Signal-to-noise Ratio Deterioration Research Articles

Channel power equalization based on joint optimization of EDFA and ROADM configuration in open optical network.

Deterioration of the signal-to-noise ratio (SNR) is an important challenge in ultra-long multi optical line system (OLS) optical transmission systems. The non-uniform gain and cascading of the Erbium-doped fiber amplifier (EDFA) lead to SNR deterioration in transmission systems. In this paper, we propose two channel power equalization methods based on joint optimization of EDFA and Reconfigurable optical add-drop multiplexer (ROADM) configurations: 1) reinforcement learning (RL)-based channel power equalization (RL-PE) and 2) covariance matrix adaptive evolution strategy (CMA-ES) channel power equalization (CMA-PE). The simulation results indicate that the power equalization effect was improved by 1.9 dB through the CMA-PE method, while the RL-PE method led to a 1.5 dB improvement in an ultra-long 80-channel 7-OLS transmission system.

Physiological artifacts in scalp EEG and ear-EEG

BackgroundA problem inherent to recording EEG is the interference arising from noise and artifacts. While in a laboratory environment, artifacts and interference can, to a large extent, be avoided or controlled, in real-life scenarios this is a challenge. Ear-EEG is a concept where EEG is acquired from electrodes in the ear.MethodsWe present a characterization of physiological artifacts generated in a controlled environment for nine subjects. The influence of the artifacts was quantified in terms of the signal-to-noise ratio (SNR) deterioration of the auditory steady-state response. Alpha band modulation was also studied in an open/closed eyes paradigm.ResultsArtifacts related to jaw muscle contractions were present all over the scalp and in the ear, with the highest SNR deteriorations in the gamma band. The SNR deterioration for jaw artifacts were in general higher in the ear compared to the scalp. Whereas eye-blinking did not influence the SNR in the ear, it was significant for all groups of scalps electrodes in the delta and theta bands. Eye movements resulted in statistical significant SNR deterioration in both frontal, temporal and ear electrodes. Recordings of alpha band modulation showed increased power and coherence of the EEG for ear and scalp electrodes in the closed-eyes periods.ConclusionsEar-EEG is a method developed for unobtrusive and discreet recording over long periods of time and in real-life environments. This study investigated the influence of the most important types of physiological artifacts, and demonstrated that spontaneous activity, in terms of alpha band oscillations, could be recorded from the ear-EEG platform. In its present form ear-EEG was more prone to jaw related artifacts and less prone to eye-blinking artifacts compared to state-of-the-art scalp based systems.

Near Vertical Incidence Skywave Propagation: Elevation Angles and Optimum Antenna Height for Horizontal Dipole Antennas

Near Vertical Incidence Skywave (NVIS) communication uses the ionosphere as a reflector to cover a continuous area with a radius of at least 150 km around the transmitter, on frequencies typically between 3 and 10 MHz. In developing countries, in areas lacking any other telecommunication infrastructure, it is used on a daily basis for voice and data communication. It may also be used in ad-hoc emergency (disaster) communication in other regions. This paper proposes optimum heights above ground for horizontal dipole antennas for NVIS, based on simulations and empirical data. First, the relationship between elevation angle and skip distance is obtained using ionospheric ray tracing. The high elevation angles found by simulation are confirmed by elevation angle measurements using a professional radio direction finder. The measurements also show the dominance of NVIS over ground wave propagation starting at a short distance. For these elevation angles, the optimum receive and transmit antenna heights above ground are derived using antenna simulations. A distinction is made between optimum transmit signal strength and optimum received signal-to-noise ratio (SNR). These optima are verified experimentally, demonstrating a novel evaluation method that can be used in the presence of the fading typical for ionospheric propagation. For farmland soil ( 20 mS/m, r 17) the optimum height above ground for the transmit antenna is 0.180.22. If the antenna is lowered to 0.02 a transmit signal loss of 12 dB occurs. This corresponds with the theory. The receive antenna height, however, while appearing uncritical in the simulations, showed a clear optimum at 0.16 and a 27 dB SNR deterioration when lowered to 0.02.

Color filter array patterns for small-pixel image sensors with substantial cross talk.

Digital image sensor outputs usually must be transformed to suit the human visual system. This color correction amplifies noise, thus reducing the signal-to-noise ratio (SNR) of the image. In subdiffraction-limit (SDL) pixels, where optical and carrier cross talk can be substantial, this problem can become significant when conventional color filter arrays (CFAs) such as the Bayer patterns (RGB and CMY) are used. We present the design and analysis of new color filter array patterns for improving the color error and SNR deterioration caused by cross talk in these SDL pixels. We demonstrate an improvement in the color reproduction accuracy and SNR in high cross-talk conditions. Finally, we investigate the trade-off between color accuracy and SNR for the different CFA patterns.

Continuous-time delta-sigma modulator using vector filter in feedback path to reduce effect of clock jitter and excess loop delay

In this paper, we propose a novel delta-sigma modulator (DSM) that reduces the effects of clock jitter and excess loop delay by using a vector filter in the feedback path. The vector filter divides the input signal into a high-frequency part and a low-frequency part. The low-pass signal is placed in the path to the first-stage digital-to-analog converter for reducing the effects of the clock jitter, and the high-pass signal is placed in the feedback path to the last integrator in order to compensate for the excess loop delay. The DSM using the vector filter in the feedback path (DSM-VF) is verified using MATLAB/Simulink. Further, a clock jitter (0.1 %) in DSM-VF leads to an improvement in the signal-to-noise-ratio (SNR) to 22.5 dB as compared to the SNR of a conventional CTDSM. Moreover, the SNR deterioration caused by the excess loop delay is improved.

