Communications Technology Satellite Research Articles

Unified M-Learning Model through Interactive Education Satellite:A Proposal for an Arab Homeland Education Satellite

In this paper, we propose a unified and interactive mobile learning (M-Learning) model to help with expanding and spreading education in the Arab Homeland countries. The model utilizes a new competitive spot beam satellite communication technology, which enables efficient channel allocation, where communication channels can be allocated to specific and precise areas. The proposed model is referred to as the interactive Arab education satellite (IAESat).The communication satellite can efficiently and effectively cover the entire Arab Homeland and reaches a wide area and mobile users that cannot be reached otherwise. The model implements existing interactivity components to enhance the learning process and meet international standards in education.

The Experimental Research of the Non-Abrasive Cryogenic Polishing on GaAs Chip Surfaces

With the development of mobile communications, gallium arsenide integrated circuits (GaAs IC) have been widely used. For example, satellite communication technology, satellite TV, wireless data transmission, fiber optic communications equipment, automatic test equipment etc. At the same time, it demands that the GaAs chips should have high quality surfaces. In this paper, it takes non-abrasive cryogenic polishing technique to polish GaAs chip surfaces. It has recorded the actual measurement results. The results show that the surface roughness of the ice disk polishing can achieve nanometer scale. Through the research of non-abrasive cryogenic polishing, it has analyzed different parameters on the impact of surface quality.

Safety and non‐safety data link technology characterization for NEWSKY aeronautical communication network

AbstractA review and characterization of possible air/ground data link technologies for aeronautical cockpit and cabin communications is presented in this study. The study was performed in the framework of the EC project NEWSKY, which aims at defining an integrated network based on IPv6 protocol, supporting both cockpit and cabin communications over different data link sub‐networks. The objective of this study is to characterize the data link technologies that could be interfaced with such a network, either for safety (cockpit) or for non‐safety (cabin) communications and to define some high‐level categories gathering technologies with common characteristics. These categories were defined to enable the NEWSKY network to interface with a large range of data link technologies, both current and future. They describe typical characteristics for the sub‐networks data links for which the networking solutions are defined.For this purpose, a thorough review of candidate technologies for cabin and cockpit applications was performed and is presented hereafter. It covers a large range of terrestrial (direct air–ground) or satellite solutions, with an emphasis on the satellite communication technologies that have more specific characteristics. Copyright © 2010 John Wiley & Sons, Ltd.

Surface Deformation Monitoring in the Goldfields Ghana Limited Area

AbstractLarge sets of remotely sensed data can be acquired using satellite communication technology and processed using high performance computers to produce interpreted images of objects on earth. The rapid advancement of remote sensing techniques has enabled these satellites to acquire data of large areas within a relatively short period. This study investigated the application of remote sensing imagery from two different platforms in monitoring land surface deformation in the Goldfields Ghana Limited Tarkwa, area. The results showed that both DInSAR and Intensity Difference Analysis are able to identify land surface deformation due to surface mining. However, it was not possible to pinpoint the location of slope failure without the knowledge of the incident.

Frequency assignment problem in satellite communications using differential evolution

Satellite communications technology has a tremendous impact in refining our world. The frequency assignment problem is of a fundamental importance when it comes to providing high-quality transmissions in satellite communication systems. The NP-complete frequency assignment problem in satellite communications involves the rearrangement of frequencies of one set of carriers while keeping the other set fixed in order to minimize the largest and total interference among carriers. In this paper, we present a number of algorithms, based on differential evolution, to solve the frequency assignment problem. We investigate several schemes ranging from adaptive differential evolution to hybrid algorithms in which heuristic is embedded within differential evolution. The effectiveness and robustness of our proposed algorithms is demonstrated through solving a set of benchmark problems and comparing the results with a number of previously proposed techniques that solve the same problem. Experimental results show that our proposed algorithms, in general, and hybrid ones in particular, outperform the existing algorithms both in terms of the quality of the solutions and computational time.

A KEY AGREEMENT SCHEME FOR SATELLITE COMMUNICATIONS

Satellite communication technology was mainly used for broadcasting service and long-hual transmission. However, it is vulnerable to unauthorized access to the transmitted data. People are worried about two major security issues; privacy and authentication. Privacy refers to the guarantee that the communicated messages are not intercepted by an eavesdropper. On the other hand, authentication is carried out to ensure that any unauthorized user cannot fraudulently obtain his/her required services from the satellite communication systems. In this paper, the authors shall propose a new secure protocol based on key agreement scheme with mutual authentication to solve these problems on the VSAT satellite communications. Comparing with other key agreement schemes for VSAT satellite communications, our proposed scheme is more secure and efficient.

