• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11C
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• pp.641-648
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• 2011

Frequency domain equalization is the most promising technology that has relatively low complexity in multipath channel. A frame of single carrier system with frequency domain equalization (SC-FDE) has cyclic prefix to mitigate effect of delay spread. After synchronization and equalization procedure on the SC-FDE system, common phase offset (CPO) that can introduce performance degradation caused by phase mismatch between transmitter and receiver oscillators is remained. In this paper, common phase offset tracking in frequency domain is proposed. To track CPO, constant amplitude zero autocorrelation code sequence as training sequence is adopted. By using numerical results, performance of mean square error is evaluated. The results show that MSE of CPO has similar performance compare to the time-domain estimation and there is no need of domain conversion.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.7
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• pp.9-16
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• 2012

In order to extend cell coverage and to cope with shadow areas, a relay-assisted wireless communications system has been widely studied. In this paper, we propose new equalization method for single carrier (SC) frequency domain equalizer (FDE) in amplify-and-forward (AF) relaying multi-path networks to improve the performance at shadow areas. The performance of SC-FDE system in 3-slot based multi-path networks can be improved considerably with the diversity gain which we obtain by equalizing the combined signal from relays by means of the minimum mean square error (MMSE) criteria. We find the weighting coefficients of maximum ratio combining (MRC) and the tap coefficients of MMSE equalizer for SC-FDE in AF relaying multi-path networks. Simulation results show that the proposed system considerably outperforms the conventional SC-FDE system.

• The Journal of Information Technology
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• v.7 no.3
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• pp.37-45
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• 2004

The representative communication method which is applied in the low-speed power line communication modem with 60bps is single carrier method. It has been used mainly for the control. The single carrier method is very sensitive to a power line communication channel environment. Specially, the severe attenuation of the transmission signal according to the notch characteristics of channel becomes the main cause of communication error. Domestic power line channel environment has this notable feature. In this paper, we implemented the low-speed power line communication system which used the chirp signal method to be strong in notch and noise characteristics. In this research, we proposed the method which transmits 1- '1 Unit symbol Chirp signal' with a 100${\mu}s$ time within 1ms for 1 bit. Also it applied for the Convolution code for an error correction and the Manchester code for a collision perception and an error detection. It used the method which uses the bit correlator for signal detection in the receiver parts. We confirmed that the communication method of the chirp method has a excellent performance compared to single carrier methods with a result of experiment of the low-speed power line communication system with the 60bps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.5C
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• pp.295-301
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• 2011

In [1], it has been shown that the energy spreading transform (EST) based iterative equalizer (IE) could enhance its performance by improving the reliability of the decision feedback symbols without the help of the complicated channel decoder. In the matched filter (MF) based IE proposed in [1], however, its feedforward filter (FFF) has been designed in the frequency domain while its feedback filter (FBF) in the time domain. So its complexity increases proportional to the channel memory length. To solve this problem, in this paper, both FFF and FBF are designed in the frequency domain. This enables the proposed frequency domain IE (FD-IE) to achieve the lower complexity over the conventional method in the highly dispersive channel. In addition, simulation results demonstrate that the BER performance of the proposed method is the same as the conventional.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.25-32
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• 2007

This paper proposes a distributed space-frequency block code (SFBC) for relay-assisted single carrier frequency-domain equalization (SC-FDE). The proposed technique achieves spatial diversity gain over fast fading channels without the complexity of multiple antennas. The mobile equipment of the proposed system has a very simple transmitter structure with constant amplitude transmit sequences, which is desirable especially for uplink communications. In order to obtain spatial diversity, the transmit sequence of relay is efficiently generated in the time domain, which is equivalent to the SFBC. Further, efficient implementation of relay and destination structures is also presented. Extensive simulation results show that the proposed system significantly outperforms the distributed space-time block code (D-STBC) SC-FDE over fast fading channels.

