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Vol.6 No.2 June, 2010
Recent Advances in Mobile and Multimedia Applications
Editorial (095-096)
Antonio Gentile and Salvatore Vitabile
Research Articles
Wireless networks have become increasingly popular and advances in
wireless communications and electronics have enabled the development of
different kind of networks such as Mobile Ad-hoc Networks (MANETs),
Wireless Sensor Networks (WSNs) and Wireless Sensor-Actor Networks (WSANs).
These networks have different kind of characteristics, therefore new
protocols that fit their features should be developed. We have developed
a simulation system to test MANETs, WSNs and WSANs. In this paper, we
consider the performance behavior of two protocols: AODV and DSR using
TwoRayGround model and Shadowing model for lattice and random
topologies. We study the routing efficiency and compare the performance
of two protocols for different scenarios. By computer simulations, we
found that for large number of nodes when we used TwoRayGround model and
random topology, the DSR protocol has a better performance. However,
when the transmission rate is higher, the routing efficiency parameter
is unstable.
Recently, a lot of researchers have directed their
attention to mobile sensor networks that are constructed by sensor nodes
with a moving facility. Mobile sensor networks enable to construct a
wide-range sensing system by the cooperative behaviours of a small
number of mobile sensors. However, because radio communication range of
the nodes does not cover the whole sensing area, every node has to move
closer to the sink to deliver its sensor readings. Thus, the power
consumption to deliver the sensed data to the sink becomes large. We
previously proposed two mobile sensor control methods to reduce the
power consumption by employing push-based broadcast, named the MST
(Moving-distance-based Static Topology) and the SR-N (Shortest Route
with Negotiation) methods for sparse mobile sensor networks. In this
paper, we propose the MST/NFD (MST with Node Failure Detection) and the
SR-N/NFD (SR-N with Node Failure Detection) methods as extensions of the
MST and the SR-N methods to detect node failures. We also conducted
simulation experiments to evaluate the performance of our methods and
confirmed that the MST/NFD method is more robust over node failures than
the SR-N/NFD method, and that the SR-N/NFD method can achieve the high
throughput than the MST/NFD method.
This paper proposes an extended COLLADA-based file
format to represent various attributes of realistic objects used in
Virtual Reality (VR) applications that support various peripherals. VR
applications provide the user with virtual objects represented as 3D CG.
To provide realistic virtual objects in VR applications, the developer
of the VR application has to define many attributes of the corresponding
real objects besides their 3D geometry and material data in his/her
program or in instance definition files of the virtual objects. In this
paper, the authors propose the use of a COLLADA file format for such
instance definition of virtual objects because it is a XML based 3D
model data format and can be easily extended to additionally include
various attributes of the virtual objects. This paper introduces the
proposed COLLADA-based file format that mainly supports four types of
attributes. Those are for haptic parameters of soft objects represented
by the spring model used for a haptic device like Phantom, sound data
for generating a sound when the user touches a 3D object, text data used
as annotations for explaining corresponding objects helpful in
simulation/training systems and smell information of objects used for
smell generator devices to enhance immersive feeling in VR applications.
This paper also clarifies the usefulness of the proposed COLLADA-based
file format by showing its examples of actual networked VR applications,
and the authors also mention its adaptability to mobile 3D graphics
applications by showing one mobile 3D graphics application.
A social network is viewed as a set of people or organizations connected
by a set of social relationships, such as friendship or common
interests. In the past people would rely on the friends or close
associates for information. Today, they search in the web for such
information and opinion. And access control to resources is one of the
most important technologies for supporting human activities in the
digital space, where confidentiality and secure data handling are two
most important issues for any such social network users. To realize this
control two schemes were proposed: RBAC (Role-Based Access Control) \cite{rbac}
and TRBAC (Temporal Role-Based Access Control) \cite{trbac} by adding
time constraints and role dependencies to RBAC. However, these methods
are not effective for temporal activities because of high maintenance
costs and inadequacy in safeness. In this paper, we focus on a flexible
and secure access control in the real space, by using relations with
users and situations, and propose a novel access control which is
effective for temporal activities. We evaluate our proposed scheme by
implementing a prototype system which shows the effectiveness of this
method.
In this paper a novel approach for the automatic representation of
pictures on mobile devices is proposed. With the wide diffusion of
mobile digital image acquisition devices, the need for managing a large
number of digital images is quickly increasing. In fact, the storage
capacity of such devices allow users to store hundreds or even
thousands, of pictures that, without a proper organization, become
useless. Users may be interested in using (i.e., browsing, saving,
printing and so on) a subset of stored data according to some particular
picture properties. A content-based description of each picture is
needed to perform on-board image indexing. In our work, the images are
analyzed and described in three representation spaces, namely, faces,
background and time of capture. Faces are automatically detected, and a
face representation is produced by projecting the face itself in a
common low dimensional eigenspace. Backgrounds are represented with
low-level visual features based on RGB histogram and Gabor filter bank.
Temporal data is obtained through the extraction of EXIF (Exchangeable
Image File Format) data. Faces, background and time information of each
image in the collection is automatically organized using a mean-shift
clustering technique. Significance of clustering has been evaluated on a
realistic set of about 1000 images and results are promising.
The emergence of
multicore platforms has tremendous potential for achieving real-time
performance of complex computer vision algorithms. However, these
applications must run on embedded, mobile platforms with stringent size
weight, power, and cost constraints. High utilization of local storage
on execution cores and low-latency, high-bandwidth data transfers
between this storage and main memory are critical for real-time mobile
system performance. General purpose processors employ hardware
techniques, such as high-speed bus architecture and efficient data
arbitration schemes, to address the memory bandwidth gap. However, these
techniques are insufficient for mobile systems requirements. Concurrent
algorithmic and architectural optimizations are necessary. This paper
uses concurrency to minimize data transfer latency when executing video
surveillance algorithms on multicore embedded architectures. It
introduces cat-tail DMA, a technique that provides low-overhead,
globally-ordered, non-blocking DMA transfers. Using this technique, data
transfer latencies are reduced by over 30% for background modeling
applications, while the local core storage utilization is increased by
60% over existing techniques.
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