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Dynamic Pilot Arrangement Scheme in Wireless OFDM Systems
Chia-Chang Hu,Hong-Da Shih 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
An adaptive pilot-symbol assignment scheme is proposed for interpolation-based channel estimation in wireless orthogonal frequency division multiplexing (OFDM) communication systems. The channel transfer functions of data tones are interpolated by the piecewiselinear and the second-order polynomial interpolation methods due to their inherent simplicity. Simulations are conducted to demonstrate system performance and bandwidth (BW) superiority. A comparative evaluation of the proposed dynamic pilot scheme with conventional fixed pilot-symbol channel estimation schemes is performed as well.
OFDM Interpolation-Based Channel Estimation Using Adaptive Pilot-Symbol Arrangement
Chia-Chang Hu,Fu-Hao Chen 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
An adaptive pilot-symbol assignment scheme is proposed for interpolation-based channel estimation in wireless orthogonal frequency division multiplexing (OFDM) communication systems. Computer simulations are conducted to demonstrate both system performance and convergence/tracking superiority and to provide a comparative evaluation of the proposed scheme with other conventional fixed pilot-symbol schemes.
Chia-Chang Hu,Chung-Lun Yang 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
In the paper, a joint linear precoder-decoder pair is considered for uplink multiuser multiple-input multiple-output (MIMO) wireless systems without perfect channel state information (CSI) at both the transmitters and the receivers. Instead of counting on complex iterative-based algorithms, an efficient and non-iterative linear transceiver design is employed. In addition, an equal power distribution (EPD) scheme is applied to adjust transmit power allocation of each mobile terminal between its symbols. Simulations are conducted to provide a comparative evaluation of the proposed EPD algorithm with other transceiver designs on the sum mean-squared error (MSE) and the average bit-error-rate (BER) performance.
Antenna Selection for MIMO-OFDM Systems in Correlated Channels
Chia-Chang Hu,Hao-Yun Yang 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
In the paper, the joint transceiver antenna selection schemes for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems are addressed in the broadband correlated channels. Modified antenna selection methods for frequency-selective fading channel are proposed and analyzed in this paper. Consequently, the use of the proposed modified antenna selection algorithms achieve a substantial saving in system-hardware complexity of the multiple radio frequency (RF) chains associated with multiple antennas without compromising overall system-capacity performance.
Low-Complexity Channel Estimation for Multi-Band OFDM Ultra-Wideband Communications
Chia-Chang Hu,Shih-Chang Lee,Ching-Wen Tang 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
In this paper, a comparative investigation on various channel estimation schemes for multi-band (MB) orthogonal frequency division multiplexing (OFDM) ultra-wideband (UWB) communication systems is presented. Consequently, the Wiener filtering (WF) technique produces a superior bit-error-rate (BER) performance. Concerning the computational complexity as well as the BER performance, the reduced-rank (RR) WF technique is introduced. Simulation results show that the proposed RR WF algorithm is capable to be implemented with a lower complexity cost without trade-off system performance.
Yu-Fang Lin,Kang-Yung Peng,Chia-Hui Chang,Ya-Hui Hu,Vin-Cent Wu,Shiu-Dong Chung,Taiwan Primary Aldosteronism Investigation (TAIPAI) Study Group 대한내분비학회 2020 Endocrinology and metabolism Vol.35 No.4
Background: Data on the effects of excess aldosterone on glucose metabolism are inconsistent. This study compared the changes in glucose metabolism in patients with primary aldosteronism (PA) after adrenalectomy or treatment with a mineralocorticoid receptor antagonist (MRA). Methods: Overall, 241 patients were enrolled; 153 underwent adrenalectomy and 88 received an MRA. Fasting glucose, homeostatic model assessment of insulin resistance (HOMA-IR), and homeostatic model assessment of β-cell function (HOMA-β) were compared between the treatment groups after 1 year. Plasma aldosterone concentration (PAC) and factors determining HOMA-IR and PAC were evaluated. Results: No baseline differences were observed between the groups. Fasting insulin, HOMA-IR, and HOMA-β increased in both groups and there were no significant differences in fasting glucose following treatment. Multiple regression analysis showed associations between PAC and HOMA-IR (β=0.172, P=0.017) after treatment. Treatment with spironolactone was the only risk factor associated with PAC >30 ng/dL (odds ratio, 5.2; 95% confidence interval [CI], 2.7 to 10; P<0.001) and conferred a 2.48-fold risk of insulin resistance after 1 year compared with surgery (95% CI, 1.3 to 4.8; P=0.007). Conclusion: Spironolactone treatment might increase insulin resistance in patients with PA. This strengthened the current recommendation that adrenalectomy is the preferred strategy for patient with positive lateralization test. Achieving a post-treatment PAC of <30 ng/dL for improved insulin sensitivity may be appropriate.