• KIPS Transactions on Computer and Communication Systems
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• v.5 no.7
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• pp.153-158
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• 2016

Delay Tolerant Network (DTN) is a network that employed method of store-carry-forward in intermittently connected networks. In DTNs, routing and buffer management scheme are important to improve successful message delivery. This paper proposes an improve spray and wait routing protocol based on delivery probability to a destination. Also, a buffer management scheme is proposed to drop the queued messages according to the number of copies (L value). Simulation results show that the proposed method provides a better delivery ratio and lower communication overhead when compared to existing schemes such as Epidemic, PRoPHET and spray and wait.

• The KIPS Transactions:PartC
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• v.13C no.4 s.107
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• pp.533-540
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• 2006

WDMB technology has merits of high bandwidth and high mobility. But WDMB also has uni-directional communication problem. This paper provides solution to supplements uni-directional communication problem of WDMB with embodying return channel using WWAN to offer high quality multimedia service to user. Also this paper proposes intelligent network interface selection algorithm using various network information and return channel type. As a result of simulation, our proposed scheme is better as compared with other handoff scheme in energy efficiency of $7{\sim}8%$ and about two time of handoff number of time decrease.

• Proceedings of the KIEE Conference
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• 2006.07e
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• pp.19-22
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• 2006

The CMD(Condition Monitoring & Diagnosis) System is used to monitor and analyze the PD(Partial Discharge), Arc, Temperature, Pressure, Gas in Oil and so on for reliability and availability of the substation. Although this system comes into the spotlight as the forecast and management of the failure and fault, there are some problems. For example, the unified standard was not defined, and the effective management of the layed communication network does not performed, limitation of physical space, etc. To resolve above problems, this paper suggests the IEC61850 compatible eCMD system architecture for monitoring and analyzing the CMD factor in substations. The suggested eCMD system consists of CMD-LU(Condition Monitoring & Diagnosis-Local Unit), IED(Intelligent Electronic Device), and engineering centers. The IEC61850 is the international standard that defines communication networks and system in substation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.58-73
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• 2014

As is well known, cooperative sensing can significantly improve the sensing accuracy as compared to local sensing in cognitive radio networks (CRNs). However, a large number of cooperative secondary users (SUs) reporting their local detection results to the fusion center (FC) would cause much overhead, such as sensing delay and energy consumption. In this paper, we propose a fast cooperative sensing scheme, called double threshold fusion (DTF), to reduce the sensing overhead while satisfying a given sensing accuracy requirement. In DTF, FC respectively compares the number of successfully received local decisions and that of failed receptions with two different thresholds to make a final decision in each reporting sub-slot during a sensing process, where cooperative SUs sequentially report their local decisions in a selective fashion to reduce the reporting overhead. By jointly considering sequential detection and selective reporting techniques in DTF, the overhead of cooperative sensing can be significantly reduced. Besides, we study the performance optimization problems with different objectives for DTF and develop three optimum fusion rules accordingly. Simulation results reveal that DTF shows evident performance gains over an existing scheme.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.7
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• pp.827-838
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• 1999

멀티미디어 통신에서 통신 성능에 관련된 요구 사항들은 QoS 매개 변수들로서 서술된다. QoS매개 변수들에서 중요한 매개 변수 중의 하나가 전송 신뢰성이다. QoS 매개 변수로서의 신뢰성은 오류 감지, 보고 그리고 정정 기법으로 정의된다. 하지만 기존의 오류 제어 기법들은 멀티미디어 데이타의 통합된 관점을 고려하지 않았다. 그래서 우리는 MEC(multimedia-oriented error control)라고 명명된 오류 제어 기법을 제안하였다. 1 본 논문에서는 MEC기법의 성능을 조사 하였다. 성능평가 결과는 MEC기법이 기존의 오류 제어 기법보다도 낮은 전송지연(lower delay)과 호손율(blocking probability) 을 갖는다는 것을 볼 수 있었다. 결국 제안된 MEC기법은 수송 프로토콜에게 유연성과 높은 성능을 갖도록 해준다.Abstract Communication performance requirements are described as QoS parameters in multimedia communication. One of the important QoS parameters is the reliability of the transfer. As a QoS parameter, the reliability defines error detection, report and correction mechanisms. Conventional error control mechanisms, however, do not consider the integrated viewpoint of multimedia data. So we have proposed the MEC(multimedia-oriented error control). 1 In this paper, we have investigated the performance evaluation of the MEC. The results show that the MEC mechanism provides lower transfer delay and blocking probability than those of the conventional error recovery mechanism. Therefore, the proposed MEC mechanism makes the transport protocol have the flexibility and high performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.627-633
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• 2007

