JMM Abstracts 

Vol.6 No.2 June, 2010

Recent Advances in Mobile and Multimedia Applications
Editorial (095-096)
Antonio Gentile and Salvatore Vitabile

Research Articles

Routing Efficiency in Wireless Sensor-Actor Networks (097-113)
Leonard Barolli, Tao Yang, Gjergji Mino, Fatos Xhafa, and Arjan Durresi 
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.

Node Control Methods To Reduce Power Consumption Using Push-Based Broadcast For Mobile Sesor Networks (114-127)
Takefumi Ogawa, Tatsuya Shinjo, Shinya Kitajima, Takahiro Hara, and Shojiro Nishio 
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.

Collada-Based File Format for Various Attributes of Realistic Objects in Networked VR Applications Supporting Various Peripherals (128-144)
Katsunori Miyahara and Yoshihiro Okada 
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 Flexible and Secure Access Control Scheme Using Social Behavior in Real World  (145-157)
Debasish Chakraborty,  Satoshi Ogawa, Gen Kitagata, Atushi Takeda, Kazuo Hashimoto, and Norio Shiratori 
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.

Automatic Image Representation and Clustering on Mobile Devices (158-169)
Marco La Cascia, Marco Morana, and Filippo Vella 
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.

Cat-Tail DMA: Efficient Image Data Transport for Multicore Embedded Mobile Systems (170-184)
Senyo Apewokin, Brian Valentine, Linda M. Wills, and Scott Wills
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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