Improvement on Diversity Gain with Filter Bandwidth Enlargement in Fractional Sampling OFDM Receiver

A diversity scheme with Fractional Sampling (FS) in an OFDM receiver has been investigated recently. Through FS, it is possible to separate multipath components and obtain diversity gain in OFDM systems. Enlargement of the bandwidth of the total frequency response between transmit and receive baseband filters allows the FS scheme to achieve path diversity. However, the transmit filter has to be designed according to the spectrum mask of the wireless standards such as IEEE802.11a/g to avoid interference to the other communication systems and the frequency response of the composite channel including the transmit and receive filters has often been set to minimal bandwidth to eliminate adjacent channel signals. In order to achieve the maximum signal-to-noise ratio (SNR), the same filter is commonly used in the transmitter and the receiver. In this paper, the trade-off among the SNR deterioration, adjacent channel interference, and the diversity gain due to the enlargement of the bandwidth of the receive filter is investigated. Numerical results from computer simulations indicate that the BER performance with wider bandwidth in the receiver shows better performance than that with the minimal bandwidth for maximizing the SNR in certain conditions.

Performance Bounds for Combined Channel Coding and Space–Time Block Coding With Receive Antenna Selection

This paper studies the performance of the concatenation of an outer channel code with an orthogonal space-time block code (STBC), where the outer code can be a convolutional code (CC) or a trellis-coded modulation (TCM) code. In particular, upper bounds on the bit error rate (BER) for this concatenation scheme with receive antenna selection are derived. In the analysis, the authors assume that 1) the receiver uses only L out of the available M receive antennas, where, typically, L/spl les/M; 2) the selected antennas are those that maximize the instantaneous received signal-to-noise ratio (SNR); 3) the channel state information is perfectly known at the receiver; 4) the underlying channel is fully interleaved; and 5) the underlying orthogonal STBC is full rate. An explicit upper bound on the BER for the above concatenation scheme for any N, M, and L is derived, where N denotes the number of transmit antennas. It has been shown that the diversity order with antenna selection is the same as that of the full-complexity system, whereas the deterioration in SNR is upper bounded by 10log/sub 10/(M/L) dB. The authors also derive a tighter upper bound on the BER for the Alamouti scheme when the receiver uses the best antenna, i.e., L=1. These upper bounds can be extended in a straightforward manner to other types of outer codes and fading channels, including fast, block, and slow fading channels. Finally, simulation results that validate the analysis are derived.

Performance Bounds for Space–Time Block Codes With Receive Antenna Selection

In this correspondence, we present a comprehensive performance analysis of orthogonal space-time block codes (STBCs) with receive antenna selection. For a given number of receive antennas M, we assume that the receiver uses the best L of the available M antennas, where, typically, L/spl les/M. The selected antennas are those that maximize the instantaneous received signal-to-noise ratio (SNR). We derive explicit upper bounds on the bit-error rate (BER) performance of the above system for any M and L, and for any number of transmit antennas. We show that the diversity order, with antenna selection, is maintained as that of the full complexity system, whereas the deterioration in SNR is upper-bounded by 10log/sub 10/(M/L) decibels. Furthermore, we derive a tighter upper bound for the BER performance for any N and M when L=1, and derive an expression for the exact BER performance for the Alamouti scheme when L=1. We also present simulation results that validate our analysis.

An Architectural Comparison and CMOS Implementationof Sixth-Order Cascaded \Sigma\Delta Modulator

A sixth-order cascaded sigma-delta modulator is reported aiming low power data-converter architectures. Behavioral simulation shows that the cascaded (2-1-1-2) architecture is the most robust in terms of noise performance and accuracy. A prototype of this architecture was fabricated using a 2 μm analog CMOS process. Measured results indicate that the modulator achieved 89 dB (14.8-b) peak in-band signal-to-noise ratio (SNR) and 92 dB (15.3-b) dynamic range (DR) for a 32 kHz bandwidth, at a sampling rate of only 1 MHz. The modulator dissipated 79 mW from a ±3.3 V supply voltage and only 45 mW from a ±2.5 V supply voltage with negligible SNR deterioration. Process scaling and supply-voltage scaling can thus drastically reduce power dissipation using this architecture while maintaining high SNR and DR performance.

Effects of error propagation on the performance of coding schemes for still pictures

AbstractThis paper investigates the effects of noise‐induced transmission errors on the performance of compression coding methods for still pictures. The following four coding methods are considered: (1) adaptive cosine transform coding; (2) DPCM coding; (3) adaptive block coding; and (4) vector quantization coding. First, the relations among the bit error rate, signal‐to‐noise ratio (SNR), and code lengths by these coding methods are compared in the case of transmission without error control. Adaptive cosine transform coding and adaptive block coding require control information for adaptivity; therefore, they are investigated with and without transmission errors in the coding control information. Further, transmission with error control is studied for sending control information. Considering the error control methods, both automatic repeat request and forward error correction are considered. In these cases SNR deterioration by transmission noise beyond error correction capability and the amount of additional data required for error detection/correction or retransmission are examined. BCH codes are used for error detection and correction.