Channel Noise Level Research Articles

Improving concatenated coding communications by employing signal editing techniques

AbstractSignal editing (SE) is a technique used to locate and erase unreliable data before error correction decoding. Consider a concatenated coding (CC) communication system in which the inner code employs convolutional encoding with Viterbi decoding (CEVD) and the outer code could employ either a convolutional or a Reed‐Solomon code. In this study, we show that useful information can be derived from the inner Viterbi decoding process to perform two special operations: (i) to locate and erase unreliable decoded data and (ii) to estimate the input channel noise level. As a result, the number of errors input to the outer decoder is reduced and the overall CC system performance is improved.

Effect of X-ray radiation on MOSFET's (SIMOX) LF excess noise

The behavior of hardened n-MOS and p-MOS transistors (silicon on insulator (SOI)-SIMOX technology) was investigated. These elementary components have been irradiated by X-ray radiation after an electrical characterization. In addition to such electrical parameters as the threshold voltage, the transconductance, and the leakage drain current, it is interesting to observe the channel noise level shift before and after irradiation at different doses. The particular interest of this analysis is found in the behavior of SOI-SIMOX technology transistors. This approach based on LF excess noise measurements is a new way to evaluate and understand the radiation-induced mechanisms. The major effects of ionizing radiation on MOS transistors are identified as the increase of the fixed oxide charge and of the interface state density, both mechanisms stemming from ionizing effects in the thin gate oxide. These densities control the channel current fluctuations and then the channel noise current.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

On two probabilistic decoding algorithms for binary linear codes

A generalization of the Sullivan inequality (1967) on the ratio of the probability of a linear code to that of any of its cosets is proved. Starting from this inequality, a sufficient condition for successful decoding of linear codes by a probabilistic method is derived. A probabilistic decoding algorithm for low-density parity-check codes is also analyzed. This method of analysis enables one to estimate experimentally the probability of successful decoding for any given linear code and for any chosen family of parity-check sets. Using the example of a linear (512,100) code, the author illustrates the dependence of the successful probability on the channel noise level. >

Adaptive speech signal detector

An adaptive speech signal detector for use in a 4-wire telephone channel performs an adaptive threshold value setting operation depending on the channel noise level on a transmitter-side channel to detect a speech signal present at the transmitter. The adaptive operation of the speed signal detector is inhibited, however, if the signal level at the related receiver-side channel becomes higher than a preset value. This permits the use of the adaptive speech signal detector with DSI (digital speech interpolation) systems without malfunction due to the operation of an echo suppressor.

A high precision automatic ellipsometer using grating goniometers

The construction and performance characteristics of a high precision automatic ellipsometer are described with particular reference to a wide set of specifications. The automatic self-nulling instrument employs two-stage Faraday modulation operating at two different, high frequencies and the channel separation, response time and noise level are all optimized. A wide spectral range may be covered without instrument calibration or readjustment. The instrument also has a wide angular-setting range achieved by using, in conjunction with the Faraday modulation, a mechanical rotation system employing aerostatic journal bearings. The maximum speed using the electromechanical system is 0.09 degrees s-1 and the ultimate resolution 0.648 second of arc.

Signal-to-Noise and Idle Channel Performance of Differential Pulse Code Modulation Systems - Particular Applications to Voice Signals

Analysis leading to a figure of merit for differential pulse code modulation (DPCM) systems with linear feedback networks is presented. It is shown that the figure of merit can be optimized. Simple DPCM has a 6-dB advantage in signal/quantizing noise ratio over pulse code modulation (PCM) for speech. Optimization yields at most 4 dB more. Computer simulation of the system using actual speech samples leads to data supporting the figure of merit as a useful measure of performance for DPCM systems with four digits or more. The simulation also provides data on the error spectrum as a function of quantizer loading and on the probability density of the quantizer input as a function of loading. Performance of the optimum system as a function of increasing feedback network complexity is also shown. Idle channel performance of a particular system is analyzed, indicating the presence of inband oscillations in many cases. The best quantizer bias from the point of view of idle channel performance is found. The level of idle channel noise in DPCM is shown to be approximately equivalent to that in PCM.