• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.235-244
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• 2014

This paper describes the subarray channel configuration and calibration method for airborne AESA radar antenna. AESA radar demonstrator was designed and implemented for the digital beam-forming performance test of the 12 channel subarray structure. Magnitude and phase difference can be exist between the manufactured subarray channel. In this paper, calibration method for the subarray difference error was suggested. We measured digital monopulse slope in the subarray channel and verified the channel calibration effect. To verify the subarray channel operation, digital monopulse channel was compared with analog monopulse channel performance. AESA radar demonstrator was tested in the ground far field test range. Emulated single target was generated to test the detection and tracking performance of the demonstrator with the same waveform and search pattern. We verified that the detection and tracking performance of the 12 subarray digital monopulse channel was similar with the conventional analog monopulse channel. Also, ABF(Adaptive Beam-Forming) function for the sidelobe jammer was tested and effective operation was verified.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.257-259
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• 2010

본 논문에서는 지상파 3D HDTV 방송 서비스를 제공하기 위해 수정된 ATSC (Advanced Television Systems Committee) 전송 시스템 [2]을 위한 시변다중경로채널에 강인한 프레임 구조를 제안하고 성능을 측정하였다. 수정된 ATSC 전송 시스템 [2]은 기존 ATSC 전송 시스템[1]의 채널 부호화부를 수정하고, 변조 성상도를 증가 시키면서 적정한 수준의 TOV (Threshold of Visibility)에서의 전송 용량 증대 가능성을 확인하였다. 이를 토대로, 증가된 전송 데이터 전송률에 대한 순수 데이터 전송률을 최대한 보장하면서 시변다중경로채널에서 효율적으로 채널을 추정하고 복구하기 위해, ISI (Inter Symbol Interference)를 방지하기 위한 프레임 헤더의 보호구간에 알려진 PN (Pseudorandom Noise) 심벌을 삽입하였다. PN 심벌을 보호 구간에 이용할 경우 시간 영역에서 채널 임펄스 응답 (CIR: Channel Impulse Response)을 추정하여, 주파수 영역에서의 채널 보상을 가능케 하여 정확한 채널 추정 및 보상을 수행할 수 있다. 또한 수신기의 속도에 따른 다양한 최대 도플러 주파수가 존재하는 채널에 강인한 프레임 구조들을 제안하였다. 컴퓨터 시뮬레이션을 통해 수정된 ATSC 전송 시스템에 제안된 프레임 구조를 적용하여 TU (Typical Urban)-6 채널에서의 SER (Symbol Error Rate) 성능을 측정하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.2
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• pp.68-74
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• 2010

In this paper, we analyze and simulate the channel capacity of a spread spectrum watermarking (SSW) technique in wireless fading channel to apply ITS system. Channel capacity analysis causing minimum effect to existing system is required necessary to apply SSW technique. We derive the channel capacity as a closed-form approximation formula in Rayleigh and Rician fading channel model. The numerical results are demonstrated and good approximated results are reported.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.3
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• pp.9-18
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• 2001

In this paper, we present the joint symbol detection and channel estimation for an orthogonal frequency division multiplexing (OFDM) system in fading channels. The proposed methods are based on decision-directed channel estimation (DDCE) method and their symbol detection is achieved by using Viterbi algorithm. This Viterbi decision-directed channel estimation (VDDCE) method tracks time-varying channels and detects a maximum likelihood symbol sequence. Recursive Viterbi decision-directed channel estimation (RVDDCE) method based on VDDCE method is proposed to shorten the detecting depth. In this method, channel estimate and Viterbi processing are recursively performed every interval of training symbol. Also, average chann'el estimation (ACE) technique to reduce the effect of additive white Gaussian noise (AWGN) is applied VDDCE method and RVDDCE method. These proposed methods arc demonstrated by computer simulation.

• Journal of Broadcast Engineering
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• v.11 no.3 s.32
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• pp.311-319
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• 2006

Platform operators adopted ATSC standard send only their own channel program schedule information, so in order for the viewer to see other channel information, they have to tune the channel to the other. This issue arises from the operators' lack of bandwidth and the business interest conflicts between the platform operators. This paper guides how ATSC standard could be used within Xlet based application to display other channel information through the ISG (Integrated Scheduling Guide) technology via interactive return channel services. Its own channel information can be displayed by using on-air PSIP (Program and System Information Protocol) data.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.5
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• pp.733-738
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• 2013

Orthogonal Frequency Division Multiplexing (OFDM) based IEEE 802.11 a/g systems which are widely used in wireless LAN carry out channel estimation in one time per packet since the systems use only preamble. Whereas, midamble based channel estimation supports continuous channel estimation by tracking the channel state information periodically. Using IEEE 802.11p Wireless Access in Vehicular Environments (WAVE) system, we analyze the performance of the proposed system via practical measurements. Based on these results, practical issues on midamble based channel estimation are investigated.

• The Journal of the Korea Contents Association
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• v.5 no.1
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• pp.147-155
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• 2005

In this paper, communication channels for the transmission of multimedia packets are modeled and evaluated. The multimedia packet traffic characterized by on-off and MMPP process for voice and data, respectively, dynamic channel allocation, queueing of data packets due to unavailability of channels and dropping of queued data packets over timeout, and guard channel for voice packets are modeled. The performance indices adopted in the evaluation of SRN model includes blocking and dropping probabilities. The SRN uses rewards concepts instead of the complicate numerical analysis required for the Markov chain. It is shown that our SRN modeling techniques provide an easier way to carry out performance analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1A
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• pp.38-47
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• 2006

In this paper, we propose a velocity-adaptive channel estimation scheme using the simple zero-forcing technique in the frequency domain. Channel estimation is performed by removing frequency components that are higher than the maximum Doppler frequency in the received signal. The proposed scheme can be extended to the combined estimation scheme for channel coefficients and mobile velocity using one FFT/IFFT module. Simulation results show that the proposed scheme outperforms conventional schemes for a wide range of mobile velocities($3{\sim}300\;Km/h$). Finally, the MSE for the proposed channel estimation scheme is analyzed.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.681-688
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• 2007

Applying an appropriate received signal processing algorithm based on the channel characteristics is important to improve the receiver performance. Wireless channels in general exhibit various time-delay characteristics depending on their power delay profile. When the estimated channel power summation is used to determine the amount of time delay, a channel adaptive receiver structure can be implemented. In this paper, we derive a closed-form expression for the error probability of the channel classification when the estimated channel power summation is used to classify channel groups having different time delay characteristics, and present the performance gain utilizing multiple estimation results.