• Journal of Broadcast Engineering
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• v.24 no.6
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• pp.1143-1151
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• 2019

In this paper, we propose a wireless transmission scheme that maximizes transmission efficiency per frequency bandwidth in a single carrier modulation scheme. The proposed scheme employs a decision directed channel tracking technique to remove both pilot signal and the guard interval signal between symbols in frames. It performs a raised cosine pulse shaping function with an roll-off factor of 0.05. In addition, 2×2 multiple input and multiple output using two polarized antennas is applied and both equalization and signal separation are performed in the frequency domain. The wireless modem with this technology confirms that the transmission speed of up to 63.3Mbps is achieved under the 5MHz frequency bandwidth

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.5
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• pp.25-36
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• 2022

This paper proposes a random sign reversal technique in space frequency block code for single carrier modulation. The traditional space time and frequency block coding technique may be confronted with radio environments openly, severe radio hijacking problems are to be overcome. In order to avoid such an open radio issue, random coded data protection technique for space-time block code was proposed, but this algorithm can change channel combination per an Orthogonal Frequency Division Multiplexing block. This kind of slow switching increases the probability that nearby receivers will detect the transmitted data. This paper proposes a fast switching algorithm per data symbols' basis which is a random sign reversal technique in space frequency block code for Single Carrier Modulation. It is shown in simulation that the proposed one has a superior performance in comparison with the performance of the receiver which do not know the random timing sequence of sign reversal.

• Polymer(Korea)
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• v.26 no.4
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• pp.543-550
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• 2002

We have synthesized a novel carrier transporting copolymer having triphenylamine moiety as a hole transporting unit and triazine moiety as an electron transporting unit in the polymer side chain. Single-layered organic electroluminescent (EL) devices consisted of ITO/copolymer and emitting materials (DCM, coumarin 6, DPvBi)/Al exhibited maximum external quantum efficiency when the ratio of hole transporting unit and electron transporting unit is 6:4 and the content of emitting material is 30 wt%. Especially, the devices emitted the light of red (620 nm), green (520 nm) and blue (450 nm) corresponding to the emitting materials, respectively. A maximum luminance of ITO/copolymer (6:4) and DCM (30 wt%)/Al EL device was about 500 cd/$m^2$ at a DC drive voltage of 12V.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1007-1013
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• 1998

The samples of Bi2Sr2Ca1-xNaxCu2O8+y with various carrier concentration were synthesized by substituting Na for Ca ion. The superconducting properties hall coefficients and X-ray powder diffraction were measur-ed the sampled. Single phase samples were obtained for 0$\leq$x<0.3 of Bi2Sr2Ca1-xNaxCu2O8+y In the single phase the critical temperature. {{{{ { T}_{c } }} and carrier concentration increase with the increase of Na concentration pass through a maximum and then decreases. In the range of x$\geq$0.7 to the Na doped samples however we observed the metal-semiconductor transition. The c-axis seemed to decrease and a and b-axes increase with increasing Na concentration in the single phase. Decreasing of c-axis while increasing x is due to the smaller size of {{{{ {Na}^{+1 } }} ions to the {{{{ { Ca}^{+2 } }} ions. In the range of x>0.3 however the trend becomes ambiguous due to the inclusion of the 10K phase and impurity phase.

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1986-1995
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• 2018

In this paper, a novel neutral-point voltage balancing scheme for NPC three-level inverters using carrier-based sinusoidal pulse width modulation (SPWM) method is developed. The new modulation approach, based on the obtained expressions of zero sequence voltage in all six sectors, can significantly suppress the low-frequency voltage oscillation in the neutral point at high modulation index and achieve a fast voltage-balancing dynamic performance. The implementation of the proposed method is very simple. Another attractive feature is that the scheme can stably control any voltage difference between the two dc-link capacitors within a certain range without using any extra hardware. Furthermore, the presented scheme is also applicable to the single-phase NPC three-level inverter. It can maintain the neutral-point voltage balance at full modulation index and improve the voltage-balancing dynamic performance of the single-phase NPC three-level inverter. The performance of the proposed strategy and its benefits over other previous techniques are verified experimentally.