Sheng-Shih Wang

Securing RFID systems conforming to EPC Class 1 Generation 2 standard

RFID, capable of remote automatic identification, is taking the place of barcodes to become electronic tags of the new generation. However, the information transmitted in the air could easily be intercepted and eavesdropped due to its radio transmission nature. On top of this, its prevalence has brought the stress on its security and privacy issues. EPC Class 1 Generation 2 (Gen 2) has served as the most popular standard for passive tags. Passive tags possess limited computation ability and capacity that just makes designing of the security protocol even more challenging. Researchers have proposed quite a few security protocols for RFID, but most of them are just too complicated to be implemented on Gen 2. Chien and Chen (2007) proposed a mutual authentication protocol conforming to this standard. However, it is found vulnerable to DoS attacks. Due to the bad properties of the CRC function used in the protocol, the claimed security objectives are also not met. Moreover, the database must use brute search for each tags authentication. This paper will give demonstrations on what have caused these weaknesses, and more of that, an improved protocol is also proposed which are free from worries of the problems mentioned above. The improved protocol could thus be applied in high security demanding environments.

LCM: A Link-Aware Clustering Mechanism for Energy-Efficient Routing in Wireless Sensor Networks

In wireless sensor networks, nodes in the area of interest must report sensing readings to the sink, and this report always satisfies the report frequency required by the sink. This paper proposes a link-aware clustering mechanism, called LCM, to determine an energy-efficient and reliable routing path. The LCM primarily considers node status and link condition, and uses a novel clustering metric called the predicted transmission count (PTX), to evaluate the qualification of nodes for clusterheads and gateways to construct clusters. Each clusterhead or gateway candidate depends on the PTX to derive its priority, and the candidate with the highest priority becomes the clusterhead or gateway. Simulation results validate that the proposed LCM significantly outperforms the clustering mechanisms using random selection and by considering only link quality and residual energy in the packet delivery ratio, energy consumption, and delivery latency.

Distributed direction-based localization in wireless sensor networks

Location awareness is an attractive research issue in the wireless sensor network (WSN). However, precise location information may be unavailable due to the constraint in energy, computation, or terrain. Additionally, several applications can tolerate the diverse level of inaccuracy in such geographic information. Thus, this paper presents a direction-based localization scheme, DLS, whose main goal is for each sensor to determine its direction rather than its absolute position. The direction we are concerned with is the one relative to the sink. Motivated by the proposed spatial locality property, DLS considers multiple messages received for a sensor to determine its direction. Furthermore, a novel scheme, anchor deployment strategy, is also proposed for the improvement of the estimated correctness in direction of the sensor within the communication range of the sink. With the aid of the virtual dual direction coordinate (VDDC) system, DLS is able to efficiently and precisely position sensors around the axes. We evaluate DLS via simulations in terms of various numbers of sensors and communication ranges for the scenarios with different numbers of directions. The average correct rates in DLS reach approximately 94%, 86%, and 81% for the networks with 4, 8, and 16 directions, respectively. DLS achieves outstanding performance for the high density networks as well. In addition, DLS also works well regardless of the sink placement. Overall, simulation results validate the practicality of DLS, and show that DLS can effectively achieve direction estimation.

CollECT: Collaborative event detection and tracking in wireless heterogeneous sensor networks

Tracking is an important application in wireless sensor networks (WSNs), especially for the urgent event of interest. Recent research has paid much attention to the WSN wherein all sensor nodes are identical in sensing units, but the utilization of different types of sensor nodes has not been widely explored. In the paper, we propose a fully distributed protocol, CollECT, to event detection and tracking in wireless heterogeneous sensor networks (WHSNs), which consists of various types of sensor nodes with different sensing units. The main idea of CollECT is collaboration, by which the same type of sensor nodes construct the attribute region, represented by a convex polygon, whereas the different types of sensor nodes determine whether the event occurs. In CollECT, three procedures, vicinity triangulation, event determination, and border sensor node selection, are proposed to construct the attribute region, to determine the occurrence of the event, and to select border sensor nodes to stand for the event boundary, respectively. Simulation results validate the performance of CollECT in terms of accuracy of event tracking and fitness of the border sensor nodes selected. Approximately 87% sensor nodes within the event region can be correctly identified on average. Additionally, the border sensor nodes selected by CollECT are beneficial to efficiently stand for the event boundary.

