BER of high-speed OFDM systems in the presence of offset mismatch of TI-ADCs

Time-interleaved analog-to-digital converters (TI-ADCs) are widely used for multi-Gigabit orthogonal frequency division multiplexing (OFDM) systems because of their attractive high sampling rate and high resolution. However, in practice, offset mismatch, one of the major mismatches of TI-ADCs, can occur between the parallel sub-ADCs. In this poster session, we theoretically analyze the BER performance of high-speed OFDM systems using TI-ADCs with offset mismatch. Gray-coded PAM or QAM signaling over an additive white Gaussian noise channel is considered. Our numerical results show that the obtained theoretical BER expressions are in excellent agreement with the simulated BER performance

BER analysis of high-speed OFDM systems in the presence of time-interleaved analog-to-digital converter's offset mismatch

Time-interleaved analog-to-digital converters (TI-ADCs) are widely used for multi-Gigabit orthogonal frequency division multiplexing (OFDM) systems because of their attractive high sampling rate and high resolution. However, mismatch between the parallel sub-ADCs can severely degrade the system performance. Several types of mismatch can be distinguished, one particular kind of mismatch is offset mismatch, which originates from the different DC offsets in the different sub-ADCs. Although some authors have studied the effect of offset mismatch on the bit error rate (BER) performance, exact close-form BER expressions in the presence of offset mismatch have not been derived yet. In this poster, we derive such BER expressions. Gray-coded PAM or QAM signaling over an additive white Gaussian noise channel is considered. Our numerical results show that the obtained theoretical BER expressions are in excellent agreement with the simulated BER performance. We also investigate simplified expressions for the error floor occurring at large SNR and large offset mismatch. Our finding shows that this error floor is essentially independent of the modulation order and the type of modulation

Accurate and efficient BER evaluation for high-speed OFDM systems impaired by TI-ADC circuit’s gain mismatch

This paper presents an efficient procedure to numerically evaluate the exact bit error rate of a rectangular quadrature amplitude modulated-orthogonal frequency division multiplexing (OFDM) system that is impaired by the gain mismatch of a time-interleaved analog-to-digital converter. As opposed to previous contributions, no approximations are involved in this procedure. The obtained results allow to accurately analyze the effect of this type of mismatch on the performance of practical high-speed OFDM systems. The accuracy and efficiency of the proposed technique are demonstrated by comparing analytical results with brute-force Monte-Carlo simulations

Offset mismatch calibration for TI-ADCs in high-speed OFDM systems

Time-interleaved analog-to-digital converters (TIADCs) are widely used for multi-Gigabit orthogonal frequency division multiplexing (OFDM) based systems because of their attractive high sampling rate and high resolution. However, when not perfectly calibrated, mismatches such as offset mismatch, gain mismatch and timing mismatch between parallel sub-ADCs can significantly degrade the system performance. In this paper, we focus on offset mismatch. We analyze two calibration techniques for the offset mismatch, based on the least-squares (LS) and linear minimum mean-squared error (LMMSE) algorithms assuming an AWGN channel. The simulation results show that our method is capable of improving the BER performance. As expected, the LMMSE estimator outperforms the LS estimator. However, at large offset mismatch levels or low noise level, both estimators converge. In this paper, we derive the condition on the mismatch level for convergence between the two estimators

Dynamic Texture Map Based Artifact Reduction For Compressed Videos

This paper proposes a method of artifact reduction in compressed videos using dynamic texture map together with artifact maps and 3D - fuzzy filters. To preserve better details during filtering process, the authors introduce a novel method to construct a texture map for video sequences called dynamic texture map. Then, temporal arifacts such as flicker artifacts and mosquito artifacts are also estimated by advanced flicker maps and mosquito maps. These maps combined with fuzzy filters are applied to intraframe and interframe pixels to enhancecompressed videos. Simulation results verify the advanced performance of the proposed fuzzy filtering scheme in term of visual quality, SSIM, PSNR and flicker metrics in comparisionwith existing state of the art methods

An identification of the tolerable time-interleaved analog-to-digital converter timing mismatch level in high-speed orthogonal frequency division multiplexing systems

High-speed Terahertz communication systems has recently employed orthogonal frequency division multiplexing approach as it provides high spectral efficiency and avoids inter-symbol interference caused by dispersive channels. Such high-speed systems require extremely high-sampling time-interleaved analog-to-digital converters at the receiver. However, timing mismatch of time-interleaved analog-to-digital converters significantly causes system performance degradation. In this paper, to avoid such performance degradation induced by timing mismatch, we theoretically determine maximum tolerable mismatch levels for orthogonal frequency division multiplexing communication systems. To obtain these levels, we first propose an analytical method to derive the bit error rate formula for quadrature and pulse amplitude modulations in Rayleigh fading channels, assuming binary reflected gray code (BRGC) mapping. Further, from the derived bit error rate (BER) expressions, we reveal a threshold of timing mismatch level for which error floors produced by the mismatch will be smaller than a given BER. Simulation results demonstrate that if we preserve mismatch level smaller than 25% of this obtained threshold, the BER performance degradation is smaller than 0.5 dB as compared to the case without timing mismatch

The Anatomical Numerical Measurement of Posterior Cruciate Ligament: A Vietnamese Cadaveric Study

BACKGROUND: The posterior cruciate ligament (PCL) is crucial to restrain the posterior translation of the tibia. Its anatomical structure is complex. A proper understanding of PCL anatomy may assist surgeon in reconstructing anatomically native PCL. AIM: To describe the anatomical numerical measurement of the PCL in Vietnamese adults. METHODS: Twenty-one fresh cadaveric knees were examined. The macroscopic details of the intra-articular PCL, the attachment of the anterolateral bundle (ALB), posteromedial bundles (PMB) to the femur and tibia were analysed. We used a digital camera to photograph the cadaveric specimens and used the ImageJ software to analyse the collected images. RESULTS: The ALB and PMB length were 35.5 ± 2.78 and 32.6 ± 2.28 mm, respectively. The smallest and the biggest diameter of middle third of the PCL were 5.9 ± 0.71 and 10.0 ± 1.39 mm, respectively. The area of cross section of middle third of the PCL was 53.6 ± 12.37 mm2. The femoral insertion area of ALB and PMB were 88.4 ± 16.89 and 43.5 ± 8.83 mm2, respectively. The distance from the central point of femoral ALB, PMB, and total PCL insertion to the Blumensaat line were 5.5 ± 0.91, 11.5 ± 1.98, and 7.6 ± 1.42 mm, respectively. The shortest distance from medial femoral cartilage rim to the central point of femoral ALB, PMB, and total PCL insertion were 7.0 ± 0.79, 7.3 ± 0.95, and 7.8 ± 1.73 mm, respectively. The tibial insertion area of ALB and PMB were 84.5 ± 12.52 and 47.8 ± 6.20 mm2 respectively. The shortest distance from the posterior cartilage corner of the medial tibial plateau to the central point of ALB, PMB, and total PCL insertion to tibia were 8.5 ± 1.02, 9.4 ± 1.11, and 8.3 ± 1.1 mm, respectively. The central point of tibial PCL insertion was 9.7±1.08 mm below cartilage plane of the medial tibial plateau. CONCLUSION: This study describes the detailed anatomical measurement of the PCL and its bundles in adults