Introducing a Satellite Communications Course in an Electrical Engineering Technology Program

Introducing a Satellite Communications Course in an Electrical Engineering Technology Program

Lozano-Nieto, Albert

Abstract

Wireless communications, especially satellite-based communications, play an increasingly important role in modern society, providing a growing number of services to the public. However, despite their rising importance, these technologies are not studied in most engineering technology programs. This paper describes an introductory course on satellite communications that balances a solid theoretical approach with meaningful laboratory experiences. Because the course is flexible, it can be implemented in various engineering technology programs as part of a broad effort to maintain technological currency.

Introduction

Today’s society has experienced an explosive development in communications technology, due primarily to both technological advances as well as decreasing costs in the supporting technologies. The use of wireless systems is a very attractive option in the design and development of communication networks, especially with the expansion of cellular telephony and wireless computer networks as these industries seek to increase the number of services and transmission speeds available to their customers.

Satellite communications play a major role in global communications networks. Services such as international telephony through public and private telephone networks, domestic and international radio and TV reception, global positioning systems (GPS), broadband Internet access, transoceanic aeronautical communications, environmental monitoring, search-and-rescue, and weather prediction all rely on the use of civilian satellites. Satellite telephone services in the commercial marketplace have grown steadily, increasing their availability while decreasing their costs. Industries that operate in remote, inaccessible areas have become dependent on satellite telephony as an integral part of their business operations. Thanks to the development and deployment of private satellite constellations such as Iridium, Globalstar, and Immarsat, communications tools that may have been considered an eccentric novelty a few years ago have become a routine part of such remote operations.1

However, despite the increasing use of wireless technology and in particular satellite systems, very few undergraduate engineering and engineering technology (ET) programs incorporate these topics into their curricula.2 This situation especially concerning for ET programs, which are focused on producing graduates with a balance of a solid theoretical background and strong hands-on experiences who are able to move into industry positions and become productive with minimal additional training.

There are several reasons why these courses have not been integrated in most electrical engineering technology (EET) curricula. First, wireless and satellite communication technologies are relatively new, so instructors simply may not be familiar with these components, especially given the complexity of microwave operating systems and the need for different analytical approaches to these systems. secondly, most ET program curricula are already packed with topics that are deemed critically important, and therefore there is little, if any, room for introducing newer topics.3 Furthermore, the majority of ET programs are taught at undergraduate levels, thus limiting the flexibility found in traditional engineering programs in which newer technologies are incorporated in graduatelevel courses. A final reason that may explain why wireless and satellite communications courses are not commonly incorporated into ET programs is the misconception that the equipment needed to develop meaningful laboratory experiments is very complex and expensive. While this may be true for some types of satellite-based services, this paper will describe low-cost alternatives for developing experimental work that address typical concepts in satellite communications.

Despite these problems and because ET programs are characterized by responding to the trends and demands from industry, it is imperative that satellite communications be part of the standard ET curricula to help maintain the respect and consideration that ET graduates receive from industry. This paper describes an introductory course in satellite communications that was developed in response to these industry demands. The course balances a solid and rigorous theoretical knowledge with a strong content of meaningful laboratory experiences while also incorporating contemporary and global societal issues, thus providing students with an integrated educational experience.

Course Goals and Description

With these considerations in mind, the author developed an introductory course on satellite communications that is offered as a senior elective in the Bachelor of Science in Electrical Engineering Technology program at the WilkesBarre campus of Penn State. The two main goals of this course were to give students an understanding of digital and analog communications that are transmitted over satellite networks and to teach students about the various elements that comprise a satellite communications system. To accomplish these goals, the mathematical contents of the course were treated as a tool to illustrate physical situations instead of as the central core of the course. Conceptual oversimplifications were employed to help students understand concepts, leaving more complex solutions such as the prediction of orbits for polar-orbiting satellites for simulation. While a primary goal of this course was to provide a broad understanding of the working principles of satellite communications, the individual elements found in satellite communications systems were explored in sufficient depth to allow students to develop a solid understanding of each element and how it interacts with other components in the overall system. Because the satellite communications course was implemented in an EET program, a strong emphasis was given to electrical system components, although mechanical, heat transfer, and other important parameters were not omitted.

The outline of the course is given in table 1. The instructor presented the basic concepts of each topic through short lectures, which were then complimented by guided student research, presentations, and discussions on specific subsections. Topics were further explored through the use of videos and CD-ROMs from commercial enterprises in satellite communications, discussion and solution of openended problems in the classroom, and experimental work. These activities were developed to create an atmosphere of active learning for students with the ultimate goal of increasing their interest and retention of course concepts.4,5

After covering the first few sections, the instructor can tailor the course outline by selecting from among the remaining topics, and determining the scope of their breadth and depth and the order in which they will be covered. This approach gives the course enough flexibility to be adapted to the goals and objectives of other academic programs.

