Browsing by Author "Hsu, Chen-Jiu"

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JOINT ESTIMATION AND COMPENSATION OF FREQUENCY, DC-OFFSET, I-Q IMBALANCE AND CHANNEL IN MIMO RECEIVERS
(2009)
Hsu, Chen-Jiu
;
Sheen, Wern-Ho
;
Cheng, Racy
;
電信工程研究所
;
Institute of Communications Engineering
Direct-conversion is a low-cost RF architecture that requires fewer external components in chip implementation. It introduces, however, extra RF impairments such as I-Q imbalance and DC-offset that degrade severely the receiver performance if left uncompensated. In this paper, a new method of joint estimation and compensation of frequency, DC-offset, I-Q imbalance and channel is developed for MIMO receivers. Numerical results show that the proposed method has a very good performance; less than 2 dB loss is observed at bit-error rate 10(-4), as compared to the ideal receiver. In addition, a new training sequence along with a low-complexity architecture is proposed to reduce largely the receiver complexity with negligible performance loss.
Joint Estimation and Compensation of Transmitter and Receiver Radio Impairments in MIMO-OFDM Receivers
(2009)
Hsu, Chen-Jiu
;
Sheen, Wern-Ho
;
電信工程研究所
;
Institute of Communications Engineering
This paper aims to improve the performance of estimation and compensation for both the transmitter and receiver radio impairments in the MIMO-OFDM (multiple-input, multiple-output orthogonal frequency-division multiplexing) systems. First, a joint least-squares estimation of channel and radio impairments is developed with a complete set of radio impairments being taken into consideration, including frequency-dependent and independent I-Q imbalances, dc-offsets and frequency-offset. Previously, only parts of the radio impairments were included and/or treated separately from the radio channel. Secood, a novel two-stage compensation scheme is proposed which is applicable to a general form of MIMO operations with any number of transmit and receive antennas. Numerical results show that the new design significantly outperforms the existing ones in error-rate performance and/or the number of training symbols required.
Joint Least Squares Estimation of Frequency, DC Offset, I-Q Imbalance, and Channel in MIMO Receivers
(2009-06-01)
Hsu, Chen-Jiu
;
Cheng, Racy
;
Sheen, Wern-Ho
;
電信工程研究所
;
Institute of Communications Engineering
Multiple-input-multiple-output (MIMO) receivers with direct-conversion radio-frequency (RF) architecture are investigated in this paper. Direct conversion is a low-cost RF design that requires fewer external components in chip implementation. Nevertheless, it introduces extra RF impairments such as I-Q imbalance and de offset in addition to frequency offset that is commonly encountered in all RF architectures. This paper proposes to do the joint least squares (LS) estimation of frequency, dc offset, I-Q imbalance, and a channel in MIMO receivers to improve performance; frequency-dependent and frequency-independent I-Q imbalances are included. Previously, RF impairments were separately estimated in MIMO receivers, which leads to inferior performance. In particular, a receiver architecture that facilitates the joint estimation of the frequency, the dc offset, the I-Q imbalance, and the channel is proposed. The LS criterion is then applied to obtain the joint estimators, with a special training-sequence design to reduce complexity. Simplified estimators on the frequency and dc offset are also proposed with almost no loss in performance. Finally, the estimators are shown through analysis to be unbiased and approach the Cramer-Rao lower bound (CRLB) for signal-to-noise ratios (SNRs) of interest. The analysis is verified by computer simulations.