Dynamic PAN-Based Virtual Device
Tore Jønvik, Paal Engelstad and Do van Thanh
Telenor R&D
{Tore-erling,jonvik, paal.engelstad, thanh-van.do}@telenor.com
Snaroyveien 30 1331 Fornebu
Norway
Abstract
In this paper we introduce a novel concept, which
considers all the autonomous devices on the user 's
Personal Area Network (PAN) as one big "Virtual
Device" having multiple input and output units and
providing a coherent and surround interface to the user.
Such a concept is quite valuable to the user since it allows
him to manage all his devices as one. The paper also
proposes and describes a PAN middleware that enables
the formation of a Virtual Device on the PAN and that is
capable of handling the dynamical presence of devices
and the diversity of device types. In order to identify the
necessary capabilities and functions of such middleware,
Two PAN configurations, namely Isolated PAN with
multiple Open devices and Networked PAN without Open
device are considered thoroughly.
the user’s point of view it is desirable to be able to handle
all the mobile devices uniformly or preferably to consider
them as “one big Virtual Device” [1].
In this paper we introduce a novel concept, which
considers all the autonomous devices on the user 's
Personal Area Network as one big "Virtual Device"
having multiple input and output units and providing a
coherent and surround interface to the user [2]. Such a
concept is quite valuable to the user since it allows him to
manage all his devices as one (See Figure 1).
Plain-old phone
Key Words
Personal communication, Wireless communications,
Personal Area Network, Communication middleware,
Wireless Distributing computing.
Mobile phone
Laptop as
SIP/H323
terminal
Cordless phone
PDA
1. Introduction
Nowadays the user is confronted with several different
communications devices as for example, a plain-old
telephone, a mobile phone, a cordless phone, and a PC or
a workstation that acts as a multimedia terminal. All these
devices are autonomous and function independently of
each other and without any coordination. In fact they are
not even aware of the presence of other devices. As the
owner the user is required to handle them all and does not
always succeed since as a human being he cannot perform
many tasks at the same time. For example, both the plainold telephone and the mobile phone start ringing
simultaneously and force the user to alternate between
calls or terminate one of them. Another inconvenience is
the repetition of the same tasks for each device. The user
has to define his profile and preferences on every device.
For example, he has to enable a voice-answering service
both on his cellular phone and his plain-old telephone
when he is busy and does not want to be disturbed. From
Laptop
User
Workstation
PC as SIP/H323
terminal
Camcorder
Personal
Area
Network
Microphone
Interactive TV
Printer
VIRTUAL
DEVICE
Figure 1 The Virtual Device on PAN
Other advantages of the Virtual Device concept are the
cost reduction and the increase of convenience. Devices
can share resources like processing power, battery power,
memory, data, applications, network access points and
user-interfaces. The user does not have to purchase the
same resource twice and can hence save money. It is also
more convenient for him to carry as less equipment as
possible when moving.
http://heim.ifi.uio.no/~paalee/research.htm
The Virtual Device concept can never be a reality without
the emergence of local short-range communication
technologies such as Bluetooth [3], WLAN [4],
HiperLAN, etc. that enable local connectivity between
devices. The devices belonging to a person will form a
private Personal Area Network (PAN) where devices
appear and disappear dynamically. However, most
importantly, connectivity does not necessarily mean
communication and many challenging issues must be
resolved before devices can collaborate and together form
a Virtual Device. This paper proposes and describes a
middleware that enables the formation of a Virtual Device
on the PAN and that is capable of handling the dynamical
presence of devices and the diversity of device types.
2. Related works
In the project EU IST-2001-34157 PACWOMAN, there
is a different definition of the Virtual Device which
consists of a Master device and several Basic, low cost,
low power radio terminals. Each device can be considered
as one device on the PAN. The PACWOMAN Virtual
Device corresponds to the idea introduced in Wearable
Computing where a main PDA is controlling and
communicating via wireless links with miniaturised
peripheral devices. The Virtual Device in this paper, on
the other hand, consists of all devices of various types
within and beyond the PAN. The Eurescom project
P1101"Always-On" Device Unifying Service, defines a
Virtual Terminal concept that consists of networked
devices without local connectivity between each other. No
clear PAN is defined. The focus is on the transfer of voice
and data sessions between devices, e.g. to move a
conversation from a mobile to fixed phone or vice-versa.