The first chapter is an introduction to the different types of satellite services, with special emphasis on those that are less familiar to students. When students were asked to identify satellite services, most responded with Direct Broadcast Systems (DBS) and Global Positioning Systems (GPS), as these services are commonly known. DBS can be considered a spinoff from the constellations of geostationary satellites used since the mid 1960s by media organizations to break down geographical barriers and provide instant news coverage around the clock, thereby breaking the monopoly of terrestrial cable television (CATV) companies. GPS is the latest technology transfer from the military to the civilian sector that, in addition to being an integral tool for thousands of outdoor enthusiasts, is also being used increasingly in vehicles. In addition to these two satellite services, students are also exposed to the use of polar-orbiting satellites, which are managed by the National Oceanic and Atmospheric Administration (NOAA) to provide accurate and complete environmental and weather information as well as being used for search-and-rescue missions of vessels in distress.

Chapters 2 and 3 describe the basic mechanical principles of satellite orbits, and includes a more detailed study of the widely used geostationary orbit. In these two chapters, students become familiar with the two-line elements that are used to describe satellite orbits, especially for computational purposes. Chapters 4 and 5 provide a detailed description of the electrical and mechanical specifications for the antennas used in satellite communications. Chapter 6 describes other radiant systems used in satellite communications. Chapters 7 and 8 describe the different components that comprise the space and earth satellite subsystems. Because of the complexity of each subsystem, they are only briefly described while more attention is given to the interconnection of the different subsystems. Chapter 9 complements the students’ previous knowledge of analog and digital signals as well as the conversion between these two domains by studying the characteristics of telephony and television signals transmitted through satellite links. Chapter 10 is the core of this course, incorporating concepts from previous chapters to calculate what is known as the Link-Power Budget Equation, which is used to estimate how the power of a transmitted signal changes as it travels through the different subsystems that comprise the communications channel. Chapter 11 presents the problems of and possible solutions to the interference among satellites and among stations using the same satellite. Finally, in chapter 12, students are introduced to the current methods used by industry to share satellite access as a tool to reduce the overall cost of operation. This chapter also presents the future trends in multimedia and broadband satellite use.6

Laboratory Experiments in Satellite Communications

Meaningful experimental and laboratory work is a pillar of engineering and ET programs, providing students not only with the corroboration of lecture fundamentals but also with practical experience with laboratory instrumentation and equipment. In recent years, however, a disturbing trend has emerged in the way some programs, especially traditional baccalaureate engineering programs, approach the experimental part of their courses. In some cases, laboratory experiments and course projects are based exclusively on computer simulations, even for strongly technological courses such as wireless communications.2 In other cases, laboratory experiences are reduced to hands-on demonstrations by instructors, where students simply observe the development of the experiment and process the acquired data.7 These approaches may seem like an adequate short-term solution to the economic cost involved in setting up undergraduate laboratories and may increase the students’ immediate satisfaction with this portion of the course because the demonstrations proceed smoothly and without mistakes. However, these “hands-off ‘ exercises do not provide all the skills needed by future graduates, such as design, assembly, testing and, ultimately, making errors and learning from them. The processes of re-evaluating their work, redesigning components, troubleshooting problems, and making mistakes and learning from them is an integral part of ET students’ education.

With these considerations in mind, the experimental part of the course was designed to include a strong handson component for students to experiment with satellite communications technology. It was also designed to be especially innovative to capture the students’ attention and consequently increase their interest in the course.8 There is, however, an important limitation in selecting satellite services for experimental exercises. The majority of satellite communication services, such as public and private telephony, are proprietary and not destined for use by the general public, while other services such as DBS television are encrypted and available only by subscription. The use of GPS systems and signals for laboratory experiments are a possible option, especially given the widespread use of this technology, and GPS systems have been incorporated in some academic programs.9 However, the majority of lowcost GPS units are extremely compact, integrating the antenna, receiver, and display section in a handheld unit, which makes it extremely difficult to study and evaluate each subsystem independently. Only the higher-end GPS systems are modular and therefore suitable for laboratory work, although their use would increase the cost of laboratory experiences. Other institutions have experimented with the use of amateur satellite systems, but given the nature of this type of service it is not possible to predict when these satellites will carry communications.10 Furthermore, the forte of amateur satellite services, specifically amateur radio, is the ability to transmit information, which would require the instructors and students to hold amateur licenses granted by the Federal Communications Commission.

For these reasons, it was decided to base the experimental section of this course on two open, nonencrypted satellite services very different in nature and in technology, and to create additional laboratory experiences to support them. These two services are NOAA’s meteorological polar-orbiting satellites operating in the VHF band and geostationary satellites operating in the Ku band that deliver noncommercial television signals carrying news feeds and ethnic programming.

