Browsing by Author "Liao, Yuan-Te"

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A Cost-Effective Adaptive Overlapped Cluster-Based MIMO Detector in a Frequency Domain Reconfigurable Modem
(2019-01-01)
Liao, Yuan-Te
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Hsu, Terng-Yin
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資訊工程學系
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Department of Computer Science
Not only to reduce the candidates but also to maintain detection performance in multiple-input multiple-output (MIMO) detection, an adaptive overlapped cluster (AOC) scheme to balance detection error and computing cost is built for 4 x 4 and 8 x 8 MIMO-OFDM systems with up to 256 quadrature amplitude modulation (QAM). The constellations are partitioned into several clusters. A cluster with size decided by channel status is chosen for signal decoding. Different partition schemes are combined to minimize the numbers of clusters required to cover a candidate symbol as the pre-estimated signal falls at cluster edges, namely overlapped clustering. The simulations of a 4 x 4 MIMO OFDM with 64 QAM and 8 x 8 MIMO OFDM with 256 QAM hint that the AOC-based detection requires an additional 0.57 dB and 1.02 dB compared to maximum likelihood (ML). Compared with K-best sphere decoding (SD), it is reduced the computing complexity to 24.50% similar to 56.25% in 4 x 4 MIMO OFDM and, 35.00% similar to 56.25% in 8 x 8 MIMO OFDM. In addition, the proposed scheme is ported to a reconfigurable frequency-domain (1-D) modem, which is designed and implemented via TSMC 45-nm technology, with multi-rate clocking and processing elements (PEs) upgrading for supporting the proposed MIMIO detection. The results show that the throughput is 1077.8 Mbps with 4 x 4 64-QAM modulations.
A Cost-Effective Preamble-Assisted Engine With Skew Calibrator for Frequency-Dependent I/Q Imbalance in 4 x 4 MIMO-OFDM Modem
(2013-08-01)
Lai, Wei-Chi
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Liao, Yuan-Te
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Hsu, Terng-Yin
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資訊工程學系
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Department of Computer Science
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 x 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 degrees phase error and worse filter mismatch. Thus, this solution not only provides adequate performance, but also makes FDI estimation and compensation more cost-effective.
Cost-Efficient Frequency-Domain MIMO-OFDM Modem With an SIMD ALU-Based Architecture
(2015-12-01)
Yeh, Shao-Ying
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Liao, Yuan-Te
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Lai, Wei-Chi
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Hsu, Terng-Yin
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資訊工程學系
In this paper, a single instruction multiple data (SIMD) arithmetic logic unit (ALU)-based architecture is proposed to improve hardware efficiency in a 4 x 4 frequency-domain multiple input multiple output-orthogonal frequency division multiplexing modem based on a space-time block code (STBC). The majority of mathematic units in the proposed architecture are centralized so that any mathematic unit can be shared with any algorithm. Six advanced instructions are also defined in the ALU: 1) complex multiplication; 2) complex division; 3) correlation; 4) channel estimation; 5) 4 x 4 matrix inversion; and 6) STBC-based decoding. A scheduler is essential to handle all data paths and signaling flows smoothly with the use of an SIMD ALU. As a result, it is relatively easy to reconfigure the proposed design for different specifications. The very large scale integration implementation of this chip, using an in-house 65-nm CMOS process, consumes a total of 1.87 M gates and draws 33.7 mW at a supply voltage of 1 V.
Digital Self-Interference Cancellation Via Dynamic Regression for In-band Full-Duplex System
(2016)
Lin, You-Hsien
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Liao, Yuan-Te
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Chu, Jian-Ya
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Su, Po-Ju
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Hsu, Terng-Yin
For enhancing spectrum efficiency, in-band full duplex technology is one of the candidate technical solution. Rut, self-interference (SI) signal causes dramatically degrade the performance. In practically, memory effect which cause harmonic in amplifier will be hard to be estimated. Therefore, we utilizes the dynamic regression (DR) to implement digital interference cancellation (DIC) for mitigate the memory effect. Two platforms are constructed to evaluate this mechanism. In both platforms, the SI signal could effectively reduction and the residual signal could be attenuated close to noise floor. In software-defined radio (SDR) platform also proves that the proposed dynamic regression based DIC (DRDIC) is sufficient to attenuate the SI signal, where successfully perform video streaming demonstration.
Implementation of Digital Self-Interference Cancellation in LTE-based CCFD Transmission
(2017-01-01)
Chu, Jian-Ya
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Liao, Yuan-Te
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Hung, Chun-Yi
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Hsu, Terng-Yin
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資訊工程學系
In this paper, we propose a real-time and scalable digital cancellation algorithm to cancel the self-interference signal. We implement this algorithm in the FPGA of NI USRP-2953R platform by using LabVIEW to program it through the PCIe. At the end of this paper, we demonstrate the real-time video stream between two platforms at the central frequency 2.2GHz to 2.5GHz with 20MHz bandwidth in the LTE framework.
Low Complexity MIMO Detection by using Overlapped Cluster Search
(2015)
Chu, Jian-Ya
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Liao, Yuan-Te
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Hsu, Terng-Yin
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交大工研院聯合研發中心
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NCTU/ITRI Joint Research Center
In this paper, a low complexity overlapped cluster search algorithm which is employed in MIMO detection is proposed. The proposed algorithm allows more than one clusters possess the same candidate constellation points to decrease the possibility of choosing the wrong cluster while picking candidates. The proposed algorithm can maintain performance within 0.57dB such that the method is suitable for practical 4T4R 64QAM MIMO system. The algorithm complexity is reduce 27.29% to 56.25% in average case and 39.06% to 57.25% in worst case. Through simulation in IEEE 802.11n platform with TGN channel E, it indicates the complexity of proposed algorithm is less than the K-best SD with the same performance. Hence, the proposed algorithm provides a near-optimal solution with low computation complexity design for wireless MIMO system.