Hyun-Sung Park

Position-Based DTN Routing in metropolitan bus network

DTN (Delay- or disruption- tolerant networking) is often found in heterogeneous networks, mobile or extreme terrestrial networks, or planned networks in space. In this paper, we examine the metropolitan bus network as a research target of DTN. We analyze the metropolitan bus network through spatial and temporal modeling by reusing the existing database of the Bus Information System (BIS). Based on our analyses, we design and suggest an appropriate DTN routing scheme for the metropolitan bus network - Position-Based DTN Routing Using Polarity. This approach uses position-based routing instead of address-based routing by exploiting the infrastructural help from bus stops via the real-time location service of BIS. We simulate our scheme by using WLAN for the wide-band DTN communication, and evaluate it by comparison with the traditional epidemic routing and strategic protocol steps of our own algorithm step by step. The results show our scheme achieves reasonably high performance in terms of packet delivery ratio and delay.

Modeling and analysis of DTN in metropolitan bus network

DTN is an approach to communicate in easily disrupted or delayed networks. Examples of such networks are often found in heterogeneous networks, mobile or extreme terrestrial networks, or planned networks in space. Recently, many studies have used wireless LAN in a DTN environment because the WLAN offers easy installation, competitive price, and popular Wi-Fi devices. This paper is about modeling and analyzing the metropolitan bus network as a DTN environment. Modern metropolitan bus networks already offer IT services such as BIS; however, their networks may be appropriate for communicating narrow-band data in real time, but not for wide-band data in a DTN environment. In order to apply WLAN as an alternative solution for communicating wide-band data in DTNs, we need to understand the DTN characteristics of metropolitan bus networks. We perform spatial, temporal, and mobility modeling via simulation. Based on our simulation results, we provide qualitative and quantitative analysis reports about the use of WLAN in metropolitan bus networks.

Wi-Fi-based modeling and hybrid routing scheme for delay-tolerant public bus network

Delay- or Disruption-Tolerant Networking DTN is a communications approach that is utilized in easily disrupted or delayed networks. Examples of such networks are often found in heterogeneous networks, mobile or extreme terrestrial networks, and planned networks in space. In this paper, we examine the metropolitan bus network as a research target of DTN for a public transport network. We analyze the metropolitan bus network through spatial and temporal modeling using an existing Bus Information System BIS database. On the basis of the results of our analysis, we propose and design an appropriate DTN routing scheme called Hybrid Position-based DTN Routing. This scheme uses position-based routing instead of address-based routing by soliciting infrastructural help from nearby Access Points for the real-time BIS location service. We simulated our scheme using a WLAN for the wideband DTN communication and evaluated it by comparing it with traditional Ad hoc flooding, Epidemic routing, and strategic protocol steps in our own algorithm. The results indicate that our scheme achieves reasonably high performance in terms of packet delivery ratio, latency, and resource usage. Copyright

Design and Implementation of WLAN-Based Automatic Vehicle Identification

In this paper, we present a WLAN-based automatic vehicle identification (AVI) technique. AVI, typically used for electronic toll collection, is a basic functional requirement for a smart car. The development of this technique is a subtask of building a WLAN-based multi-purpose vehicular terminal device providing various functions, such as AVI, car-to-car communication and vehicular internet access. The design and implementation of our WLAN-based AVI system was based on reducing the identification time in order to cover high-speed cars. As time is required to establish a network connection between a roadside access point and a car station, identifying a high-speed car by communicating through that network connection is not feasible. We utilize IEEE 802.11 management frame such as probe request frame in order to identify a station without establishing a network connection. We also control the timing of the scanning procedure in order to generate enough frames for reliable identification of high speed-cars. Based on the experimental results, our WLAN-based AVI system achieves an identification ratio of nearly 100% for various car speeds ranging from 40km/h to 100km/h, whereas, active RFID, one of the representative technologies for AVI, does not show reliable identification performance, especially at high-speeds.

Design and implementation of a high-speed RFID data filtering engine

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.

Bandwidth-aware DDS communication in WLAN

Recent trend in the research of networking in defense development tends to communicate via DDS (Data Distribution Service)-based middleware, since target environments often integrate thousands of nodes through heterogeneous networks. Heterogeneous network often consists of wired and wireless co-existed network; however constructing DDS-based system in the wireless network is challenging work because recent DDS is originally designed for the wired network. In this paper, we aim to evaluate the performance of the DDS-based middleware in the wireless environment. We preceded several experiments in the wired and wireless LAN. After analysis on the experimental results, we suggest a new bandwidth-aware design scheme for the DDS communication in WLAN for the better performance.

Design of an RFID Air Protocol Filtering Technique

To develop a ubiquitous environment, object identification is very important. We expect there to be a huge number of IDs. In this paper we focus on RFID, which is one of the prominent technologies of object identification. We present an ID filtering technique for the air protocol. Filtering of the air protocol between RFID tags and a reader has some advantages over filtering in the reader and middleware. This is because air protocol filtering reduces the amount of filtering required, before readers and middleware start filtering.We introduce geometrical algorithms for generating air protocol filters, and verify their performance via a filtering simulation with analytical time models. The results for dense RFID reader environment show that air protocol filtering algorithms reduce the total filtering time almost by half compared to the results for no air protocol filters.