• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.246-252
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• 2012

STBC is a technique where a multiple antenna signals are transmitted. With this technique, antenna diversity can be achieved. The performance of STBC OFDM system using pilot symbol for the channel estimation is analyzed. IEEE 802.16e standards suggest that the BER performance of STBC system can be improved using channel state information. Pilot symbol is used for the channel estimation in OFDM systems. However, imperfect channel estimates in this systems degrade the performance. The performance of this STBC OFDM systems using channel state information, gauged by the average bit error rate, is analyzed considering the channel estimation error.

• Journal of Positioning, Navigation, and Timing
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• v.4 no.3
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• pp.97-105
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• 2015

A navigation signal based on orthogonal tiered polyphase code was proposed. For the proposed signal, tiered polyphase code was used as the code of a pilot channel. Tiered polyphase code is a complex number type code, and thus the pilot channel and data channel were separated using the Walsh code which makes the correlation between different codes become 0. The results of the simulation indicated that the correlation characteristics and signal acquisition performance of the proposed signal were identical to those of tiered polyphase code, and that the disadvantage of tiered polyphase code could be supplemented through a data channel in terms of signal tracking.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.4
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• pp.209-221
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• 2008

In this paper, we propose a subcarrier allocation method and a composite linear minimum mean square error (LMMSE) channel estimator to increase spectrum efficiency in orthogonal frequency division multiplexing (OFDM) transmit diversity. The pilot symbols for OFDM transmit (Alamouti) diversity are exclusively allocated in two OFDM symbols in different antennas, which causes serious degradation of spectrum efficiency. To reduce the number of pilot symbols, our subcarrier allocation method uses repetition-coded data symbols, and the proposed channel estimator maintains good bit error rate (BER) performance.

• International Journal of Contents
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• v.14 no.1
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• pp.39-44
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• 2018

Today, cars have developed into intelligent automobiles that combine advanced control equipment and IT technology to provide driving assistance and convenience to users. These vehicles provide infotainment services to the driver, but this does not improve the safety of the driver. Accordingly, V2X communication, which forms a network between a vehicle and a vehicle, between a vehicle and an infrastructure, or between a vehicle and a human, is drawing attention. Therefore, various techniques for improving channel estimation performance without changing the IEEE 802.11p standard have been proposed, but they do not satisfy the packet error rate (PER) performance required by the C-ITS service. In this paper, we analyze existing channel estimation techniques and propose a new channel estimation scheme that achieves better performance than existing techniques. It does this by applying the updated matrix for the data pilot symbol to the construct data pilot (CDP) channel estimation scheme and by further performing the interpolation process in the frequency domain. Finally, through simulations based on the IEEE 802.11p standard, we confirmed the performance of the existing channel estimation schemes and the proposed channel estimation scheme by coded PER.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.435-441
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• 2001

In this paper, we proposed adaptive MMSE receiver, which use channel equalizer to eliminate the interference due to multi-path fading and adaptive filter to eliminate the multiple access interference. The unique features of proposed receiver schemes are as following. We use pilot channel to estimate the channel coefficients exactly and guard symbols which are inserted periodically to estimate channel coefficients exactly without interference from user signals. The length of channel equalizer also can be reduced with the help of guard symbols. Especially utilizing adaptive code-matched filter(AMMSE) when the user population is high and SNR is not low we accepts excellent performance improvement.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.19-24
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• 2010

This paper proposes a unified time-domain channel estimator (UTD-CE) for ubiquitous wireless broadband access based on orthogonal frequency division multiplexing (OFDM) systems. As a part of a software radio platform for ubiquitous services, the proposed UTD-CE can be exploited with the simply changeable parameters, pilot symbols and pilot subcarriers allocation, which are usually different according to the system specifications such as IEEE802.11x WiFI, IEEE802.16x WiMAX, DMB, Media FLO, DVB-H, etc. Given the pilot information, the channel frequency responses (CFRs) of data subcarriers will be analogously estimated by Wiener filtering and discrete Fourier transform (DFT)-based interpolation in the UTD-CE. Simulation results indicate that the proposed method significantly outperforms the conventional time-domain channel estimator when the pilot information is changed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.126-136
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• 1997

When we apply the spectrally efficient quadrature amplitude modulation(QAM) to mobile communications, it is necessary to estimate and compensate the channel charac- teristics. In this paper, a new type fading estimation method for PSAM using sinc function is presented. Gaussian interpolation method has a drawback that the performance degrades rapidly if pilot symbol period increases even though pilot sysbol period is less than Nyquist sampling rate. The Wiener filter method does not degrade until pilot symbol period is equal to the Nyquist sampling rate. It is difficult for Wiener filter method to be applied to real system because autocorrelation function of channel gain, Doppler frequency and SNR(signal to noise ratio) must be known to optimize the filter coefficients. But proposed method has a similar performance to the Wiener filter method, and does not need to know the autocorrelation function of channel gain, the doppler frequency and SNR. Therefore the proposed method cna be applied to real system easily.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.545-551
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• 2011

In this paper, we described a measurement method of an EIRP(Effective Isotropic Radiated Power) of a WCDMA base station using a pilot channel in line-of-sight environments. Especially we measured it in real base station environments in order to apply this method to domestic base station inspection test. Estimated EIRP results from measured value is -2 dB lower than theoretical values, which is calculated by the data of transmit antenna. The deviation of -2 dB is verified as a polarization mismatch between the base station antenna and a receiver antenna, and it can be calibrated. Therefore, we verified that our measurement method could be an effective tool to measure an EIRP in WCDMA base station inspection test.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.87-90
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• 2000

Differential channel 정보를 feedback 하는 close loop Tx diversity를 제안한다. 본 Tx diversity는 기존의 channel feedback Tx diversity 보다 W-CDMA의 forward link와 reverse link channel 용량을 더 많이 늘린다. Differential channel 정보를 estimation 하는 방법을 제안한다. 부가적으로 보내는 정보 없이 W-CDMA의 forward power control 에 사용하는 dedicated pilot 심볼을 이용해 differential channel 정보를 estimation한다. 기존에 제안된 channel feedback Tx diversity들과 성능을 비교한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1179-1186
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• 1999

Multi-carrier CDMA technique is more attractive in wireless communication system. It can support the effect of frequency diversity with higher spectral efficiency. In this paper, pilot symbol structure was proposed to estimate chann디 paramenters for MC-CDMA system and we analyzed the perfoemance of proposed MC-CDMA which compensates the received signals using the pilot symbols for link transmission. At first, we proposed the new method of pilot's usage for reverse link transmission that can distinguish accessing users whose signals undergo diggerent channels. And we analyzed the performance of coherent MC-CDMA reception using estimated channel parameters