Validating the Farsi version of the Pregnancy Worries and Stress Questionnaire (PWSQ): An exploratory factor analysis.

INTRODUCTION: Biological, environmental, inter- and intrapersonal changes during the antenatal period can result in anxiety and stress in pregnant women. It is pivotal to identify potential stressors and prevent their foetal and maternal consequences. The present study was conducted to validate and examine the factor structure of the Farsi version of the Pregnancy Worries and Stress Questionnaire (PWSQ). METHODS: In 2015, 502 Iranian healthy pregnant women, referred to selected hospitals in Tehran for prenatal care at 8-39 weeks of pregnancy, were recruited through a randomized cluster sampling. The PWSQ was translated into Farsi, and its validity and reliability were examined using exploratory factor analysis by SPSS version 21. RESULTS: The content validity of items on the PWSQ was between 0.63-1. The content validity index for relevance, clarity and simplicity were 0.92, 0.98, and 0.98, respectively, with a mean of 0.94. The Kaiser-Meyer-Olkin measure of sampling adequacy was 0.863. Test-retest reliability showed high internal consistency (α=0.89; p<0.0001). CONCLUSION: The psychometric evaluation and exploratory factor analysis showed that the translated questionnaire is a valid and reliable tool to identify stress in Iranian pregnant women. Application of the questionnaire can facilitate the diagnosis of stress in pregnant women and assist health care providers in providing timely support and minimizing negative outcomes of stress and anxiety in pregnant women and their infants

Performance Analysis of Coded MC-CDMA in Powerline Communication Channel with Implusive Noise

Abstract — Broadband communications for indoor power-line networks with impulsive noise using Multicarrier CDMA (MC-CDMA) is considered. From earlier investigations, it is known that this channel suffers from multipath fading and frequency selectivity along with man-made impulsive bursty noise. Nevertheless, the calculated channel capacity limit promises very high data rates over this channel. Enhancement techniques, such as coding can help a Multicarrier system to tackle impulsive noise burst. In this paper the bit error rate (BER) performance of the MC-CDMA system under impulsive noise and frequency fading is theoretically analyzed and closed form expression for this performance is derived. Furthermore, a theoretical upper bound for performance of coded MC-CDMA system is derived, given perfect interleaving and effect of interleaver length on coding performance is also studied. Simulations show that the upper bound is quite tight for the case of employing a longer interleaver. I

BER performance of free-space optical transmission with spatial diversity

Abstract — Free space optical (FSO) communications is a cost-effective and high bandwidth access technique, which has been receiving growing attention with recent commercialization successes. A major impairment in FSO links is the turbulenceinduced fading which severely degrades the link performance. To mitigate turbulence-induced fading and, therefore, to improve the error rate performance, spatial diversity can be used over FSO links which involves the deployment of multiple laser transmitters/receivers. In this paper, we investigate the bit error rate (BER) performance of FSO links with spatial diversity over lognormal atmospheric turbulence fading channels, assuming both independent and correlated channels among transmitter/receiver apertures. Our analytical derivations build upon an approximation to the sum of correlated log-normal random variables. The derived BER expressions quantify the effect of spatial diversity and possible spatial correlations in a log-normal channel. Index Terms — Atmospheric turbulence, bit error rate, error rate performance analysis, free space optical communication, lognormal channel, MIMO. I