Burst Communication Research Articles

Probability density function of amplitude decay constant on meteor burst communication channel

Lack of accurate characterisation for the amplitude decay constant on the meteor burst channel makes most existing analytical methods of systems on this channel approximate. It is shown that the probability density function of the amplitude decay constant can be approximated by the log-normal density. An expression for the density of the burst duration is also given. These results will allow for a more in depth analysis of meteor burst communication systems.

Signalling efficiency modelling and measurement of simplex block encoded MBC systems

A theoretical technique is developed to estimate the signalling efficiency of a meteor burst communications (MBC) system which uses a block encoded simplex protocol over underdense trails. The signalling efficiency is determined for various information block durations and compared to experimental results from the BLOSSOM (beyond line of sight signalling over meteors) MBC system, which could vary its information block duration. Although the general shape of both the theoretical and experimental results are similar there are detailed differences. Reasons for these discrepancies are suggested.

Meteor burst propagation

Meteor burst communication systems are introduced with emphasis placed on the unusual propagation mode which they employ. The origin of meteors and their trails is reviewed and the trail characteristics relevant to communication systems described. The restriction on scattering geometries for viable transmission paths is exlained and the related footprint and hot-spot properties of meteor burst systems outlined. Meteor burst transmission loss is formulated in the conventional way as a modified bistatic radar equation and the origins of the modifying factor qualitatively explained. Meteor burst equipment, operating principles and applications are also briefly discussed. Finally, important quantities for assessing the performance of meteor burst systems are defined and typical values quoted.

Investigation into adaptive-rate modems for meteor burst communication

Current meteor burst communication systems operate at constant bit rates of 4 kbit/s and are limited to average throughputs of 50 bit/s. The paper documents the design and implementation of an adaptive-bit-rate modem for optimising the throughput. A novel extension of differentially encoded binary phase shift keying is proposed so that two frequency division multiplexed baseband channels can be transmitted: a main channel for the data and an auxiliary channel for conveying bit rate change information. In this way, two modems, one at each end of the link, can automatically adapt to a new operating speed without the intervention of a host computer. The results prove that the two channels can operate independently with minimal mutual interference. A theoretical improvement in bit rate of 18 times over the fixed-bit-rate modem is possible.

QUANTUM LIMITATIONS ON THE STORAGE AND TRANSMISSION OF INFORMATION

Information must take up space, must weigh, and its flux must be limited. Quantum limits on communication and information storage leading to these conclusions are described here. Quantum channel capacity theory is reviewed for both steady state and burst communication. An analytic approximation is given for the maximum signal information possible with occupation number signal states as a function of mean signal energy. A theorem guaranteeing that these states are optimal for communication is proved. A heuristic "proof" of the linear bound on communication is given, followed by rigorous proofs for signals with specified mean energy, and for signals with given energy budget. And systems of many parallel quantum channels are shown to obey the linear bound for a natural channel architecture. The time-energy uncertainty principle is reformulated in information language by means of the linear bound. The quantum bound on information storage capacity of quantum mechanical and quantum field devices is reviewed. A simplified version of the analytic proof for the bound is given for the latter case. Solitons as information caches are discussed, as is information storage in one-dimensional systems. The influence of signal self-gravitation on communication is considered. Finally, it is shown that acceleration of a receiver acts to block information transfer.

Meteor burst communications

The characteristics of meteor burst communications are described and compared to those of HF and satellite systems. The two generic types of MB systems, broadcast and channel-probing systems, are explained. In systems using the broadcast protocol, the transmitter knows nothing about the occurrence of bursts or trails and transmits continuously for a sufficient duration to permit all recipients to receive the message/data with the desired probability. For practical purposes, the optimum burst or block duration for such systems is around 100-200 ms, based on the characteristics of the predominant trails. Channel-probing MB systems are more common and are commercially available in several versions. Here the transmitter repeatedly sends a short (typically 5-20 ms) probe signal until it receives a similarly short message response, indicating the availability of a suitable trail. A third, intermediate type of protocol with hybrid features does not probe the channel with a short signal, but starts repeatedly transmitting the first packet, in effect using it as a probe signal. Fundamental design issues and/or parameters of specific relevance to MB communication systems are discussed. Some historical and more recent MB systems are examined. >

