Decentralized Approach
for Distributed Service Environments
JIN Yuhan, TIAN Hui and Liu Zemin
Key Laboratory of Universal Wireless Communication, Ministry of Education
Beijing University of Posts and Telecommunications (BUPT)
10 Xitucheng Road, Beijing, P.R.China 100876
Email: jinyuhan.bupt@gmail.com, {tianhui,liuzemin}@bupt.edu.cn
Abstract— Universal Service Terminal(UST) has been proposed
as a novel virtual distributed terminal supporting pervasive applications. It provides proactive services via aggregating diverse
capabilities of devices around the user and auto-configuring them
accordingly to the capabilities, availability, user’s preference and
application context, which results in Always the Best Experience (ABE). The issues related to concept, architecture, design,
and simulation are addressed and some basic procedures are
introduced. Moreover, the results of simulation comparing two
scenarios are given to validate the mechanisms designed in UST.
Keywords: PAN, UST, terminal, dynamic
I. I NTRODUCTION
Emerging technologies for short-range personal communication [1] and the ever-growing number of wireless terminals,
such as smart phones, PDAs and laptops etc, both raised
the need to set up, configure and reconfigure personal area
networks (PANs) [2] in an easy and ergonomic way [3][4]. We
envision a future cyberworld where pervasive or ubiquitous
services will be reality. These kinds of services are mainly
supported via pervasive facilities embedded in the living space
surrounding the human beings and provided proactively and
adaptively according to context and preference.
In order to enable smart and portable devices surrounded
user to work cooperatively to represent the services, we have
proposed a novel concept called as Universal Service Terminal
(UST) to present the characteristics of pervasive terminal
environment and support the deployment of ubiquitous application, whether locally or remotely. UST is a virtual terminal, which can utilize pre-defined transport interconnection
established by wireless or wired network technologies, e.g.
PAN, BAN, VAN, etc., and dynamically aggregate components
with one or more terminal capabilities. The components in
UST range from cellular phones, apparatuses, laptops, PC,
vehicle devices to gadgets like sensors and actuators. UST
is also an intelligent terminal network, and it supports autoconfiguration of the capabilities according to user’s preference
and temporal service context, which aims to provide users with
Always the Best Experience (ABE) [5] mode services. From
the point of view of applications and core networks, UST can
be treated as a universal auto-configured entity rather than
complex combination of components in terms of deployment
and development. However, little is known about the actual
performance of the combination, and no attempt has previously
been made to directly compare the UST’s performance in
different scenarios in a realistic manner.
In this paper, we address the dynamic aggregation and component invocation of UST, by which the needs of ’ABE’ mode
service provisioning can be fulfilled. Besides, we analyze the
performance of UST in different scenarios and explain the
design choices that account for the performance.
The paper proceeds as following. In section II, the definition
and architecture of UST are introduced. Section III shows the
basic mechanisms designed for UST. In section IV, simulation
is given to validate the concept and evaluate the performance.
Finally, section V concludes the paper and discusses the future
work.
II. D ISTRIBUTED T ERMINAL S YSTEM
A. Basic Concept of UST
UST is an application layer middleware which can combine
a set of ambient devices, i.e. laptop, PDA, TV. These devices
have their own capabilities respectively and can use each
other’s capabilities to provide a complex multimedia service,
since in some cases it is difficult for an individual device to
provide all the capabilities needed in a multimedia service.
The combination of devices is based on user’s preference and
the ubiquitous context information. UST can also cognize the
changes of devices and environment and make re-configuration
of the devices automatically. In this way, the combined devices
act as a virtual terminal for the user and can provide the best
service.
B. Universal Service Terminal Architecture
For the sake of proposing a network-supported terminal
service environment, the design of UST architecture refers
two kinds of service models, which are MExE [6] and OSA
[7]. According to MExE, UST provides a service execution
environment and interaction mechanisms for terminals, networks and service providers; by bringing in OSA’s framework
mechanism, UST provides facilities for a distributed terminal
system.
We have proposed the UST architecture (Fig.1) for the
distributed terminal system, which is mainly composed of
Framework (FW), Execution Environment (EE), Capability
Server(CS) and Aggregation Control (AC). FW takes the
responsibility of the organization and information management
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This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE CCNC 2008 proceedings.
Fig. 1.
