• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.12
• /
• pp.2805-2812
• /
• 2015

For the purpose of estimation of time variant frequency selective transmission channels, reference symbols are usually employed. The bit error performance of LTE OFDM systems is analyzed in the case of LTE standard reference symbol arrangement. Results show that LTE OFDM system with this LTE reference symbol arrangement is robust against Doppler time variant fading. However, the performance of that system is degraded due to channel estimation error in frequency domain. An equidistant arrangement with a diamond shape structure of reference symbols, however having 4 subcarriers distance in frequency domain, is suggested for the optimal channel estimation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.3
• /
• pp.289-293
• /
• 2013

In the noncoherent methods for UWB-IR (ultra-wideband impulse radio), block coded modulation (BCM) is better than the transmitted reference (TR) systems in terms of the energy efficiency and data rate. However, even BCM suffers from the performance degradation in the presence of strong inter-frame interference and inter symbol interference. We propose the transmitted reference based on the BCM (TR-BCM) which is the hybrid system of TR and BCM. Performance evaluation shows that the performance of TR-BCM is better than that of BCM in the high SNR range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.15 no.4
• /
• pp.414-420
• /
• 2004

Partial transmit sequence(PTS) scheme has been widely studied to reduce the peak-to-average power ratio(PAPR) of Orthogonal frequency-division multiplexing(OFDM) signal since it is flexible ad any spectral regrowth is not made. A necessity of the PTS scheme is to transmit the side information about the phase rotation factors for correct OFDM symbol recovery. In this paper, a new side information embedded PTS scheme using the reference symbols is proposed fur the PAPR reduction and the BER(bit error rate) performance is analyzed when the erroneous side information is received. In this proposed method, the information about the rotation factors is expressed by the phase of reference symbols. The proposed method maintains the same PAPR reduction performance as the conventional PTS scheme and OFDM symbols are correctly recovered by the side information to meet the required BER level, which is verified via the computer simulation. Also, it is shown that the proposed method can be easily realized and can be used for all kinds of digital modulation formats in the OFDM communication system.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.33B no.3
• /
• pp.176-185
• /
• 1996

Transformin the huge size of drawings into a suitable format for CAD system and recognizng the contents of drawings are the major concerans in the automated analysis of engineering drawings. This paper proposes some methods for text/graphics separation, symbol extraction, vectorization and symbol recognition with the object of applying them to electronic cirucit drawings. We use MBR (Minimum bounding rectangle) and size of isolated region on the drawings for separating text and graphic regions. Characteristics parameters such as the number of pixels, the length of circular constant and the degree of round shape are used for extracting loop symbols and geometric structures for non-loop symbols. To recognize symbols, nearest netighbor between FD (foruier descriptor) of extractd symbols and these of classification reference symbols is used. Experimental results show that the proposed method can generate compact vector representation of extracted symbols and perform the scale change and rotation of extracted symbol using symbol vectorization. Also we achieve an efficient searching of circuit drawings.

• Journal of electromagnetic engineering and science
• /
• v.1 no.1
• /
• pp.105-111
• /
• 2001

This paper presents a new and robust technique for a coarse frequency offset estimation in OFDM systems. As an evaluation of the proposed algorithm, we apply it to Eureka 147 DAB system. The proposed coarse frequency offset estimation algorithm is based on the differential detection technique between adjacent subcarriers to eliminate the phase shift effects of symbol timing offset and fractional frequency offset. A coarse frequency offset is determined from the correlation output between a received interarrier differential phase reference symbol and several locally generated but frequency-shifted intercarrier differential phase reference symbols. The performance of our estimation algorithm is evaluated by means of computer simulation and is compared with those of previous proposed algorithms for DAB transmission modes I, II, III, and IV. Simulation results show that the proposed algorithm generates extremely accurate estimates with low complexity irrespective of the symbol timing offset.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.187-190
• /
• 1998

In this paper, a synchronization method of OFDM signals are introduced and its performance is estimated. A proposed method can perform a frame/symbol timing, carrier frequency synchronizations. Reference symbols consist of two duplicate OFDM symbols carrying signals on every sub-carriers. Performances of synchronization under 60GHz millimeter-wave indoor channels are evaluated, which were measured with frequency-sweeping method in common office buildings. A proposed method has improved performances owing to long averaging durations of synchronization metrics in frame/symbol timing, carrier frequency synchronization procedures.

• The Journal of the Korea Contents Association
• /
• v.7 no.7
• /
• pp.77-86
• /
• 2007

These days, universities are establishing new image; UI(University Identity) for them because of rapid change of education environment in 21st century, The objective of UI is expressing university's image externally and unifying members internally. In the process of establishing university's image, Symbol mark plays a key role in differentiating other universities because of its visual effect as well as enhancing self-confidence. In this study, I suggest that symbol mark is an important brand asset in point of differentiation and identification and analyze 36 domestic universities' symbol mark designs. In the way of this analysis, I classified these symbol marks in the aspect of shapes and colors and studied current design along with character of each symbol marks by examining usage of emblem. Therefore this paper will be used as a basic reference to understand domestic universities' symbol mark trend and to establishing differentiating strategy in the future.

• Journal of the Korean Society of Costume
• /
• v.54 no.8
• /
• pp.35-48
• /
• 2004

This thesis researches consumers' behaviors in Purchasing avatar fashion products depending on their motives and point of reference as the avatar fashion marketing is conducted. Also, it explores the correlation between avatar's fashion products and the point of reference by which consumers actually purchase casual wear. The results were as follows: First, Avatar's fashion product purchasing motivation is done through four classified dimensions, conformity, differentiation, fashionability, and substitution. The standard of Avatar's fashion product choice was classified by the symbol (Product name recognition) and two dimensions of aesthetics. Second. the more valued the aesthetic component of Avatar's fashion product the greater effect on the order the dimensions used in correlation in this case being substitution, differentiation, conformity, and fashionability. Should the consumer place greater value on the Product symbol the dimension order is affected in order by fashionability, conformity, and differentiation. Third, fashionability was a stronger consideration for women as opposed to men in terms of demographical feature. whereas symbol (Product recognition) was of greater importance to higher income people. Last, when aesthetics is considered to buy Avatar's fashion products it is favorably comparable to other casual wear lines. In other words, symbol is considered to buy casual's, it brings to the same result when buying Avatar's. Avatar's fashion product was great tool to research new casual wear line because of approving by the correlation to each other.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.86-89
• /
• 1999

In this paper, we propose a new architecture of the fast symbol timing synchronization system which has some shared hardware blocks in order to reduce the hardware complexity. The proposed system consists of received power detector, correlation power detector using shared complex moving adders, and 2-step peak detector. Our system has detected FFT starting point within three Symbols using first two reference symbols of the frame in wireless ATM system. The new architecture was designed and simulated using VHDL. Our proposed architecture also detects a correct symbol timing synchronization within three symbols under a multi-path fading channel.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.5
• /
• pp.117-121
• /
• 2014

In the orthogonal frequency division multiplexing system, the prefix inserted between data symbols should be eliminated to apply the Fourier transform on the valid symbol interval. This functional procedure should be based on the accurate symbol timing detection. The symbol timing detection at the receiver side provides the reference for determining the beginning time index of each symbol whose initial point is located at the boundary between the preamble and the payload part. Also, the detection error is one of the main factors in the overall system performance. In this paper the effect of the bandwidth of the moving average filter on the symbol timing detection is discussed. Simulations are carried out to analyze the detection performance for the varying values of the window size of the moving average filter which is related to the filter bandwidth.