Terng-Yin Hsu

National Chiao Tung University, Hsin-chu-hsien, Taiwan, Taiwan

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Publications (45)22.75 Total impact

  • Wei-Chi Lai, Yuan-Te Liao, Terng-Yin Hsu
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    ABSTRACT: Variations in I/Q gains, phases, and filters of the RF frontend, namely frequency-dependent I/Q imbalance (FDI), are an important factor in OFDM-based wireless access. To enable the proper function of a 4 × 4 MIMO-OFDM receiver this work proposes a low-complexity preamble-assisted solution using only one complex divider and one complex multiplier to handle significant FDI distortions. An all-digital multiphase and multi-rate clock generator (MPRCG) was built to support fast dynamic frequency scaling for FDI estimation and compensation and for efficient implementation. Based on the proposed MPRCG, a skew calibration was also realized to tune I/Q timing coherently via multiphase A/D clocking. Performance evaluation showed that the proposed approach incurs an SNR loss of 1.5 dB to maintain a packet-error rate of less than 10% under a 1 dB gain error, 15 phase error and worse filter mismatch. Thus, this solution not only provides adequate performance, but also makes FDI estimation and compensation more cost-effective.
    Circuits and Systems I: Regular Papers, IEEE Transactions on 01/2013; 60(8):2199-2212. DOI:10.1109/TCSI.2013.2239431 · 2.30 Impact Factor
  • Terng-Yin Hsu, Shau-Yu Cheng
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    ABSTRACT: Based on the frequency-domain analog-to-digital conversion (FD ADC), this work builds a low-complexity sequential searcher for robust symbol synchronization in a 4$\,\times\,$ 4 FD multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) modem. The proposed scheme adopts a symbol-rate sequential search with simple cross-correlation metric to recover symbol timing over the frequency domain. Simulation results show that the detection error is less than 2% at signal-to-noise ratio (SNR) $\leqq $5 dB. Performance loss is not significant when carrier frequency offset (CFO) $\leqq $100 ppm. Using an in-house 65-nm CMOS technology, the proposed solution occupies 84.881 k gates and consumes 5.2 mW at 1.0 V supply voltage. This work makes the FD ADC more attractive to be adopted in high throughput OFDM systems.
    IEEE Transactions on Very Large Scale Integration (VLSI) Systems 05/2012; 20(5):959-963. DOI:10.1109/TVLSI.2011.2136390 · 1.14 Impact Factor
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    ABSTRACT: For wireless packet transmissions, preambles are essential to make packet synchronization function. Impulsive interference not only distorts datum, but also degrades link reliability. To deal with such distortions, a peak-to-average ratio (PAPR) detection is adopted to search impulsive positions and the convolution with the estimated time-domain response is used to recovery the distorted preambles. Simulations of a 2×2 MIMO-OFDM system with RF impairments in frequency-selective fading indicate that the SNR loss is about 2.5 dB ~ 4.6 dB to ensure synchronization working at a signal-to-impulse ratio (SIR) of -10 dB.
    Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC), 2012; 01/2012
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    ABSTRACT: A novel blind statistical algorithm for obtaining the optimal receive beam vector with maximum time-domain effective SNR in OFDMA systems under multipath environment is proposed. The basic procedure of the proposed approach is obtained via the coarse cyclic prefix (CP) detection first and the sample average of the correlation matrices is calculated from selected signal samples for later singular value decomposition (SVD) on the averaged correlation matrix. The proposed approach has the following advantages: First, it is accurate even in the presence of high noise power and when the process of the OFDMA sampled signals are not white (i.e. not all subcarriers are allocated for data transmission). Secondly, it can be operated in time-domain with no training signals and no pre-assumption of the antenna array structure. Hence, it could be applied directly to a variety of existing OFDMA systems and its design can be made relatively simple for implementation. Theoretical proofs of its optimality and the guarantee of convergence are also provided in this paper. Finally, simulation results verifies the theoretical analysis and shows that the proposed approach can accurately achieve a near optimal SNR gain even in low SNR environment and has a convergence speed within two OFDM symbols.