High Data Rate Meteor-Burst Communications

The meteor burst communications channel offers a largely untapped means of communications that can alleviate congestion in many existing communications systems. It also provides some interesting advantages over other beyond-line-of-sight systems, including lower susceptibility to atmospheric perturbations, a limited footprint, and relatively low cost. Past system applications have been quite limited, however, due to the random nature of the meteor burst phenomenon which has resulted in relatively low throughput and lengthy wait-times.This paper presents the results of an experimental study of the meteor burst channel which illustrates its time-varying bursty nature. In addition, the authors describe an innovative approach to data transmission over meteor burst systems, ie, the use of the Feedback Adaptive Variable Rate (FAVR) system which allows the maximum amount of information to be transmitted over each meteor burst channel.For underdense meteor channels the FAVR performance is compared to an optimum system, ie, a system capable of changing its bit rate instantaneously to channel conditions so as to maintain a constant SNR in each bit, and to a constant optimum rate/burst system. It is shown that for such a system FAVR can result in a throughput increase exceeding a factor of 10.

Positioning requirements for the tsunami warning system

Abstract Canada has increased the number of tsunami warning stations on the Pacific Coast from two to three. The last gauge was installed at the north end of Vancouver Island, thereby filling a large gap previously existing and providing full coverage along the coast. The record of gauges at two of the three locations is accessible either by telephone or by means of meteor burst communication, alleviating the difficulties experienced during the tsunami threat of May 6, 1986, when telephone communications were disrupted by heavy use. The gauge at Langara Island will be relocated in a more accessible and also a more tsunami‐responsive location at Rennell Sound in the Queen Charlotte Islands. All tsunami gauges also serve as tide gauges, recording the water level every 15 min. In the event of a tsunami, the recording interval can be altered to every 60 s. Suggestions have been made that Canada attempt deep‐sea recording of tsunamis off its Pacific Coast. Although this would be of great scientific value, no such program is contemplated at this time.

Communicating Via Meteor Burst at Short Ranges

This paper examines the relationship between range and performance of meteor burst communication systems. Three performance measures are considered: average duty cycle, average throughput for a system which transmits fixed length message packets at a fixed data rate, and waiting time to deliver a fixed length message. In particular, we examine the range dependence of the three measures at ranges of less than 400 km. It will he demonstrated that communication connectivity can be maintained at short ranges by a combination of efficient protocol and proper antenna pattern designs.

Characterizing the Multipath and Doppler Spreads of the High-Latitude Meteor Burst Communication Channel

High-latitude propagation phenomena, such as scatter from the aurora and sporadic- E propagation, can alter the communication characteristics of the meteor communication channel. This paper describes an experiment in which the fading and multipath profiles of the high-latitude meteor communication channel were characterized. The effects of high-latitude propagation phenomena on the capacity and reliability of meteor burst communication are discussed.

Narrowband digital voice communications over a meteor burst channel

We report the first successful narrowband digital transmissions of voice messages via meteor trail scatter propagation. A 12-word message, which took 6s to recite, was represented by a compressed data stream of 43 characters and required 86 ms for transmittal over the meteor scatter channel. The experiment used state-of-the-art speech recognition/digitisation equipment, a digital meteor burst communication system and a speech synthesiser.

The evolution of meteor burst communications systems

The background theory and fundamentals of meteor burst propagation are described by reference to the astronomical and ionospheric properties of the meteors and their ionized trails. Those special properties which distinguish meteor burst communications (MBC) from other radio communication modes are highlighted and within this framework the evolution of MBC systems design is traced. In so doing, the design and operation of several MBC systems are compared and evaluated.

Predicting the arrival of meteors useful for meteor burst communication

Renewed interest in meteor scatter propagation for cummunication applications has created a need for better and more accurate techniques to investigate the complex relationship between the arrival rate of usable meteors and antenna patterns, link parameters, Faraday rotation loss and polarization. In past efforts, the complexity of the models predicting the arrival of meteors was limited by the cost of computing resources on large main‐frame computers. The rapid decrease in computing costs has allowed more advanced and computationally intensive modeling techniques to be applied to meteor burst modeling. This paper surveys the development of previous models and describes a new model which has been developed as a research tool to allow investigation of the relationship between the arrival rate of meteors and antenna patterns, Faraday rotation, polarization and link parameters. Preliminary results from the model are compared to data from several meteor links.

