• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.30-34
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• 2008

In this paper, we analyze the performance of pulse position modulation-time hopping ultra wide band (PPM-TH UWB) systems with antenna diversity technique in indoor wireless channel. A modified Saleh and Valenzuela (SV) model is adopted as a UWB indoor channel model. Perfect synchronization between a transmitter and a receiver is assumed. Therefore, coherent equal gain combining (EGC) scheme to collect the energy available in the multipath components is investigated. It is shown that the performance is improved by increasing the number of antennas at the receiver. The results of this paper can be applied to the applications of UWB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.4
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• pp.423-429
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• 2011

Cooperative spectrum sensing is proposed to overcome some problem such as multipath fading and shadowing and to improve spectrum sensing performance. There are different combining methods for cooperative spectrum sensing: hard decision method and soft decision method. In this paper, we analysis the performance of cooperative spectrum sensing with distance based weight that is kind of a soft decision rule for cognitive radio(CR) systems and CR systems sense the spectrum of the licensed user by using a energy detection method. Threshold is determined in accordance with the constant false alarm rate(CFAR) algorithm for energy detection. The signal of licensed user is OFDM signal and the wireless channel between a licensed user and CR systems is modeled as Gaussian channel. From the simulation results, the cooperative spectrum sensing with distance based weight combining(DWC) and equal gain combing(EGC) methods shows higher spectrum sensing performance than single spectrum sensing does. And the detection probability performance with the DWC is higher than that with the EGC.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.65-70
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• 2013

In this paper, we propose a multi-hop cooperative transmission protocol to obtain energy savings in static wireless networks. Each terminal in the network is equipped with a single antenna and each receiver uses equal gain combining technique (EGC) to combine received signals. We also propose a power allocation strategy which optimizes the total transmit power at each stage. Monte-Carlo simulations are presented to evaluate and compare performance of the proposed protocol with the multi-hop direct transmission (MDT) and the cooperative routing protocol proposed by Khadani [8], in terms of the average total transmit power and the average number of required stages.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1588-1603
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• 2014

In space diversity combining, conventional methods such as maximal ratio combining (MRC), equal gain combining (EGC) and selection combining (SC) are commonly used to improve the output signal-to-noise ratio (SNR) provided that the channel is perfectly estimated at the receiver. However, in practice, channel estimation is often imperfect and this indeed deteriorates the system performance. In this paper, diversity combining techniques based on two evolutionary algorithms, namely genetic algorithm (GA) and particle swarm optimization (PSO) are proposed and compared. Numerical results indicate that the proposed methods outperform the conventional MRC, EGC and SC methods when the channel estimation is imperfect while it shows similar performance as that of MRC when the channel is perfectly estimated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.9
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• pp.535-547
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• 2014

We investigate BER (Bit Error Ratio) performance according to the gain of spatial and frequency diversities in uplink SC-FDMA of SIMO (Single Input Multiple Output) systems. The main results of the analysis in this paper are as follows. First, we prove that performance of integrated system for considering spatial and frequency diversity combining in parallel is equivalent with the performance of sequential system for performing diversity combining in sequence. By signal modeling, it is demonstrated that the performances of both systems are the same when the frequency diversity combining technique of the sequential system is equal to diversity combining technique of the integrated system, and spatial diversity combining technique of the sequential system is performed as MRC in advance of frequency diversity combining. Secondly, it is found that effect on the BER performance is different according to the gain of spatial and frequency diversities, respectively. The frequency diversity gain increases by increasing the number of subcarrier. It might affect the performance improvement of high SNR(Signal to Noise Ratio) while it maintains gap between performances of ZF(Zero Forcing) and MMSE(Minimum Mean Square Error) in frequency diversity combining schemes. Also, spatial diversity gain increases as the number of receiving antennas increases. It means that it can reduce performance gap between ZF and MMSE in frequency diversity combining schemes by increasing the number of receiving antennas. In addition, it might affect the performance improvement of the whole SNR. Finally, through the analysis of performance according to the spatial diversity gain, the performance of ZF in frequency diversity combining is equal to the MMSE if the number of receiving antennas is 6 or more.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.45-50
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• 2010