Architecture of UST
of devices, as well as service composition and adaptation
according to the application requirements. EE is configured
by FW dynamically to support provision of composite services
and harmony between the co-operative devices. In the system
all the devices have the capability servers which abstract and
encapsulate different service capabilities, such as video, audio
and network communication. Also, AC may be regarded as
a SC which takes charge of the registration to UST. FW and
EE provide mechanisms to construct the virtual terminal, by
which the management, configuration and service deployment
will be facilitated in complex pervasive environment.
C. Devices deployed with UST
By using the UST to set up a personal area network, each
device should be deployed with UST. But not all of the
components in the UST architecture are necessary for each
device. Depending on what capabilities devices have, we could
divide them into two categories.
1) First level device. This kind of devices have FW. They
can organize and manage the information of other devices and
also takes responsibility of service composition and adaptation.
So these devices are necessary in the process of setting up
a personal area network. Devices like PDA, mobile phone,
computer, etc. can be seen as the first level devices.
2) Second level device. These devices can provide some
basic capacities they have for a multimedia application, which
only rely on the first level devices to accomplish the task.
Microphone, video box, TV, etc. belong to the second level
devices.
III. O RGANIZATION M ECHANISM
To ensure the reliability and scalability of the system,
we introduce some mechanisms in the UST procedure, e.g.
the aggregation of the devices, attaching/detaching from the
system, invocation of the capability servers and migration
of the framework functionality. By facilitating mechanisms
mentioned above, the devices can work cooperatively to provide the most appropriate capability servers under ambient
environment and user preference.
1) The first step of the aggregation of the devices is to construct a minimum UST system. A first level device activates
its Framework and Execution Environment functionalities,
then registers its capability servers to Framework. After the
minimum UST system has been established, other devices
which want to join in the system begin to register their
capabilities respectively.
2) When the user’s context information changes, the attaching/detaching procedure will occur. In the procedure, some
devices modify the information registered to Framework and
launch or shut down the relevant capability servers. Meanwhile, Framework updates the capability server information
stored in the database and re-configures Execution Environment. Due to the changes of the capabilities provided by the
system, the application running in Execution Environment has
to react to ensure the seamless service provision to the user.
3) The invocation procedure consists of the discovery,
acquisition and invocation of capabilities. First, the application
requests the capability servers depending on the user preference, available capabilities and current system environment.
Next, according some specific resource allocation policies,
Framework distributes the most appropriate capabilities to
the application. Then, the application acquires the invocation
approaches of the capability servers and accesses them via
remote method invocation.
4) Framework migration procedure occurs when a device
is more suitable to be the master of the system than the
current one. The candidate activates its Framework and Execution Environment functionalities, copies the capability server
database and runtime Execution Environment information and
informs all the devices within the system the migration of
the framework. Then, the old master device shuts down its
Framework functionality without influencing the application
running in the system.
IV. S IMULATION
We use OPNET [8], a system simulation tool, to simulate
the UST environment. The overall goal of our experiments are
to measure the ability of UST to react to environment change
when devices communicate among each other.
In this section we first describe the simulation model. Then
two kinds of simulation scenarios are presented to evaluate
the performance of UST and a comparison is made between
them. Finally, we analyze the results of the simulation.
A. Simulation Model
As described above, devices in the UST system can be
divided into two kinds of level: the first level devices and
the second level devices. Correspondingly, we use two kinds
of node models to describe different devices.
Figure 2 shows the first level devices’ node model.
In figure 2, EE module stands for execution environment;
FW module stands for the framework; AC module stands for
the aggregation control; CS module stands for the capacity
server. The capabilities contained in the devices have been set
before simulation. Mobility module is used to control the node
model moving in the network and I/O module is used to deal
with the communication between node models.
Figure 3 shows the second level devices’ node model.
Second level devices have no functions of framework and
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Fig. 4.
Fig. 2.
The first level devices’ node model
execution environment, so the model of them in figure 3 is
not have EE module and FW module.
Fig. 3.
The second level terminals’ node model
In the simulation, we only pay attention to some typical
applications in a video phone scenario. So only the capabilities related with video phone application were referred. The
simulation needs seven capabilities: User interface, SIP proxy,
RTP transmit, Audio-in, Audio-out, Video-in, Video-out.
Video phone application will use these seven capabilities
during the simulation. We assume that video phone application
must have the first five capabilities listed above. In the case
of no video-in and video-out capabilities, the video phone
application only performs audio service.
