This text is intended to provide a senior undergraduate student in electrical or computer engineering with a systems-engineering perspective on the design and analysis of a wireless communication system. The focus of the text is on cellular telephone systems, as these systems are familiar to students; rich enough to encompass a variety of propagation issues, modulation techniques, and access schemes; and narrow enough to be treated meaningfully in a text that supports a single course. The presentation is limited to what cellular systems engineers call the "air interface" and what network engineers call the "physical layer."
The presentation is unique in a number of ways. First, it is aimed at undergraduate students, whereas most other textbooks written about wireless systems are intended for students either at the graduate level or at the community college level. In particular, the presentation combines a clear narrative with examples showing how theoretical principles are applied in system design. The text is based on ten years' experience in teaching wireless systems to electrical and computer engineering seniors. The lessons learned from their questions and responses have guided its development. The text not only presents the basic theory but also develops a coherent, integrated view of cellular systems that will motivate the undergraduate student to stay engaged and learn more.
Second, the text is written from a systems-engineering perspective. In this context a "system" comprises many parts, whose properties can be traded off against one another to provide the best possible service at an acceptable cost. A system with the complexity of a cellular network can be designed and implemented only by a team of component specialists whose skills complement one another. Top-level design is the responsibility of systems engineers who can translate market requirements into technical specifications, who can identify and resolve performance trade-off issues, and who can set subsystem requirements that "flow down" to the subsystem designers. The text introduces students to the concept that specialists from a wide range of engineering disciplines come together to develop a complex system. Theory and contemporary practice are developed in the context of a problem-solving discipline in which a divide-and-conquer approach is used to allocate top-level functional system requirements to lower-level subsystems. Standard analysis results are developed and presented to students in a way that shows how a systems engineer can use these results as a starting point in designing an optimized system. Thus an overlying systems-engineering theme ties together a wide variety of technical principles and analytical techniques.
This text comprises eight chapters. An introductory chapter sets out the systems-engineering story. Chapters 2 and 3 introduce the air interface by considering how to provide enough power over a wide enough area to support reliable communication. Chapter 2 introduces the free-space range equation and thermal noise. On completing this chapter, students should be aware of the dependence of received power on range and of the role of noise in determining how much power is enough for quality reception. Chapter 3 introduces the terrestrial channel and its impairments, including the effects of shadowing and multipath reception. Next, Chapter 4 introduces the principle of frequency reuse and the resulting cellular system structure. The goal of this chapter is to show how a communication system can be extended to provide service over a virtually unlimited area to a virtually unlimited number of subscribers.
Once a power link is established, information must be encoded to propagate effectively over that link. Chapter 5 introduces modulation. The emphasis is on digital techniques common to cellular systems. Of particular interest are frequency efficiency, power efficiency and bit error rate, bandwidth, and adjacent-channel interference. Chapter 5 also introduces spread-spectrum modulation, emphasizing the ability of spread-spectrum systems to provide robust communication in the presence of narrowband interference and frequency-selective fading.
On completion of Chapter 5, students will have an appreciation of the factors involved in designing a point-to-point data link between a single transmitter and a single receiver. Chapter 6 introduces methods for multiple access, including FDMA, TDMA, and an introduction to CDMA. The ability of spread-spectrum systems to support multiple users over a single channel is emphasized.
Wireless systems carry information from a wide variety of sources, from speech to music to video to short text messages to Internet pages. When digitized, information from various sources produces data streams with differing properties. Further, subscribers apply different criteria to assessing the quality of different kinds of received information. Chapter 7 distinguishes streaming from bursty information streams. As second- and subsequent-generation cellular systems are highly dependent on effective use of speech compression, examples are given showing traditional digitization of speech and a brief introduction to linear predictive coding. Chapter 7 concludes with presentations of convolutional coding for error control and the Viterbi decoding algorithm. The systems-engineering story is pulled together in Chapter 8.
This text has been written to support a one-term senior elective course. It is assumed that students taking the course will have completed conventional courses in signals and systems and an introduction to communication systems. The signals and systems background should include a thorough introduction to the Fourier transform. It is also assumed that readers of the text will have completed an introductory course in probability, including coverage of probability density functions, expectations, and exposure to several conventional probability distributions. The material included in this text should be more than sufficient to support a one-semester course. At Rose-Hulman Institute of Technology the book is used to support a one-quarter course that includes four instructional meetings per week for ten weeks. The course covers all of Chapter 2, selections from Chapter 3, all of Chapter 4, and most of Chapter 5. The CDMA material from Chapter 6 is included as time permits.