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For OFDM systems with multiple transmit antennas, it is necessary to obtain a reliable CFR of each transmitted signal from the received signal which is the superposition of transmitted signals. Generally, pilot symbol aided frame structure is used for bandwidth efficient frame structure; hence interpolation method can be used to separate CIR of each transmitted signal for channel estimation. However,...
In this paper, we propose a coarse and fine frequency synchronization method which is suitable for the 3rd Generation Partnership Project (3GPP) long term evolution (LTE) orthogonal frequency division multiple access (OFDMA) system in time division duplexing (TDD) mode. In general, primary synchronization signal (PSS) correlation based estimation method and cyclic prefix (CP) correlation based tracking...
In 3GPP long term evolution (LTE) system, initial cell search procedure comprises two steps using primary synchronization signal (PSS) and secondary synchronization signal (SSS). This paper presents SSS detection method for second step of initial cell search. In general, coherent detection using estimated channel frequency response (CFR) at PSS is used for SSS detection, but performance degradation...
In this paper, we propose two robust frequency offset estimation methods for OFDM systems in single frequency network (SFN) with large delay spread. Conventional guard-interval-based (GIB) estimation method is very sensitive to intersymbol interference (ISI) caused by long and strong echoes of the SFN channel. In order to minimize ISI-dependent performance degradation, we first introduce a suboptimal...
Wnt inhibitory factor (WIF)-1 belongs to the members of secreted modulators of Wnt proteins. Secreted frizzled-related proteins (sFRPs), another member of Wnt modulators, have been shown to play differential roles in Wnt signaling depending on the subtypes and cell models. This study was undertaken to investigate the functional role of WIF-1 in osteoblastic differentiation of mouse mesenchymal C3H10T1/2...
A precise estimation of SFO (Sampling Frequency Offset) is an important issue in OFDM (Orthogonal Frequency Division Multiplexing) system. However, the conventional method causes serious performance degradation of SFO estimation in low SNR (Signal to Noise Ratio) or large Doppler frequency environment. Therefore, in this paper, we propose a SFO estimation method which can achieve stable operation...
In this paper, we propose a robust soft decision method based on channel state information (CSI) for coded orthogonal frequency division multiplexing (COFDM) systems. In the presence of co-channel interference (CCI), conventional soft decision decoding is performed by a simple erasing method for frequency selective CCI. But the conventional method cannot obtain sufficient performance gain because...
To mitigate the asynchronous ICI (inter-cell interference), SCM (spatial covariance matrix) of the asynchronous ICI plus background noise should be accurately estimated for MIMO-OFDMA (multiple-input multiple-output-orthogonal frequency division multiple access) system. Generally, it is assumed that the SCM of the asynchronous ICI plus background noise is estimated by using training symbols. However,...
To mitigate the asynchronous ICI (Inter-Cell Interference), the CFR (Channel Frequency Response) and SCM (Spatial Covariance Matrix) should be accurately estimated. Therefore, we propose the ML (Maximum Likelihood)-based iterative method which can effectively reduce the estimation error of both CFR and SCM, and improve the performance for OFDMA system such as LTE (3GPP Long Term Evolution).
Channel impulse response (CIR) can be estimated on the basis of cyclic correlation in time-domain for orthogonal frequency division multiplexing (OFDM) systems. This article proposes a generalized channel estimation method to reduce the estimation error by taking the average of different CIRs. Channel impulse responses are derived according to the different starting points of cyclic correlation. In...
In this paper, we propose a method to reduce operational complexity of the conventional maximum-likelihood based double correlation algorithm for frame synchronization. The proposed method is based on frequency-domain processing by fast Fourier transform and a corresponding observation length for full-size shift of training sequence. Simulation result shows that the proposed algorithm can achieve...
For T-DMB service, it requires a relay system such as the digital on-channel repeater which is usually called gapfiller to deal with radio wave shadowing region and additional coverage. In this paper, we propose a new architecture of T-DMB gapfiller and algorithms for the proposed architecture.
In this paper, enhanced DFT-based channel estimation for OFDM system is proposed. Conventional DFT-based channel estimations improve the performance by suppressing time-domain noise. However, the disadvantage is that it cannot distinguish each path from the aliasing components of CIR when the periodic replicas of the estimated CIR are overlapped each other in very large delay spread channels. If any...
For T-DMB service, it requires a relay system such as the digital on-channel repeater which is usually called gapflller to deal with radio wave shadowing region and additional coverage. In this paper, we propose a new architecture of T-DMB gapflller and algorithms for the proposed architecture.
In this paper, we propose a method to reduce operational complexity of the conventional maximum-likelihood based double correlation algorithm for frame synchronization. The proposed method is based on frequency-domain processing by fast Fourier transform and a corresponding observation length for full-size shift of training sequence. Simulation result shows that the proposed algorithm can achieve...
In this paper, we introduce a novel pilot mapping method for channel-quality (CQ) estimation of each user in single carrier-frequency division multiple access (SC-FDMA) system. In case of conventional code division multiplexing (CDM) method, it enables measurement of CQ levels over all sub-carriers. The method, however, has a limit on estimating the accurate channel frequency response for coherent...
Channel impulse response (CIR) can be estimated by time-domain processing (TDP) based on cyclic correlation in orthogonal frequency division multiplexing (OFDM) systems. We propose an improved generalized TDP method to reduce the estimation error by taking the average of different CIR values which are derived according to the different starting points of cyclic correlation. Moreover, an effective...
Cellular OFDMA system is susceptive to inter-cell interference when a frequency reuse factor is one and all neighboring cells are fully loaded. At the cell edge, particularly, a severe synchronization error may occur due to decreased signal-to-interference ratio. In this paper, therefore, we propose a robust frame synchronization method in inter-cell interference for OFDMA systems. The proposed algorithm...
In this paper, we propose a frequency domain (FD) MMSE equalizer for M-ary bi-orthogonal keying direct sequence UWB (MBOK DS-UWB) systems considered as a PHY proposal for high-speed wireless communication in IEEE 802.15.3a. The conventional FD MMSE equalization scheme has a structural limit due to insertion of the cyclic prefix (CP) in all transmit packets, but the proposed scheme is able to equalize...
In IEEE 802.15.4 LR-WPAN(Low-Rate Wireless Personal Area Network) specification, the frequency offset of 80 ppm on 2.45 GHz band is recommended for low-cost implementation. For robustness to the specified frequency offset, non-coherent detection-based symbol detector algorithm is typically applied in the LR-WPAN receiver modem. However, the noncoherent symbol detector has more performance degradation...
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