B. Simulation Environment
We first introduce a simple scenario, shown as figure 4.
This scenario contains a PC and some affiliated equipment,
including a camera, a sound box and a microphone. In the
simulation of video phone application, we will only take
one end into account and suppose the other end of the
communication is a powerful device that can satisfy any need
of capability for a multimedia communication. The devices
configurations in figure 4 are shown in table 1.
Under the present configuration, user can only initiate one
video phone communication instance each time, for that the
camera, sound box and microphone can only be used for
A simple scenario
one service instance meantime. This scenario contains one
first level device which is PC.The PC has FW and can
initiate a construction process of UST and sponsor one or
more video phone communication instances via the execution
environment.
In the process of the simulation, if any device in the network
will not move at all, the configuration of UST will not change.
Under this situation, the UST can maintain a video phone
communication instance continuously. In case that a device
is departing from the UST and there is no other device
substituting to provide the same capability, the communication
will stop.
In figure 4, we set a move track for the microphone which
will move along the track clockwise at a constant speed. The
cover range of the PC is within the four panes as shown in
the figure 5. Once the microphone goes out of the cover range
area, it will depart from the UST system. Reversely, if the
microphones comes back to the cover range area of the PC, it
will be detected by PC and can join in the UST system again.
We set the simulation time as one hour. During the simulation,
PC will initiate 20 times video phone communication instances
to construct a UST system.
The complicated scenario is the same as the simple scenario
except that it has more devices, especially more first level
devices.
Figure 5 shows the complicated scenario. Besides containing the same devices as the simple scenario has, this
scenario also has a wireless laptop, which is configured with
a microphone, a PDA, a TV and an advanced sound box.
Just like the simple scenario, PC will initiate a construction
of the UST system. And the PDA, laptop and common
microphone will move along their own tracks that have been
set at the beginning of the simulation. They all move at a
constant speed. The simulation time is set as one hour and
there will be 20 times initiation communication instance to
construct a UST system sponsored by the PC. The PC’s cover
range is within 9 panes.
C. Simulation Results
In this section we will analyze the results of our simulation.
We devote our mind on the aggregation and separation of the
devices, the dynamic variety of the capability, the dynamic
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TABLE I
T HE TERMINALS ’ CONFIGURATION
Terminal name
PC
Camera
Common sound box
Advance mike
Fig. 5.
Terminal level
First level
Second level
Second level
Second level
Basic terminal or not
Yes
No
No
No
Capacity
UI, SIP, RTP, Video-out
Video-in
Audio-out
Audio-in
Fig. 7.
Existing communication instance number
Fig. 8.
Capacities used in the simulation process
A complicated scenario
support for the communication instance to compare the performance of UST system in two different scenarios.
Firstly, Figure 6 shows the number of devices which can be
used during the simulation. We could notice that the number of
the available devices is variable. That’s because some devices
in UST are moving during the whole process of simulation.
Fig. 6.
Available devices’ number during the simulation
Figure 7 shows the effect caused by the number of available
devices on the existing communication instances. Since there
are more devices to be used in the complicated scenario than
that in the simple scenario, the max number of communication
instances meantime in the complicated scenario is larger than
that in the simple scenario. We can conclude that the capability
of UST system could be enhanced when there are more
available devices.
As the moving of the devices during the simulation, the
available capability in the UST system is also variable. Figure
9 shows the number of capabilities used in the UST system.
From the simulation figures above, we can get the results
that UST has a better performance with more available devices.
In the simple scenario the performance of UST is lower than
that in the complicated scenario, and the performance is almost
the same as the devices without UST which means that it has
little enhancement with UST. Because in the simple scenario,
the number of devices is very limited, if the communication
instance is lack of one device, there is no other device could
replace it to provide the same capability, the communication
instance has to stop running. With the number of devices
increasing, the support capability for the communication instance will also be strengthened. In the complicated scenario,
it has more devices than that in the simple scenario. The basic
terminal can utilize the idle terminals’ capabilities to support
the video phone application. If the device’s cover range is
extended and the device’s number increases, the performance
of UST will be much more excellent than a common device.
V. R ELATED W ORK
In recent years, pervasive research on PAN technologies has
been developed rapidly. MOBY [9] extends the Jini architecture to enable the exchange of services and data in a mobile
peer-to-peer manner. The motivation of MOBY is to provide a
seamless network for the user, integrate a wide rang of wired
and wireless components into the network and provide open
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This full text paper was peer reviewed at the direction of IEEE Communications Society subject matter experts for publication in the IEEE CCNC 2008 proceedings.
