• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.8
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• pp.34-41
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• 2017

Vehicle to Infrastructure(V2I) communication means the technology between the vehicle and the roadside unit to provide the Intelligent Transportation Systems(ITS) and Telematic services. The vehicle collects information about the probe data through the evolved Node B(eNodeB) and after that eNodeB provides road conditions or traffic information to the vehicle. To provide these V2I communication services, we need a link adaptation technology that enables reliable and higher transmission rate. The receiver transmits the estimated Channel State Information(CSI) to transmitter, which uses this information to enable the link adaptation. However, due to the rapid channel variation caused by vehicle speed and the processing delay between the layers, the estimated CSI quickly becomes outdated. For this reason, channel interpolation and prediction scheme are needed to achieve link adaptation in V2I communication system. We propose the Advanced Discrete Prolate Spheroidal Sequence(ADPSS) channel interpolation and prediction scheme. The proposed scheme creates an orthonomal basis, and uses a correlation matrix to interpolate and predict channel. Also, smoothing is applied to frequency domain for noise removal. Simulation results show that the proposed scheme outperforms conventional schemes with the high speed and low speed vehicle in the freeway and urban environment.

• The KIPS Transactions:PartC
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• v.12C no.4 s.100
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• pp.597-602
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• 2005

In this study, file size for measurement and the service system's billing data were submitted to a comparative analysis by performing a verification test on the billing system of three major mobile communication services providers, based on the wireless Internet service packet. As shown in the result of the verification test, there were some differences in the billing data due to transmission overhead, according to the network quality that is affected by the wireless environment of mobile operators. Consequently, the packet analysis system was proposed as a means of applying consistent packet billing to all service providers being compared. If the packet analysis system is added to supplement the current billing system various user requirements can be met. Billing by Packet among mobile operators and differentiated billing based on the content value are available, since the packet data can be extracted through protocol analysis by service, and it can be classified by content tape through traffic data analysis. Furthermore, customer's needs can be satisfied who request more information on the detailed usage, and more flexible and diverse billing policies can be supported like application of charging conditions to the non-charging packet handling. All these services are expected to contribute to the popularization of the wireless Internet service, since user complaints about the service charge could be reduced.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.3
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• pp.62-73
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• 2008

In this paper, domestic standard revision plan of dynamic frequency method which is used both in unmanned automatic toll collection system and manned collection system of the express highway is presented. For such ETCS, the infrared rays (870 nm) of active frequency method and the frequency integrated method (5.8 GHz) are adopted and extended to be operated to the all around the Toll Gate. This standardization plan is based on inter connection reference model between OSI (Open System Interconnection) in process of ITS short range radio communication standardization of 5.8 GHz bandwidth to support traffic information and control system service, and the derived revision plan by starting from physical layer which support interoperability for multiple access between RSE (Road Side Equipment) and OBE (On Board Equipment), in which is categorized into physical layer, data link layer, and application layer. In case of radiation power, existing standard is divided by class1 (within 10 m) and Class2 (within 100 m) according to transmission lengthwhile it is operated with just single standard 'Class1' because of notification of Ministry of Information and Communication in 2004. In the case of the limitation value of incident power in communication area, considering operation plan of ETCS that is on actuality operation the measurements are reflected to the standard. In other wort this paper proposed the improvement standard of incident power, pseudo response in the communication area and radiated power in order to secure stability and compatibility among operator systems about the needed part on ETCS operation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.1-8
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• 1998

In this paper, we analyze the probability of soft handoff and hard handoff which served in DS-CDMA cellular system, and propose a new handoff control scheme. The object of proposed scheme is to reduce the hard handoff probability of delay sensitive calls which are very sensitive to transmission errors. In this scheme, if soft handoff is not possible, for a delay sensitive call, a delay insensitive call using the same frequency channel that a handoff call is using is handed off to one of other frequency channels and the traffic channel released by delay insensitive call's handoff is assigned to a delay sensitive call for soft handoff. A performance of the proposed scheme was evaluated through computer simulation.

• Journal of Digital Contents Society
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• v.3 no.1
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• pp.101-111
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• 2002

Lately development of network around Internet expands range of data traffic to multimedia information, and so for the guarantee of multimedia services end-to-end QoS(Quality of Service) must service because comparing with existing Internet service can not support For satisfying those QoS requirements, network have to guarantee not only network on parameter, such as delay, jitter, throughput but also system resources like CPU utilization, memory usage. Therefore it is urgent to develop QoS based middleware to distribute multimedia data and maximize network utilization in the limited resource environment. And it must be necessary of network to provide end-to-end QoS(Quality of Service) for multimedia applications. Multimedia applications want that QoS which satisfy their own service properties be guaranteed Then, We must analyze those necessary QoS requirements md define QoS parameter which specify as two viewpoint, user's and network's perspective. Therefore network provider supplying network for usual user and university, enterprise must want to find about their own network performance and problem. It is essential for network manager to want to use a tool like this. On the basis of technique about QoS test-bed in the AIM network, We studied on the method of QoS measurement and management about end-to-end connection in the Internet. We measured network status about end-to-end connection and analyze the result of performance.