Chaos-based secure satellite imagery cryptosystem

With the large-scale development in satellite and network communication technologies, there is a great demand for preserving the secure storage and transmission of satellite imagery over internet and shared network environment. This brings new challenges to protect sensitive and critical satellite images from unauthorized access and illegal usage. In this paper, we address the aforementioned issues and develop techniques to eliminate the associated problems. To achieve this, we propose a new chaos-based symmetric-key encryption technique for satellite imagery. This scheme utilizes multiple chaotic maps e.g. Logistic, Henon, Tent, Cubic, Sine and Chebyshev for enhancing the key space, robustness and security of satellite imagery. We perform key sensitivity, statistical and performance analysis experiments to determine the security, reliability, and speed of our algorithm for satellite imagery. The proposed algorithm presents several interesting features, such as a high level of security, large enough key space, pixel distributing uniformity and an acceptable encryption speed as compared to AES, 3-DES, and DES.

Fade Slope Analysis of Ka-Band Earth-LEO Satellite Links Using a Synthetic Rain Field Model

Because the motion of a low Earth orbit (LEO) satellite across the sky causes the Earth-space path to very quickly pass through any rain cells in the vicinity, the degree of rain fading on such paths changes more rapidly and leads to steeper fade slopes than in the geostationary case. Because comprehensive measurement data have not yet been compiled for fading on LEO links in the Ka-band, we have used simulations based on Goldhirsh's method for determining the key parameters of the well-known EXCELL model of a horizontal rain structure from long-term global rain statistics to obtain plausible estimates of the fade slope distributions for selected scenarios. The results that we obtained for geostationary satellites closely match those observed at selected sites during the Advanced Communications Technology Satellite program. The results that we obtained for LEO satellites show how fade slopes will steepen as 1) the altitude of the satellite decreases; 2) the frequency band of operation increases; and 3) the average rain rate increases. Furthermore, they suggest that, at a given probability level, the fade slopes could be between two and ten times greater than those for geostationary satellites and that mobile terminals with a clear view of the sky will experience fade slopes that are similar to those encountered by fixed or transportable terminals. These results have important implications for the design of power control algorithms and other fade-mitigation techniques.

Space-based societal applications—Relevance in developing countries

Space technology has the vast potential for addressing a variety of societal problems of the developing countries, particularly in the areas of communication, education and health sectors, land and water resources management, disaster management and weather forecasting. Both remote sensing and communication technologies can be used to achieve this goal. With its primary emphasis on application of space technology, on an end-to-end basis, towards national development, the Indian Space Programme has distinguished itself as one of the most cost-effective and development-oriented space programmes in the world. Developing nations are faced with the enormous task of carrying development-oriented education to the masses at the lower strata of their societies. One important feature of these populations is their large number and the spread over vast and remote areas of these nations, making the reaching out to them a difficult task. Satellite communication (Satcom) technology offers the unique capability of simultaneously reaching out to very large numbers, spread over vast areas, including the remote corners of the country. It is a strong tool to support development education. India has been amongst the first few nations to explore and put to use the Satcom technology for education and development-oriented services to the rural masses. Most of the developing countries have inadequate infrastructure to provide proper medical care to the rural population. Availability of specialist doctors in rural areas is a major bottleneck. Use of Satcom and information technology to connect rural clinics to urban hospitals through telemedicine systems is one of the solutions; and India has embarked upon an effective satellite-based telemedicine programme. Space technology is also useful in disaster warning and management related applications. Use of satellite systems and beacons for locating the distressed units on land, sea or air is well known to us. Indian Space Research Organisation (ISRO) is already a part of the International initiative called Satellite Aided Search and Rescue System. The programme to set up satellite-based Village Resource Centres (VRCs) across India, for providing a variety of services relevant to the rural communities, is also a unique societal application of space technology. The VRCs are envisaged as single window delivery mechanism for a variety of space-based products and services, such as tele-education; telemedicine; information on natural resources for planning and development at local level; interactive advisories on agriculture, fisheries, land and water resources management, livestock management, etc.; interactive vocational training towards alternative livelihood; e-governance; weather information; etc. This paper describes the various possibilities and potentials of Satcom and Remote Sensing technologies for societal applications. The initiatives taken by Indian Space Research Organisation in this direction are highlighted.

