Si-Ho Cha

Grid-Based Predictive Geographical Routing for Inter-Vehicle Communication in Urban Areas

Vehicular ad-hoc networks (VANETs) are highly mobile wireless ad hoc networks for vehicular safety and other commercial applications, whereby vehicles move non-randomly along roads while exchanging information with other vehicles and roadside infrastructures. Inter-vehicle communication (IVC) is achieved wirelessly using multihop communication, without access to fixed infrastructure. Rapid movement and frequent topology changes cause repeated link breakages, increasing the packet loss rate. Geographical routing protocols are suitable for VANETs. However, they select the node nearest to the destination node as a relay node within the transmission range, increasing the possibility of a local maximum and link loss because of high mobility and urban road characteristics. We propose a grid-based predictive geographical routing (GPGR) protocol, which overcomes these problems. GPGR uses map data to generate a road grid and to predict the moving position during the relay node selection process. GPGR divides roads into two-dimensional road grids and considers every possible node movement. By restricting the position prediction in the road grid sequence, GPGR can predict the next position of nodes and select the optimal relay node. Simulation results using ns-2 demonstrated performance improvements in terms of local maximum probability, packet delivery rate, and link breakage rate.

Applying Connected Dominating Set to Broadcasting in Vehicular Ad Hoc Networks

This paper proposes a Connected Dominating Set (CDS) based clustering algorithm to prevent the broadcast storm problem in Vehicular Ad-hoc Networks (VANETs). The proposed algorithm accounts for the mobility and degrees of vehicles, and matches the highly dynamic nature of VANETs. VANETs are infrastructure less multihop wireless networks. Routing in VANETs is a one of the challenging task to accomplish. Broadcasting is a typical message dissemination mechanism for various VANETs applications such as emergency notifications, traffic information, notice and advertisement messages, etc. Even though VANETs have no physical backbone, a virtual backbone can be constructed by finding a CDS in the network graph. Clustering using a CDS-based virtual backbone can help in improving network scalability. Therefore CDS-based broadcasting can prevent the broadcast storm problem in VANETs.

A Cluster Based Multi-Path Routing Protocol for Support Load-Balancing in Content-Centric Network

Content-Centric Network (CCN) is communication method based on contents to use voluminous information in internet and it is next generation internet technology to provide new paradigm. CCN is communicated by both interest packet and data packet. Interest packet is required content by user and data packet is responded data to contents. CCN use interest packet driven communication re-tracing routing path of interest packet. In CCN, unidirectional routing has low load-balancing only if data traffic is increasing. Therefore, turnaround time, which is time of transmission content to user, was increased by this problem. To resolve this problem, in this paper we proposed cluster based multi-path routing protocol for support load-balancing.

Ontology-Based Methodology for Managing Heterogeneous Wireless Sensor Networks:

With the growing interest in ubiquitous technologies recently, many studies have been conducted in order to manage wireless sensor network, which is the central component in ubiquitous environment. To manage a certain wireless sensor network, a variety of techniques can be applied and thereby the network can be managed. However, it is very complicated and time-consuming to incorporate and manage more than a heterogeneous wireless sensor network since each network has different data, meanings, and terms. Instead of conducting verification through examining the detailed technology or simulation in order to manage a variety of wireless sensor networks, we suggest a methodology which manages data coming from the various sensors mentioned above, a technique by which those data from various sensor networks are managed in each different network, and a methodology which manages sensor networks where management languages exist. This paper defined the network-related terminology using Protégé for the tools and definitions necessary for ontology-based methodology, thereby defined OWL and the related rules, and suggested a methodology for incorporated management. In addition, this study showed that the methodology presented in this study has expandability and it can incorporate and manage a variety of wireless sensor networks.

Ontology-Based Context-Aware Management for Wireless Sensor Networks

Wireless sensor network (WSN) can provide the popular military and civilian applications such as surveillance, monitoring, disaster recovery, home automation and many others. All these WSN applications require some form of self-managing and autonomous computing without any human interference. Recently, ontology has become a promising technology for intelligent context-aware network management. It may cope with various conditions of WSNs. This paper describes an ontology-based management model for context-aware management of WSNs. It provides autonomous self-management of WSNs using ontology-based context representation, as well as reasoning mechanisms.

Measuring the Performance of Packet Size and Data Rate for Vehicular Ad Hoc Networks

Since 2004, Vehicular Ad-hoc Networks (VANETs) is core technology of Intelligent Transportation System (ITS), in which standardize the Wireless Access in Vehicle Environments (WAVE) based on IEEE 1609 and IEEE 802.11p. WAVE is a field of study to provide safety service and information to person such as driver and passenger. Recently, many researchers have been proposed resolution for high velocity and rapid topology change. However, it assume equal to packet size. Therefore, this assumption could not provide various services for VANETs due to limited data packet size. To do resolve this problem, in this paper, we analyzed transmission rate of differences data packet in VANETs environment and proposed future research about improving transmission method according to difference packet size.

