• Journal of Advanced Navigation Technology
• /
• v.22 no.6
• /
• pp.602-609
• /
• 2018

Differential GPS (DGPS) is known as a positioning method using pseudo range correction (PRC) which is communicating between a refence receiver and moving receivers. In real world, a moving receiver loses communication with the reference receiver, resulting in loss of PRC real-time communication. In this paper, we assume that the transmission of the pseudo range correction isinterrupted in the middle of real-time positioning situations, in which calibration information is received in the DGPS method. Under the disconnected communication, we propose 'predict DGPS' that real-time virtual PRC model which is modeled by a machine learning algorithm with previously acquired PRC data from a reference receiver. To verify predict DGPS method, we compared and analyzed positioning solutions acquired from real PRC and the virtual PRC. In addition, we show that positioning using the DGPS prediction method on a real road can provide an improved positioning solution assuming a scenario in which PRC communication was cut off.

• Journal of the Korea Society for Simulation
• /
• v.18 no.4
• /
• pp.165-173
• /
• 2009

Recent portable devices are so versatile that they have multiple communication channels and play several multimedia formats. Especially, many services are under development for users who connect Internet or nearby devices via WWAN (Wireless Wide Area Network) and/or WLAN (Wireless LAN). In case of paying the telecommunication cost proportional to the amount of data downloaded, it is necessary to reduce the cost by constructing a special ad hoc network in which each participating peer downloads a specific portion of the want-to-be-shared content over the payable WWAN channel and exchanges the remaining portion with other peers using the cost-free WLAN channel. If all peers participate in forwarding packets, some transmissions are redundant which results in the unnecessary consumption of bandwidth as well as the delayed content distribution time. In order to reduce the redundant transmission, this paper proposes both the excluding method which discourages some peers not to forward redundant packets, and the minimum cover set method in which only the minimum number of peers are in charge of forwarding packets. These two methods obviate redundant packet forwarding, and result in reduction of content distribution time by up to around 29%.

• Journal of Korea Spatial Information System Society
• /
• v.1 no.2 s.2
• /
• pp.21-31
• /
• 1999

In accordance with the completion of the spatial database building works in the central and/or local government authorities as well as the rapid popularization of various information services through internet, it is heavily required to provide spatial information services through World Wide Web. To provide a qualified spatial information service, it is crucial to have a Web-based GIS (Geographic Information Service) service system equipped with the publicity, the convenient accessibility, and the easy-to-use user interface. In this paper, we introduce a new component system for Web-based spatial information services based on the OpenGIS Simple Feature specification for OLE/COM[3] and OLE DB specification[4]. The important functionality of a Web-based spatial information service system includes its accessibility of various existing GIS server system and huge databases in addition to the resolution of response-time delay problems caused by transmitting a large amount of digital maps via internet[6]. To cope with these problems, our component system has been designed to access heterogeneous databases in transparent manner and to support vector-based and/or image-based image production techniques for shortening transmission time.

• The KIPS Transactions:PartC
• /
• v.14C no.3 s.113
• /
• pp.277-284
• /
• 2007

The routing algorithm many used in the wireless sensor network features the clustering method to reduce the amount of data transmission from the energy efficiency perspective. However, the clustering method results in high energy consumption at the cluster head node. Dynamic clustering is a method used to resolve such a problem by distributing energy consumption through the re-selection of the cluster head node. Still, dynamic clustering modifies the cluster structure every time the cluster head node is re-selected, which causes energy consumption. In other words, the dynamic clustering approaches examined in previous studies involve the repetitive processes of cluster head node selection. This consumes a high amount of energy during the set-up process of cluster generation. In order to resolve the energy consumption problem associated with the repetitive set-up, this paper proposes the Round-Robin Cluster Header (RRCH) method that fixes the cluster and selects the head node in a round-robin method The RRCH approach is an energy-efficient method that realizes consistent and balanced energy consumption in each node of a generated cluster to prevent repetitious set-up processes as in the LEACH method. The propriety of the proposed method is substantiated with a simulation experiment.

• The Transactions of the Korea Information Processing Society
• /
• v.3 no.1
• /
• pp.127-143
• /
• 1996

Advanced countries are very active in deploying the National Information I infrastructure which provides universal service to promise fruitful quality of futuree life. Even in the distributed environment, we can closely converse, work together, and share information in a very convenient way. This is actually enabled with the help of groupware technology, which are currently focused and researched in a larger popularity. The aim of this study is to design a portable pack for group communications management to support the development of groupware application. In the paper we begin with technical survey, continue to build our own model for group communications man agement, and design its architecture and procedure. We also suggest group addressing mechanism under Internet environment such as how to create IP multicast address and IP port number dynamically and as a globally unique value for the communication session, with the help of the hierarchical and distributed address managers. We also indicate the reliable data transmission services to remedy the unreliable feature of the UDP multicast services, and finally the architecture/ applied to support the practical applications is briefly discussed for verification of the designed concept.