Polarization rotation in meteor burst communication systems

The problems of polarization rotation losses, in meteor burst communication systems, are examined using a theoretical model developed for the purpose. The paper takes into account both the polarization changes due to ionospheric Faraday rotation and the rotation of the wave polarization that takes place as a result of scattering from underdense meteor trails. Linearly polarized systems, employing copolar transmitting and receiving antennas, and hybrid systems, employing a linearly polarized transmitting antenna and a circularly polarized receiving antenna, are studied. It is shown that, particularly in linearly polarized systems, polarization rotation may introduce unexpected diurnal performance variations in systems operating at frequencies ∼40 MHz. For the two 40‐MHz linearly polarized links investigated in detail the model predicts that, for noon summer solstice conditions during periods with a high solar sunspot number, these losses cause a reduction in data throughput to between 15 and 70% of the value expected had no polarization rotation occurred. By using a cross polarization approach, qualitative experimental confirmation of the predictions is also given.

Storage & Control Unit for Meteor Burst Communication System

Meteor Burst Communication Channel opens at random for varying periods of time (average 500 ms), Duty cycle of Meteor Burst Communication System is very low, expected around 2.5 %. Storage of data and a higher rate of transmission compensate the low duty cycle of MBCS. The non-continuous nature of MBC channel dictates constraints on the choice of link control protocols and terminal controls. Rapid channel acquisition, handshake and data synchronisation are the few aspects which decide the link control protocols.This paper brings out the importance of storage and control unit. Hardware realisation of data storage, higher rate of transmission, and link control protocols are discussed in detail. Features of microprocessor based memory and control unit, more flexible and sophisticated version of the above IC based unit are mentioned.

An Estimate of the Capacity of the Meteor Burst Channel

An estimate of the capacity of the meteor burst communication channel is given. The model takes into account both overdense and underdense trails as well as the effects of wind-induced trail warping.

Centralized data collection systems via meteor burst

AbstractIonized trails caused by the entry of meteors into the atmosphere provide probabilistic communication paths between two points over the horizon. Three protocols for a data collection system via meteor burst communication channels are studied and evaluated. the first is merely the pure ALOHA protocol applied to the probabilistic channel. the second is called the IT protocol. It has a frequency division idle‐tone channel. A terminal which has a message observes this channel and determines whether the main channel is open or closed for it. the third protocol, the so‐called ITT protocol, also has idle‐tone channel. Messages are divided into many blocks (this message structure is called “Tokage (lizard)” type) and go‐back‐N ARQ protocol is utilized. We show that the idle‐tone and the lizard‐type message with ARQ, are extremely effective to increase the channel utilization in such systems. It is also shown that high channel utilization can be achieved by the use of the ITT scheme even in a probabilistically generated and terminated communication channel such as meteor burst communication path.

An Analysis of Meteor Burst Communications for Military Applications

This paper presents a methodology for the design and analysis of meteor burst communication systems, with special emphasis on system characteristics of importance to military applications (intercept resistance, jam resistance, nuclear survivability, and encryption considerations). Using stochastic models for the meteor burst process, expressions for the average throughput and average message waiting time are derived. These equations are used to estimate the anticipated performance of several kinds of meteor burst communications systems m a number of military applications ranging from data collection from unattended sensors to facsimile transmission.

Impulse Response of a Meteor Burst Communications Channel Determined by Ray-Tracing Techniques

Ray-tracing techniques are used to derive the impulse response at VHF of a meteor burst communications channel. An approach to analyze the effects of multipath arising from wind shear is also presented and is applied to a simplified model of trail distortion. Within the limitations of the models adopted, we have found that a single path with a spread of approximately 0.2 μs adequately describes the channel behavior within roughly half a second from trail formation, and that a multipath structure with several paths and a total multipath spread of approximately 2 μs is typically associated with the channel at later times, when the wind shear substantially affects the trail shape. These results are consistent with experimental findings according to which a meteor trail communications channel is capable of transmitting beyond-the-horizon bursts of television images of broadcast quality typically for a fraction of a second after trail formation.

Power Spectra of Sinusoidal Amplitude-Modulated Binary Signals

Power spectra for binary phase-shift keyed (PSK) and frequency-shift keyed (FSK) signals with combined sinusoidal amplitude modulation by the bit rate clock are presented. Such signal formats have application in burst communication systems wherein reliable bit synchronization is provided with relative receiver simplicity. Effects of the clock amplitude modulation index and phase are considered, and corresponding power spectra are illustrated. Further, effects of the clock parameters on the rate of spectral rolloff are given and compared with those of conventional PSK and FSK spectra.