Browsing by Author "Juan, Ta-Yang"

Now showing 1 - 4 of 4

A 62.8 mW 4x4 MIMO-OFDM Modem with One-Symbol-Locked Timing Recovery, Frequency-Dependent I/Q Mismatch Estimation and Adaptive Equalization
(2009)
Sun, Ming-Fu
;
Lin, You-Hsien
;
Lai, Wei-Chi
;
Juan, Ta-Yang
;
Lee, Cheng-Yuan
A 4x4 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-mu m CMOS library. This chip occupies 4.6x4.6 mm(2) and consumes 62.8 mW at 1.2 V.
Adaptive Frequency-Domain Channel Estimator in 4 x 4 MIMO-OFDM Modems
(2009-11-01)
Sun, Ming-Fu
;
Juan, Ta-Yang
;
Lin, Kan-Si
;
Hsu, Terng-Yin
;
資訊工程學系
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-m CMOS library occupies an area of 3 X 3.1 mm(2), and the 4 X 4 MIMO-OFDM modem consumes about 62.8 mW at 1.2 V supply voltage.
Cross-Validation Estimation for Frequency-Dependent I/Q Imbalance in MIMO-OFDM Receivers
(2010-07-01)
Lai, Wei-Chi
;
Juan, Ta-Yang
;
Hsu, Terng-Yin
;
Chiou, Sheng-Lun
;
資訊工程學系
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 x 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 x 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, 10A degrees-phase error and the worst 180A degrees-filter mismatch. In addition, this algorithm is well-matched to IEEE 802.11n and new specifications discussed in IEEE 802.11 VHT study group.
Synchronous sampling and SNR-based gain control in DS/CDMA systems
(2007)
Lin, You-Hsien
;
Lo, Shih-Lin
;
Lai, Wei-Chi
;
Juan, Ta-Yang
;
Hsu, Terng-Yin
Timing synchronization is an important component in a receiver designed to recover data form sampling digital waveform. A synchronous sampling recovery with dual correlator differential (DCD) based acquisition with effects of auto-gain controller (AGC) is proposed to achieve fast timing acquisition for direct sequence / code division multiple access (DS/CDMA) system over frequency-selective fading channel in this paper. It measures both received DCD difference power to determine the good sampling phase from an all-digital phase interpolator based multiphase generator. This solution can tolerate 50ppm system clock offset (SCO) under frequency-selective fading channel. Hence, we not only to determine the good sampling phase fast, but also to arrive stable variable gain amplifier (VGA) with AGC controller in DS/CDMA system approaches.