In this paper, we analysis the performance of cooperative spectrum sensing with distance based weight for cognitive radio (CR) systems and CR systems sense the spectrum of the licensed user by using a energy detection method. Threshold is determined in accordance with the constant false alarm rate (CFAR) algorithm for energy detection. The signal of licensed user is OFDM signal and the wireless channel between a licensed user and CR systems is modeled as Gaussian channel. From the simulation results, the cooperative spectrum sensing with distance based weight combining (DWC) and equal gain combing (EGC) methods shows higher spectrum sensing performance than single spectrum sensing does. And the detection probability performance with the DWC is higher than that with the EGC.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.198-204
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• 2011

Acoustic communication system is a transmission technology sending sound and data simultaneously. However, data signal can be audible in this system when data is transmitted with high transmission power. The more transmission power is reduced, the more distance that can transmit data is shortened. Therefore, the study that increase the transmission distance is needed. In this paper, we would like to increase transmission distance by adapting receive diversity in acoustic communication system. We measure received performance of both proposed system and Single Input Sing Output (SISO) system according to distance with same transmission power. When SISO satisfies Bit Error Rate (BER) of $7{\times}10^{-3}$ at about 2m, Selection Combining (SC) technique satisfies 2 meters, and Equal Gain Combining (EGC) technique satisfies 4 meters.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.470-477
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• 2001

Multucarrier code-division multiple access(MC-CDMA) is one of the promising technique for high capacity wireless communication. Hower the carrier phase error and frequency offest cause the performance degradation of MC-CDMA due to the inter-carrier interference. In this work, downlink performance of the partially coherent MC-CDMA is analytically derived in Rayleigh fading channels. The bit error rate sensitivity by combining method, Maxiaml ratio combining (MRC)and Equal gain combining(EGC), is compared as functions of phase errors. multi-user interference, and received signal-to-noise ratio. The results show that the susceptibility for the performance degradation of EGc and MRC is negligible for loop SNR's of above 15 dB and above 10 dB, respectivtely.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.5
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• pp.21-29
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• 2008

This paper proposes a carrier frequency of set estimation algorithm for IEEE802.11n system. As IEEE802.11n is a multiple input multiple output(MIMO) system, so there are several combining techniques which are used in multiple receive antenna system. In this paper, we propose hybrid carrier frequency offset estimation algorithms using combining techniques in multiple receive antenna systems, and show that the proposed selection combining carrier frequency offset (CFO) estimation algorithm can estimate carrier frequency offset within 1/10 MSE error at SNR 10 dB in channel B and within 1/2 MSE error at SNR 10 dB in channel D rather than the conventional MIMO CFO one.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.344-348
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• 2009

Cognitive Radio(CR)는 특정 주파수 대역을 사용하도록 할당된 유저가 사용하지 않을 때, 이를 탐지하여 해당 주파수 대역을 이용함으로써 주파수 스펙트럼 효율을 향상시킬 수 있는 기술이다. 특히, CR에서 스펙트럼 센싱(Spectrum Sensing)은 중요한 기술의 하나라고 말할 수 있다. 기존의 스펙트럼 센싱 성능을 향상시키기 위한 방법으로, 다수의 노드가 각각 판정한 결과를 이용하는 OR-Rule, AND-Rule 등의 기법이 제안된 바 있다. 본 논문에서는 수신 다이버시티 기법 중의 하나인 Equal Gain Combiner(EGC) 알고리듬 이용하여 스펙트럼 센싱 성능을 알아보고 특히, 기존의 방법은 각 노드에서 판정 후 판정부에서 그 결과를 결합하여 최종 판정하는 방법이나, 본 논문에서 적용한 EGC 기법은 각 노드에서 수신된 신호에 대한 검출된 에너지 값을 융합센터(Fusion Center)로 보내어 최종 판정하는 방법이다. 각 노드에서 검출된 에너지 값을 융합센터가 수신한 신호에는 실질적으로 잡음이 섞이게 되므로 이로 인하여 발생할 수 있는 전송 오류를 추가적으로 고려하였다. 또한, 각 노드에서 검출한 에너지 값이 융합센터로 전송될 때에는 양자화 되어서 전송된다. 이에 따라서 양자화 bit수와 관련된 센싱 성능과 데이터의 반복 전송의 필요성, 그리고 그 횟수에 대해 제시하고자 한다.