Catálogo de publicaciones - libros

Advances in wireless and mobile communication technologies have enabled the development of various RFID-based systems and applications in addition to the extension of the tag reading range of mobile readers. Thus, it has become commonplace that multiple readers concurrently attempt to read tags within ranges of the readers. However, this concurrent access among multiple mobile readers brings about a new problem called reader collision, where a reader’s transmission is interfered by other readers. There have been several studies focusing on solving the reader collision problem. These studies employ time division, frequency division, space division, or the centralized scheduling approach. In this paper, a cooperative, distributed reader collision avoidance algorithm is introduced. In particular, the proposed DiCa (Distributed Tag Access with Collision-Avoidance) is considerably suitable for energy-efficient wireless mobile network environments cooperated with RFID, since the DiCa is capable not only of avoiding collisions, but also changing power states autonomously through simple interaction of adjacent readers.

In this paper, we present a high-speed RFID data filtering engine designed to carry out filtering under the conditions of massive data and massive filters. We discovered that the high-speed RFID data filtering technique is very similar to the high-speed packet classification technique which is used in high-speed routers and firewall systems. Actually, our filtering engine is designed based on existing packet classification algorithms, Bit-Parallelism and Aggregated Bit Vector (ABV). In addition, we also discovered that there are strong temporal relations and redundancy in the RFID data filtering operations. We incorporated two kinds of caches, tag and filter caches, to make use of this characteristic to improve the efficiency of the filtering engine. The performance of the proposed engine has been examined by implementing a prototype system and testing it. Compared to the basic sequential filter comparison approach, our engine shows much better performance, and it gets better as the number of filters increases.

Radio Frequency Identification (RFID) systems have become popular for identifying not only objects but also persons. For example, in supply chain applications, the company can constantly track the movements of goods. Also, for Body Area Network or Personal Area Work, the tag is used for identifying a person. However, the movements and current locations of goods and a person’s activity profiles are the sensitive information and should be kept secret. This paper develops the interaction protocols between readers and tags to address this privacy issue of protecting tagged objects from tracking and tracing by non-authorized readers.

In this paper, we propose a new medium access control protocol for wireless sensor networks, named LE-MAC (Latency and Energy aware MAC) that aims to minimize data delivery latency as well as energy consumption. To achieve both goals, we exploit a physical carrier sensing feature in CSMA/CA and combine it with a cross-layer technique. When nodes that are in routing path between source and sink become aware of the traffic based on the carrier signal, they wakeup once more during the sleep period for transmitting data over multiple hops. We evaluated the proposed scheme compared with S-MAC on the ns-2 simulator. The results show that our scheme outperforms S-MAC protocols in balancing the need of low latency and energy consumption.

In this paper, we propose a new self-organization scheme, DICSION (Data-centrIC Self-organizatION), which can improve the energy efficiency and prolong network lifetime of wireless sensor networks. Since a large number of sensor nodes are densely deployed, neighboring nodes may be very close to each other. Therefore, we assume that sensor nodes have a high possibility to collect the duplicate data about the same event. DICSION can considerably reduce the energy consumption because a zone head only can transmit and receive a representative data to base station or neighboring zone heads after zone formation. Our performance evaluation results demonstrate that DICSION outperforms to STEM.

Wireless sensor network consisting of a large number of small sensors is efficient in gathering data in a variety of environments. Since the sensor nodes operate on batteries, energy efficient operations are indispensable to maximize the lifetime of the network. Among the schemes proposed to improve the lifetime of the network, the cluster-based schemes aim to evenly distribute the energy consumption among all the nodes in the network. In this paper we propose an approach for finding an optimal number of clusters which allows minimal energy consumption of the network. The key idea of the proposed approach is to model the energy consumption with independent homogeneous spatial Poisson process, while considering the distribution of cluster-heads and other sensor nodes. With the number of cluster-heads obtained by the proposed approach, the energy consumption can be significantly reduced and consequently the lifetime of the sensor network is increased compared to the existing schemes. Computer simulation confirms this with practical operational environment.

Utilization of an ultrasound tracking system in wireless sensor networks is a well-known technique with low-cost and high-accuracy advantages in an indoor environment. In this paper, we present the implementation of an active tracking system based on an ultrasonic sensing device using the IEEE 802.15.4 compatible radio. IEEE 802.15.4 is used in wireless sensor networks because of its low power consumption and high bit-rate. Many of the technical issues for actual deployment of the system in an indoor environment are herein analyzed and solved.

In many applications of wireless sensor networks (WSNs), the location information of users is very important. In this paper we present a localization method without on-body sensor (LWOS). The basic idea is that when a person is standing between a pair of transceivers, the human body will attenuate the received signal. From the detected attenuation of Received Signal Strength Indication (RSSI), LWOS can detect and localize people directly utilizing the wireless communication in WSNs. No additional sensor is needed and users do not need to wear a sensor node any more. A signal-shielding device is used at the transmitter side to minify the interference of RSSI variability from multi-path effects. Experiment results show a good capability of localizing a single user in an indoor environment.

“Ubiquitous” has been the key buzzword in the research community as well as in everyday life these days. In Korea, ubiquitous become decorative words for many new products, which has not necessarily enough link to the world of ubiquitous. In research field, many public, private sectors research activities decorated with the word of “ubiquitous” has drawn so much attention, but still, little examples are shown which truly implements the ideals of “Ubiquitous”. In this paper, we review the research activities under the flag of “ubiquitous”, and then present possible research directions for proper research directions which can prompt practical incorporation of ubiquitous concept in the near future.

Sensor networks are characterized by their large-scale and unattended deployment that invites numerous critical attacks, thereby necessitating high-level security support for their intended applications and services. However, making sensor networks secure is challenging due mainly to the fact that sensors are battery-powered and it is usually very difficult to change or recharge their batteries. In this paper, we give a comprehensive overview of recent research results for securing such sensor networks, and then describe how to build a security framework, called a (LiSA), for sensor networks, which achieves via closely-coupled, mutually-complementary security solutions.