Indian Space Research Organization and Telemedicine in India

Telemedicine in India is spearheaded by the Indian Space Research Organization (ISRO) and has matured beyond technology demonstration to enter an operational phase in its history. This article attempts to bring out the evolution and development of telemedicine in India: the genesis, the approach followed, the stakeholders involved, and the results so far, with an outline for the future. ISRO has coupled its prowess in satellite communication technology with medical science and information technology to project specialty healthcare to the doorsteps of the rural, remote, and distant populace across the country. Having set the telemedicine program as a model for benefiting society with advances in modern technology, India is advancing to international dimensions the proven domestic program to people in other parts of the globe. More specifically, the article attempts to bring out the role played by ISRO, its vision, goals, and partners in the program along with the technology and observed impact.

Critical Issues in Medical Education and the Implications for Telemedicine Technology

Ensuring quality medical education in all the medical colleges across India based on uniform curriculum prescribed by a regulatory body and maintaining a uniform standard are dependent on availability of an excellent infrastructure. Such infrastructure includes qualified teachers, knowledge resources, learning materials, and advanced education technology, which is a challenge in developing countries due to financial and logistic constraints. Advancement in telecommunication, information science, and technology provides an opportunity to exchange knowledge and skill across geographically dispersed organizations by networking academic medical centers of excellence with medical colleges and institutes to practice distance learning using information and communication technology (ICT)-based tools. These may be as basic as commonly used Web-based tools or may be as advanced as virtual reality, simulation, and telepresence-based collaborative learning environment. The scenario in India is no different from any developing country, but there is considerable progress due to technical advancement in these sectors. Telemedicine and tele-education in health science, is gradually getting adopted into the Indian Health System after decade-long pilot studies across the country. A recent recommendation of the National Knowledge Commission, once implemented, would ensure a gigabyte network across all the educational institutions of the country including medical colleges. Availability of indigenous satellite communication technology and the government policy of free bandwidth provision for societal development sector have added strength to set up infrastructure to pilot several telemedicine educational projects across the country.

Protocol Testing of SCPS-TP over NASA's ACTS Asymmetric Links

As the transport layer protocol of the Space Communication Protocol Standard (SCPS) suite, SCPS-Transport Protocol (SCPS-TP) is actually transmission control protocol (TCP), with a set of extensions aimed at improving TCP performance in space communications. Some work has been done on the performance evaluation of SCPS-TP in comparison with TCP. However, those works have been done by testing SCPS-TP via emulation test-beds. We present the file transfer experimental work of testing the SCPS protocol stack over NASA's geostationary orbit (GEO) Advanced Communications Technology Satellite (ACTS). Considering that space communication channels in practice are frequently asymmetric in terms of channel bandwidth, our work is concentrated on the evaluation of the effectiveness of SCPS-TP in coping with channel rate asymmetry. We conclude that SCPS-TP is better suited than TCP over long-delayed, asymmetric, satellite channels with a throughput advantage of over 30 Kbyte/s for the transmission of a 10 Mbyte file. A hybrid of the channel rate control and acknowledgment frequency reduction mechanisms makes significant contributions to the performance enhancement of SCPS-TP over asymmetric space channels.

Sources, characteristics and effects of emerging technologies: Research opportunities in innovation

Diverse technological developments across information technology, biotechnology, nanotechnology, and satellite communications technology are dramatically altering industry landscapes, with important economic and policy implications. Not surprisingly, therefore, managers are challenged to develop strategies to cope with the threats posed by emerging technologies and leverage the opportunities posed by them. Indeed, there is growing anecdotal evidence that firms' inabilities to cope with emerging technologies have produced high product and firm failure rates. From an academic perspective, I argue that emerging technologies have important distinctive features that have not been examined in current theory in marketing, and specifically, in organizational innovation. In this article, I identify several research questions that emerge from the sources, characteristics and effects of emergent technologies in the area of organizational innovation. Insights generated from such a line of inquiry have the potential to broaden the canvas of innovation theory and provide valuable insights to managers who confront these onerous challenges on a daily basis.

