• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.6
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• pp.1477-1486
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• 2013

In this paper, Implementation of location estimation system using wireless communication technology based on Zigbee. Using wireless communication technology, calculation more accurate location information and service location information to the H/W and S/W has been developed. Receivers, repeaters, smart tag(location device), was developed for implement a location estimation system. The smart tag is built the 120~130KHz, 13~14MHz, 2.0~3.0GHz radio frequency tag. Receiver and repeater is applied to the tag module to recognize the location device's active RFID tags transmit a wireless signal for tag identification. Common Entrance control system in contact with a smart tag, It was implemented to transfer the value of the tag to the access control server over a LAN.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2102-2112
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• 2015

In this paper, we propose a new positioning scheme for accuracy improvement of Relay-based Navigation System. The conventional relay-based system occurs larger vertical error than horizontal one due to structural characteristics that positioning references are located toward same direction and a location of user is estimated by triangulation technique. In the proposed positioning scheme, the user position is reestimated using an additional virtual reference which is generated based on position information of reference stations in navigation signals and estimated initial user position. The nearest reference station from the estimated user position is selected as a virtual reference to minimize the effect of geometrical factor. The vertical error decreases by using reference points on multi planes, therefore, accurate positioning is possible than the conventional scheme. We demonstrated that the accuracy of a user is improved through simulation results.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.53-58
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• 2011

Recently, MIMO technology, which can improve data rate, link reliability and diversity order, has been widely studied. However, due to the limitation of size, cost and complexity, it is difficult to equip multiple antennas in mobile devices. To overcome this problem, the cooperative communication scheme has been proposed. In this scheme, each terminal shares its single antenna to form a virtual MIMO environment. However, in conventional cooperative scheme, e.g, decode-and-forward, amplify and forward, the spectral efficiency is decreased if there are many terminals taking part in the cooperation. Therefore, the incremental relaying scheme has been proposed to solve this problem. In this paper, we consider various models using incremental relaying technique. In addition, the position of relay is investigated in order to obtain optimal performance.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.224-231
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• 2010

In this paper, we analyze the performance of the cooperative relay communication system which uses orthogonal frequency division multiplexing(OFDM) with hierarchical subcarrier modulation. In the cooperative relay communication system, data transmission is accomplished in two time slots. In the first time slot, the source broadcasts the signal to the relay and to the destination. The relay demodulates the received signal, remodulates and forwards it to the destination in the second time slot. The source uses hierarchical modulation for subcarriers to deal with the signal-to-noise power ratio (SNR) difference in the source-relay and source-destination links. The bit error rate (BER) of the relay transmission system with hierarchical modulation depends on the hierarchical modulation parameter. First, we derive the relationship between BER and the parameter, and find the optimal parameter giving the minimum BER through computer simulations. Then, we analyze the performance of the proposed cooperative relay communication system according to the relay location. From this results, we find optimal relay location to maximize the BER performance.

• Land and Housing Review
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• v.13 no.4
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• pp.105-114
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• 2022

Non-fire activated fire alarms caused by such actions as cigarette smoke, cooking, and high humidity are fire safety risk factors. In such instances, it is important to quickly locate and replace the actuated detector. However, it is difficult to locate those detectors because most do not have an address function. While new apartments can incorporate addressable fire alarm detectors, in existing apartments there are limitations in converting over to addressable detectors due to cost and power line issues. This study developed an efficient address function for fire alarms in existing apartments. The newly developed system consists of the existing receiver, and a proposed addressable repeater and detector. Utilizing an experimental setup, the performance of the proposed address monitoring system was confirmed to be stable and compatible with the receiver and existing detectors.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.47-53
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• 2007

The purpose of IEEE 802.16j is to extend coverage and to enhance throughput by using relay station additionally to conventional IEEE 802.16e . The cellular system experiences performance degradation at the cell edge due to pathloss, shadow and multipath fading. We can get advantage of spatial diversity gain by using relays more than two cooperatively in the IEEE 802.16j system. Cooperative relaying using space-time code provides better performance under multipath fading and has more robustness against the shadow fading than single relaying. In this paper, we investigate the performance of IEEE 802.16j using cooperative relaying by link level simulation. We also show that the cooperative relaying system achieves better performance than the conventional single relaying system. We apply realistic shadow model considering correlations between shadow fadings of different relaying paths. It is shown that the performance of the system depends highly on the spatial location of relay stations.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.7
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• pp.805-810
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• 2014

Cooperative communication, which transmit signal via arbitrary number of relays, enhances the overall communication performance by providing virtual Multi-Input Multi-Output (MIMO) gain without imposing multiple antennal limitation in physical system. There are two representative relaying protocols, i.e., Amplify-and-Forward (AF) and Decode-and-Forward (DF), where we analyze the performance of cooperative communication by adopting DF relaying protocol applying partially differential modulation. The performance is based on symbol error rate (SER), and the effect of relay location on the performance is analyzed. We also compare the performance of the proposed scheme with the system which uses differential modulation scheme.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.11-21
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• 2000

을 합하여 얻을 수 있다. 이와 같은 광선 추적법을 적용한 해석적 방법은 디지털 방송의 수신 영역을 결정하는 중요한 두 요소인 수신 전계강도 및 다중 경로 간섭을 비교적 정확히 예측할 수 있다. 개발된 모델을 이용하여 디지털 방송 환경에서 동일채널 중계기로 인한 방송 수신 영역의 확대 또는 축소를 예측할 수 있으며, 중계기의 최적화 위치를 찾는 데 활용할 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.27 no.1
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• pp.62-68
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• 2023

An aerial relay system utilizing an unmanned aerial vehicle(UAV) or drone is addressed for event-driven operations such as temporary communication services for disaster affected area, military and first responder support. UAV relay system (URS) targets to provide a reliable communication service to a remote user equipment or an operator, therefore, a fast UAV placement to guarantee a minimum quality of service(QoS) is important when an operation is requested. Researches on UAV utilization in communication systems mostly target to derive the optimal position of UAV to maximize the performance, however, fast deployment of UAV is much more important than optimal placement under emergency situations. To this end, this paper derives the feasible area for UAV placement, investigates the effect of performance requirements on that area, and suggests UAV placement to certainly guarantee the performance requirements. Simulation results demonstrate that the feasible area derived in this paper matches that obtained by an exhaustive search.

• Journal of Advanced Navigation Technology
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• v.24 no.5
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• pp.408-414
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• 2020

The method of overcoming the limitation of optical phase conjugator applied into optical long-haul link for transmitting high capacity wavelength division multiplexed (WDM) channels was investigated. The configuration of optical link was based on dispersion-managed link, in which dispersion compensating fiber inserted into each fiber span with single mode fiber, and optical phase conjugator was added into suitable location of link. The maximum number of fiber spans as a function of the launch power of WDM channels in optical link with optical phase conjugator placed at the proposed location was induced and compared for analyzing the compensation performance of the distorted WDM channels. It was confirmed that the more optical phase conjugator depart from the midway of total transmission length, the less the distorted WDM channels was compensated, however, it was also confirmed that the degradation of compensation can be overcome by the suitable value of residual dispersion per span and by the reasonable choice of fiber span controlling total dispersion accumulated in overall transmission link.