All the laboratory experiences in this course were developed by the author using resources available on campus as well as equipment purchased through a mini-grant received from the Engineering Technology Division of the American Society for Engineering Education (ASEE). These laboratory experiences, listed in table 2, were developed to combine the reinforcement of lecture concepts with the introduction of new topics that are focused on specific characteristics and performances of equipment. Table 3 lists the objectives and applications for the laboratory exercises and how they are applied to each laboratory experience.

In the first laboratory experience, students are exposed to the concepts of frequency and service allocation, commercial and federal users of the radio spectrum, and the broader issues of public policy and spectrum management. In the second laboratory exercise, students learn how to use a medium-frequency digital spectrum analyzer, utilized in the third laboratory experiment, to characterize parameters such as bandwidth, frequency separation, and power levels from over-the-air, CATV, and commercial FM signals. These parameters will be compared with similar parameters from Ku-band television signals to help students learn about the similarities and differences between signals. By the fourth laboratory experiment, students have already been exposed to the principles of nongeostationary orbits, the prediction of windows of visibility, and other concepts needed to detect weather satellite images. In this experiment, students assemble an outdoor antenna specifically designed for the 137 MHz band used by the NOAA’s polar-orbiting satellites that continuously send Automatic Picture Transmissions (APT) from the areas below them. These satellites are almost sun-synchronous, which means they are visible in a specific location on the Earth’s surface at approximately the same time every day. Currently, there are three NOAA polarorbiting satellites in APT operation, although some are sporadically turned off by NOAA managers when there is the possibility of interference with satellites in nearby orbits. The orbital period of these satellites causes them to pass over a specific location on Earth twice a day, giving name to what is known as morning pass and evening pass. These satellites transmit two channels of information, visible and infrared wavelengths, that once combined by the detecting software gives origin to images in which changes of temperature between objects (land, sea, clouds, etc.) are clearly distinguishable. Figure 1 shows an image received from a NOAA satellite, with the captured information in the visible range on the left of the image and the infrared range on the right of the image. These two images are then combined using software tools to produce the image shown in figure 2, in which different colors or shades represent different temperatures. Before starting this laboratory exercise, students were required to use NASA resources to calculate the rise and set time for these satellites from the campus location as well as the duration in minutes of the orbit, its maximum elevation, and other parameters that help determine the quality and length of the detected images.

Experiment 5 introduces students to a high-frequency analog spectrum analyzer that will be used in a later experiment to analyze the characteristics of television signals in the Ku band. In experiment 6, students characterize antennas used for weather images as well as parabolic dishes that are used in the next laboratory exercise. They are asked to predict parameters such as gain and angular bandwidth, based on the physical measurements of the parabolic dishes, and compare them with specification sheets. Finally, in experiment 7, students are exposed to the particularities of geostationary satellites carrying television signals in the Ku band. These signals are used mainly by television networks to distribute live feeds and by foreign TV stations with ethnic programming in both analog and digital formats, thus giving students the opportunity to experiment with both types of receivers. One of the main problems in this experiment was that a large number of transponders in the Ku band are inactive, activated only as needed by the television networks. Students had to calculate the true azimuth and elevation of the geostationary satellite to locate its position, and then correct those numbers for magnetic declination and other local parameters. Figure 3 shows students adjusting a parabolic dish to receive television signals from a geostationary satellite. Once the students locate video and audio signals from this satellite, they can see how lecture concepts such as polarization, signal-to-noise ratio, and half-power bandwidth affect the quality of video and sound, thus making these parameters less abstract and more visible in their implications. In addition, these laboratory experiments can easily be adapted to the infrastructure, equipment, and academic goals of other institutions.

Course Assessment and Student Feedback

Various methods were used to formally assess the satellite communications course, including narrowly focused tests, the evaluation of student work, and the instructor’s assessment of laboratory work. In addition, anonymous student feedback was obtained from surveys that were given at the end of selected topics as well as at the end of the course. These surveys focused on the students’ perceptions of their interest in the topic, the difficulties encountered in the coursework, and the most challenging and rewarding experiences in the course. An important part of this survey involved analyzing the students’ responses on the technical communication and social issues activities in the course.

