On the Throughput of Channels that Wear Out

This work investigates the fundamental limits of communication over a noisy discrete memoryless channel that wears out, in the sense of signal-dependent catastrophic failure. In particular, we consider a channel that starts as a memoryless binary-input channel and when the number of transmitted ones causes a sufficient amount of damage, the channel ceases to convey signals. Constant composition codes are adopted to obtain an achievability bound and the left-concave right-convex inequality is then refined to obtain a converse bound on the log-volume throughput for channels that wear out. Since infinite blocklength codes will always wear out the channel for any finite threshold of failure and therefore cannot convey information at positive rates, we analyze the performance of finite blocklength codes to determine the maximum expected transmission volume at a given level of average error probability. We show that this maximization problem has a recursive form and can be solved by dynamic programming. Numerical results demonstrate that a sequence of block codes is preferred to a single block code for streaming sources.Comment: 23 pages, 1 table, 11 figures, submitted to IEEE Transactions on Communication

The study of an adaptive bit rate modem for meteor scatter communications

Includes bibliographical references

Master of Science

thesisGlobal analysis fields, infrared and passive microwave satellite observations, lightning data, and airborne radar reflectivity and dual-Doppler wind analyses show the evolution of environmental conditions, precipitation characteristics, and kinematic structure before, during, and after the rapid intensification (RI) of Hurricane Earl (2010). The relationship between the RI and environmental conditions, intense inner-core convection, inner-core precipitation coverage, core cold-cloud precipitation symmetry, and the radial distribution of convection is examined. The onset of RI occurs despite moderate vertical wind shear. An episode of intense convection occurs before the RI onset, but an examination of the mesoscale and convective-scale kinematic processes during this convective ‘burst' suggests that the strength of convection alone did not cause the onset of RI. Instead, the dual-Doppler, lightning, and microwave data suggest that the precipitation characteristic that ultimately led to the onset of RI was an increasing trend in cold-cloud precipitation symmetry following the migration of inner-core convection into the northeastern and northern quadrants of the storm within a few hours before RI onset. The evolution of precipitation during the RI suggests that the most important inner-core precipitation characteristics supporting RI are the cold-cloud precipitation symmetry and the predominance of strong convective updrafts within (instead of outside of) the radius of maximum wind (RMW). The wind and precipitation data from Earl indicate that the RMW at multiple levels must be examined. When the RMW is substantially slanted, only considering the low-level RMW can lead to the false conclusion that the strongest convection is located outside of the RMW

Neural networks and early fast Doppler for prediction in meteor-burst communications systems.

Thesis (Ph.D.)-University of Natal, Durban, 1994.In meteor-burst communications systems, the channel is bursty with a continuously fluctuating signal-to-noise ratio. Adaptive data rate systems attempt to use the channel more optimally by varying the bit rate. Current adaptive rate systems use a method of closed-loop decision-feedback to control the transmitted data rate. It is proposed that an open-loop adaptive data rate system without a decision feedback path may be possible using implicit channel information carried in the first few milliseconds of the link establishment probe signal. The system would have primary application in low-cost half-duplex telemetry systems. It is shown that the key elements in such a system would be channel predictors. The development of these predictors is the focus of this research. Two novel methods of predicting channel parameters are developed. The first utilises early fast Doppler information that precedes many long duration, large signal-to-noise-ratio overdense trails. The presence of early fast Doppler at the trail commencement is used as a toggle to operate at a higher data rate. Factors influencing the use of early fast Doppler for this purpose are also presented. The second method uses artificial neural networks. Data measured during trail formation is processed and presented to the neural networks for prediction of trail parameters. Several successful neural networks are presented which predict trail type, underdense or overdense, and peak trail amplitude from the first 50ms of the trail's lifetime. This method allows better estimation of the developing trail. This fact can be used to implement a multi-rate open-loop adaptive data rate system

Military Radio Communications Research in Australia

An overview of recent research by the Australian Defence Science and Technology Organisation in the field of military radio communications is presented. A philosophy for improving digital radio system performance over complex, variable channels is outlined. A key breakthrough, called PDF-directed adaptive radio, which can provide substantially greater throughput over HF channels whilst minimising bit-error rate and delay, is described. Simulation results for fast adaptive Schemes applied to both serial-tone and parallel-tone HF modems are presented and shown to significantly out-perform fixed rate modems and modems employing hybrid automatic-repeat-request schemes. A new detector scheme is discussed which has superior performance to conventional detectors for digital traffic in the presence of inter-symbol interference and impulsive noise

Applications Technology Satellite and Communications Technology Satellite user experiments for 1967 - 1980 reference book, volume 1

A description of each of the satellites is given and a brief summary of each user experiment is presented. A Cross Index of User Experiments sorted by various parameters and a listing of keywords versus Experiment Number are presented

A comparison of airborne and ground-based radar observations with rain gages during the CaPE experiment

The vicinity of KSC, where the primary ground truth site of the Tropical Rainfall Measuring Mission (TRMM) program is located, was the focal point of the Convection and Precipitation/Electrification (CaPE) experiment in Jul. and Aug. 1991. In addition to several specialized radars, local coverage was provided by the C-band (5 cm) radar at Patrick AFB. Point measurements of rain rate were provided by tipping bucket rain gage networks. Besides these ground-based activities, airborne radar measurements with X- and Ka-band nadir-looking radars on board an aircraft were also recorded. A unique combination data set of airborne radar observations with ground-based observations was obtained in the summer convective rain regime of central Florida. We present a comparison of these data intending a preliminary validation. A convective rain event was observed simultaneously by all three instrument types on the evening of 27 Jul. 1991. The high resolution aircraft radar was flown over convective cells with tops exceeding 10 km and observed reflectivities of 40 to 50 dBZ at 4 to 5 km altitude, while the low resolution surface radar observed 35 to 55 dBZ echoes and a rain gage indicated maximum surface rain rates exceeding 100 mm/hr. The height profile of reflectivity measured with the airborne radar show an attenuation of 6.5 dB/km (two way) for X-band, corresponding to a rainfall rate of 95 mm/hr

Pacific Basin Communication Study, volume 2

Users' meeting summary report, chronology of visits, economic data for forum countries, techniques used in the study, communication choices, existing resources in the Pacific Basin, and warc 79 region 3 rules and regulations were presented in volume 2

Optimization of communication data rates under fading conditions

Imperial Users onl