Advances in Space Traveling-Wave Tubes for NASA Missions

Significant advances in the performance and reliability of traveling-wave tubes (TWTs) utilized in amplifying space communication signals for NASA missions have been achieved over the last three decades through collaborative efforts between NASA and primarily L-3 Communications Electron Technologies, Inc. (L-3 ETI). This paper summarizes some of the key milestones during this period and includes development of TWTs for the Communications Technology Satellite, Cassini, and Lunar Reconnaissance Orbiter missions. Technical advances in computer modeling, design techniques, materials, and fabrication have enabled power efficiency to increase by almost 40% and the output power/mass figure-of-merit to increase by an order of magnitude during this period.

Argo-type profiling float observations under the Arctic multiyear ice

To monitor and better understand temperature and salinity conditions in the Arctic Ocean interior, we developed a new Argo-type ocean profiling system for the polar oceans. This Polar Ocean Profiling System (POPS) consists mainly of an ice platform and an Argo-type subsurface CTD profiler. The ice platform includes a system controller that manages all data acquisition, processing, formatting, and messaging. Iridium satellite communication technology sends the observation data and also allows remote commands to be sent from the laboratory to the buoy. The profiler is mounted on an oceanographic cable interfaced to the platform; the profiler moves along the cable between depths of 10 and 1000 m. The inductive modem system provides data transfer between the ice platform and the profiler. In April 2005, field tests of the POPS were conducted in the Arctic Ocean near the North Pole. Later on, commands were sent via Iridium from the laboratory to the buoy to change the data sampling acquisition frequency, allowing us to obtain 14 temperature and salinity profiles during the first 22 days. We confirmed that POPS could measure temperature and salinity with conservative accuracies better than 0.01 °C for temperature and 0.01 for salinity. Following this test, we initiated the observation of the Arctic Ocean from 10 m down to 1000 m depths in April 2006 using POPS, and we also started sending the data to the global telecommunication system (GTS) in real time. These data are the first Argo data sent from the Arctic Ocean. Not only Arctic oceanographers but also everyone who is interested in Arctic oceanographic conditions can easily access these data from the Argo data server.

Modeling study for evaluation of aeronautical broadband data requirements over satellite networks

We focus on the modeling and evaluation of the bandwidth requirements of the next generation of satellite communication technologies, which support future aeronautical applications. For modeling purposes, we chose the real-time delivery of high resolution weather maps to the cockpit as a particularly demanding future application. Focusing on this application, we investigate the use of low and geosynchronous Earth orbit (LEO and GEO) satellite networks for efficient delivery of the data. We propose a joint uni-cast and broadcast communication technique that offers bandwidth reduction. We quantify our results through simulation and compare the techniques with other methods.

Satellite and Mobile Wireless Transmission of Focused Assessment with Sonography in Trauma

Objectives: Focused assessment with sonography in trauma (FAST) can define life‐threatening injuries in austere settings with remote real‐time review by experienced physicians. This study evaluates vest‐mounted microwave, satellite, and LifeLink communications technology for image clarity and diagnostic accuracy during remote transmission of FAST examinations. Methods: Using a SonoSite, FAST was obtained on three patients with pericardial and intraperitoneal effusions and two control subjects in a remotely located U.S. Army Combat Support Hospital. A miniature vest‐mounted video transmitter attached to the SonoSite sent wireless ultrasound video 20 m to a receiving antenna. The signal was then transferred over VSAT satellite systems at 512 kilobaud per second (kbps), INMARSAT satellite systems at 64 kbps, and over LifeLink on a moving ambulance through a metropolitan wireless traffic–management network. Clarity and absence or presence of effusions were recorded by 15 staff emergency physicians. Results: Average sensitivity, specificity, and accuracy were 87% (95% confidence interval [CI] = 79% to 95%), 85% (95% CI = 81% to 89%), and 86% (95% CI = 82% to 90%) for the Premier Wireless Vest; 98% (95% CI = 97% to 99%), 83% (95% CI = 75% to 91%), and 86% (95% CI = 82% to 90%) for VSAT; 95% (95% CI = 94% to 96%), 70% (95% CI = 58% to 82%), and 75% (95% CI = 70% to 80%) for INMARSAT; and 82% (95% CI = 73% to 91%), 83% (95% CI = 74% to 92%), and 82% (95% CI = 78% to 86%) for LifeLink with clarity of 3.0 (95% CI = 2.7 to 3.3), 2.9 (95% CI = 2.6 to 3.2), 1.3 (95% CI = 1.2 to 1.4), and 2.1 (95% CI = 1.8 to 2.4), respectively. Conclusions: Accuracy correlated with clarity. Roaming vest transmission of FAST provides interpretable, diagnostic imagery at the distances used in this study. VSAT provided the best clarity and diagnostic value with the lighter, more portable INMARSAT serving a lesser role for remote clinical interpretation. LifeLink performed well, and further infrastructure improvements may increase clarity and accuracy.