This paper describes position tracking system of a container trailer approaching to a gantry crane for loading or unloading a container into or from a ship, respectively. Proposed position tracking system informs the trailer driver of right position to stop the car under a gantry crane. To measure the location of a trailer, we used Cricket Mote modules which adopted RF and ultrasound technology. We present an elaborate method to improve position errors occurring at sensing and calculate three dimensional position by triangulation along with how to reduce location tracking interval for real-time monitoring. The location information was transmitted to a Personal Digital Assistant (PDA) periodically through Bluetooth communication for guidance of the trailer driver. In indoor and outdoor tests, position errors were less than 3 cm and location tracking interval was 0.5 second on average.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.157-162
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• 2007

With the success of wireless technologies in consumer electronics, standard wireless technologies are envisioned for the deployment in industrial environments as well. Industrial applications involving mobile subsystems or just the desire to save cabling make wireless technologies attractive. Nevertheless, these applications often have stringent requirements on reliability and timing. In wired environments, timing and reliability are well catered for by fieldbus systems. When wireless links are included, reliability and timing requirements are significantly more difficult to meet, due to the adverse properties of the radio channels. In this paper, we thus discuss some key issues coming up in wireless fieldbus and wireless industrial communication systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.2
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• pp.416-421
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• 2007

ZigBee is becoming a promising communication protocol for wireless sensor networks based on low-power consumption. In case of a ZigBee network requesting continuous transmission of sensed data, the required bandwidth can be overwhelm the maximum transmission rate of 150Kbps. However, the ZigBee router which delivers data from source node to destination node can transmit data at most in a half of maximum rate because the router can not send and receive the data simultaneously. In this paper, we propose and implement a dual-channel router which can send and receive data simultaneously. Also, we propose a centralized channel allocation algorithm to allocate different channels to each module. The experiment result by the proposed dual-channel router shows a maximum throughput of 150Kbps as large as twice of normal single-channel router.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1793-1798
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• 2007

Recently there are some trends to construct smart home system infrastructure depending upon the development of Information and Communication Technology. Also requirements of the Ubiquitous Healthcare Systems at home which can monitor the status of health continuously are increased rapidly comparing with hospitals. Healthcare service can be divided into two categories. The first one is Alarm Service that can be used for the emergency status and the other one is Remote Support Service which can monitor the patient including home environments and give those diagnosis information to medical office or to his family. Generally wired networks and fixed healthcare measuring system have some limits to transmit reliable realtime based information for both categories described above comparing with portable monitoring system. Getting over the inefficiency we will design and implement portable healthcare system under the wireless Zigbee network environments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.281-286
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• 2009

The proposed technique uses cyclic frame structure, where three periods such as beacon period (BP), mesh contention access period (MCAP) and slotted period (SP) are in a data frame. This paper studies on a mechanism to allow communication nodes (6lowpan) in a PAN with different logical channel for global healthcare applications monitoring technology. The proposed super framework structure system has installed 6lowpan sensor nodes to communicate with each other. The basic idea is to time share logical channels to perform 6lowpan sensor node. The concept of 6lowpan sensor node and various biomedical sensors fixed on the patient BAN (Body Area Network) for monitoring health condition. In PAN (hospital area), has fixed gateways that received biomedical data from 6lowpan (patient). Each 6lowpan sensor node (patient) has IP-addresses that would be directly connected to the internet. With the help of IP-address service provider can recognize or analyze patient data from all over the globe by the internet service provider, with specific equipments i.e. cell phone, PDA, note book. The NS-2.33 result shows the performance of data transmission delay and data delivery ratio in the case of hop count in a PAN (Personal Area Networks).