Youngyoon Lee

Sungkyunkwan University, Sŏul, Seoul, South Korea

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Publications (16)0 Total impact

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    ABSTRACT: In this paper, we propose a new periodogram-based integer frequency offset (IFO) estimation scheme robust to the fractional frequency offset (FFO) variation. We first observe the reason why the conventional IFO estimation scheme in is sensitive to the variation of the FFO, and then, propose a new IFO estimation scheme using the modified maximum-likelihood (ML) metric. The numerical results demonstrate that the proposed scheme is more robust to the variation of the FFO and has better IFO estimation performance than the conventional scheme in.
    Proceedings of the 7th International Wireless Communications and Mobile Computing Conference, IWCMC 2011, Istanbul, Turkey, 4-8 July, 2011; 01/2011
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    ABSTRACT: This paper proposes a novel two-stage detection scheme based on multiple correlator outputs to enhance the de- tection performance in ultra-wideband (UWB) signal acquisition. Due to the rich multipath of UWB channels, the signal energy spreads over multiple correlator outputs, which makes each cor- relator output have only a portion of the signal energy, and thus, degrades the detection performance of the conventional scheme where a single correlator output is used as the decision variable for detection. In the proposed two-stage detection scheme, the decision variable is formed by combining multiple correlator outputs, making it possible to collect the signal energy spread by the multipath. Simulation results show that the proposed scheme can provide a better detection performance over the conventional scheme in various UWB channel environments.
    Proceedings of the 7th International Wireless Communications and Mobile Computing Conference, IWCMC 2011, Istanbul, Turkey, 4-8 July, 2011; 01/2011
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    ABSTRACT: In this paper, we propose a novel maximum-likelihood (ML) decoding scheme based on the combination of depth- and breadth-first search methods on a partitioned tree for multiple input multiple output systems. The proposed scheme first partitions the searching tree into several stages, each of which is then searched by a depth- or breadth-first search method, possibly exploiting the advantages of both the depth- and breadth-first search methods in an organized way. Numerical results indicate that, when the depth- and breadth-first search algorithms are adopted appropriately, the proposed scheme exhibits substantially lower computational complexity than conventional ML decoders while maintaining the ML bit error performance.
    Seventh International Conference on Information Technology: New Generations, ITNG 2010, Las Vegas, Nevada, USA, 12-14 April 2010; 01/2010
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    ABSTRACT: This paper deals with the integer frequency offset (IFO) estimation issue for reliable transmission in orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting-terrestrial (DVB-T) systems. To estimate the IFO the conventional scheme uses only partial information of combinations that pilots provide. However, since the conventional scheme exploits a small number of correlations, it does not use sufficient signal energy for the IFO estimation. Thus, in this paper, we propose novel IFO estimation schemes efficiently using the additional correlations between pilots. The simulation results show that the proposed schemes are highly accurate in terms of the IFO detection probability.
    The 35th Annual IEEE Conference on Local Computer Networks, LCN 2010, 10-14 October 2010, Denver, Colorado, USA, Proceedings; 01/2010
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    ABSTRACT: In this paper, we propose a novel code acquisition scheme called modified multiple-shift (MMS) for optical code division multiple access (CDMA) systems. By using the modified local code whose sign is positive or negative, the proposed MMS scheme provides a shorter mean acquisition time (MAT) than the conventional multiple-shift (MS) scheme. The simulation results demonstrate that the MAT of the MMS scheme is shorter than that of the MS scheme in both single-user and multi-user environments.
    Computational Science and Its Applications - ICCSA 2010, International Conference, Fukuoka, Japan, March 23-26, 2010, Proceedings, Part III; 01/2010
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    ABSTRACT: This paper proposes two novel schemes for pilot-aided integer frequency offset (IFO) estimation in orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting-terrestrial (DVB-T) systems. The conventional scheme proposed for estimating the IFO uses only partial information of combinations that pilots can provide, which stems from a rigorous assumption that the channel responses of pilots used for estimating the IFO change very rapidly. Thus, in this paper, we propose the novel IFO estimation schemes exploiting additional information of combinations that pilots can provide to improve the performance of the IFO estimation. The simulation results show that the proposed schemes are highly accurate in terms of the IFO detection probability.
    Proceedings of the 6th International Wireless Communications and Mobile Computing Conference, IWCMC 2010, Caen, France, June 28 - July 2, 2010; 01/2010
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    ABSTRACT: A pilot-aided integer frequency offset (IFO) estimation scheme robust to the timing offset is proposed for orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting-terrestrial (DVB-T) systems. The proposed scheme first produces correlation values between each continual pilot (CP) and a predetermined scattered pilot (SP), and then, recorrelates the correlation values in order to reduce the influence of the timing offset. Simulation results show that the proposed IFO estimation scheme is robust to the timing offset and has better estimation performance than the conventional scheme.
    01/2010;
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    ABSTRACT: In this paper, new integer frequency offset estimation schemes are proposed for orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting (DVB) systems. Several pilot-aided integer frequency offset estimation schemes have been proposed for OFDM-based DVB systems. However, the conventional schemes use only some parts of pilot combinations. Thus, in this paper, we propose new integer frequency offset estimation schemes exploiting the additional information of pilot combinations. The simulation results show that the proposed schemes outperform the conventional schemes in terms of the probability of carrier frequency offset estimation failure.