• The KIPS Transactions:PartC
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• v.11C no.5
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• pp.683-688
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• 2004

NAT is a very useful IP address translation technique that allows two connected networks using different and incompatible IP address schemes. But it is impractical to use NAT for an application which uses the encrypted IP packet, embedding IP addresses inside of data payloads, to guarantee End-to-End Security such as IPSec. In addition to rewriting the source/destination IP addresses in the packet, NAT must modify IP checksum every time, which could lead to considerable performance decrease of the overall system in the process of the address translation. RSIP is an alternative to solve these disadvantages of NAT and the address shortage problems. Both NAT and RSIP divide networks into inside and outside addressing realms. NAT translates addresses between internal network and external network, but RSIP uses a borrowed external address for outside communications. RSIP server assigns a routable public address to a RSIP client temporarily to communicate with public net-work outside of the private network. In this paper, RSIP gateway for intranet environment is designed and its performance is evaluated. From the results of performance evaluation, we knew that RSIP is operated less sensitive to the data traffic. Also, the experiment shows that RSIP performs better than NAT when the transmission data grows larger.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.288-300
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• 2002

In this paper, a novel method of equalization of RF transceivers is suggested for MIMO(Multiple Input Multiple Output) antenna actively studied for high speed data transmission in the recent IMT-2000 system. The core of suggestion is in equalizing the transfer characteristics of multiple transceivers using feedback and memory during the predefined calibration time. This makes it possible to weight the signals in the intermediate frequency, which is easier in the application of recently developed DoA(Direction of Arrival) algorithms. In addition, the time varying optimum cell formation according to traffic is feasible by antenna beam-forming based on the DoA information. The suggested method of equalizing multiple transceivers are successfully verified using envelope simulation. two outputs. This paper is concerned with the diagnosis of multiple crosstalk-faults in OSM. As the network size becomes larger in these days, the convent.
nal diagnosis methods based on tests and simulation be.
me inefficient, or even more impractical. We propose a simple and easily implementable alg？ithm for detection and isolation of the multiple crosstalk-faults in OSM. Specifically, we develop an algorithm for isolation of the source fault in switc.
ng elements whenever the multiple crosstalk-faults are.
etected in OSM. The proposed algorithm is illustrated by an example of 16$\times$16 OSM.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.445-450
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• 2018

AIS is the most important navigation equipment for the identification of other ships, etc. However, the AIS overload problem has been raised recently due to an increase in AIS equipped vessels. The government is planning to introduce the wireless LTE network at 100 km offshore as part of the SMART-Navigation project. Continuous development and dissemination of the services available through such platforms will be necessary to achieve major goals such as marine accident prevention and environmental protection. In this study, we applied a WAVE communication system, which could be the basis for the development of such services. As a result, reliable data transmission was confirmed for a range of communication of approx. 5 miles, although the service was limited to 1 km in road traffic. Therefore, it is expected that WAVE communication technology will be used to prevent marine accidents through such efforts as collision avoidance and the transfer of marine safety information between ships.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.497-500
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• 2010

Wireless sensor network is the system for data collection and data process between many nodes. For this work, Synchronization of operation execution and ordering many events are needed. Reference the external time information is the most accurate way to have same time information for all nodes but it's hard to apply these to sensor network. So there are many study of time synchronization there are many error occurred when the time synchronization is executed in the sensor network and minimizing these errors is important. In this paper, we propose how to minimize errors using several time stamp information exchanging when the network is initialized. When the big difference is occurred between receive time and send time in the node communication(cause of traffic overhead and etc), it shows big error of time correction and transfer delay time. but it's hard to detect these errors when it exchanges time stamp information just one time. so we try to reduce these errors using the median value of transfer delay and time correction value with many times of time stamp information exchange.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.286-290
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• 2008

As the number of mobile device users increases, many researches on peer-to-peer(P2P) systems in mobile environments have been carried out. In this paper, we propose a couple of double-layered P2P file sharing systems to overcome the 'flooding' problem in previous mobile P2P systems. We classify peers into two groups, super peers and sub-peers to establish new routing tables. A super peer manages its sub-peers in the systems. The first proposed system partitions the service area into small cells, each of which is a square. Each super peer is located near the center of the square. The second system selects super peers which have the largest number of adjacent peers. As file transmission and file searches are managed mainly by super peers, unnecessary multi-broadcasting could be avoided. The experimental results show that the proposed systems outperform a typical file sharing system in terms of the amount of message traffic with about $1.2{\sim}1.6$ times improvement on the average.