08-07-2014, 03:05 PM
Mobile, Distributed, and Pervasive
Computing
[attachment=65757]
Abstract
Pervasive computing can be defined as access to information and software applications
anytime and anywhere. This form of computing is highly dynamic and
disaggregated. Users are mobile and services are provided by collections of distributed
components collaborating together. Recent advances in mobile computing,
service discovery, and distributed computing are key technologies to support pervasive
computing.
This chapter is about software technologies designed to address problems in
mobile, distributed, and pervasive computing. Characteristics of pervasive computing
applications are reviewed. Architecture of pervasive computing software is discussed.
Key open communication technologies to support pervasive computing are presented
in detail, namely, service discovery and distributed computing.
1.1 INTRODUCTION
Pervasive computing aims at availability and invisibility. On the one hand, pervasive
computing can be defined as availability of software applications and information
anywhere and anytime. On the other hand, pervasive computing also means that
computers are hidden in numerous so-called information appliances which we use in
our day-to-day life [Bir97], [Wei91], [Wei93]. Personal Digital Assistants (PDAs)
and cell phones are the first widely available and used pervasive computing devices.
Next generation devices are being designed. Several of them will be portable and
even wearable, such as glass embedded displays, watch PDAs, and ring mouses.
Several pervasive computing devices and users are wireless and mobile. Devices
and applications are continuously running and always available. From an architectural
point of view, applications are non-monolithic, but rather made of collaborating
parts spread over the network nodes. These parts are hereafter called distributed
components. As devices and users move from one location to another, applications
must adapt themselves to new environments. Applications must be able to discover
services offered by distributed components in new environments and dynamically
i
ii
reconfigure themselves to use these new service providers. From a more general
point of view, pervasive computing applications are often interaction transparent,
context aware, and experience capture and reuse capable. Interaction transparency
means that the human user is not aware that there is a computer embedded in the
tool or device that he or she is using. Context awareness means that the application
knows, for instance, the current geographical location. An experience capture and
reuse capable application can remember when, where, and why something was done
and can use that information as input to solve new tasks.
Pervasive computing is characterized by a high degree of heterogeneity: devices
and distributed components are from different vendors and sources. Support of
mobility and distribution in such a context requires open distributed computing architectures
and open protocols. Openness means that specifications of architectures
and protocols are public documents developed by neutral organizations. Key specifications
are required to handle mobility, service discovery, and distributed computing.
In this chapter, we review the main characteristics of applications of pervasive
computing in Section 1.2, discuss the architecture of pervasive computing software
in Section 1.3, and review key open protocols in Section 1.4.
OPEN PROTOCOLS
Open protocols are required by pervasive computing for establishing communication
and collaboration between distributed components in a global infrastructure-based
manner as well as in an ad hoc manner. Mobility, service discovery, and distributed
computing are issues that need to be addressed.
The problem of mobility of devices, from network to network, is not solved by
plain IP. It is, however, addressed by the mobile Internet Protocols (IPs). Mobile
IPs are discussed in more detail in Chapter 25 of this book. In the context of the
current chapter, it is worth mentioning that IPv6 is a better candidate than IPv4 for
pervasive computing [Pau01]. Indeed, pervasive computing puts enormous pressure
on the demand of IP addresses. The number of devices will be high and they will
be continuously running, hence there is little possibility of temporal sharing of IP
addresses as does DHCP. The 128-bit addresses of IPv6 can support considerably
more devices than IPv4 32-bit addresses of IPv4. There is a movement in the
wireless industry towards IPv6. For instance, the Third-Generation Partnership
OPEN PROTOCOLS v
Project (3GPP) [Pro01] has adopted IPv6 for their next generation of wireless network
specification.
In the subsequent subsection, we focus on application support protocols. Service
discovery and distributed computing are discussed in more detail.
SUMMARY
Characteristics of pervasive computing applications have been discussed in Section
1.2. Interaction transparency means that human-to-computer interaction is natural
and based on ordinary life objects and operations. Context awareness means
that applications can sense and exploit information about the physical environment in
which they are running. Automated capture of experiences exploits knowledge about
actions performed in the past bound to contextual information to assist and make the
resolution of new problems easier and faster.
Issues of architectures of pervasive computing that have to do with mobility and
distribution were reviewed in Section 1.3. Pervasive computing platforms may be
characterized by relatively narrow-bandwidth channels, slow processing power, and
limited input/output capabilities. To cope with these issues, some tasks can be
delegated by a pervasive computing device to a server. This approach is called
application partitioning. The component-based distributed computing model is well
suited to the design of such applications.
xx
We raised the need of open protocols to enable inter-operability between the
elements of pervasive computing. Service discovery protocols and distributed components
architectures were addressed in more detail. Service discovery protocols,
such as SLP and Jini, provide mechanisms with which distributed components can
discover what each has to offer to other in terms of services. With an open distributed
computing architecture, components can collaborate together using a common communication
language. CORBA is an open distributed components architecture that
achieves location transparency, programming language independence, and platform
independence of service providers. Other open protocols not discussed in this chapter,
such as mobile Internet protocols and ad hoc networking protocols, are also required
to support mobile and distributed pervasive computing.
