Basic communication sciences

1969 ◽  
Vol 308 (1493) ◽  
pp. 183-198
Keyword(s):  
Long Distance ◽  
Earth Station ◽  
Early Communication ◽  
Technical Developments ◽  
Radiated Power ◽  
The Earth ◽  
Distance Communication ◽  
Quality Of Transmission ◽  
Communication Equipment

The feasibility and utility of long-distance communication via Earth-orbiting satellites has been demonstrated during recent years and it is appropriate therefore to focus attention on the more important scientific studies and technical developments that will be needed if full use is to be made of this valuable mode of communication in the future. The early communication satellites (the Telstar and Relay series) were pioneers in a relatively unknown propagation environment. The satellites themselves were conceptually simple and the communication equipment consisted essentially of a frequency-changing transponder with an r. f. power output of a few watts and a bandwidth some tens of megahertz. Carrier frequencies in the range 2 to 6 GHz were employed; typically either 2 or 6 GHz was used for transmission and 4 GHz for reception at the Earth station. To obtain an adequate signal/noise ratio at the output of the Earth station receiver, frequency modulation was employed, the frequency deviations being greater than those used on terrestrial microwave links. Launcher limitations and other factors meant that the satellites had to be placed in inclined elliptical orbits (see figure 1) with maximum heights of only a few thousand miles. Nevertheless, these satellites demonstrated that some hundreds of frequency-division multiplex telephony circuits, or a television channel, could be achieved with generally satisfactory quality of transmission. It is to be noted, however, that the satellite transponders accommodated only one, or at the most two, r. f. carriers at any time, and that the transmission performance was at times marginal due to limitations of the satellite effective radiated power. Furthermore, these relatively low orbit satellites provided communication in periods of generally less than an hour at a time and required continuous tracking by the Earth station aerials, due to movement of the satellites relative to the Earth.

scholarly journals On some direct evidence for downward atmospheric reflection of electric rays

1925 ◽  
Vol 109 (752) ◽  
pp. 621-641 ◽  
Keyword(s):  
Direct Evidence ◽  
Wireless Transmission ◽  
Long Distance ◽  
Wireless Receiver ◽  
Negative Results ◽  
The Earth ◽  
Apparent Direction ◽  
Distance Communication ◽  
The Waves ◽  
The Magnetic Field

In a recent paper in these Proceedings (Series A, vol. 107, p. 587) Smith-Rose and Barfield have called attention to the two outstanding problems of the propagation of wireless waves over the earth s surface. A complete theory of wireless transmission must explain ( a ), why long-distance communication is possible, and ( b ), why large and rapid variations of signal intensity and apparent direction of propagation of the waves are observed at night, and, to some extent, during daylight, particularly in winter. Smith-Rose and Barfield further point out that both phenomena can be explained to some extent by the well-known Kennelly-Heaviside layer theory, but that it is generally admitted that further evidence of the existence of the layer is needed. They also describe accurate experiments designed to detect the existence of waves arriving at a wireless receiver in a downward direction ( i . e ., inclined to the horizontal), such as must be present if the Heaviside layer theory is correct. In these experiments Smith-Rose and Barfield sought, by directional methods, to detect a departure of the electric field of the waves from the vertical by means of a large Hertzian oscillator, and a departure of the magnetic field from the horizontal by means of a rotating frame aerial. It was, however, found that the conductivity of the ground was sufficiently high to make it act very nearly as a perfect reflector, and, because of the presence of the reflected wave from the ground, none of the effects sought for could be detected even in conditions such as are normally associated with signal strength and directional variations. These authors therefore concluded that the results of their experiments could not be considered as evidence for or against the Heaviside layer theory. In a later paper, Smith-Rose and Barfield describe further experiments of this type, again with negative results, and state that “ adequate experimental evidence on the existence of the Heaviside layer is still lacking.”

scholarly journals Basics Telecommunication System Covers Working Principles and Emerging Problems

2021 ◽  
Vol 1 (5) ◽  
pp. 10-16
Author(s):  
Que Duc Chinh ◽  
Bui Thuan Nguyen
Keyword(s):  
Packet Loss ◽  
Telecommunication System ◽  
Long Distance ◽  
Telecommunications Infrastructure ◽  
Distance Communication ◽  
The Media ◽  
Pass Through ◽  
Different Characteristics

This article discusses the basics of the telecommunications system covering developments, working principles and emerging problems in telecommunications. The telecommunications system is all elements of both telecommunications infrastructure, equipment, facilities and infrastructure, as well as telecommunications operators, so that long-distance communication can be carried out. During the journey the information will pass through various media with different characteristics. So that it allows the occurrence of high delays and large packet loss, all of which will reduce the quality of the information received. The quality of the transmission medium determines the quality of the information received. Because as long as it is in the media, it is certain that the information will experience damping which will reduce the quality of the information. In order to communicate properly, the channel provided is not only physical media but also logical lines (frequency channels), considering that these frequency channels are expensive and limited.

scholarly journals On the determination of the directions of the forces in wireless waves at the earth's surface

1925 ◽  
Vol 107 (743) ◽  
pp. 587-601 ◽  
Keyword(s):  
Three Dimensions ◽  
Electric Force ◽  
Long Distance ◽  
Quantitative Measurements ◽  
The Earth ◽  
Apparent Direction ◽  
The Hours ◽  
Distance Communication ◽  
The Waves