The Virtual Device in this paper may also be confused
with Jini from Sun Microsystems. Jini enables services
and resources offered by devices over a network to be
shared by users. No attempt is made to exploit the benefits
of integrating devices together as defined by our Virtual
Device.
•
A Persistent storage
•
An Input and Output unit which manages a serie
of terminals
The heart of the mainframe is the CPU but the main vein
is the bus system. The bus system is used to convey both
the control information necessary for the control and
synchronisation in the system and the data that is
exchanged between the units. Generally speaking, it is
possible for the bus to convey both operations and data
streams although, at the implementation level, a bus
system may consist of two separate parts, one for control
and one for data.
Wired Network
CPU
CPU
Input Unit
Memory
Output Unit
Data &
Control Bus
•
location transparency
3. The Virtual Device - the natural and
inevitable evolution
•
relocation transparency
•
migration transparency
The computer, from its infancy until now has a constant
evolution and has experienced several paradigm shifts:
•
persistence transparency
•
failure transparency
•
replication transparency
•
transaction transparency
•
Distributed system and network system
•
Wireless distributed system and personal area
networks
From the 50s till the 80s, the computing world is
dominated by mainframes and minicomputers. They have
a monolithic architecture composed of:
•
A Central Processing Unit (CPU)
•
A Memory system (Volatile Storage)
http://www.unik.no/~paalee/research.htm
Data &
Control
Bus
Output Unit
Memory
During the 80s, microprocessors, workstations and PCs
made their appearance and in very short time forcing the
mainframes to retreat. However, they would not have
such a success without the breakthrough in data
communications. With Ethernet, higher data rate can be
exchanged between computers in the Local Area
Networks. The Distributed Computing paradigm is
introduced and the goal is to build a huge mainframe
based upon independent computers. The transparency
concept is aimed at hiding the complexity created by the
communication distribution such that developers can
concentrate on the development of their applications
[5][6][7]. The following transparencies are defined:
access transparency
Mainframe and monolithic architecture
Input Unit
Figure 2 Distributed Computing
•
•
PC
Workstation
Wireless Network
CPU
CPU
Memory
Input Unit
Data &
Control Bus
Input
Unit
Output Unit
Output
Unit
Memory
Figure 3 Wireless Distributed Computing
•
On-body or Off Body
To realize the Distributed Computing paradigm a software
layer or more precisely, a middleware is introduced
between the applications and the infrastructure. A well known example of such a middleware is CORBA
(Common Object Request Broker Architecture) promoted
by the Object Management group [8].
•
Mobile or stationary
•
With or without Network connections
•
With or without local wireless connections
With the emergence of short-range wireless technologies
like Bluetooth and WLAN, the natural evolution is to
replace the wired network with the wireless network to
obtain the wireless distributing computing paradigm as
shown in Figure 3.
It will be necessary with a careful and unambiguous
definition of device types but for the time being it is
sufficient to consider the device types at a coarse level as
follows:
•
Primitive device: Simple devices that cannot
operate alone but are slave to other devices, e.g.
earphone, microphone, display, etc.
•
Open device: Devices allowing the installation
and execution of PAN Middleware and other
applications, e.g. PDA, laptop, workstation, etc.
•
Closed device: Devices that can operate standalone but are like a black box i.e. its internal
structure and functions are totally hidden and
communicate with the environment though only
well defined interfaces. For instance, a digital
camera is advanced device having processor,
memory, input and output units but does not
allow the installation and execution of foreign
applications. It communicates with the rest of the
word via interfaces like serial, parallel, USB, etc.
4. The Virtual Device Middleware
Although sharing some similarities with the traditional
Distributed Computing the Wireless Distributed
Computing has also major differences and to realize the
Virtual Device requires also another type of middleware
(Figure 4). The main difference is that all the
transparencies except Access Transparency are not
desirable. Indeed, one of the goals of the Virtual Device is
to be in control of the location of the applications and to
do relocation, migration, duplication, etc. The other
differences are the heterogeneity and dynamic of the
devices on the PAN. In the traditional Distributed
Computing, the computing nodes are supposed to be
stable and equal or at least having the minimum of
capabilities e.g. processing, storage, communication, etc.
