• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.140-146
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• 2018

Recently, VLC(Visible Light Communication) fusing with LED(Light Emitting Diode) used in indoor lighting and wireless communication technology has attracted attention. However, the VLC can communicate only within the coverage to measure the optical signal and the communication disconnection phenomenon is occur in the NLoS(Non-Line-of-Sight) area. In this paper, we propose VLC relay module to extend the coverage of VLC and improve the communication disconnection phenomenon in NLoS area. The proposed VLC relay module transmits the packet received from the transmitter to the VLC relay module and receiver. The experiment was carried out by installing one VLC transmitter and three VLC relay modules, communication coverage expansion and the improvement of communication disconnection phenomenon in the NLoS were confirmed by the increase of the VLC relay module. Also, we confirmed that the optical signal measurement performance is improved 2.4 times by using the dual sampling method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.289-293
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• 2013

In the noncoherent methods for UWB-IR (ultra-wideband impulse radio), block coded modulation (BCM) is better than the transmitted reference (TR) systems in terms of the energy efficiency and data rate. However, even BCM suffers from the performance degradation in the presence of strong inter-frame interference and inter symbol interference. We propose the transmitted reference based on the BCM (TR-BCM) which is the hybrid system of TR and BCM. Performance evaluation shows that the performance of TR-BCM is better than that of BCM in the high SNR range.

• The KIPS Transactions:PartC
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• v.13C no.6 s.109
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• pp.677-684
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• 2006

This paper investigates the link margin of MB-OFDM UWB system quantitatively. Various simulations are performed considering the implementation loss by imperfect synchronization unit and the effect of multi-path fading channels. MB-OFDM UWB system uses ZP(Zero Padding) instead of CP(Cyclic Prefix) and supports two transmission modes; one is TFI(Time Frequency Interleaving) mode that transmits OFDM symbols using different carrier frequency from symbol to symbol according to Time Frequency(TF) codes, the other is FFI(Fixed Frequency Interleaving) mode that transmits OFDM symbols using a specific carrier frequency. The advantage of if and TFI is to be able to increase the transmitting power effectively compared to the existed OFDM systems that transmit the signal continuously at the same average transmitting power. From the analysis results of Ink margin, to guarantee the service range of 4m in 200Mbps mode, TFI mode must necessarily be implemented and the service range of 480Mbps mode is estimated about 1-2m in the line-of-sight multi-path channel (CMI).