Minh Tran

A random perturbation-based scheme for pairwise key establishment in sensor networks

A prerequisite for secure communications between two sensor nodes is that these nodes exclusively share a pairwise key. Although numerous pairwise key establishment (PKE) schemes have been proposed in recent years, most of them have no guarantee for direct key establishment, no resilience to a large number of node compromises, no resilience to dynamic network topology, or high overhead. To address these limitations, we propose a novel random perturbation-based (RPB) scheme in this paper. The scheme guarantees that any two nodes can directly establish a pairwise key without exposing any secret to other nodes. Even after a large number of nodes have been compromised, the pairwise keys shared by non-compromised nodes remain highly secure. Moreover, the scheme adapts to changes in network topology and incurs low computation and communication overhead. To the best of our knowledge, the RPB scheme is the only one that provides all these salient features without relying on public key cryptography. Through prototype-based evaluation, we show that the RPB scheme is highly efficient and practical for current generation of sensor nodes. In particular, to support a sensor network with up to 216 nodes, establishing a pairwise key of 80 bits between any two 8-bit, 7.37-MHz MICA2 motes only requires about 0.13 second of CPU time, 0.33 KB RAM space, and 15 KB ROM space per node.

Peers-assisted dynamic content distribution networks

Content distribution networks (CDNs) have been proposed to primarily distribute Web and some limited streaming audio/video content over the Internet. Current CDNs consist of fixed content nodes placed at strategic locations on the Internet to improve the service latency and to reduce server and network load. Although the approach of delivering content with a fixed CDN has enjoyed some successes, it is often difficult to upgrade and extend a CDN to serve more users due to a very high deployment cost. In this paper, we propose that a CDN be agile while delivering content. We make the case for a dynamic CDN architecture in which a CDN leverages local peers to deliver the CDNs content to local users. We define a formal problem for using peers to increase the capacity of a CDN and we propose an algorithm to help a CDN to dynamically recruit local peers to be part of the CDN. The CDN and the recruited local peers cooperate to serve content to other local users. Our performance evaluation shows promising results with the new dynamic CDN architecture. Our simple CDN growing strategies dramatically improve the average service latency in streaming video content

Effect of citrate ratio and temperature on gold nanoparticle size and morphology

Gold nanoparticles (Au NPs) were synthesized by the citrate reduction method. The evolution of NP size and morphology was closely studied by varying temperature and citrate to gold precursor (Na3Ct/HAuCl4) ratio. The reaction temperatures below 100 °C were mainly studied. A Na3Ct/HAuCl4 ratio range of 1.25:1 to 4.33:1 was the focus of our investigation. The NP size and morphology was strongly influenced by the Na3Ct/HAuCl4 ratio, while the temperature played a subtle role. The reaction times were also monitored. The higher concentration samples required almost an order of magnitude longer reaction time compared to the low concentration samples.

On using a CDN’s infrastructure to improve file transfer among peers

Content Distribution Network (CDN) technology has been proposed to deliver content from content nodes placed at strategic locations on the Internet. However, only companies or organizations, who can pay for the services of CDNs, have the privilege of using CDNs to distribute their content. Individual users (peers) have to resort to more economical peer-to-peer (P2P) technologies to distribute their content. Although P2P technologies have demonstrated tremendous successes, they have inherent problems such as the instability and the limited bandwidth of peers. In this paper, we propose a new approach to build bandwidth bounded data distribution trees inside a CDN so that external peers can leverage the power of a CDN’s infrastructure for distributing their content. Our performance evaluation shows that, with some limited help from a CDN, the content distribution time among peers can be speeded up from 1.5 to 3 times.

Distributed core selection with QoS support

Core-based routing with quality of service (QoS) support is essential in facilitating multi-sender multimedia multicast applications such as video conferencing and virtual collaboration applications. In this paper, we introduce a new distributed core selection protocol that has the following desirable properties. First, the protocol utilizes a new distributed primary core selection algorithm that selects as many primary cores per multicast group as necessary, to maximize the number of group members with satisfied QoS requirements. Second, the protocol is distributed, preventing a single router from becoming a hot spot and a single point of failure during core selection. Lastly, the protocol employs a distributed backup core selection algorithm to provide quick recovery should some primary cores fail. Our analytical experiments show that the proposed protocol significantly satisfies more group members with noticeably less communication overhead than a recent core selection algorithm with QoS support using a single core.

