RESUMO
Objective: Measurement invariance assesses the psychometric equivalence of a construct across groups or across time. This study aimed to find out whether the newly modified 5-point Likert scale SEGUE Framework for evaluating doctor's communication skills demonstrates measurement invariance among Chinese and Ghanaian patients. Methods: Measurement invariance tests were conducted using two samples collected from the two cultures respectively (China: N = 598 and Ghana: N = 591). Confirmatory Factor Analysis (CFA) was used to test for the factor structure. Multiple-group CFA was used to test the measurement invariance of the SEGUE between the two samples. Results: The same five-factor model showed acceptable model fit in both Chinese and Ghanaian samples. Cross-cultural measurement invariance tests revealed that scalar invariance was observed across the two samples. Conclusion: Cross-cultural adaptations of instruments should exhibit measurement invariance to ensure that measures are interpreted and used consistently. Findings of our study suggest that the SEGUE Framework is invariant across the two cultures, which increases confidence in data collection and comparison. Innovation: This is the first study to establish measurement invariance among Chinese and Ghanaians using the SEGUE Framework which assesses doctors' communication from patients' perspectives.
RESUMO
A code reservation technique is proposed to reduce the peak-to-average power ratio (PAPR) of digital code-division multiplexing (CDM) based channel aggregation for mobile fronthaul. We numerically investigate the relationship between the PAPR and the number of aggregated channels during the CDM based channel aggregation, and experimentally verify the transmission performance with the code reservation technique. The PAPR of aggregated signal, which is composed of 48x20MHz Long Term Evolution (LTE) signal mapped with 64 quadrature amplitude modulation (QAM), is reduced with the help of code reservation technique. The PAPR reduction enables larger optical modulation index (OMI) per channel at the linear operation region of a directly modulated laser (DML), leading to the optical signal-to-noise ratio (OSNR) improvement. After the transmission over 10km standard single mode fiber (SSMF), the receiver sensitivity can be improved by 4dB owing to the PAPR reduction.
RESUMO
We present the first experimental demonstration of orthogonal frequency division multiplexed (OFDM) modulation using the probabilistic shaping (PS) technique in visible light communication (VLC) systems, in order to increase the achievable information rate (AIR) according to the pre-estimated signal to noise ratio (SNR) of VLC channel. We numerically investigate the performance of PS technique and make a fair comparison with bit-loading technique under different scenarios. By using a phosphor-LED based VLC system with available bandwidth of ~45-MHz, OFDM with PS technique can experimentally realize an AIR of 204.1-Mb/s over 1-m free space transmission, leading to a 26.8% increment in comparison with OFDM using bit-loading technique at the expense of 16% overall forward error correction (FEC) overhead (OH).
RESUMO
Due to the non-rectangular distribution of the constellation points, traditional fast Fourier transform based frequency offset estimation (FFT-FOE) is no longer suitable for 32-QAM signal. Here, we report a modified FFT-FOE technique by selecting and digitally amplifying the inner QPSK ring of 32-QAM after the adaptive equalization, which is defined as QPSK-selection assisted FFT-FOE. Simulation results show that no FOE error occurs with a FFT size of only 512 symbols, when the signal-to-noise ratio (SNR) is above 17.5 dB using our proposed FOE technique. However, the error probability of traditional FFT-FOE scheme for 32-QAM is always intolerant. Finally, our proposed FOE scheme functions well for 10 Gbaud dual polarization (DP)-32-QAM signal to reach 20% forward error correction (FEC) threshold of BER=2×10-2, under the scenario of back-to-back (B2B) transmission.
