• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12C
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• pp.1175-1187
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• 2007

This paper proposes a novel crest factor reduction (CFR) algorithm to be deployed on WCDMA basestation. Generally speaking, it is well described that the reduction of peak-to-average ratio (PAR) yields the possibility of using low cost power amplifier such that the basesation becomes economic However, the simple reduction of PAR could degrade the signal quality measured by either peak code domain error (PCDE) or error vector measurement (EVM), and the level of channel interference constrained by adjacent channel leakage ratio (ACLR). Regarding these imperfections, this paper introduces an effective CFR algorithm in which the function of filter-dependent CFR (FDCFR) incorporated with the histogram-based waterfilling code domain compensation (HBWCDC) carries out. To verify the performance of the proposed CFR technique, substantial simulations including comparative works are conducted with obeying W-CDMA basestation verification specification. To exploit the superiority, the performance of the proposed method is tentatively compared with that associated to the simple memoryless clipping method and the memory-required filter-dependent clipping method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.573-587
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• 2007

In this paper, we analyze the adjacent interference between WCDMA and M-WiMAX systems in the 2.6GHz Band under the SISO (Single Input Single Output) configuration. The interference scenarios are characterized into 8 scenarios with different victim and interfering links. Among the 8 scenarios, we find that the most performance loss is observed in the scenarios of victim uplink suffering interference from downlink in both systems. Besides, guard band is applied to mitigate the adjacent interference in all the scenarios. Especially, we reveal that M-WiMAX system is much more sensitive to adjacent interference than WCDMA system due to the lower transmission power. In this paper, we consider the worst interference environment, where interferers always transmit with the maximum power, a loose spectrum mask is adapted, and no additional channel fitters are equipped in both systems.

• Journal of Sensor Science and Technology
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• v.23 no.5
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• pp.349-355
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• 2014

In this paper, we developed a new method to transmit multiple visible light channels in time division mode using the AC power line frequency in order to prevent the crosstalk between adjacent optical signals. Synchronizing pulses are generated from the 220 V power line, and one pulse period is subdivided into several time slots for visible light channels. Each channel transmits data in a predefined time slot without interfering adjacent channels. In experiments, synchronizing pulses with a repetition rate of 240 Hz were generated from the 60 Hz power line, and three VLC channels with a bit rate of 9.6 kbps transmitted data independently using the time slots between synchronizing pulses. This configuration is very useful in constructing time division VLC networks for multiple sensors.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.289-290
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• 2008

We consider cooperative opportunistic beamforming that can mitigate the other cell interference (OCI) in correlated multi-user multiple-input single-output (MISO) cellular environments. By only exploiting the spatial channel information of adjacent cells, the proposed scheme generates the cooperative random beam that statistically avoids the OCI from adjacent cells. Each cell selects a user in an opportunistic manner. Thus, the proposed scheme can simultaneously achieve the multi-user diversity (MUD) gain and the OCI avoidance gain.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.46-55
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• 2009

In RFID field, when the neighboring readers try to occupy the same or adjacent channel simultaneously, there exists reader-to-reader interference; it calls reader collision. From the reader collision, the tags cannot response correctly query from the reader. Reader anti-collision schemes have been developed, and particularly, the Listen-Before-Talk(LBT) scheme is proposed to avoid reader collision in ETSI in multi channel environment. However, in ETSI, there is a drawback that the reader collision does not decreases effectively because the reader selects randomly a channel without considering the channel environment and readers try to occupy the channel concurrently. In this paper, we propose a algorithm based on LBT scheme considering multi channel environment as well as made up for the drawbacks of LBT The proposed algorithm applies random backoff, the collision avoidance mechanism. And it can reduce delay because of our proposed estimation mechanism Simulation using OPNET shows that the proposed algorithm achieves higher superiority than that of the simple algorithms in sparse and dense reader mode.