    Personal Indoor and Mobile Radio Communications (PIMRC), 2012 IEEE 23rd International Symposium on; 01/2012
  • Terng-Yin Hsu, Wei-Chi Lai, Shao-Ying Yeh
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    ABSTRACT: Variations of I/Q gains and phases of RF frontend, namely I/Q mismatch (I/Q-M), are the important impact in OFDM-based wireless accesses. Making a 2×2 MIMO-OFDM modem of 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) work properly, this work investigates a low computing cross-ratio engine to deal with serious I/Q-M by using only synchronization signal (SS). Through performance evaluation, our approach incurs a 0.3-dB SNR loss to maintain BER
    Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC), 2012; 01/2012
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    ABSTRACT: The complexity of beamforming, such as complexity complex weighting and combining process, are extremely important for implementation. This work presents a low complexity time-domain statistic noise suppression and beam steering algorithm based on binary search strategy to estimate the optimal beam vector at the receivers. The beam steering algorithm based on binary search strategy could achieve closely (about 99%) optimal SNR gain within only two binary search. It is desirable choice to archive the suitable trade-off between the performance and the processing overhead. Hence, it could obtain a near-optimal performance with considerably low complexity and high convergence speed. In addition, this algorithm is well-matched to different specifications.
    Intelligent Signal Processing and Communications Systems (ISPACS), 2012 International Symposium on; 01/2012
  • Terng-Yin Hsu, Wei-Chi Lai, Tsung-Yeh He
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    ABSTRACT: Radio frequency (RF) imperfections, such as DC offset, frequency offset and I/Q imbalance, are important issues in wireless broadband systems. In this paper, preamble-aided estimation and compensation of I/Q imbalance with filter mismatch are proposed to enhance signal quality and link reliability for 2×2 MIMO-OFDM systems. The proposed preamble-aided estimation is able to detect filter, gain and phase mismatches by using the cross-ratio property of preambles. Then the estimated result is programmed to correct this distortion. Through simulations in frequency-selective fading, they hint that this solution can solve I/Q imbalance with 2 dB gain error, 20° phase error and 180° filter mismatch.
    Engineering and Technology (S-CET), 2012 Spring Congress on; 01/2012
  • Chi-Liang Chao, Shang-Ho Tsai, Terng-Yin Hsu
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    ABSTRACT: The adoption of equal gain transmission (EGT) in MIMO systems can greatly reduce the computational complexity and the design effort of power amplifier. In a temporally correlated channel environment, the channel varies slowly and so does the corresponding beamforming vector. If the slowly varying channel condition can be taken into consideration while designing the feedback schemes of EGT, the computational complexity and feedback overhead of EGT are expected to be further diminished dramatically. In this paper, we propose a differential feedback scheme (DFS) with two algorithms to further improve the performance in EGT. Simulation results show the advantages of the proposed DFS in terms of the feedback overhead and the system performance.
    Acoustics, Speech and Signal Processing (ICASSP), 2012 IEEE International Conference on; 01/2012
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    ABSTRACT: The complexity of beamforming, such as complexity complex weighting and combining process, are extremely important for implementation. This work presents a low complexity time-domain statistic noise suppression and hierarchical beam search algorithm to improve performance in receivers. For SIMO-OFDM systems, the complexity of the hierarchical beam search algorithm is O(n2log2n). This work proposes a simple hierarchical beam search to find the best steering vector. Through performance evaluation, the BER performance is significantly improved with about 3dB under 10^−5 BER in the case that L1=6 and L2=2 compared to that in the case L1=4 and L2=2. Besides, the BER performance is already quietly close to that achieved by the ideal beamform in the case of L1=6 and L2=4. This setting is a good choice which achieves a good tradeoff between the performance and the computational complexity. In addition, this algorithm is well-matched to different specifications.
  • Chi-Liang Chao, Shang-Ho Tsai, Terng-Yin Hsu
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    ABSTRACT: We design equal gain precoders with scalar quan- tization in MIMO systems with limited feedback, which do not require the predefined codebook. In such precoders, bit allocation can be used to quantize the precoding vector/matrix to further improve the system performance. There are two conventional bit allocation schemes. One is the uniform bit allocation and the other is the optimal bit allocation obtained by using exhaustive search. The uniform bit allocation is simple but turns out to have obvious performance degradation. On the other hand, the exhaustive search method leads to the optimal performance. However, its computational complexity is extremely high and may be somewhat impractical to be realized. In this paper, we propose two bit allocation schemes for the MIMO equal gain precoder with scalar quantization. Both of the proposed methods are with low complexity and their performance is close to the optimal scheme. Consequently, the proposed bit allocations provide good trade-off between performance and complexity.
