Large-System Analysis of Joint Channel and Data Estimation for MIMO DS-CDMA Systems

This paper presents a large-system analysis of the performance of joint channel estimation, multiuser detection, and per-user decoding (CE-MUDD) for randomly-spread multiple-input multiple-output (MIMO) direct-sequence code-division multiple-access (DS-CDMA) systems. A suboptimal receiver based on successive decoding in conjunction with linear minimum mean-squared error (LMMSE) channel estimation is investigated. The replica method, developed in statistical mechanics, is used to evaluate the performance in the large-system limit, where the number of users and the spreading factor tend to infinity while their ratio and the number of transmit and receive antennas are kept constant. The performance of the joint CE-MUDD based on LMMSE channel estimation is compared to the spectral efficiencies of several receivers based on one-shot LMMSE channel estimation, in which the decoded data symbols are not utilized to refine the initial channel estimates. The results imply that the use of joint CE-MUDD significantly reduces rate loss due to transmission of pilot signals, especially for multiple-antenna systems. As a result, joint CE-MUDD can provide significant performance gains, compared to the receivers based on one-shot channel estimation.Comment: The paper was resubmitted to IEEE Trans. Inf. Theor

On an Achievable Rate of Large Rayleigh Block-Fading MIMO Channels with No CSI

Training-based transmission over Rayleigh block-fading multiple-input multiple-output (MIMO) channels is investigated. As a training method a combination of a pilot-assisted scheme and a biased signaling scheme is considered. The achievable rates of successive decoding (SD) receivers based on the linear minimum mean-squared error (LMMSE) channel estimation are analyzed in the large-system limit, by using the replica method under the assumption of replica symmetry. It is shown that negligible pilot information is best in terms of the achievable rates of the SD receivers in the large-system limit. The obtained analytical formulas of the achievable rates can improve the existing lower bound on the capacity of the MIMO channel with no channel state information (CSI), derived by Hassibi and Hochwald, for all signal-to-noise ratios (SNRs). The comparison between the obtained bound and a high SNR approximation of the channel capacity, derived by Zheng and Tse, implies that the high SNR approximation is unreliable unless quite high SNR is considered. Energy efficiency in the low SNR regime is also investigated in terms of the power per information bit required for reliable communication. The required minimum power is shown to be achieved at a positive rate for the SD receiver with no CSI, whereas it is achieved in the zero-rate limit for the case of perfect CSI available at the receiver. Moreover, numerical simulations imply that the presented large-system analysis can provide a good approximation for not so large systems. The results in this paper imply that SD schemes can provide a significant performance gain in the low-to-moderate SNR regimes, compared to conventional receivers based on one-shot channel estimation.Comment: re-submitted to IEEE Trans. Inf. Theor

Risk for lung cancer in workers exposed to benzidine and/or beta-naphthylamine: a protocol for systematic review and meta-analysis.

BACKGROUND:Risk for lung cancer in workers exposed to benzidine (BZ) and/or beta-naphthylamine (BNA), which are well-known bladder carcinogens, has been examined in many epidemiological studies, but individual epidemiological studies generally lack the power to examine the association between BZ/BNA exposure and lung cancer. We conduct a systematic review and meta-analysis to determine the risk for lung cancer among workers exposed to BZ/BNA occupationally. METHODS/DESIGN:Studies will be identified by a MEDLINE, EMBASE, CDSR, and CINAHL search and by the reference lists of articles/relevant reviews. Eligible studies will be cohort and case-control studies that report occupational BZ/BNA exposure and the outcome of interest (lung cancer death/incidence). The method of meta-analysis will be used to combine standardized mortality ratios (SMRs) and/or standardized incidence ratios (SIRs) from retrospective and prospective cohort studies and odds ratios (ORs) from case-control studies. Two reviewers will independently screen articles, extract data, and assess scientific quality using standardized forms and published quality assessment tools tailored for each study design. Overall pooled risk estimates and their corresponding 95% confidence intervals (CIs) will be obtained using random effects model. This systematic review and meta-analysis will be conducted following the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines, and results will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.DISCUSSION: This review will identify and synthesize studies of the association between occupational BZ/BNA exposure and lung cancer. The findings will help to identify whether BZ/BNA could cause lung cancer and might indicate whether workers with exposure to BZ/BNA have a need for preventive measures against non-urological cancer besides bladder cancer.© 2014 Tomioka et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article,unless otherwise stated