In order to identify and define the capabilities and
functions in the PAN Virtual Device Middleware
(PVDM) let us consider two PAN configurations:
User
PAN Applications
Applications
Virtual Device Middleware
•
Isolated PAN with multiple open devices
•
Networked PAN without Open device
Personal Area Network
Device 1
Device 1
Device 1
3.1 Isolated PAN with multiple open devices
Figure 4 The Virtual Device Architecture
Indeed, on the PAN there are a variety of devices such as:
•
Communications devices (fixed, mobile &IP
phones)
•
Computing devices (Computer, PC, laptop, PDA,
etc.)
•
Peripheral devices (Printer, scanner, digital
camera, camcorder, etc.)
•
Electronic devices (TV, stereo equipment,
loudspeakers, etc.)
•
Electronic appliances (fridge, expresso machine,
washing machine, etc.)
Figure 5 A PAN with multiple Open devices
In this PAN configuration, there are multiple Open
devices, multiple Closed devices and multiple Primitive
devices on the PAN. Figure 5 shows a PAN with two
Primitive devices: microphone and earphone, two Closed
devices: Mobile phone and Camcorder, and three Open
device: PDA, Laptop and PC. The PAN Virtual Device
Middleware should have the following capabilities and
functions:
A. Device Profile
The PVDM should be able to detect and to recognise what
are the devices present in the PAN, what type they are and
what capabilities they have or what service they are
offering, e.g. printing, sound input, text displaying, etc.
The definition of device types must be logical and
unambiguous. It must be logical to address both
composite devices and inherited devices. It must be
unambiguous to guarantee the identification of a device
type. The definition of device types should be
standardised.
B. Device Discovery and Updating
To support the PAN's dynamic, where devices appear and
disappear, the PVDM should be equipped with
mechanisms for Device Discovery and Updating. One
method is to carry out polling periodically. Since
Primitive devices may be tied to their master and not
visible to others, the PVDM should also ask also Open
and Closed devices for Primitive devices which are
connected. In a second method, the PVDM only runs the
device discovery once and relies on triggering from the
network layer to update its device set. In a third method,
the changes are only updated when an attempt to reach a
device upon request from an application fails. The best
options will be determined based upon the operational
scenarios of Activity 2. The PVDM should also store
information about the present devices. It is necessary to
have a naming convention, e.g. PDA 1, Mobile 2, etc. The
network addresses (IP, Bluetooth, etc.) and protocols for
each device must also be stored.
C. Device Input and Output redirection
The PVDM should be able to redirect an output stream
from one device to the input stream of another one. For
example the sound output stream from the PDA can be
redirected to an earphone and the sound input redirected
to a microphone. It must intercept the output stream
addressed to a device at an output port, perform the
necessary transformation and send it to another device on
the PAN. An API (Application Programming Interface)
will be defined for this functionality.
D. Application/Service Input and output
redirection
The input and output redirection should also be done at
the application/service level, i.e. one application can be
redirected to one device while a second one to another
device. However, this capability is more difficult since it
depends on the feature of the operating system and may
also require a new application structure as shown in
Figure 6. An application consists of three components:
Core, Input and Output. The Core component contains the
main logic of the application and should remain invariant.
The Input and Output Components should be specified
according to the services supported such as sound input,
text input, graphic display, colour printing, etc. If a device
offers a service matching the one required then it can be
used for the application.
Figure 6 PAN Application structure
E. User Profile
The user and owner of the PAN should be reserved the
right to define the following:
•
What devices are allowed to participate to her
PAN when present within the PAN's coverage?
•
How the devices should be used at a particular
location or at a particular time or according to a
certain timetable. How should the redirection
between devices occur?
•
Which devices should be internal and which one
should be global and visible to the outside
world?
•
Which applications can execute and their
settings?
•
How should the applications be distributed
among the devices, i.e. how the components
should distribute among devices according to
criteria as quality, price, battery level, etc ?
In addition, the user must have the ability to alter, remove,
and add device and applications at any time and
anywhere. These hard requirements induce a serious
challenge on the design of the User Profile structure and
the architecture of the system around it.
F. Interface to the user
Since the user, as owner of the PAN, should be the one
having the right to decide everything, there is a need for
an application for PAN Control that offers interfaces
allowing him/her to communicate and control the PAN
Virtual Device. As with other applications, the PAN
Control should also be structured as Core, Input and
Output and should support a variety of input and output
services.
