Analysis and Compensation of DC Offset in OFDM Systems Over Frequency-Selective Rayleigh Fading Channels

99學年度易志孝教師升等代表著作[[abstract]]Direct-conversion receivers have become popular in radio-frequency (RF) circuit design for their advantages of low cost, low power consumption, and fewer chip components over other architectures such as heterodyne receivers. However, the direct-conversion receiver architecture often suffers from direct current (dc) offset, which is a consequence of the imperfect direct-conversion process. In this paper, we study the effects of dc offset on the symbol error rate (SER) performance of orthogonal frequency-division multiplexing (OFDM) systems in multipath Rayleigh fading channels. Since OFDM system performance is sensitive to carrier frequency offset (CFO), the CFO must be estimated and compensated at the receiver. Due to CFO compensation, the dc offset caused by direct-conversion receivers and/or mixed-signal circuits no longer only affects the dc subcarrier and is spread over all subcarriers. By deriving the analytical SER formulas for OFDM systems with various modulation formats, the dependency of SER on dc offset and CFO is clearly quantified. These SER formulas can help system designers determine suitable specifications of RF components and understand whether digital DC offset compensation is necessary or not. Finally, we propose and analyze a simple DC offset estimation and cancellation scheme under the assumption that DC offset holds constant in one OFDM symbol duration. Numerical results demonstrate the effectiveness of the proposed DC offset-cancellation scheme.[[notice]]補正完畢[[booktype]]紙

BER Analysis of OFDM Systems Impaired by Phase Noise in Frequency-Selective Rayleigh Fading Channels

[[abstract]]In this paper, we study the effect of finite-power, phase-locked-loop (PLL) based phase noise on the bit-error-rate (BER) of orthogonal frequency division multiplexing (OFDM) systems in frequency-selective Rayleigh fading channels. Based on the conditional Gaussian approximation technique, we derive the BER formulas for BPSK and 16-QAM modulated OFDM signals impaired by phase noise in frequency-selective Rayleigh fading channels. Simulation results not only validate the accuracy of our analysis but also show the dependency of BERs on the shapes of phase noise spectra.[[conferencetype]]國際[[conferencedate]]20081130~20081204[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]New Orleans, U.S.A

Differential BPSK Modulation for Cooperative Communication Systems in Time-Selective Rayleigh Fading Channels

[[abstract]]the AF relaying system based on the maximum likelihood criterion. Since the optimum combining rule depends on the channel gains of the relay-to-destination links which are usually unavailable in the context of differential modulation, we propose a suboptimal diversity combining rule which replaces the instantaneous channel gains by their second order statistics. Compared with the performance of the diversity combining rule without taking the time-selectivity into account, computer simulation results show that the proposed diversity combining rule has superior performance for the AF relaying system in time-selective Rayleigh fading channels, especially when the relay and destination nodes have different Doppler spreads.[[conferencetype]]國際[[conferencedate]]20120712~20120714[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]Bali, Indonesi

Effects of channel estimation error on the BER performance of OFDM systems in multipath Rayleigh Fading channels

[[abstract]]In this paper, we study the effects of channel estimation error on the bit error rate (BER) of orthogonal frequency division multiplexing systems in multipath Rayleigh fading channels. Due to the additive white Gaussian noise and the intercarrier interference caused by the residual carrier frequency offset, the channel estimation based on the training symbols is not perfect. We characterize the performance degradation resulting from imperfect channel state information by deriving the BER formulas for BPSK, QPSK, and 16-QAM modulation schemes. Simulation results validate the accuracy of our derived formulas.[[conferencetype]]國際[[conferencedate]]20070930~20071003[[iscallforpapers]]Y[[conferencelocation]]Baltimore, US

Performance of Fixed Gain Amplify-and-Forward Relay Systems with Partial Channel State Information

[[abstract]]For amplify-and-forward (AF) relay systems employing coherent modulation, the receiver at the destination requires the full channel state information (CSI) of the sourcerelay-destination (SRD) links and the amplified relay-destination (RD) links to perform maximal ratio combining (MRC). To reduce the burden of channel estimation and CSI forwarding in AF relay systems, we propose an MRC receiver with partial CSI which needs the CSI of the SRD links and the variance of the source-relay (SR) links. We analyze the bit-error-ate (BER) of the proposed scheme based on the moment generating function approach. Compared with the full CSI case, the BER performance degradation due to partial CSI depends on the channel variances of the SR and RD links. When the channel variances of the SR links are much larger than those of the RD links, the performance loss due to partial CSI is negligible.[[sponsorship]]台南大學[[conferencetype]]國內[[conferencedate]]2013111115~20131116[[booktype]]電子版[[iscallforpapers]]Y[[conferencelocation]]臺南, 臺

Finding a Fair Land Dispute Settlement Mechanism Between Adat Law Community Vs. Investor

Land utilization for investment in local areas raises various land related problems that ends with conflicts within the community. A conflict that occurs, usually begins with the management of communal land “tanah ulayat” within the adat law community environment, and in this case, land utilization that is managed by the third party (investors). The basic problem is the difference of perception and expectations toward the company that exists in the land which is claimed by the community. Both parties have their own claim on the land based on each legal systems, in this situation adat law or local law faced with state law which is used by investors. So far, the Indonesian government has yet to have legal grounds in giving a directions for land dispute/conflict settlement mechanism. This paper attempts to give an input regarding a land dispute settlement mechanism that can be accepted for all disputing parties. The paper features critical analysis using legal pluralism approach towards related government policies and technical regulations in the ministerial level. These regulations, among others are, Minister of Agrarian Regulation No. 5 of 1999 on the Guidance for Dispute Settlement of Communal Land Rights, and Ministry of Agrarian and Spatial Affairs Regulation No. 9 of 2015 on Procedures of Appointment of Communal Land Rights for Adat Law Community and Communities Located in certain regions, also the draft of Law regarding Recognition and Protection of Adat Law Community