APIs for developers to ease the application integration. In [10]
an approach for peer-to-peer capable mobile communication
environment was presented. This environment was based on a
concept of Personal Trusted Device (PTD) and its operation
on some very local communication environment. A PTD
constantly scans the changing environment for other devices.
And the implementation is restricted to the Bluetooth communication technology as it allows limited neighborhood sizes. In
[11] introduces the notion of Virtual Devices encapsulating and
hiding multiple devices in the Personal Area Network (PAN)
of the user to provide one interface. Meanwhile a middleware
is proposed for the realization of Virtual Device.The Ninja
project [12] targets robust, scalable, distributed internet services for highly heterogeneous devices. Ninja consists of the
following components: Bases, which are powerful workstation
cluster environments; Units, which are service access devices;
Active Proxies, for unit or service based adaptation, and Paths,
which tie together units, services, and active proxies. It has
been shown that the Ninja architecture provides the needed
flexibility, facilitates application integration, and rapid service
evolution.
Our approach mainly focuses on encapsulating the diverse
capabilities of ambient devices and taking user preference into
account. The proposed UST can be regarded as a middleware
by which the status of the system and the information of the
capabilities are hidden from the running application.
[5] P. Zhang, Y. Ji, Y. Zhang, ”MUSE: a vision of service and architecture
for beyond 3G networks,” Proc. of the International Symposium on
Autonomous Decentralized Systems (ISADS’2005), pp.109-115, 2005.
[6] 3GPP specification TS 23.057.
[7] 3GPP specification TS 29.198.
[8] Available Online. http://www.opnet.com/.
[9] T. Horozov, A. Grama, V. Vasudevan and S. Landis, ”MOBY- A Mobile
Peer-to-Peer Service and Data Network,” in Proceedings of the 2002
International Conference on Parallel Processing (ICPP02), 2002.
[10] J. Porras, P. Hiirsalmi and A. Valtaoja, ”Peer-to-peer Communication
Approach for a Mobile Environment,” in Proceedings of the 37th Hawaii
Internation Conference on System Sciences, 2004.
[11] T. E. Jonvik, P. Engelstad and D. van Tanh, ”Building a Virtual Device
on Personal Area Network,” in Proceedings of the 2nd International
Conference on Communications, Internet & Information Technology,
Scottsdale, Arizona, Nov 17-19, 2003.
[12] S. D. Gribble, M. Welsh, R. von Behren, E. A. Brewer and B. Y. Zhao,
”The ninja architecture for robust internet-scale systems and services,”
Computer Networks, 35(4):473-497, 2001.
VI. C ONCLUSION
In this paper, we presented an innovative approach UST,
which can provide user the best experience in PAN. The
UST can make good use of the idle devices in the PANs
to work cooperatively and use each other’s capabilities. This
can not only enhance the performance of common devices,
but also take full advantages of the present resources. UST
hides the individual devices of the PAN and abstracts the
capacities of these devices for user to use. The simulation
results also clearly shows that it is very suitable for the
dynamic environment in the distributed manner.
ACKNOWLEDGMENT
This work is supported by National High Tech R&D Program of China, No. 2006DFA11050 and National Natural
Science Foundation of China (NSFC), No. 60502035.
We thank the reviewers for their many valuable comments
and our colleagues for their suggestion and encouragement.
R EFERENCES
[1] P. Johansson and Ericsson Research, ”Bluetooth: An Enabler for Personal Area Networking,” IEEE Network, Sep 2001.
[2] E. L. Nygren, S. J. Garland and M. F.Kaashoek, ”PAN: A HighPerformance Active Network Node Supporting Multiple Mobile Code
Systems,” Proceedings of the 1999 IEEE 2nd Conf, on Open Architecture and Network Programming,1999.
[3] K. Sethom, M. Sabeur and B. Jouaber, ”Distributed Virtual Network
Interfaces to support intra-PAN and PAN-to-infrastructure Connectivity,”
IEEE Globecom 2005.
[4] C. Bisdikian, P. Bhagwat and B. P. Gaucher, ”WiSAP: A Wireless
Handheld Personal Access Network for Computing Devices,” IEEE
Personal Communications, December 1998.
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