Satellite and mobile wireless transmission of focused assessment with sonography in trauma.

Focused assessment with sonography in trauma (FAST) can define life-threatening injuries in austere settings with remote real-time review by experienced physicians. This study evaluates vest-mounted microwave, satellite, and LifeLink communications technology for image clarity and diagnostic accuracy during remote transmission of FAST examinations. Using a SonoSite, FAST was obtained on three patients with pericardial and intraperitoneal effusions and two control subjects in a remotely located U.S. Army Combat Support Hospital. A miniature vest-mounted video transmitter attached to the SonoSite sent wireless ultrasound video 20 m to a receiving antenna. The signal was then transferred over VSAT satellite systems at 512 kilobaud per second (kbps), INMARSAT satellite systems at 64 kbps, and over LifeLink on a moving ambulance through a metropolitan wireless traffic-management network. Clarity and absence or presence of effusions were recorded by 15 staff emergency physicians. Average sensitivity, specificity, and accuracy were 87% (95% confidence interval [CI]=79% to 95%), 85% (95% CI=81% to 89%), and 86% (95% CI=82% to 90%) for the Premier Wireless Vest; 98% (95% CI=97% to 99%), 83% (95% CI=75% to 91%), and 86% (95% CI=82% to 90%) for VSAT; 95% (95% CI=94% to 96%), 70% (95% CI=58% to 82%), and 75% (95% CI=70% to 80%) for INMARSAT; and 82% (95% CI=73% to 91%), 83% (95% CI=74% to 92%), and 82% (95% CI=78% to 86%) for LifeLink with clarity of 3.0 (95% CI=2.7 to 3.3), 2.9 (95% CI=2.6 to 3.2), 1.3 (95% CI=1.2 to 1.4), and 2.1 (95% CI=1.8 to 2.4), respectively. Accuracy correlated with clarity. Roaming vest transmission of FAST provides interpretable, diagnostic imagery at the distances used in this study. VSAT provided the best clarity and diagnostic value with the lighter, more portable INMARSAT serving a lesser role for remote clinical interpretation. LifeLink performed well, and further infrastructure improvements may increase clarity and accuracy.

Airborne imaging and Ka-band satellite communications in an experimental disaster management system

A disaster monitoring, management and mitigation (DM3) system using satellite communications technologies has been developed through cooperation of the Communications Research Laboratory (CRL), the...

Analysis of the effects of water on the ACTS propagation terminal antenna

The NASA advanced communications technology satellite (ACTS) propagation experiment was designed to observe the attenuation produced by rain on Earth-satellite paths operating in the Ka-band. Unwanted effects of water on the antenna reflector surface were noted. Wet-antenna attenuation could be attributed to the combined effect of a water layer on the reflector surface and water wetting the feed window surface. A model was developed to calculate the antenna reflector and feed surface water layer thickness values as a function of position on each surface. The thickness values were used to calculate the additional attenuation produced by the water layers as a function of rain rate on the antenna. The wet-antenna-attenuation prediction model was verified by sprayer tests. The goal of the ACTS propagation experiment was to obtain path attenuation statistics, statistics that represent the effects of rain on the Earth-satellite path but not on the antenna itself. The wet-antenna attenuation prediction model was used to remove the effects of water on the antenna from the combined antenna-plus-path attenuation statistics produced by the experiment. The overall efficacy of the model was demonstrated by comparing the corrected path loss statistics from two ACTS propagation experiment sites with earlier COMSTAR path loss measurements made at or near those sites. The empirical distribution functions from both the ACTS and COMSTAR experiments were identical within the expected uncertainty of an empirical annual distribution of attenuation by rain.