Molecular analysis of afibrinogenemic mutations caused by a homozygous FGA1238 bp deletion, and a compound heterozygous FGA1238 bp deletion and novel FGA c.54+3A > C substitution

We identified two afibrinogenemic girls in two Japanese families and performed molecular analysis to clarify the mechanisms of fibrinogen defects. Genetic analyses were performed by PCR amplification of the fibrinogen gene and DNA sequence analysis. To analyze the mechanisms of mature fibrinogen defects in plasma, we cloned minigenes from the proposita's PCR-amplified DNA, transfected them into CHO cells, and sequenced the cDNA amplified with the RT reaction followed by PCR. Sequence analyses indicated that one was caused by a homozygous 1238 bp deletion of the fibrinogen A alpha-chain gene (FGA Delta 1238) and the other was a compound heterozygous FGA Delta 1238 and novel FGA c.54+3A > C substitution. The minigene corresponding to FGA Delta 1238 generates two aberrant mRNAs, both of which may induce a frameshift and terminate prematurely. In contrast, the minigene corresponding to FGA c.54+3A > C generates two aberrant mRNAs, one of which may induce a frameshift and terminate prematurely, and the other uses a cryptic 5' splice site in exon 1, resulting in the deletion of six amino acids in signal peptides. Molecular analyses of both genetic variants suggest that the lack of a mature A alpha-chain, impaired assembly, and/or secretion of the fibrinogen molecule may lead to afibrinogenemia.ArticleINTERNATIONAL JOURNAL OF HEMATOLOGY. 96(1):39-46 (2012)journal articl

白内障手術既往のある高齢者は視力と独立して高い認知機能を維持する : 平城京コホート研究横断解析

Cataract surgery improves visual acuity and drastically increases the capacity for light reception to the retina. Although previous studies suggested that both light exposure and visual acuity were associated with cognitive function, the relationships between cataract surgery, visual acuity, and cognitive function have not been evaluated in large populations. In this cross-sectional study, we measured cognitive function using the Mini-Mental State Examination and best-corrected visual acuity in pseudophakic (previous cataract surgery) and phakic (no previous cataract surgery) elderly individuals. Of 945 participants (mean age 71.7 years), 166 (17.6%) had pseudophakia and 317 (33.5%) had impaired cognitive function (score ≤26). The pseudophakic group showed significantly better visual acuity than the phakic group (p = 0.003) and lower age-adjusted odds ratio (ORs) for cognitive impairment (OR 0.66; p = 0.038). Consistently, in multivariate logistic regression models, after adjusting for confounding factors, including visual acuity and socioeconomic status, ORs for cognitive impairment were significantly lower in the pseudophakic group than in the phakic group (OR 0.64; 95% confidence interval 0.43-0.96; p = 0.031). This association remained significant in sensitivity analysis, excluding participants with low cognitive score ≤23 (n = 36). In conclusion, in a general elderly population, prevalence of cognitive impairment was significantly lower in pseudophakic individuals independently of visual acuity. The association was also independent of several major causes of cognitive impairment such as aging, gender, obesity, socioeconomic status, hypertension, diabetes, sleep disturbances, depressive symptoms, and physical inactivity.博士（医学）・甲第666号・平成29年3月15日© Mary Ann Liebert, Inc.This is a non-final version of an article published in final form in "http://dx.doi.org/10.1089/rej.2015.1718