    IEEE Transactions on Wireless Communications 05/2011; 10(5):1345-1350. DOI:10.1109/TWC.2011.030311.100106 · 2.76 Impact Factor
  • Shau-Yu Cheng, Chueh-An Tsai, Terng-Yin Hsu
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    ABSTRACT: Without a cyclic prefix (CP), most single-carrier (SC) transmissions can not adopt frequency-domain equalizer (FDE) directly. This work utilizes frequency-domain channel estimator (FD-CE) and decision-feedback aliasing canceller (DF-AC) to produce single-FFT SC-FDE. In this way, non-CP single-carrier block transmission (SCBT) can be decoded using sphere decoder of MIMO-OFDM modems to support multimode and backward compatibility under an acceptable complexity in IEEE 802.11 very high throughput (VHT). An iV-point FFT is sufficient to measure channel frequency responses (CFR) from .L-sample preambles (L ≤ JV/2). And then, M-bit block codes (M ≤ L) are decodable over frequency domains with DF-AC's help. Simulations and measurements imply that this work can ensure adequate performance, even if there is no CP existed against the distortions of multipath propagation.
    IEEE Transactions on Very Large Scale Integration (VLSI) Systems 02/2011; DOI:10.1109/TVLSI.2009.2031137 · 1.14 Impact Factor
  • Source
    You-Hsien Lin, Terng-Yin Hsu
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    ABSTRACT: Based on phase adjustment, this work investigates a low-complexity all-digital sample clock dither (ADSCD) to perform coherent sampling for orthogonal frequency-division multiplexing (OFDM) timing recovery. To reduce complexity, only tri-state buffers are acquired to build a multiphase all-digital clock management (ADCM), which can generate more than 32 phases over gigahertz without phase-locked or delay-locked loops. Following divide-and-conquer search and triangulated approximation, the phase adjustment is simple but efficient, such that four preambles are adequate to make analog-to-digital (A/D) sampling coherent. Performance evaluation indicates that the proposed ADSCD can tolerate ±400-ppm clock offsets with 0.8 ~ 1.3-dB signal-to-noise ratio (SNR) losses at 8% PER in frequency-selective fading. Hence, this scheme involves a little overhead to ensure fast recovery and wide offset tolerance for OFDM packet transmissions.
    IEEE Transactions on Very Large Scale Integration (VLSI) Systems 08/2010; DOI:10.1109/TVLSI.2009.2019079 · 1.14 Impact Factor
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    ABSTRACT: In this work, we base on multi-layered perceptron neural networks with backpropagation algorithm (MLP/BP) to construct soft decision feedback equalizers (DFEs). The proposal is used to recover distorted 16-point quadrature amplitude modulation (16-QAM) signal. For better performance, error control codes (ECC) are applied to enhance the accuracy of the transmitted data. From the simulations, we note that the MLP/BP-based soft DFEs with bit-interleaved TCM can recover severe distorted 16-QAM data as well as suppress intersymbol interference (ISI) and background additive white Gaussian noise (AWGN). As compared with the LMS DFE, the proposed scheme can provide better bit-error-rate (BER) and packet-error-rate (PER) performance.
    01/2010; DOI:10.1109/IMPACT.2010.5699585
  • Chi-Liang Chao, Shang-Ho Tsai, Terng-Yin Hsu
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    ABSTRACT: We consider the design of the equal gain precoder in flat-fading and limited feedback multiple-input multiple-output (MIMO) systems. The advantage of the equal gain precoder based on the scalar quantization (SQ) is that it is easier to encode the feedback information and no need to construct codebook in advance. In the sort of precoder, the bit allocation methods will dominate the system performance. In this paper, we explore an efficient bit allocation algorithm for the scalar quantized equal gain precoder. The proposed bit allocation scheme can improve the performance of the straightforward scalar quantized equal gain precoder. Compared to the optimal bit allocation scheme with exhaustive search, the proposed algorithm greatly reduces the computational complexity while the performance is near to the optimal scheme.