Design dual-band microstrip monopole antenna for 3G mobile handsets

This paper concentrates on studying, designing and manufacturing a dual-band and high-bandwidth antenna applied for 3G mobile handsets. This antenna can work in GSM/UMTS bands by generating two resonant modes of 900 MHz and 1900 MHz frequencies. Antenna is printed on FR4 substrate with size of 58 mm × 80 mm, thickness of 1.6 mm and relative permittivity of 4.4. The proposed antenna is experimentally studied.

A case for a generalized periodic broadcast server: design, analysis, and implementation

Periodic broadcast is an effective paradigm for large-scale dissemination of popular videos. Considerable research efforts have gone into designing many excellent periodic broadcast protocols in terms of minimizing the server network bandwidth and the client resources. However, there are only a few implementations of periodic broadcast protocols available. This is probably because little has been documented on how the memory and disk bandwidth resources of a periodic broadcast server should be allocated. In this paper, we present a generalized periodic broadcast server (GPBS) model that supports any periodic broadcast protocol. Based on this model, we formulate and solve a new optimization problem whose solution provides insights into the server s memory and disk resources allocation. We also discuss our prototype implementation of GPBS. Our work facilitates future implementation and deployment of many existing periodic broadcast protocols.

Exploring the Efficacy of Platinum and Palladium Nanostructures for Organic Molecule Detection via Raman Spectroscopy

Noble transition metals, like palladium (Pd) and platinum (Pt), have been well-known for their excellent catalytic and electrochemical properties. However, they have been considered non-active for surface enhanced Raman spectroscopy (SERS). In this work, we explore the scattering contributions of Pd and Pt for the detection of organic molecules. The Pd and Pt nanostructures were synthesized on silicon substrate using a modified galvanic displacement method. The results show Pt nanoparticles and dendritic Pd nanostructures with controlled density and size. The influence of surfactants, including sodium dodecyl sulfate and cetyltrimethylammonium bromide, on the size and morphology of the nanostructures was investigated. The Pd and Pt nanostructures with a combination of large size and high density were then used to explore their applicability for the detection of 10−5 M Rhodamine 6G and 10−2 M paraoxon.

OCS: An effective caching scheme for video streaming on overlay networks

Video streaming is vital for many important applications such as distance learning, digital video libraries, and movie-on-demand. Since video streaming requires significant server and networking resources, caching has been used to reduce the demand on these resources. In this paper, we propose a novel collaboration scheme for video caching on overlay networks, called Overlay Caching Scheme (OCS), to further minimize service delays and loads placed on an overlay network for video streaming applications. OCS is not a centralized nor a hierarchical collaborative scheme. Despite its design simplicity, OCS effectively uses an aggregate storage space and capability of distributed overlay nodes to cache popular videos and serve nearby clients. Moreover, OCS is light-weight and adaptive to clients’ locations and request patterns. We also investigate other video caching techniques for overlay networks including both collaborative and non-collaborative ones. Compared with these techniques on topologies inspired from actual networks, OCS offers extremely low average service delays and approximately half the server load. OCS also offers smaller network load in most cases in our study.

Core selection with end-to-end QoS support

Core-based routing with Quality of Service (QoS) support is essential to facilitate multi-sender multimedia multicast applications such as video conferencing and virtual collaboration applications. In this paper, we introduce (i) a new application-level service class framework that allows group members to easily indicate their desired service quality and (ii) the use of as many cores per group as necessary in corebased routing to maximize the number of group members with satisfied QoS requirements. Under the service class framework, we formulate the novel core selection problem that selects as many cores as necessary while maximizing the number of satisfied group members. We propose a new core selection algorithm to address the problem and provide a complete core selection protocol using the algorithm. Experimental results show that our core selection algorithm performs as well as the optimal algorithm and significantly outperforms a recent core selection algorithm with QoS support using a single core.