Location Prediction for Grid-Based Geographical Routing in Vehicular Ad-Hoc Networks

Inter-vehicle communication (IVC) is wirelessly connected using multi-hop communication without access to some fixed infrastructure. Because of the rapid movement of vehicles and the frequent topology change, link breakages occur repeatedly and the packet loss rate increases. Geographical routing protocols are known to be very suitable and useful for vehicular ad-hoc networks (VANETs). However, they just select the node nearest to the destination node as a relay node within its transmission range. This increases the possibility of a local maximum and link loss in IVC. This paper presents the location prediction method for the grid-based predictive geographical routing (GPGR) protocol to overcome the problems. GPGR makes use of map data to generate the road gird and to predict the exact moving position of vehicles in the relay vehicle selection process. It regards every vehicle moves only along the road grid. Simulation results using ns-2 show performance improvement in terms of packet delivery rate than existing routing protocols.

Directed broadcasting with mobility prediction for vehicular sensor networks

This article suggests a new directed broadcasting method with mobility prediction of moving vehicles in vehicular sensor networks (VSNs). VSNs can play a critical role to ensure prompt delivery of real-time sensing data and be able to prevent various road dangers. The suggested method is particularly for vehicle safety communication (VSC) on highway roads by using directed broadcasting between vehicles. In VSNs, broadcasting is the most suitable communication mechanism for VSC. The simplest broadcasting mechanism is flooding, which introduces the redundant message retransmission and the broadcast storm problem. It is because all vehicles rebroadcast the messages in flooding. The broadcast storm problem can be addressed with selective flooding schemes which select rebroadcast vehicles to perform rebroadcasting. However, selective flooding schemes cannot promise enough reliability for VSC because of the highly dynamic topology and frequent disconnections of vehicular networks. Fast movement and frequent topology changes cause repeated link breakages and it increases the packet loss rate of vehicular networks. In this article, we propose a mobility prediction-based directed broadcasting (MPDB) protocol to achieve a reliable broadcasting in VSNs. MPDB protocol broadcasts emergent messages only to the rear vehicles on the same road. MPDB protocol consists of two phases: (i) mobility prediction phase and (ii) broadcasting phase. The mobility prediction can be acquired through periodical beaconing. In mobility prediction phase, each vehicle gets its rear vehicle set on the same road through neighbour’s position, inter-vehicle distance, relative speed and moving direction. In broadcast phase, MPDB protocol selects a vehicle having the largest link available time (LAT) values acquired by the mobility prediction as a rebroadcast vehicle among the rear vehicle set acquired in previous phase. By using LAT for broadcasting propagation, MPDB protocol can intensify the reliability of the message dissemination and also prevent the broadcast storm problem in vehicular networks. The simulation results show that MPDB protocol has better performance improvement in terms of average packet rate and packet delay.

An Approach to Segmenting Initial Object Movement in Visual Sensor Networks

This paper suggests a new method to extract the initial movement of moving objects in digital image data obtained in visual sensor networks. First, consecutive images are received as input. Then, the frames are partitioned into nonoverlapping square blocks of pixels, and finally, the block-based motion vectors, which represent the movement information between two adjacent frames, are extracted from the received images using a block-matching algorithm. The extracted motion vectors are subsequently applied to an outlier-elimination algorithm called robust estimation to discriminate between the background motion vectors and those of noise or moving objects. The motion vectors corresponding to the noise or objects are clustered with an unsupervised clustering algorithm to segment the individual moving objects. Experimental results prove that the proposed method can effectively detect the initial movement of objects in various indoor and outdoor environments.

Mobility Information and Road Topology Based Inter-vehicle Routing Protocol in Urban

Vehicular ad-hoc networks (VANETs) are special cases of mobile ad-hoc networks (MANETs) where nodes are highly mobile, so network topology is changing very fast. In VANET, vehicles move non-randomly along roads. Inter-vehicle communication is wirelessly connected using multi-hop communication without access to some fixed infrastructure. Because of the rapid movement of vehicles and the frequent topology change of VANET, link breakages occur repeatedly and the packet loss rate increases. Geographical routing protocols such as greedy perimeter stateless routing (GPSR) are known to be very suitable and useful for VANET. However, they can select stale nodes for relay nodes and generate the local maximum problem. This paper presents an inter-vehicle routing protocol based on mobility information of vehicles and digital map on city roads to solve those problems in urban area. Mobility information includes the position, velocity, and direction of vehicles. Road topology is used to obtain the location of intersections and whether it is an overpass or a dead end road. Simulation results using ns-2 show performance improvement in terms of packet delivery ratio than existing routing protocols.