    Proceedings of the 71st IEEE Vehicular Technology Conference, VTC Spring 2010, 16-19 May 2010, Taipei, Taiwan; 01/2010
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    ABSTRACT: The effects of variation in RF, such as I/Q imbalance and filter mismatch, are extremely important for OFDM wireless accesses. This work presents a low-computational estimation of I/Q imbalances with filter mismatches to improve performance in MIMO-OFDM receivers. For N × N MIMO-OFDM systems, the proposed cross-validation estimation is such that, only N + 1 preambles are required to extract the mismatches of filters, gains and phases. With the estimated parameters, frequency-domain filters are exploited to correct frequency-dependent I/Q imbalances. Through performance evaluation of a 2 × 2 MIMO-OFDM system, with ideal channel estimations this study incurs a SNR loss of 1–1.2 dB to maintain a 10% PER at 1-dB gain error, 10°-phase error and the worst 180°-filter mismatch. In addition, this algorithm is well-matched to IEEE 802.11n and new specifications discussed in IEEE 802.11 VHT study group.
    Journal of Signal Processing Systems 01/2010; 60(1):59-70. DOI:10.1007/s11265-009-0403-y · 0.56 Impact Factor
  • Ming-Fu Sun, Terng-Yin Hsu
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    ABSTRACT: In direct-conversion orthogonal frequency division multiplexing (OFDM) receivers, the impact of frequency-dependent I/Q mismatch (IQ-M) with carrier frequency offset (CFO) must be considered. A preamble-assisted estimation is developed to circumvent the frequency-dependent IQ-M with CFO. The results of a simulation and an experiment show that the proposed method could provide good estimation efficiency and enhance the system performance. Moreover, the proposed scheme is compatible with current wireless local area network standards.
    IEICE Transactions on Communications 07/2009; 92-B(7):2426-2432. DOI:10.1587/transcom.E92.B.2426 · 0.33 Impact Factor
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    ABSTRACT: This work presents an adaptive frequency-domain channel estimator (FD-CE) for equalization of space-time block code multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems in time-varying frequency-selective fading. The proposed adaptive FD-CE ensures the channel estimation accuracy in each set of four MIMO-OFDM symbols. Performance evaluation shows that the proposed method achieved a 10% packet error rate of 64 quadrature amplitude modulation (QAM) at 29.5 dB SNR under 120 km/h (Doppler shift is 266 Hz) in 4 × 4 MIMO-OFDM systems. To decrease complexity, the rich feature of Alamouti-like matrix is exploited to derive an efficient very large-scale integration (VLSI) solution. Finally, this adaptive FD-CE using an in-house 0.13-µm CMOS library occupies an area of 3 × 3.1 mm2, and the 4 × 4 MIMO-OFDM modem consumes about 62.8 mW at 1.2 V supply voltage.
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    ABSTRACT: A 4�?4 multi-input multi-output (MIMO) orthogonal frequency-division multiplexing (OFDM) modem with one-symbol-locked timing recovery, anti-I/Q mismatch frequency recovery, frequency-dependent I/Q mismatch estimation and adaptive equalization is implemented in 0.13-¿m CMOS library. This chip occupies 4.6�?4.6 mm2 and consumes 62.8 mW at 1.2 V.
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    ABSTRACT: In this work, we base on multi-layered perceptron neural networks with backpropagation algorithm (MLP/BP) to construct multi-input multi-output (MIMO) decision feedback equalizers (DFEs). The proposal is used to recover distorted 16-point quadrature amplitude modulation (16-QAM) signal. From the simulations, we note that the proposed approach can recover severe distorted signals as well as suppress intersymbol interference (ISI), adjacent channel interference (ACI) and background additive white Gaussian noise (AWGN). As compared with a set of LMS DFEs, the proposed scheme can provide better BER and PER performance.
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we base on multi-layered perceptron neural networks with backpropagation algorithm (MLP/BP) to construct multi-input multi-output (MIMO) decision feedback equalizers (DFEs). The proposal is used to recover distorted quadrature phase-shift keying (QPSK) signal. From the simulations, we note that the proposed scheme can recover severe distorted signals as well as suppress intersymbol interference (ISI), adjacent channel interference (ACI) and background additive white Gaussian noise (AWGN). The better bit-error-rate (BER) and packet-error-rate (PER) performance as compared to a set of least-mean-square (LMS) DFEs is achieved. The presented MLP/BP-based MIMO DFE under the severe ISI channels with ACI and AWGN can improve over 1.5dB at PER=10<sup>-1</sup> and BER=10<sup>-3</sup>.
    Electronic Materials and Packaging, 2008. EMAP 2008. International Conference on; 11/2008