• The Transactions of the Korea Information Processing Society
• /
• v.5 no.6
• /
• pp.1610-1619
• /
• 1998

The ABR service class provides feedback based traffic control to transport bursty data traffic efficiently. Feedback based congestion control has first been studied to be applied to unicast connections. Recently. several congestion control algorithms for multicast connections have also been proposed as the number of ABR applications requiring multicast increases. With feedback based congestion control, the effectiveness of a traffic control scheme diminishes as propagation delay increases. Especially for a multicast connection, a remote destination may suffer unfair service compared to a local destination due to the delayed feedback. Amelioration of the disadvantages caused by feedback delay is therefore more important for remote destinations in multicast connections. This paper proposes a new switch behavior to provide effective feedback based mathc control for rentoh destinations. The proposed switches adjust the service rate dynamically in accordance woth the state of the downstream, that is, the congestion of the destinaion is immediately controlled by the nearest apstream switch before the source to ramp down the transmission rate of the connection. The proposed switch has an implementation overhead to have a separate buffer for each VC to adjust the service rate in accordance with a backward Rm cell of each VC. The buffer requirement id also increased at intermediate switches. Simulation results show that the proposed switch reduces the cell loss rate in both the local and the remote destinations and slso amelioratd the between the two destinations.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.7 no.1
• /
• pp.51-58
• /
• 2013

As it is changing into aging society, rehabilitation, welfare and sports industry markets are being expanded fast. Especially, the field of vital signals interface to control welfare instruments like wheelchair, rehabilitation ones like an artificial arm and leg and general electronic ones is a new technology field in the future. Also, this technology can help not only the handicapped, the old and the weak and the rehabilitation patients but also the general public in various application field. The commercial bio-signal measurement instruments and interface systems are complicated, expensive and large-scaled. So, there are a lot of limitations for using in real life with ease. this thesis proposes a wireless transmission interface system that uses EMG(electromyogram) signals and a control module to manipulate hardware systems with portable size. We have designed a hardware module that receives the EMG signals occurring at the time of wrist movement and eliminated noises with filter and amplified the signals effectively. DSP(Digital Signal Processor) chip of TMS320F2808 which was supplied from TI company was used for converting into digital signals from measured EMG signals and digital filtering. We also have used PCA(Principal Component Analysis) technique and classified into four motions which have right, left, up and down direction. This data was transmitted by wireless module in order to display at PC monitor. As a result, the developed system obtains recognition success ratio above 85% for four different motions. If the recognition ratio will be increased with more experiments. this implemented system using EMG wrist direction signals could be used to control various hardware systems.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.1
• /
• pp.96-107
• /
• 2015

VANET technologies provide real-time traffic information for mitigating traffic jam and preventing traffic accidents, as well as in-vehicle infotainment service through Telematics/Intelligent Transportation System (ITS). Due to the rapid increasement of various requirements, the vehicle communication with a limited resource and the fixed frame architecture of the conventional techniques is limited to provide an efficient communication service. Therefore, a new flexible operation depending on the surrounding situation information is required that needs an adaptive design of the network architecture and protocol for efficiently predicting, distributing and sharing the context-aware information. In this paper, Vehicle-to-Infrastructure (V2I) based on communication between vehicle and a Road Side Units (RSU) and Vehicle-to-Vehicle (V2V) based on communication between vehicles are effectively combined in a new MAC architecture and V2I and V2V vehicles collaborate in management. As a result, many vehicles and RSU can use more efficiently the resource and send data rapidly. The simulation results show that the proposed method can achieve high resource utilization in accordance. Also we can find out the optimal transmission relay time and 2nd relay vehicle selection probability value to spread out V2V/V2I collaborative schedule message rapidly.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.13 no.4
• /
• pp.803-812
• /
• 2018

The Morse code was firstly used for a wire telegraph service on May 1884 in USA. After about 10 years Korean researchers developed the Morse code in 1884 and the Morse code was firstly introduced in Korea for the wire telegraph service in September 1885. For about 130 years later, the Hangul Jamo Morse code has been used without any serious modification up to now. The Morse code is the variable length code system which each codes have a different code length. The related reference shows that English alphabet Morse code was applied in the coding theory. However, a result of analysis showed that the Hangul Jamo Morse code was not applied in the coding theory as the english alphabet code system. This paper presents the analysis result of Hangul Jamo Morse code according to the variable length coding theory. As a result of the analysis, when Hangul Jamo are coded with application of the variable length coding theory, the transmission data rate could be increased up to 25% compare to the existing code system. This paper shows a new Hangul Jamo Morse code system based on the analysis result.

• Journal of Internet Computing and Services
• /
• v.23 no.3
• /
• pp.21-33
• /
• 2022

This paper is to suggest the secure secret sharing system in order to outstandingly reduce the damage caused by the leakage of the corporate secret. This research system is suggested as efficient P2P distributed system kept from the centrally controlled server scheme. Even the bitcoin circulation system is also based on P2P distribution scheme recenly. This research has designed the secure circulation of the secret shares produced by Threshold Shamir Secret Sharing scheme instead of the shares specified in the torrent file using the simple, highly scalable and fast transferring torrent P2P distribution structure and its protocol. In addition, this research has studied to apply both Shamir Threshold Secret Sharing scheme and the securely strong multiple user authentication based on Collaborative Threshold Autentication scheme. The secure transmission of secret data is protected as using the efficient symmetric encryption with the session secret key which is safely exchanged by the public key encryption. Also it is safer against the leakage because the secret key is effectively alive only for short lifetime like a session. Especially the characteristics of this proposed system is effectively to apply the threshold secret sharing scheme into efficient torrent P2P distributed system without modifying its architecture of the torrent system. In addition, this system guaranttes the confidentiality in distributing the secret file using the efficient symmetric encryption scheme, which the session key is securely exchanged using the public key encryption scheme. In this system, the devices to be taken out can be dynamically registered as an user. This scalability allows to apply the confidentiality and the authentication even to dynamically registerred users.