Jung-Shian Li

Distributed K-coverage self-location estimation scheme based on Voronoi diagram

The success of many wireless sensor network (WSN) applications, such as moving target tracking or environment monitoring, is dependent upon achieving ‘k-coverage’ of the sensed area, that is every point in the surveillance area is monitored by at least k sensors. This study presents a novel distributed self-location estimation scheme based on a Voronoi diagram to achieve k-coverage in a WSN with mobile nodes. The simulation results show that the proposed scheme effectively to perform k-coverage within the sensing field and fast convergent to fulfil more than 88% k-coverage ratio following three movements for the minimal required sensor deployment.

Voronoi-based relay placement scheme for wireless sensor networks

Energy consumption is a crucially important issue in battery-driven wireless sensor networks (WSNs). In most sensor networks, the sensors near the data collector (i.e. the sink) become drained more quickly than those elsewhere in the network since they are required to relay all of the data collected in the network to the sink. Therefore more balanced data paths to the sink should be established in order to extend the lifetime of the sensor network. Accordingly, a novel relay deployment scheme for WSNs based on the Voronoi diagram is proposed. The proposed scheme is applicable to both two-dimensional and three-dimensional network topologies and establishes effective routing paths that balance the traffic load within the sensor network and alleviate the burden on the sensors around the sink. Simulation results indicate that the number of relays deployed in the proposed scheme is similar to that deployed in the predetermined location scheme and is significantly less than that deployed in the minimum set cover scheme. Furthermore, the lifetime of the sensor network containing relay nodes deployed using the current scheme is longer than that achieved using either the predetermined location scheme or the minimum set cover scheme.

A hidden mutual authentication protocol for low-cost RFID tags

Radio-frequency identification (RFID) technology enables the identification and tracking of objects by means of the wireless signals emitted by a tag attached to the objects of interest. Without adequate protection, however, malicious attackers can easily eavesdrop, scan or forge the information within the tag, thereby threatening the integrity of the system. Previous research has shown that the basic security requirements of RFID systems, i.e. identity authentication, information privacy and location privacy, can be satisfied using conventional cryptographic components. However, such components are expensive, and therefore conflict with the general requirement for low-cost tag designs. Accordingly, this paper presents a low-cost challenge-response security protocol designated as the hidden mutual authentication protocol (HMAP) to accomplish both a mutual authentication capability between the tag and the reader and information privacy. The results show that HMAP provides an efficient means of concealing the authentication messages exchanged between the tag and the reader and is robust toward replay attacks. In addition, it is shown that HMAP is easily extended to provide complete location privacy by utilizing a hash function to generate different tag identifiers in each authentication session. Copyright

An Efficient Time-Bound Collision Prevention Scheme for RFID Re-Entering Tags

The efficiency of RFID applications is severely degraded when multiple tags transmit their IDs simultaneously. As a result, many anticollision algorithms have been proposed for reducing collisions at the reader. However, these algorithms focus only on the tags within communication range of the reader in the previous or current frames. That is, they ignore tags which move out of range of the reader in one frame, but then move back within range several frames later. As a result, the identification performance of the reader is seriously degraded. The present study analyzes the effect of re-entering tags on the performance of three common anticollision algorithms and proposes a new reblocking algorithm (RBA) to alleviate the problem. The lower and upper bounds of the collision probability for re-entering tags are derived using a multinomial coefficients approach. The performance evaluation results show that the proposed algorithm consumes fewer cycles and provides a more robust identification performance than existing blocking algorithms in real-world RFID systems characterized by re-entering tags.

Topology-transparent link activation scheduling schemes for multihop CDMA ad hoc networks

In this paper, we study topology-transparent node activation transmission scheduling protocols for multihop TDMA ad hoc networks. We focus on quality-of-service (QoS) provisioning for each node, particularly when node mobility is considered. A framework for topology-transparent node activation scheduling based on theory of block designs is proposed. The proposed framework guarantees conflict-free transmission slots for each node in each frame by mathematical properties of block designs. Based on two mapping methods, called mapping I and mapping II, the proposed framework can be categorized into two types. With the proposed framework, we study and evaluate some series of block constructions. We then propose several topology-transparent scheduling algorithms based on the results derived. The proposed schemes maximize the minimum system throughput. Numerical results show that the proposed algorithms can outperform existing algorithms in achieving a higher minimum system throughput.