G. Interface to applications and services
With the apparition of the PAN, a brand new type of
PAN-based applications is born. This new type of
applications will actively take advantage of the unique
properties of the PAN: device dynamic and resource
sharing. A typical example of PAN-based applications is
an application, which focuses on the control of existing
applications, their parallel execution, their flexible and
dynamic composition, the distribution of their input and
output. The PVDM should provide an Application
Programming Interface (API) allowing the application
access to the PAN capabilities and functions. It is also
necessary with careful study to decide which technology,
e.g. Java, CORBA, XML Web service, etc. should be
used to implement such an API.
F. Optimal Resource Sharing
Concerning the Core, it could only be moved and resumed
to a compatible Open device.
The functionalities of the PVDM are depicted in Figure 7.
3.2 Networked PAN without Open device
In this configuration the PAN does not have any Open
device but only either Primitive or Closed devices.
Usually without an Open device, the PAN will collapse
but fortunately there is a way to remedy the situation if
there is one device with network connection. As shown in
Figure 10, the mobile phone allows communication with a
Computer running the PAN Virtual Device Middleware
(PVDM). In this case the PAN can function very well
because it is logically equivalent to the configuration
Isolated PAN with unique Open device if the Computer
on the network is considered as a PAN device. This
configuration is, however, very interesting since it opens
for several relevant usage scenarios. Indeed, the network
computer can be a Home PC or an office workstation that
the user always leaves behind when traveling, but it can
still participate and give support to her PAN. This
network computer can also be provisioned and managed
by a Service Provider that offers PAN service to the users.
Figure 7 PVDM for PAN with multiple Open devices
In addition, it is desirable to achieve better collaboration
and more optimal resource sharing between the Open
devices. There are several alternatives to achieve
improved Resource Sharing as follows:
1. Distributed Operating System: Such an alternative
demands the implementation of the Distributed OS on all
of the Open device types. With rapid growth in type of
mobile devices this could be difficult.
2. Distributed Computing: The traditional Distributed
Computing Middleware must be extended with
functionality to cope with the dynamic of devices.
3. XML Web Services: The devices are more loosely
coupled in this alternative and it can cope better with
device dynamic [9][10].
4. Application distribution, coordination and control: the
PVDM performs the distribution, coordination and control
of applications based on the Core, Input and Output,
application structure. The distribution of the input and
output components is already taken care of by the
Application Redirection Function described earlier.
Figure 8 A PAN without Open Device
It is essential to consider the role of the network operator.
This is a consideration for activity 8 to investigate the
newly associated business model.
5. Conclusion
In this paper we introduce a novel concept, which
proposes to realise a Virtual Device based on autonomous
devices on the Personal Area Network. We also propose a
PAN middleware necessary for the realisation of the
Virtual Device. The capabilities and functions of the
proposed PAN Middleware are identified and explained.
However, we are still in the analysis phase. In order to
obtain a running PAN Middleware, the design,
implementation and testing should be carried out and
many challenging issues such as the device discovery, the
design of the user profile, the choice of appropriate
approach for resource sharing, etc. must be treated. Last
but least, the PAN will only take off with the wide
availability of short-range wireless technologies that
consume less energy.
References
[1] Do, van Thanh, Jønvik Tore, Vanem Erik, Tran, Dao
van & Audestad, J.A.: The Device Management Service,
Proceedings of The IEEE Intelligent Network Workshop
2001 (IN2001), Boston, USA, ISBN 0-7803-7047-3, May
6-9, 2001.
[2] Vanem Erik, Tran, Dao van, Jønvik Tore & Do, van
Thanh: Extending VHE with the Device Unifying
Service, Proceedings of The IEEE International
Conference on Comunications ICC 2002, ISBN 0-78037400-2 (sofbound) ISBN 0-7803-7401-0 (CD-ROM),
New York, USA, April 28 – May 2, 2002.
[3] https://www.bluetooth.org/
[4] http://standards.ieee.org/getieee802/portfolio.html
[5] ITU-T X.901 | ISO/IEC 10746-1 Open Distributed
Processing Reference Model Part 1.Overview
[6] ITU-T X.901 | ISO/IEC 10746-2 Open Distributed
Processing Reference Model Part 2.Foundations
[7] ITU-T X.901 | ISO/IEC 10746-3 Open Distributed
Processing Reference Model Part 3.Architecture
[8] Object Management Group: CORBA 2.0 Specification
[9] “Executive Overview: Web Services”, The Forrester
Brief, Forrester Research Inc. October 2001
[10] “What are Web Services”, DestiCorp Ltd.,
http://www.desticorp.com/focus_ws.html