Dong-Ryeol Shin

A Survey of Intelligent Transportation Systems

With the rapid increase of modern economical and technical development, the Intelligent Transportation System (ITS) becomes more and more important and essential for a country. Practice shows that relying only on the construction of transport infrastructure and expansion does not fundamentally solve the existing transportation problems and sometimes it even makes such problems more severe. So every country is actively exploring ITS technology to solve traffic problems. But due to the different situations of the fund investment, current technology merit and the various traffic problems for each country, the development level of ITS and research areas are distinct. This paper focuses on the comparison and analysis of international ITS research and integrates the ITS technologies to design an integration model. We regard the traffic problem as not only a problem for individual countries, but also a global topic. Countries should improve the technology communication, update and enhance ITS techniques.

Improved Particle Filtering-Based Estimation of the Number of Competing Stations in IEEE 802.11 Networks

This letter proposes a new method to estimate the number of competing stations in IEEE 802.11 networks. Due to the nonlinear/non-Gaussian nature of measurement model, a nonlinear filtering algorithm, called the Gaussian mixture sigma point particle filter (GMSPPF), is proposed herein to estimate the number of competing stations. Since GMSPPF represents a better alternative to the conventional extended Kalman filter (EKF), unscented Kalman filter (UKF), particle filter (PF), and unscented particle filter (UPF) for nonlinear/non-Gaussian (or Gaussian) tracking problems, we apply this filter for IEEE 802.11 WLANs. GMSPPF provides a more viable means for tracking in any conditions the number of competing stations in IEEE 802.11 WLANs relative to EKF, UKF, PF, and UPF. Further, GMSPPF presents both high accuracy as well as prompt reactivity to changes in the network occupancy status. For the more accurate method (GMSPPF), the combined access mode is shown to maximize the system throughput by switching between the basic access mode and the RTS/CTS access mode.

Handoff Triggering and Network Selection Algorithms for Load-Balancing Handoff in CDMA-WLAN Integrated Networks

This paper proposes a novel vertical handoff algorithm between WLAN and CDMA networks to enable the integration of these networks. The proposed vertical handoff algorithm assumes a handoff decision process (handoff triggering and network selection). The handoff trigger is decided based on the received signal strength (RSS). To reduce the likelihood of unnecessary false handoffs, the distance criterion is also considered. As a network selection mechanism, based on the wireless channel assignment algorithm, this paper proposes a context-based network selection algorithm and the corresponding communication algorithms between WLAN and CDMA networks. This paper focuses on a handoff triggering criterion which uses both the RSS and distance information, and a network selection method which uses context information such as the dropping probability, blocking probability, GoS (grade of service), and number of handoff attempts. As a decision making criterion, the velocity threshold is determined to optimize the system performance. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations. The optimal velocity threshold is adjusted to assign the available channels to the mobile stations using four handoff strategies. The four handoff strategies are evaluated and compared with each other in terms of GOS. Finally, the proposed scheme is validated by computer simulations.

A novel vertical handoff strategy for integrated IEEE 802.11 WLAN/CDMA networks

The integration of WLANs and CDMA networks has recently evolved into hot issue. We propose a vertical handoff algorithm between WLAN and CDMA network. In this algorithm, a vertical handoff is classified into handoff decision making and MIP (mobile IP) registration process. Then, a handoff initiation is decided by the received signal strength (RSS). To reduce the unnecessary handoff probability, we consider a hand-off initiation model based on the criteria of RSS. As a mechanism of network selection, we also propose a context based network selection and the corresponding algorithms between WLAN to CDMA network, based on wireless channel assignment. We focus on a handoff initiation criteria which uses both the RSS and the network selection method which uses context information such as dropping probability, blocking probability, GOS (grade of service), velocity. As a decision making criterion, velocity threshold is determined to optimize the system performance. The optimal velocity threshold is adjusted to assign available channels to the mobile stations. The proposed scheme is validated by computer simulation.

