Here, the density of interactions has to fall off as one moves away; otherwise, both the user and his computing system will be overwhelmed by distant interactions that are of little relevance. Although a mobile user far from home will still generate some distant interactions with sites relevant to him, the preponderance of his/her interactions will be local. 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 — The fourth thrust is the development of techniques for masking uneven conditioning of environments. The rate of penetration of pervasive computing technology into the infrastructure will vary considerably depending on many nontechnical factors such as organizational structure, economics, and business models. Uniform penetration, if it is ever achieved, is many years or decades away. In the interim, there will persist huge differences in the “smartness” of different environments — what is available in a well-equipped conference room, office, or classroom may be more sophisticated than in other locations. 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/her personal computing space compensate for “dumb” environments. As a trivial example, a system that is capable of disconnected operation is able to mask the absece of wireless coverage in its environment. Complete invisibility may be impossible, but reduced variability is well within our reach.

Pervasive computing technologies

Pervasive computing involves three converging areas of ICT: computing (‘devices’), communications (‘connectivity’) and ‘user interfaces’.

Devices

PCS devices are likely to assume many different forms and sizes, from handheld units (similar to mobile phones) to near-invisible devices set into ‘everyday’ objects (like

furniture and clothing). These will all be able to communicate with each other and act ‘intelligently’. Such devices can be separated into three categories:

• sensors: input devices that detect environmental changes, user behaviours, human commands etc;

• processors: electronic systems that interpret and analyse input-data;

• actuators: output devices that respond to processed information by altering the environment via electronic or mechanical means. For example, air temperature control is often done with actuators. However the term can also refer to devices which deliver information, rather than altering the environment physically. There are many visions for the future development of PCS devices. Several research groups are endeavouring to produce networks of devices that could be small as a grain of sand. The idea is that each one would function independently, with its own power supply, and could also communicate wirelessly with the others. These could be distributed throughout the environment to form dense, but almost invisible, pervasive computing networks, thus eliminating the need for overt devices.2

At the other extreme, augmented reality would involve overlaying the real world with digital information. This approach emphasises the use of mobile technologies, geographical positioning systems and internet-linked databases to distribute information via personal digital companions. Such devices could come in many forms:

children might have them integrated into school bags, whereas adults might use devices more closely resembling personal digital assistants (PDAs). Ultimately a spectrum of devices may become available. These will range from miniaturised (potentially embedded in surrounding objects) to a variety of mobile (including handheld and wearable) devices. While these could exist as standalone systems, it is likely that many will be interlinked to form more comprehensive systems.

Connectivity

Pervasive computing systems will rely on the interlinking of independent electronic devices into broader networks. This can be achieved via both wired (such as Broadband (ADSL) or Ethernet) and wireless networking technologies (such as WiFi or Bluetooth), with the devices themselves being capable of assessing the most effective form of connectivity in any given scenario. The effective development of pervasive computing systems depends on their degree of interoperability, as well as on the

convergence of standards for wired and wireless technologies.

User interfaces

User interfaces represent the point of contact between ICT and human users. For example with a personal computer, the mouse and keyboard are used to input information, while the monitor usually provides the output. With PCS, new user interfaces are being developed that will be capable of sensing and supplying more information about users, and the broader environment, to the computer for processing. With future user interfaces the input might be visual information – for example recognising a person’s face, or responding to gestures. It might also be based on sound, scent or touch recognition, or other sensory information like temperature. The output might also be in any of these formats. The technology could ‘know’ the user (for example through expressed preferences, attitudes, behaviours) and tailor the physical environment to meet specific needs and demands. However, designing systems which can adapt to unforeseen situations presents considerable engineering challenges.3 There is debate over the degree of control users will have over future pervasive computing user interfaces as the technology develops. Three very different forms of human-computer interaction are postulated: active, passive and coercive .