Topology-Independent Link Activation Scheduling Schemes for Mobile CDMA Ad Hoc Networks

In this paper, we study medium access control (MAC) protocols with quality-of-service (QoS) support, that is, topology-independent link activation transmission scheduling, for mobile code-division multiple-access (CDMA) ad hoc networks. QoS provisioning for each communication link is guaranteed without the need to adopt transmission schedules in mobile environments. An interference model, which captures the difference between transmission and interference ranges, is considered. Under this interference model, an approach to guaranteeing conflict-free transmission slots in each frame (QoS provisioning) for each communication link is proposed. Compared with the previously known method, superior performance is obtained. We then present a topology-independent link activation scheduling framework based on the theory of group-divisible (GD) designs. By the mathematical properties of GD designs, the proposed framework guarantees conflict-free transmission slots in each frame for each communication link, without the overhead due to the recomputation of transmission schedules when the network topology changes. With the proposed framework, we study and evaluate one series of GD design constructions. Based on the results derived, topology-independent link activation scheduling algorithms are then presented. The proposed schemes are designed for different objectives: maximizing the minimum system throughput and/or minimizing the schedule frame length. Numerical results show that the proposed algorithms outperform previously known schemes. The average performance of the proposed schemes is also derived.

Improve routing trust with promiscuous listening routing security algorithm in mobile ad hoc networks

In this paper, we propose a novel routing security algorithm, called promiscuous listening routing security algorithm, for mobile hosts to detect malicious attacks in the middle, such as packet dropping or modifying. After identifying the malicious nodes, mobile hosts can isolate these nodes. The proposed algorithm is distributed and does not need any communications between hosts. It only switches on the promiscuous listening mode in hosts. Through detailed simulations, the performance of data transmission is improved by the proposed algorithm. Even only when parts of hosts employ the algorithm intermittently, the improvement is obvious.

VoIP secure session assistance and call monitoring via building security gateway

A secure architecture is proposed in the home/office networking environment with a special appliance, called Building Security Gateway (BSG), for cheap SIP devices and unsupported soft user agents (UAs) performing security functions successfully, such as construction of secure sessions and encrypting/decrypting media. Therefore, we apply BSG procedure to VoIP for getting secure session. Furthermore, VoIP call monitoring and intercepting functions are also implemented in BSG. Secure session monitoring is supported in this architecture. A prototype BSG is built in a home/office network, and BSG-based session mobility cases between UAs are examined and the protocol primitives for security and call intercepting are verified. Copyright

An Efficient Superpeer Overlay Construction and Broadcasting Scheme Based on Perfect Difference Graph

Two-layer hierarchy unstructured peer-to-peer (P2P) systems, comprising an upper layer of superpeers and an underlying layer of ordinary peers, are commonly used to improve the performance of large-scale P2P systems. However, the optimal superpeer network design involves several requirements including superpeer degree, network diameter, scalability, load balancing, and flooding performance. A perfect difference graph has desirable properties to satisfy the above design rationale of superpeers overlay network. This paper proposes a two-layer hierarchical unstructured P2P system in which a perfect difference graph (PDG) is used to dynamically construct and maintain the superpeer overlay topology. In addition, the broadcasting performance of the P2P system is enhanced through the use of a PDG-based forwarding algorithm, which ensures that each superpeer receives just one lookup query flooding message. The theoretical results show that the proposed system improves existing superpeer hierarchical unstructured P2P systems in terms of a smaller network diameter, fewer lookup flooding messages, and a reduced average delay, and the experimental results show that the proposed two-layer hierarchy P2P system performs very well in the dynamic network environment.

Providing proportional differentiated services using PLQ

The focus of this paper is to provide a scheme that a router should treat each packet differently according to its class. We propose a novel scheme that can provide both delay and loss proportional differentiated services. The scheme employs a probabilistic longest queue first (PLQ) mechanism, which reacts effectively to the queue-length fluctuation of each class. The proposed scheme is proven to achieve differentiated services after detailed evaluations. Furthermore, its implementation cost is much less than traditional schemes, such as WTP and PLR.