There is currently a conscious effort in many academic institutions to solve the seemingly endemic problem of the inability of engineering and ET graduates to communicate effectively with their peers and the general public.” Technical courses can help address this widespread problem by including activities geared specifically to facilitate communication and teamwork. The Technology Accreditation Commission of the Accreditation Board for Engineering and Technology (TAC of ABET) has adopted specific technical communications requirements in both its old and newer accreditation criteria. Furthermore, there is also an increasing need, in part driven by ABET, to ensure that students are aware of the social implications of the technologies being studied. To address these issues, students were divided into groups twice during the semester and required to research specific satellite topics, as listed in table 4. These topics address not only the technical aspects of satellite communications but also the social and global concerns involved in this technology, such as the roles that satellite communications play in worldwide events, how different satellite systems are grouped to create a global telecommunications network, and how different countries use satellites for domestic and international communications. The student groups were required to present their findings to the class for questions and analysis.

Following university policy, the satellite course was evaluated at the end of the semester using a standardized evaluation form. However, because this form gives only a numerical value for a set of questions focused on the instructor’s performance, and does not allow students to expand and comment on their responses, the author decided to perform an additional assessment to extract more meaningful information from the students.12 This extra assessment asked students to respond to a series of short questionnaires at the end of selected course activities and to an overall questionnaire, shown in table 5, at the end of the semester. Results from this assessment provide a general picture of the students’ perceptions of the course throughout the semester.

Based on the results shown in table 5, the overall response from students regarding whether the course met their expectations was positive, especially considering that it was the first time that the course was offered. Through informal student comments as well as formal survey results, it is clear that students valued the hands-on experiences gained during the laboratory portion of the course and would like for these practical exercises to be expanded. These results are consistent with the general preference of ET students in receiving thorough training in the practical use of equipment. At the same time, some students may feel reticent to increase these practical experiences, given the time needed to prepare for the laboratory activity, to conduct the activity, and to write a meaningful report. Dissatisfaction with written and oral communications is common to most ET students, but given the importance of these skills, it becomes necessary that instructors stress the value of good communications skills at the beginning of the course. It is critical to include applications that can help students become more confident in their communication skills, such as requiring students to give several short presentations, and to conduct those activities in a relaxed atmosphere that, in turn, will benefit their overall learning experience.13 Selecting the appropriate level of mathematics for the course was also an issue, and students were not able to reach a consensus on this matter as shown by the student responses in table 5. However, the majority of students agreed that the course difficulty was appropriate.

The technical goals of the course were achieved as students learned about the general and specific concepts of satellite communications and, in particular, the differences between this type of communication and the general concepts studied in broader signal communication courses. Students learned to operate new types of electronic instruments such as spectrum analyzers, and began to effectively interconnect the different subsystems that comprise a general satellite communications system. One of the goals in this course was to raise the level of student exposure to contemporary and global issues. Survey responses indicated not only that students had achieved this exposure, but that they were able to identify specific issues they had learned, mostly centered around the study of satellite networks used by other countries, as shown in table 4. It is important to note the apparent dichotomy between the students acknowledging their exposure to contemporary and social issues and identifying their public presentations as the less satisfactory part of the course. Written and oral communications appear to be the area in which engineering and ET graduates wished they had devoted more attention to while they were in college, as they become aware of the importance of communication skills in their first professional job.14 Overall, it seems that students clearly achieved the instructional goals developed for the satellite course.

Conclusion

In recent years the telecommunications area, and in particular the wireless sector, has experienced unprecedented growth due to the integration of traditional communication technologies with increased computing power and the miniaturization of electronic components and devices. However, despite the explosion in the wireless market, engineering and ET programs have not responded to this demand by including these technologies in their curricula. Because they are characterized by providing an educational experience that integrates solid theoretical knowledge with a strong hands-on experiences, it is critical that ET programs revisit their curricula periodically to keep pace with current technological developments.

With satellite communications being an integral part of modern wireless communication systems, an introductory course in satellite communications was developed for the EET baccalaureate degree at Penn State. This course balances a solid theoretical background with meaningful laboratory experiences that provide students with the practical knowledge to assimilate lecture concepts. The structure of this course is flexible enough to be adopted by other institutions, and the laboratory applications dispel the myth of complex and costly laboratory work in wireless communications. The feedback received from the students during the inaugural course offering indicated their satisfaction with the course, its cutting-edge and modern contents, and especially the laboratory experiences. Because students are aware that they are working with real-world equipment instead of scaled-down versions or simulations, they become interested in the concepts being developed in the classroom, thus increasing their learning.

Acknowledgements

This work was partially funded through a mini-grant from the Engineering Technology Division of ASEE.

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Dr. Albert Lozano-Nieto is an associate professor of Engineering at Penn State, teaching in the Electrical Engineering Technology and Telecommunication Engineering Technology programs at the Wilkes-Barre Campus. In addition, he is the program head for the Nanofabrication Manufacturing Technology program, being one of the members who developed this new program. His research interests involve bioelectrical impedance and the development of active learning approaches in engineering technology.

Copyright American Society for Engineering Education Fall 2004

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