• Journal of Satellite, Information and Communications
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• v.10 no.1
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• pp.29-32
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• 2015

It has been a big trend of the convergence technologies about communication systems and vehicular industry to improve safety and convenience. To achieve a number of infotainment vehicular applications, vehicles should transmit information with high reliability. A robust and accurate channel estimation scheme is of great importance to achieve the goal. In this paper, we present a novel enhanced decision-directed channel estimation scheme called FADP (Frequency Averaging Data Pilot) for dynamic time-varying vehicular channels in IEEE 802.11p. We use linear averaging filtering in frequency domain, and utilize the correlation characteristic of the channels between the adjacent two data symbols, update the CR in time domain to get more accuracy. Finally, analysis and simulation results reveal that compared with exist schemes, the proposed scheme has a good performance in mean square error (MSE) and bit error rate (BER).

• Journal of Environmental Science International
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• v.14 no.8
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• pp.739-748
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• 2005

The purpose of this study is to analyze seasonal changes in structure and landscape of Gongji stream corridor in Chuncheon, and to suggest some guidelines to contribute to creating a desirable close-to- nature stream. The study seasonally surveyed floodplain and revetment conditions, channel micro-topography, streamflow level and velocity, and vegetational cover. Flooding, water level, and vegetation were major factors of affecting seasonal changes in streambed structure and stream landscape. Small sand bars and islands were considerably disturbed by flooding and water level change. However, large islands and sand bars in the upper and middle section of the study stream remained or reappeared even after flooding. Flooding also tended to repeat channel sedimentation at the same spot. Controlling water volume of the Euiam Lake, which is adjacent to the study stream, caused higher water level downstream in the dry seasons. The majority of vegetation in sand bars and islands was washed away by the floods. Vehicle passing, crop cultivation, and ball game were other elements which disturbed vegetation in the floodplain. Creating a close-to-nature stream should reflect micro-topographical changes of channel by flooding, prevent improper vehicle entry and human use, and remove concrete material in the revetment and floodplain.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.156-160
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• 2002

In this paper, we have estimated by means of the theoretical analysis and the simulation of FCA(Fixed Channel Assignment) and CB(Channel Borrowing) in order to consider the CB as a technique to meet ducting interference from adjacent countries. Also, we assumed that the receiving power level of ducting interference with time rate can be characterized by the normal distribution due to the previous measured results, and the ducting interferences which are exceeding the reference power level can be regarded as calls. These calls can be processed by CR assignment and by which sharing channels between cells brings to us the method of meeting the ducting interference to use spectrum resources effectively. However, the spectrum frequency reusing and the interference effects between channels should be considered in CB simulation in the future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.54-61
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• 2010

We propose a subspace interference alignment by orthogonalization of reference vectors. The proposed method improves the sum-rate capacity degradation due to the channel decomposition error and channel estimation error in the real environment. Using the proposed method, each cell uses the reference vector that is orthogonal to the adjacent cells. Then the residual interference produced by the channel decomposition error and the channel estimation error is decreased. The simulation results demonstrate that the proposed method achieves the enhanced sum-rate capacity.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.4 no.1 s.6
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• pp.63-71
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• 2005

This paper proposes the channel estimation method robust to severe frequency selective fading channels in O%M system using wide bandwidth for the high data rate transmission. DDCE, which uses data between the high correlated symbols, is usually used for channel estimation in the slow fading channels. DDCE can get high gains in the non-selective channels. As the bandwidth of system gets wider, it becomes more severe frequency selective fading environments so that the reliability of data becomes lower and error flow is occurred. FE method, this paper proposed, uses the relation between sub-carriers of OFDM in frequency selective fading channels so FE method gets some gains by adapting the power value at a target frequency to the mean value of channel estimated values of adjacent sub-carriers. Because FE uses only preamble unlike DDCE using data, it is independent of data rate related to the reliability of data and the number of multipath. Consequently, FE can obtain considerable gains in the wideband systems where the errorflow of DDCE is occurred, and FE is applicable to frequency selective fading environments.