• International Journal of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.34-40
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• 2019

In spatial modulation (SM), both the signal symbol and spatial symbol, i.e., the index of the antenna from which signal symbol is transmitted, carry information. To increase the number of bits carried by spatial symbols, more transmit antennas are required. In the generalized SM (GSM), the same signal symbol is transmitted from a combination of antennas, resulting in a reduction in the number of antennas required to achieve a given spectral efficiency. In this paper, we propose a rotated-symbol GSM (RGSM), in which the signal symbol is rotated with an angle corresponding to the position of the antenna index within the combination. This increases the number of spatial symbols by a factor equivalent to the length of the antenna combinations of the GSM. Numerically, SM, GSM and RGSM require 128, 17 and 12 transmit antennas to convey seven bits through the spatial symbols. Simulation results show that RGSM performs relatively close to GSM, and in several system settings, their error performances coincide.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.157-165
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• 2004

The synchronization algorithm of IEEE 802.11a WLAN(Wireless Local Area Network) has three consecutive processes, which use a short code training symbol, a long code training symbol and a pilot symbol respectively. But in using this synchronization processes, the actual embodiment has two problems. First, the synchronization process has the complex structure using a long code training symbol and a pilot symbol. Second, since the long training symbol is only compensated with the offset correction coefficient, it can not be trusted perfectly. If the equalizer coefficient is obtained in this unstable period, the system performance is degraded. In particular, the system performance becomes worst in case of the 54 Mbps transmission system using the maximum length of data. In this paper, the new algorithm is proposed which can resolve the embodiment complexity of synchronization processes and structural defect, and also it is confirmed by simulation.

• Journal of Advanced Navigation Technology
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• v.15 no.6
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• pp.1042-1046
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• 2011

In this paper, we analyze the STO (Symbol Timing Offset) problem in conventional ZP-OFDM (Zero Padding-Orthogonal Frequency Division Multiplexing) systems and propose a robust ZP-OFDM system with bi-directional overlap-add scheme to overcome the problem. The proposed ZP-OFDM system is able to preserve the orthogonality between subcarriers and reduce the interference from other ZP-OFDM symbols due to the BOA scheme, which exploits both ZP intervals of the previous and the current ZP-OFDM symbols, even though serious STOs result from inaccurate symbol timing synchronization. Simulation results verify that the proposed ZP-OFDM system is superior to the conventional ZP-OFDM system.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.2
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• pp.225-231
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• 2010

This paper proposes the strategy of ladder trades in a symbol pool and simulates a performance of it on the Multicharts' system trading tool. The ladder trading strategy is based on a multi-entry strategy which is efficient for several symbols. A symbol pool is composed of verified stocks comprising KOSPI200 and 17 symbols are selected for an examination which equity is over 10 billion. From July to December in 2009, optimum parameters are searched and the results are delta is 4% and ladder is 5. When those parameters are adopted, the profit is 1,000,000 won as a single trade and the number of trade is 188. The next study is to modify a ladder shape for increasing probability and to find the difference of optimum parameters according to trading months.

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

• Proceedings of the KSRS Conference
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• v.2
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• pp.896-898
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• 2006

Geological symbols are used for describing geological information. But it's not ease to represent them in commercial GIS s/w, because of their complexity and diversity. This study aims at developing the geological symbol mapping tool for representing geological symbol on user's geological information. Geological symbol mapping too is a web application which can handle SHP format and map geological symbols based on user's requests. It manages geological symbols and mapping codes and symbols are mapped within the geological boundary according to the corresponding non-spatial field that is a mapping code. The system has functions to upload a user's GIS file, and download the converted image file which is mapped geological patterns. The system displays converted images to be check mapping results. Because the symbols are simple bitmap files, user(system manager) can design and apply them rapidly without considering specific commercial S/W. Thus, it is expected that this system plays an important role to disseminate geological standards such as geological symbols. And the results of this study can be used for developing global geological symbols and applying them easily

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.6
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• pp.1914-1925
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• 2014

Inter-symbol interference (ISI) problem is inevitable when the guard interval (GI) is shorter than the delay spread (DS) for an orthogonal frequency division multiplexing (OFDM) system. Iterative techniques have been proposed to overcome such a problem. However, most of existing algorithms are not efficient for an OFDM system with a small GI working under the channel with a large DS. Especially in the case of the DS spans a longer time than the half of the OFDM symbol duration. On the other hand, conventional algorithms, which can reduce the effects of the severe ISI, often employ several impractical assumptions to support the conclusions. In this paper, we present a robust decision feedback equalizer (DFE) for the OFDM system to overcome the severe ISI problem. The proposed DFE removes the ISI in a same manner as the residual inter-symbol interference cancellation (RISIC) algorithm. However, the inter-carrier interference (ICI) is reduced via cyclicity removal instead of the cyclicity restoration used in the conventional algorithms. The link-level simulation (LLS) results indicate that our proposed DFE scheme can dramatically improve the BER performance when the DS spans longer than the half of ODFM symbol duration.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.574-577
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• 2002

In this paper, we propose a new symbol time synchronization scheme suitable for the OFDM system with an interpolator. The proposed performs the following three steps. In the first step, the coarse symbol time synchronization is achieved by continuously measuring the average power of the received envelope signal. Based on this average power, the detection possibility for the symbol time synchronization is determined. If the signal is sufficient for synchronization, we next perform a relatively accurate symbol time synchronization by measuring the correlation a short training signal and the received envelope signal. Finally, an additional frequency synchronization is performed with a long training signal to correct symbol synchronization errors caused by the phase rotation. From the simulation results, one can see that the proposed synchronization scheme provides a good synchronization performance over frequency selective channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1864-1871
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• 2001

In this paper, new symbol timing recovery algorithm is proposed, which is suitable for the digital communication system with Multi-level PAM signals. In the newly proposed symbol timing recovery algorithm, the timing error function is derived by compensating the several difference values between sampled symbol and neighboring symbol every symbol period with mid samples and decided symbol values. Conventional symbol timing recovery methods did not work well in Multi-level PAM signals, but the newly proposed method can be applied to Multi-level PAM signals as well as QPSK. For the performance analysis, the derived variance of the timing error function and the timing error characteristics of S-curve show that the proposed method has better performance than Gardner method and the modified Gardner method.

• 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.