A noise-whitening approach to multiple access noise rejection .I.Theory and background

Minimum probability of bit error is difficult to achieve in a DS-CDMA receiver. Since multiple-access noise is the sum of many independent random processes, it is reasonable to approximate it by a Gaussian process of the same power spectral density. This leads to the criterion of maximizing signal-to-noise ratio (SNR). In this paper, receivers that maximize SNR in a particular DS-CDMA system model under various constraints are proposed and analyzed. The method proposed here does not require locking and despreading multiple arriving CDMA signals. The maximization of SNR is compared with the minimization of probability of error, when the receiver is constrained to operate bit-by-bit, in the absence of knowledge of the other users' spreading codes, timing, and phase     

Computing the distribution of sums of random sine waves and ofRayleigh-distributed random variables by saddle-point integration

The method of saddle-point integration is applied to calculating the cumulative distribution of sums of independent random variables that either have a Rayleigh distribution or are sine waves with independently random phases in the presence of Gaussian random noise     

Analysis of avalanche diode receivers by saddlepoint integration

The error probability in a binary fiber-optical communication system whose receiver utilizes an avalanche-diode detector is calculated by applying the method of numerical saddlepoint integration to Laplace inversion integrals for the probabilities of errors of the first and second kinds. It is shown how to choose the contours of integration for efficient numerical quadrature. The effects of shot noise, intersymbol interference, and additive Gaussian noise are taken into account, and the decision level on the receiver output is set to minimize the average probability of error. Examples show how the method can be used in receiver design to select system parameters such as the output pulsewidth and the sampling time in order to minimize the probability of error     

A psychometric evaluation of the Smoking Consequences Questionnaire-Adult in smokers with psychiatric conditions.

Rates of smoking among individuals with psychiatric conditions are much greater than those seen in the general population, yet little is known about the psychometric properties of commonly used instruments that assess smoking-related variables among smokers with psychiatric conditions. The present study examined the factor structure and psychometric characteristics of the Smoking Consequences Questionnaire-Adult (SCQ-A; Copeland, Brandon, & Quinn, 1995, Psychological Assessment, 7, 484-494) among smokers with psychiatric conditions. A confirmatory factor analysis of the instrument indicated that the factor structure derived by the instrument's authors provided an adequate fit to the data. In addition, many of the 10 subscales of the SCQ-A demonstrated adequate internal consistency as assessed by Cronbach's alpha as well as adequate test-retest reliability over the course of 1 week. Based on the data derived from this sample, the SCQ-A has adequate psychometric properties for applications involving smokers with psychiatric conditions.     

Computing the performance of optical receivers with avalanche diodedetectors

A method is described for exactly computing the probability distribution of the sum of the output of an avalanche diode and Gaussian noise using the Personick-McIntyre model of the random electron multiplication in the diode. A saddlepoint approximation is also presented. Both are incorporated in an optimization procedure for efficiently calculating the minimum input signal strength and the decision level that are needed to attain a preassigned error probability when the diode is embodied in a binary optical communication receiver     

Calculating Error Probabilities for Intersymbol and Cochannel Interference

The probability of error in a binary symmetric channel with intersymbol interference and additive noise is efficiently calculated by numerical quadrature of a Laplace inversion integral along a contour in the complex plane passing through a saddlepoint of the integrand. For Gaussian noise, a bound is set on the truncation error incurred by necessarily restricting the integration to a finite interval. The probability of error resulting from cochannel interference is calculated by a similar technique.