• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.11 no.1
• /
• pp.98-104
• /
• 2012

In RFID Systems, collisions between multiple tags frequently arise due to simultaneous responses from multiple tags using the same communication channel. Most of anti-collision protocols such as QT regard these collisions as useless cycles, thereby wasting the channel bandwidth. In this paper, we propose a new anti-collision protocol, namely ASP (Adjustable splitting by patterns of collisions) protocol that utilizes the patterns collision for noticeable performance enhancements.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.6
• /
• pp.32-41
• /
• 1996

We propose the improved GMSK (gaussian-filtered minimum shift keying) quadrature modulator using the FIR(finite impulse response )filter whose coefficients are obtained form the differnce of phase response, and design its ASIC (applicaton specific integrated circuit) which can be used for GSM (global system for mobile communication) digital cellular system and DCS 1800 (digital cellular system at 1800MHz) personal communication system. Input data become quantized I and Q channel 10 bit signal through cosine and sine ROM mapping after being filtered by the FIR filter whose normalized bandwidth is 0.3 and designed by considering intersymbol interference as well as sampling ratio. These two signals become the GMSK modulated I and Q channel signal through DAC (digital-to-analog converter) and 7th order analog chebyshev LPF(low pass filter) respectively. The difference between the ideal analog signal and its digitized signal is analyzed in terms of sampling noise, quantization noise, truncation noise and coefficient noise. And the effect of the LPF following the DAC is considered. The ASIC design of the GMSK quadrature modulator is also confirmed by an experiment.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.41 no.4
• /
• pp.49-55
• /
• 2004

This paper describes a 1550 nm multichannel source using Quatemary/quatemary multiple quantum well (MQW) InGaAsP/InGaAsP quantum confined Stark effect (QCSE) tuning for dense wavelength division multiplex (DWDM) systems with 140 ㎓ channel spacing and 32 nm channel selection bandwidth.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.12
• /
• pp.1401-1412
• /
• 1992

On band limited channel like satellite communication and voice communication. TCM(Trellis Coded Modulation) is a communication method that has coding gain which combines modulation with channel coding without bandwidth expansion. In this paper, we apply PAM, PSK, QAM to TCM, and propose the extended path back method decoding algorithm which improved drawback of viterbi decoding algorithm and apply to TCM this decoding algorithm. Using Monte Carlo simulation, we analyze performance of each modulation technique and efficiency of decoding algorithm.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.38 no.7
• /
• pp.486-492
• /
• 2001

We propose a novel optical channel-selective filter whose center wavelength and bandwidth can be fully controlled. The Proposed filter consists of three identical chirped fiber Bragg gratings (CFBG’s) with fiber stretchers which is to control the reflection spectra of the CFBG’s. We experimentally demonstrate that the proposed tunable filter can select arbitrary channels from a WDM signal.

• Journal of IKEEE
• /
• v.5 no.1 s.8
• /
• pp.85-90
• /
• 2001

In this paper, we analyzed the envelope correlation of wideband signals modulated on two separate subcarriers in a Nakagami-Rice fading channel with exponential power delay profile. The results show that the envelope correlation of resolvable paths is implicated by the ratio of the specular wave power to the mean multipath power as well as the signal bandwidth and the rms delay spread of the multipath waves.

• The Journal of the Acoustical Society of Korea
• /
• v.30 no.2
• /
• pp.86-91
• /
• 2011

In the underwater communications, the acoustic channel is in poor communication conditions, such as long propagation delay, narrow bandwidth, and high bit-error rate. For these bad acoustic channels, we propose an efficient automatic repeat request (ARQ) for multi-hop underwater network by using the concepts of concurrent bi-directional transmission, multiple sub-packets, and overhearing data packet instead of the acknowledgement signal. Our results show that the proposed ARQ significantly reduces the transmission latency especially in high BER compared with the existing Stop and Wait ARQ.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.5A
• /
• pp.500-508
• /
• 2008

Direct-sequence ultra-wideband(DS-UWB) system is being considered as one of promising transmission technologies for wireless personal area networks(WPANs). Due to relatively low spreading factors and huge bandwidth of transmit signal, a DS-UWB receiver needs to be equipped not only with a rake receiver but also with an equalizer, of which the equalizer is not required for traditional direct-sequence code division multiple access(DS-CDMA) systems. The number of rake fingers is limited in practice, influencing the performance of the subsequent equalizer. In this paper, we derive a decision feedback equalizer(DFE) for DS-UWB systems based on the minimum mean square error(MMSE) criterion, and investigate the impact of various parameters on the DFE performance in realistic scenarios. In particular, we propose an approach to improving the performance of the DFE using additional channel estimates for multipaths not combined in the rake receiver, and discuss how the accuracy of channel estimation affects desirable DFE configuration. Moreover, we present simulation results that show the impact of turbo equalization on the DFE performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.10a
• /
• pp.389-391
• /
• 2011

This paper has been studied about design of linear 25Watt Power amplifier for VDR(VHF Data Radio). VDR's frequency band is 117.975~137MHz, and CSMA(Carrier Sense Multiple Access), D8PSK(Differential Eight Phase Shift Keyed), 25KHz's channel bandwidth use. It also stated in DO-281A MOPS output power, symbol constellation error, spurious emissions, adjacent channel power must be met. HPA is designed to meet DO-281A standard.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.11
• /
• pp.1663-1668
• /
• 1993

An X-band contiguous band diplexer is realized by using asymmetrical coupled microstrip lines. The design is based on the singly terminated low pass prototype filter and optimized by using SuperCompack. The designed channel 1 and channel 2 bandwidth is 22%, and 18% respectively, where the center frequency is 9,11 GHz. The measured results of the fabricated diplexer are in good agreement with the designed ones, but the measured insertion loss is slightly highier(0.5dB) than those of the designed value.