AM baseband telemetry systems. Volume 1 - Factors affecting a common pilot system

Coherent demodulation in single and double side bands with frequency modulation telemetry system

Signal-to-noise ratio estimation in digital computer simulation of lowpass and bandpass systems with applications to analog and digital communications, volume 3

Techniques are developed to estimate power gain, delay, signal-to-noise ratio, and mean square error in digital computer simulations of lowpass and bandpass systems. The techniques are applied to analog and digital communications. The signal-to-noise ratio estimates are shown to be maximum likelihood estimates in additive white Gaussian noise. The methods are seen to be especially useful for digital communication systems where the mapping from the signal-to-noise ratio to the error probability can be obtained. Simulation results show the techniques developed to be accurate and quite versatile in evaluating the performance of many systems through digital computer simulation

Am-baseband Telemetry Systems. Volume 4 - Problems Relating to Am-baseband Systems

Distortion of amplitude modulated radio signals passing within passband of bandpass filter

AM-baseband telemetry systems. Volume 5 - Summary

Demodulation process for AM baseband telemetry system

Conference Tutorials-An Opportunity For Continuing Education

The Educational Services Committee of the IEEE Communications Society has sponsored eleven tutorial short courses at its major conferences over the past six years. The experience gained in developing and presenting these tutorials is shared with others so that they may be in a better position to sponsor similar continuing education activities in the future. The conference tutorial is one example of a continuing education activity that can be sponsored by an IEEE Group or Society as a service to its members. Copyright © 1978 by The Institute of Electrical and Electronics Engineers, Inc

Sanitizing the fortress: protection of ant brood and nest material by worker antibiotics

Social groups are at particular risk for parasite infection, which is heightened in eusocial insects by the low genetic diversity of individuals within a colony. To combat this, adult ants have evolved a suite of defenses to protect each other, including the production of antimicrobial secretions. However, it is the brood in a colony that are most vulnerable to parasites because their individual defenses are limited, and the nest material in which ants live is also likely to be prone to colonization by potential parasites. Here, we investigate in two ant species whether adult workers use their antimicrobial secretions not only to protect each other but also to sanitize the vulnerable brood and nest material. We find that, in both leaf-cutting ants and weaver ants, the survival of the brood was reduced and the sporulation of parasitic fungi from them increased, when the workers nursing them lacked functional antimicrobial-producing glands. This was the case for both larvae that were experimentally treated with a fungal parasite (Metarhizium) and control larvae which developed infections of an opportunistic fungal parasite (Aspergillus). Similarly, fungi were more likely to grow on the nest material of both ant species if the glands of attending workers were blocked. The results show that the defense of brood and sanitization of nest material are important functions of the antimicrobial secretions of adult ants and that ubiquitous, opportunistic fungi may be a more important driver of the evolution of these defenses than rarer, specialist parasites

Simulation of Communication Systems

When both a complex system and a complex channel model are encountered, the result is typically a design or analysis problem that cannot be solved using traditional (pencil and paper) mathematical analysis. Computer-aided techniques, which usually involve some level of numerical simulation, can be a very valuable tool in these situations. The purpose of this article is to provide a tutorial review of some of the basic techniques of communication system simulation. The authors consider the basic techniques used to represent signals, generate signals, and model linear systems, nonlinear systems, and time-varying systems within a simulation. They consider the important problem of using a simulation to estimate the performance of a communication syste

Efficient Simulation Of Multicarrier Digital Communication Systems In Nonlinear Channel Environments

The effectiveness of computer simulation as a tool for the design and analysis of communication systems is often limited by the long execution times required for many simulations. When simulating multicarrier digital communication systems operating over nonlinear channels, the required high sampling rate contributes significantly to long execution times. A new method that reduces the sampling rate of simulations of such systems is developed. This Partial Sum of Products (ParSOP) method reduces the sampling rate by generating only the intermodulation products that lie in a frequency band of interest. The ParSOP method requires that the bandpass nonlinearity be represented by memoryless operations on the complex envelope of the signal and that the subcarriers constituting the frequency-division multiplexed signal are sufficiently separated to prevent significant adjacent channel interference. Simulation results for such systems show that an order of magnitude reduction in the sampling rate is possible while producing only minimal error in the bit error rate estimate. © 1993 IEE

Baseband AGc In An AM-FM Telemetry System

The use of AGc loops at the input and output of the FM link in an AM-FM telemetry system allows the mean-square transmitter deviation to be maintained near maximum value, even though data may be nonstationary. However, errors result because of the inability of the receiver AGc loop to track perfectly gain variations in the transmitter loop. In this paper the general characteristics of AGc are discussed, and a theoretical analysis is performed to determine the time constant, steady-state error, and tracking error for a first-order loop. Also, tracking error for first order and second-order loops is investigated by simulation. Curves are presented to illustrate the principal results. Copyright 1970 by the Institute of Electrical and Electronics Engineers, Inc

Quality and quantity: transitions in antimicrobial gland use for parasite defense

Parasites are a major force in evolution, and understanding how host life history affects parasite pressure and investment in disease resistance is a general problem in evolutionary biology. The threat of disease may be especially strong in social animals, and ants have evolved the unique metapleural gland (MG), which in many taxa produce antimicrobial compounds that have been argued to have been a key to their ecological success. However, the importance of the MG in the disease resistance of individual ants across ant taxa has not been examined directly. We investigate experimentally the importance of the MG for disease resistance in the fungus-growing ants, a group in which there is interspecific variation in MG size and which has distinct transitions in life history. We find that more derived taxa rely more on the MG for disease resistance than more basal taxa and that there are a series of evolutionary transitions in the quality, quantity, and usage of the MG secretions, which correlate with transitions in life history. These shifts show how even small clades can exhibit substantial transitions in disease resistance investment, demonstrating that host–parasite relationships can be very dynamic and that targeted experimental, as well as large-scale, comparative studies can be valuable for identifying evolutionary transitions