Computing
[attachment=65757]
Abstract
Pervasive computing can be defined as access to information and software applications
anytime and anywhere. This form of computing is highly dynamic and
disaggregated. Users are mobile and services are provided by collections of distributed
components collaborating together. Recent advances in mobile computing,
service discovery, and distributed computing are key technologies to support pervasive
computing.
This chapter is about software technologies designed to address problems in
mobile, distributed, and pervasive computing. Characteristics of pervasive computing
applications are reviewed. Architecture of pervasive computing software is discussed.
Key open communication technologies to support pervasive computing are presented
in detail, namely, service discovery and distributed computing.
1.1 INTRODUCTION
Pervasive computing aims at availability and invisibility. On the one hand, pervasive
computing can be defined as availability of software applications and information
anywhere and anytime. On the other hand, pervasive computing also means that
computers are hidden in numerous so-called information appliances which we use in
our day-to-day life [Bir97], [Wei91], [Wei93]. Personal Digital Assistants (PDAs)
and cell phones are the first widely available and used pervasive computing devices.
Next generation devices are being designed. Several of them will be portable and
even wearable, such as glass embedded displays, watch PDAs, and ring mouses.
Several pervasive computing devices and users are wireless and mobile. Devices
and applications are continuously running and always available. From an architectural
point of view, applications are non-monolithic, but rather made of collaborating
parts spread over the network nodes. These parts are hereafter called distributed
components. As devices and users move from one location to another, applications
must adapt themselves to new environments. Applications must be able to discover
services offered by distributed components in new environments and dynamically
i
ii
reconfigure themselves to use these new service providers. From a more general
point of view, pervasive computing applications are often interaction transparent,
context aware, and experience capture and reuse capable. Interaction transparency
means that the human user is not aware that there is a computer embedded in the
tool or device that he or she is using. Context awareness means that the application
knows, for instance, the current geographical location. An experience capture and
reuse capable application can remember when, where, and why something was done
and can use that information as input to solve new tasks.
Pervasive computing is characterized by a high degree of heterogeneity: devices
and distributed components are from different vendors and sources. Support of
mobility and distribution in such a context requires open distributed computing architectures
and open protocols. Openness means that specifications of architectures
and protocols are public documents developed by neutral organizations. Key specifications
are required to handle mobility, service discovery, and distributed computing.
In this chapter, we review the main characteristics of applications of pervasive
computing in Section 1.2, discuss the architecture of pervasive computing software
in Section 1.3, and review key open protocols in Section 1.4.
OPEN PROTOCOLS
Open protocols are required by pervasive computing for establishing communication
and collaboration between distributed components in a global infrastructure-based
manner as well as in an ad hoc manner. Mobility, service discovery, and distributed
computing are issues that need to be addressed.
The problem of mobility of devices, from network to network, is not solved by
plain IP. It is, however, addressed by the mobile Internet Protocols (IPs). Mobile
IPs are discussed in more detail in Chapter 25 of this book. In the context of the
current chapter, it is worth mentioning that IPv6 is a better candidate than IPv4 for
pervasive computing [Pau01]. Indeed, pervasive computing puts enormous pressure
on the demand of IP addresses. The number of devices will be high and they will
be continuously running, hence there is little possibility of temporal sharing of IP
addresses as does DHCP. The 128-bit addresses of IPv6 can support considerably
more devices than IPv4 32-bit addresses of IPv4. There is a movement in the
wireless industry towards IPv6. For instance, the Third-Generation Partnership
OPEN PROTOCOLS v
Project (3GPP) [Pro01] has adopted IPv6 for their next generation of wireless network
specification.
In the subsequent subsection, we focus on application support protocols. Service
discovery and distributed computing are discussed in more detail.
SUMMARY
Characteristics of pervasive computing applications have been discussed in Section
1.2. Interaction transparency means that human-to-computer interaction is natural
and based on ordinary life objects and operations. Context awareness means
that applications can sense and exploit information about the physical environment in
which they are running. Automated capture of experiences exploits knowledge about
actions performed in the past bound to contextual information to assist and make the
resolution of new problems easier and faster.
Issues of architectures of pervasive computing that have to do with mobility and
distribution were reviewed in Section 1.3. Pervasive computing platforms may be
characterized by relatively narrow-bandwidth channels, slow processing power, and
limited input/output capabilities. To cope with these issues, some tasks can be
delegated by a pervasive computing device to a server. This approach is called
application partitioning. The component-based distributed computing model is well
suited to the design of such applications.
xx
We raised the need of open protocols to enable inter-operability between the
elements of pervasive computing. Service discovery protocols and distributed components
architectures were addressed in more detail. Service discovery protocols,
such as SLP and Jini, provide mechanisms with which distributed components can
discover what each has to offer to other in terms of services. With an open distributed
computing architecture, components can collaborate together using a common communication
language. CORBA is an open distributed components architecture that
achieves location transparency, programming language independence, and platform
independence of service providers. Other open protocols not discussed in this chapter,
such as mobile Internet protocols and ad hoc networking protocols, are also required
to support mobile and distributed pervasive computing.