There are two outstanding problems relating to the propagation of wireless waves over the earth’s surface which at present remain unsolved, viz.— What is the agency which causes the waves to follow the curvature of the earth, thus rendering long-distance communication possible ? And what is the cause of the large and rapid variations of the intensity and apparent direction of the waves, very commonly observed at the receiving station and confined almost entirely to the hours of darkness ? Both phenomena can be explained to some extent by the well-known Heaviide-layer theory, with the modifications proposed by Eccles, but it is generally admitted that further experimental evidence of the existence of the layer is needed. If the theory is correct and is sufficient, it follows that, a receiver experiencing either of the above phenomena, part of the energy must be arriving in a downward direction ( i. e ., inclined to the horizontal); and that during the occurrence of directional variations, this downcoming wave must have at horizontally polarised component ( i. e ., with its electric force horizontal). I has, therefore, been generally recognised for some time that a conclusive experimental demonstration of the presence or absence of such waves, by suit able quantitative measurements in three dimensions, would aid considerably in proving or disproving the Heaviside-layer theory.

scholarly journals A Long-Distance Communication Architecture for Medical Devices Based on LoRaWAN Protocol

Electronics ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 940
Author(s):  
Nicoleta Cristina Gaitan
Keyword(s):  
Energy Consumption ◽  
Long Range ◽  
Medical Devices ◽  
Low Energy ◽  
Area Network ◽  
Wide Area Network ◽  
Long Distance ◽  
Communication Architecture ◽  
Low Energy Consumption ◽  
Distance Communication

Recent market studies show that the market for remote monitoring devices of different medical parameters will grow exponentially. Globally, more than 4 million individuals will be monitored remotely from the perspective of different health parameters by 2023. Of particular importance is the way of remote transmission of the information acquired from the medical sensors. At this time, there are several methods such as Bluetooth, WI-FI, or other wireless communication interfaces. Recently, the communication based on LoRa (Long Range) technology has had an explosive development that allows the transmission of information over long distances with low energy consumption. The implementation of the IoT (Internet of Things) applications using LoRa devices based on open Long Range Wide-Area Network (LoRaWAN) protocol for long distances with low energy consumption can also be used in the medical field. Therefore, in this paper, we proposed and developed a long-distance communication architecture for medical devices based on the LoRaWAN protocol that allows data communications over a distance of more than 10 km.

scholarly journals Quantum repeaters based on concatenated bosonic and discrete-variable quantum codes

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Filip Rozpędek ◽  
Kyungjoo Noh ◽  
Qian Xu ◽  
Saikat Guha ◽  
Liang Jiang
Keyword(s):  
Continuous Variable ◽  
Quantum Codes ◽  
Discrete Variable ◽  
Long Distance ◽  
Concatenated Code ◽  
Different Types ◽  
Optical Modes ◽  
Distance Communication ◽  
Quantum Repeaters ◽  
Quantum Error

AbstractWe propose an architecture of quantum-error-correction-based quantum repeaters that combines techniques used in discrete- and continuous-variable quantum information. Specifically, we propose to encode the transmitted qubits in a concatenated code consisting of two levels. On the first level we use a continuous-variable GKP code encoding the qubit in a single bosonic mode. On the second level we use a small discrete-variable code. Such an architecture has two important features. Firstly, errors on each of the two levels are corrected in repeaters of two different types. This enables for achieving performance needed in practical scenarios with a reduced cost with respect to an architecture for which all repeaters are the same. Secondly, the use of continuous-variable GKP code on the lower level generates additional analog information which enhances the error-correcting capabilities of the second-level code such that long-distance communication becomes possible with encodings consisting of only four or seven optical modes.

scholarly journals Measuring Disability Inclusion Performance in Cities Using Disability Inclusion Evaluation Tool (DIETool)

2020 ◽  
Vol 12 (4) ◽  
pp. 1378 ◽  
Author(s):  
Nataša Rebernik ◽  
Marek Szajczyk ◽  
Alfonso Bahillo ◽  
Barbara Goličnik Marušić
Keyword(s):  
Quality Of Life ◽  
Theory And Practice ◽  
The Political ◽  
Sustainable Cities ◽  
Evaluation Tool ◽  
Sustainable City ◽  
Evaluation Systems ◽  
European Cities ◽  
Technical Developments

Cities are exposed to a growing complexity, diversity and rapid socio-technical developments. One of the greatest challenges is as of how to become fully inclusive to fit the needs of all their citizens, including those with disabilities. Inclusive city, both in theory and practice, still lacks attention. Even in the context of ambitious contemporary concepts, such as smart and sustainable city, the question remains: Do smart and sustainable cities consider inclusiveness of all their inhabitants? Among numerous evaluation systems that measure city’s smartness, sustainability or quality of life, those tackling inclusion are very rare. Specifically, disability inclusion is hardly covered. This may be one of the reasons why cities struggle with applying disability inclusion to practice in a holistic and integrative way. This paper proposes a Disability Inclusion Evaluation Tool (DIETool) and Disability Inclusion Performance Index (DIPI), designed to guide cities through a maze of accessibility and disability inclusion related requirements set within the political, legislative and standardization frameworks. The testing in two European cities shows that the tool is beneficial for providing diagnosis as to how disability friendly a city is, and as such offers an opportunity for designing informed corrective measures towards disability inclusive city design.

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