    Proceedings of the 3rd International Conference on Ubiquitous Information Management and Communication, ICUIMC 2009, Suwon, Korea, January 15-16, 2009; 01/2009
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    ABSTRACT: Binary offset carrier (BOC) signal synchronization is based on the correlation between the received and locally generated BOC signals. Thus, the multiple side-peaks in BOC autocorrelation are one of the main error sources in synchronizing BOC signals. Recently, new correlation functions with no side-peak were proposed for sine and cosine phased BOC signal synchronization, respectively, by the authors [3]. In this paper, we propose new correlation functions with no side-peak for alternative BOC (AltBOC) and composite BOC (CBOC) signals by using the similar approach to the previous work.
    Computational Science and Its Applications - ICCSA 2009, International Conference, Seoul, Korea, June 29-July 2, 2009, Proceedings, Part II; 01/2009
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    ABSTRACT: In this paper, we propose a novel code acquisition scheme called enhanced multiple-shift (EMS) for optical code division multi- ple access (CDMA) systems. By using multiple thresholds, the proposed EMS scheme provides a shorter mean acquisition time (MAT) than that of the conventional mutiple-shift (MS) scheme. The simulation results demonstrate that the MAT of EMS scheme is shorter than that of MS scheme in both single-user and multi-user environments.
    Computational Science and Its Applications - ICCSA 2009, International Conference, Seoul, Korea, June 29-July 2, 2009, Proceedings, Part II; 01/2009
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    ABSTRACT: The single delta delay lock loop is the most widely used code tracking scheme for the GALILEO system that employs the binary offset carrier modulated spreading signal. When only a line-of-sight signal is received, the single delta delay lock loop is the optimal code tracking scheme. However, when the multipath signals are received, the correlation values are distorted, and thus, the tracking bias arises, which is defined as the difference between correct and estimated synchronization points. To tackle this problem, many tracking schemes have been proposed, e.g. narrow correlator DLL, high resolution correlator DLL, and so on. These schemes use the correlation values nearby the offset of the peak correlation values. However, the coherent auto-correlation function of the binary offset carrier modulated spreading signal has additionally two locally minimum correlation values whose offsets are plusmnT<sub>c</sub> /2 , respectively, where T<sub>c</sub> is the chip duration. In multipath environments, the correlation values nearby the locally minimum correlation value are less distorted compared with those nearby the one whose offset is plusmnT<sub>c</sub> /2 . From this observation, we propose a novel tracking scheme, and then, its tracking accuracy is assessed using Monte-Carlo simulation.
    Advanced Communication Technology, 2008. ICACT 2008. 10th International Conference on; 03/2008
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    ABSTRACT: In this paper, a new integer frequency offset estimation method is proposed for orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting (DVB) systems. Several pilot-aided frequency offset estimation methods have been proposed for OFDM-based DVB systems. In the conventional methods, however, the information of some combinations that pilots provide is used only. Thus, in this paper, we propose a new integer frequency offset estimation method exploiting the information of all combinations that pilots provide. The simulation results show that the proposed method outperforms the conventional method in terms of the probability of integer frequency offset estimation failure.
    Advanced Communication Technology, 2008. ICACT 2008. 10th International Conference on; 03/2008
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    ABSTRACT: This paper addresses a tracking bias compensation scheme for location systems and analyzes tracking bias and its running average via simulation. The proposed scheme can be well combined with double delta typed DLL. In this case, it can be implemented without supplementary engines. Also, it can be combined with single delta typed DLL if two correlators can be used.
    Proceedings of the 2nd International Conference on Ubiquitous Information Management and Communication, ICUIMC 2008, Suwon, Korea, January 31 - February 01, 2008; 01/2008
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    ABSTRACT: This paper proposes two novel schemes for pilot-aided integer frequency offset (IFO) estimation in orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting-terrestrial (DVB-T) systems. The conventional scheme proposed for estimating the IFO uses only partial information of combinations that pilots can provide, which stems from a rigorous assumption that the channel responses of pilots used for estimating the IFO change very rapidly. Thus, in this paper, we propose the novel IFO estimation schemes exploiting all information of combinations that pilots can provide to improve the performance of IFO estimation. The simulation results show that the proposed schemes are highly accurate in terms of the IFO detection probability.
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    ABSTRACT: Due to its capability to resist jamming signals, chirp spread spectrum (CSS) technique has attracted much attention in the area of wireless communications. However, there has been little rigorous analysis for the performance of the CSS communication system in jamming environments. In this paper, we present analytic results on the performance of a CSS system by deriving symbol error rate (SER) expressions for a CSS M -ary phase shift keying (MPSK) system in the presence of broadband and tone jamming signals, respectively. The numerical results show that the empirical SER closely agrees with the analytic result.
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    ABSTRACT: This paper proposes a novel spectrum sensing technique for the digital video broadcasting-terrestrial (DVB-T) systems, which utilizes the periodicity of pilot signals in the orthogonal frequency division multiplexing (OFDM) symbols. The proposed scheme can overcome the effect of the timing synchronization error by re-correlating the correlation values in the same sample distances. The numerical results demonstrate that the detection probability perfor-mance of the proposed scheme outperforms that of the conventional scheme when there exists a timing synchronization error.