Cluster Head Selection for Equal Cluster Size in Wireless Sensor Networks

The goal of wireless sensor networks is to collect sensing data on a specific region using wireless communication. The sink node gathers all local sensing data, processes them, and transmits them to users who use sensor networks. Generally, sensor nodes are low-cost, low power devices with limited sensing, computation and wireless communication capabilities. A sensor network applies to multi-hop communication on a large-scale network. As neighboring sensor nodes have similar data, clustering is an effective technique for ‘data-aggregation’. In the multi-hop based cluster formation technique, it is necessary that the number of cluster member nodes should be distributed equally due to the balance of cluster formation. Therefore, this paper proposes a method of cluster head selection to form equal cluster sizes in wireless sensor networks

Multi-Hop Routing-Based Optimization of the Number of Cluster-Heads in Wireless Sensor Networks

Wireless sensor networks require energy-efficient data transmission because the sensor nodes have limited power. A cluster-based routing method is more energy-efficient than a flat routing method as it can only send specific data for user requirements and aggregate similar data by dividing a network into a local cluster. However, previous clustering algorithms have some problems in that the transmission radius of sensor nodes is not realistic and multi-hop based communication is not used both inside and outside local clusters. As energy consumption based on clustering is dependent on the number of clusters, we need to know how many clusters are best. Thus, we propose an optimal number of cluster-heads based on multi-hop routing in wireless sensor networks. We observe that a local cluster made by a cluster-head influences the energy consumption of sensor nodes. We determined an equation for the number of packets to send and relay, and calculated the energy consumption of sensor networks using it. Through the process of calculating the energy consumption, we can obtain the optimal number of cluster-heads in wireless sensor networks.

Mobile Healthcare System based on Collaboration between JADE and OSGi for Scalability

The mobile healthcare system has not been standardized and has been developed as an embedded system lacking interoperability. We are going to eventually face such problems as excessive load in the network, which is caused by the uncontrolled spread of the system and un-guaranteed interoperability among the heterogeneous systems. We suggest the possibility that the JADE and the OSGi can be accepted as a solution for the above problems. In this paper, we tried to develop interoperating technology between the OSGi and the JADE.

A State-Space Approach to Multiuser Parameters Estimation Using Central Difference for CDMA Systems

In this paper, it is shown that a state-space model applies to the code-division multiple-access (CDMA) channel, and Central Difference Filter (CDF) produces channel estimates with the minimum mean-square error (MMSE). This result may be used as compare to Extended Kalman Filter (EKF) which used as channel estimator in CDMA system. The main purpose of this paper is to compare robustness of channel estimator for realistic rapidly time-varying Rayleigh fading channels. To overcome the highly nonlinear nature of time delay estimation and also improve the accuracy, consistency and efficiency of channel estimation, an iterative nonlinear filtering algorithm, called the CDF has been applied in the field of CDMA System. The proposed channel estimator has a more near-far resistant property than the conventional Extended Kalman Filter (EKF). Thus, it is believed that the proposed estimator can replace well-known filters, such as the EKF. The Cramer-Rao lower bound (CRLB) is derived for the estimator, and simulation result show that it is nearly near-far resistant and clearly outperforms the EKF.

A Remote Control Service for OSGi-based Unmanned Vehicle Using SmartPhone in Ubiquitous Environment

Recently, Nationally and internationally, increased interest in electric vehicles for the development of vehicles has also been done with. In addition, due to the development of Smart phone to integrate technology in the development of life is being made. In this paper, according to this flow of unmanned electric vehicles we proposed the architecture that the control the vehicle and management by the Smart phone. We use OSGi framework for designed this architecture. OSGi middleware starts at home, but recent increases in the API, the increase of services about the vehicles and possible benefits are extended to mobile. We aim to create a new service as refer to useful OSGi services. We were converting to control the car, make OSGi modules and the mobile application. As a Smart phone, we studied how to manage the vehicle. In addition, this part seems to control the vehicle remotely. We performed the result that made of our architecture.

Adaptive multiuser receiver with joint channel and time delay estimation of CDMA signals based on the square-root unscented filter

The paper discusses an adaptive multiuser receiver for CDMA systems in which the scaled unscented filter (SUF) and the square root unscented filter (SURF) are used for joint estimation and tracking of the code delays and multipath coefficients of the received CDMA signals. The proposed channel estimators are more near-far resistant than the conventional extended Kalman filter (EKF) and present lower complexity than the conventional particle filter (PF) based methods. To present meaningful performance measures, the modified Cramer-Rao lower bound (CRLB) and computational complexity metrics are derived for the proposed and existing channel estimators. Computer simulation results demonstrate the superior performance of the proposed channel estimators. The proposed estimators are also shown to exhibit lower complexity relative to the PF.