PassCAR: A passive clustering aided routing protocol for vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) are a promising architecture for vehicle-to-vehicle communications in the transportation field. However, the frequent topology changes in VANETs create many challenges to data delivery because the vehicle velocity varies with time. Thus, designing an efficient routing protocol for stable and reliable communication is essential. Existing studies show that clustering is an elegant approach to efficient routing in a mobile environment. In particular, the passive clustering (PC) mechanism has been validated as a more efficient approach compared to traditional clustering mechanisms. However, the PC mechanism was primarily designed for mobile ad hoc networks (MANETs), and may be unsuitable for constructing a cluster structure in VANETs because it does not account for vehicle behavior and link quality. In this paper, we propose a passive clustering aided routing protocol, named PassCAR, to enhance routing performance in the one-way multi-lane highway scenario. The main goal of PassCAR is to determine suitable participants for constructing a stable and reliable cluster structure during the route discovery phase. Each candidate node self-determines its own priority to compete for a participant using the proposed multi-metric election strategy based on metrics such as node degree, expected transmission count, and link lifetime. Simulation results show that, compared with the original PC mechanism, PassCAR not only increases the successful probability of route discovery, but also selects more suitable nodes to participate in the created cluster structure. This well-constructed cluster structure significantly improves the packet delivery ratio and achieves a higher network throughput due to its preference for reliable, stable, and durable routing paths.

CollECT: Collaborative Event deteCtion and Tracking in Wireless Heterogeneous Sensor Networks

Event detection and tracking are attractive research issues in the wireless sensor network (WSN). The paper proposes a fully distributed protocol, CollECT, to event detection and tracking in a Wireless Heterogeneous Sensor Network (WHSN), composed of many kinds of sensors. In CollECT, three major procedures, vicinity triangulation, event determination, and border sensor selection are used to construct the logical triangle in the vicinity of a sensor, to determine the event, and to select the border sensor to identify the event boundary, respectively. The procedures perform repeatedly to both detect and track events. Simulation results demonstrate that CollECT is promising for event detection and tracking due to satisfactory event accuracy and reasonable fitness of border sensors.

An Effective Path Selection Metric for IEEE 802.16-based Multi-hop Relay Networks

For usage models of coverage extension and throughput enhancement, a novel framework, Multi-hop Relay (MR) network, which consists of various kinds of stations such as the base station (MR-BS), the relay station (RS), and the mobile station (MS) is proposed by the study group under the IEEE 802.16 WG. With the help of RSs, data transmissions between MR-BS and MS become more reliable and effective. In the paper, we propose a new measurement, called effective radio resource index (ERRI), to indicate the effectiveness of radio resource of a link used to transmit data. The ERRI of a link is normalized and compared to the metric defined as the bandwidth unit required for transmitting a fixed amount of data using 64-QAM CC 5/6 with repetition 1. Additionally, a cost function of a relay path between MR-BS and MS is also proposed to efficiently facilitate the evaluation of path selection schemes for MR networks. Simulation results show that the relay path selection scheme with ERRI considerations is indeed effective in terms of network throughput.

VEHICLE CLASSIFICATION USING ADVANCED TECHNOLOGIES

Applying advanced technologies to existing problem domains is a highly desirable approach in many research areas. Among these techniques, image processing has been shown useful in transportation fields for such tasks as traffic pattern recognition, data collection, accident detection, and pavement evaluation. The integrated model with artificial neural networks (ANNs) has promising potential applications. The image processing and ANN model are combined to explore the feasibility of vehicle classification in real-world situations. Three methods were developed during the research process: ground segmentation, background subtraction, and window segmentation. The first two methods were used to separate the objects of scene and nonscene from the actual traffic image. To reduce the complexity of neural networks, the image was divided into 16 windows and three characteristics (occupation rates of vehicles, of horizontal image lines, and of vertical image lines) of each window were extracted to generate 48 factor...

LASER: A load-aware spectral-efficient routing metric for path selection in IEEE 802.16j multi-hop relay networks

For coverage extension and throughput enhancement, the IEEE 802.16j task group has developed a novel multi-hop relay network architecture to enable typical IEEE 802.16 networks to achieve data transmission between base stations and mobile stations via a multi-hop path with relay stations deployment. How to determine an effective path for throughput gain and overhead reduction is emerging and crucial in IEEE 802.16 multi-hop relay networks. This paper introduces a load-aware spectral-efficient routing metric, called LASER, to evaluate paths, and proposes an efficient scheme to determine a proper path. Based on the LASER metric, the proposed path selection scheme formulates the path cost as the summation of cost of each link, and the path with the minimum cost will be selected as the appropriate one. Simulation results show that the proposed LASER-based path selection scheme significantly outperforms existing path selection schemes in network throughput and map overhead.

Performance evaluation of passive clustering based techniques for inter-vehicle communications

Inter-vehicle communication is one of the most significant transmission behaviors for diverse transportation applications in the vehicular ad hoc network (VANET). The existing studies have showed that clustering is a promising solution to data communication under the mobile environment, and especially the passive clustering (PC) technique is the efficient one compared to other clustering techniques. However, the original PC technique does not take into account the unique characteristics of VANETs, and thus it may face many challenges to inter-vehicle communication. This paper proposes three PC-based techniques, called VPCs, to determine the suitable vehicles to become the main participants in cluster structure formation. VPCs consider numerous metrics, such as vehicle density, link quality, and link sustainability. Simulation results demonstrate that VPCs collectively exhibit better performance than the PC technique in packet delivery ratio, delivery delay, and network throughput.