An Analysis of Managing Sustainable Competitiveness for Semiconductor Manufacturers

Innovative capability is considered inevitable for firms to sustain their competitiveness. In the recent rapidly changing global competition environment, the traditional integrated device manufacturer (IDM) model in semiconductor industry is facing the limitation of sustaining its profitability and competitiveness. IDM’s focusing both chip design and manufacturing for various application segments disperse its resources of innovating sustainable competiveness. This study develops an analysis framework with incorporating data envelopment analysis (DEA) approach to measure the efficiency through proper input and output variables setting. This framework aims at providing guidelines for developing firm’s business and technology strategies. We conducted a DEA analysis by collecting financial data from twenty-six leading semiconductor manufacturing companies, including twenty IDMs and six foundries. The results reveal that the foundry companies have higher competitive efficiency than those of IDMs. The empirical analysis suggests that adopting the asset-light business model may provide IDMs a better resource allocation and help the increase of relative efficiency scores

The Volcanic Earthquake Swarm of October 20, 2009 in the Tatun Area of Northern Taiwan

On October 20, 2009, a series of felt earthquakes with local magnitudes ranging from 2.8 - 3.2 occurred in the Tatun volcanic area off the northern tip of Taiwan. Although there was no damage caused by those earthquakes, many residents in the Taipei metropolitan area, particularly for people who live near the Yangminshan National Park, felt strong ground shaking. In order to know what the possible mechanisms were that generated those earthquakes, we carefully examined seismic data recorded by a dense seismic array in the Tatun volcanic area. During the period between October 18 and 22, 2009 we detected at least 202 micro-earthquakes. Most of the earthquakes were relocated using the double-difference method and were clustered in the shallow crust beneath the Dayoukeng area, which is the strongest fumarole in the Tatun volcanic area. Among these earthquakes, 72 focal mechanisms were determined by polarizing the first P-wave motion. Most earthquakes belonged to normal faulting. An extremely high b-value of 2.17 was obtained from those earthquakes. Based on the seismic variations in both the temporary and spatial distribution as well as an extremely high b-value, we conclude that the earthquake sequence on October 20, 2009 was a typically seismic swarm associated with possible active volcanism in the Tatun volcanic area

Clinical meaning of age-related expression of fecal cytokeratin 19 in colorectal malignancy

<p>Abstract</p> <p>Background</p> <p>Colorectal cancer (CRC) is one of the leading causes of malignant death worldwide. Because young age of onset is often considered a poor prognostic factor for CRC, it is important to identify the poor outcomes of CRC in a younger population and to consider an aggressive approach by implementing early treatment. Our aim was to specifically quantify the fecal cytokeratin 19 (CK19) transcript from CRC patients and investigate its correlation with clinical stage, tumor malignancy, and age.</p> <p>Methods</p> <p>The quantitation of fecal CK19 transcript was determined by a quantitative real-time reverse transcription polymerase chain in 129 CRC patients (45 younger than 60 years at diagnosis) and 85 healthy controls. The levels of CK19 protein were examined both in colonic cell lines and tissues.</p> <p>Results</p> <p>The analysis of 45 younger CRC patients (age ≤ 60 years) revealed that patients at the M1 stage had significantly higher expression levels of fecal CK19 mRNA when compared with healthy controls (<it>p </it>< 0.001) and patients at the M0 stage (<it>p </it>= 0.004). Additionally, the degree of consistency between the mean level of fecal CK19 mRNA and the distant metastatic rate in each age interval was up to 89% (<it>p </it>= 0.042).</p> <p>Conclusion</p> <p>These results indicate that high levels of fecal CK19 mRNA represent a potential marker for colorectal malignancy and for aggressive treatment of younger CRC patients.</p

Functional roles of arginine residues in mung bean vacuolar H+-pyrophosphatase

AbstractPlant vacuolar H+-translocating inorganic pyrophosphatase (V-PPase EC 3.6.1.1) utilizes inorganic pyrophosphate (PPi) as an energy source to generate a H+ gradient potential for the secondary transport of ions and metabolites across the vacuole membrane. In this study, functional roles of arginine residues in mung bean V-PPase were determined by site-directed mutagenesis. Alignment of amino-acid sequence of K+-dependent V-PPases from several organisms showed that 11 of all 15 arginine residues were highly conserved. Arginine residues were individually substituted by alanine residues to produce R→A-substituted V-PPases, which were then heterologously expressed in yeast. The characteristics of mutant variants were subsequently scrutinized. As a result, most R→A-substituted V-PPases exhibited similar enzymatic activities to the wild-type with exception that R242A, R523A, and R609A mutants markedly lost their abilities of PPi hydrolysis and associated H+-translocation. Moreover, mutation on these three arginines altered the optimal pH and significantly reduced K+-stimulation for enzymatic activities, implying a conformational change or a modification in enzymatic reaction upon substitution. In particular, R242A performed striking resistance to specific arginine-modifiers, 2,3-butanedione and phenylglyoxal, revealing that Arg242 is most likely the primary target residue for these two reagents. The mutation at Arg242 also removed F− inhibition that is presumably derived from the interfering in the formation of substrate complex Mg2+–PPi. Our results suggest accordingly that active pocket of V-PPase probably contains the essential Arg242 which is embedded in a more hydrophobic environment