Practical Digital Wireless Signals

Course 232

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Summary

This three day course is designed to provide all participants with a physically intuitive understanding of wireless communication signals and why they work the way they do. With the growing impact of wireless communications on the basic operation of society, the need for a more general understanding of the basis for this technology is more important than ever.

This course approaches wireless communications signals through the window of physics and physical principles. While a solid understanding of the mathematical theory of wireless communications signals is essential for detailed system design and analysis, the fundamental choices in system application and approach are often best approached physically. We do not shun math in this presentation, but instead of using math as the presentation base we instead use it as a follow up illustrator of the principles discussed.

The sessions cover all of the major modulations used in digital wireless communication, including ASK, FSK, PSK, QAM, and OFDM. Spread spectrum operation is included, comparing the relative performances of Direct Sequence (DS) and Frequency Hopping (FH) techniques. System principles are also presented such as an extensive discussion of the Shannon Capacity Limit, the physical basis of Nyquist filtering, plus an introduction to antennas and wireless signal propagation. Important system parameters and analysis tools which are common to any modulation type are presented and demonstrated. Public course attendees will receive a copy of the book - Practical Digital Wireless Signals by Dr. Earl McCune.

Physically intuitive understanding is the purpose for this course on Wireless signal and system fundamentals. Understanding why these signals and techniques work, not just how, is the key objective of this course.

Learning objectives

Upon completing the course you will be able to:

• Explain the fundamental differences among ASK, FSK, and PSK wireless signals
• Understand the demodulation effort (cost) differences among digital wireless signals
• Understand the basic performance metrics of any digital wireless system
• Explain the principles of modern QAM and OFDM signals
• Understand what is a spread spectrum modulation (and what is not), and the differences between direct sequence and frequency hopping techniques
• Show how the Shannon Limit predicts the many difficulties in building high data rate, long range, finite bandwidth wireless systems
• Understand the relationship between antenna gain and directivity
• Understand the need for coding, the fundamental types of coding, and their top level costs and benefits

Target Audience

This course will be of interest to people new to wireless communications design, and to communication specialists who are very familiar with the mathematics of wireless signals but may desire broadening this understanding with a physical perspective. It will also be interesting to technical marketing engineers who desire a physical intuition into the tradeoffs that the corresponding design engineering teams are wrestling with.

Outline

Common Background Issues and Tools

 • What is keying? • Signaling definitions • polar and rectangular equivalence • time-spectrum correspondences • symbol construction • filtering characteristics • the special properties of Nyquist filters • simples vs. duplex • constellation and vector diagrams • eye diagrams • SNR vs. Eb/No

Modulation Types

ASK (Amplitude-shift keying)

 • Definitions • constellations • occupied bandwidth • bandwidth efficiency • power efficiency • PAPR • envelope statistics • energy efficiency • demodulation principles • introduction to noise performance

FSK (Frequency-shift keying)

 • Definitions • phase tree • occupied bandwidth • bandwidth efficiency • power efficiency • Doppler shift • energy efficiency • signal limiting • demodulation principles • introduction to noise performance • FM threshold effect

PSK (Phase-shift keying)

 • Definitions • constellations • Why nearly all PSK signals are really QAM • CPM is not a PSK • offset PSK • occupied bandwidth • bandwidth efficiency • power efficiency • PAPR • envelope statistics • energy efficiency • Doppler tolerance • demodulation principles • introduction to noise performance

QAM (Quadrature Amplitude Modulation)

 • Definitions • constellations and signal structure • occupied bandwidth • bandwidth efficiency • power efficiency • PAPR • envelope statistics • offset QAM • Doppler tolerance • energy efficiency • demodulation principles • introduction to noise performance

OFDM (Orthogonal Frequency Division Multiplex)

 • Definitions • constellations • occupied bandwidth • bandwidth efficiency • power efficiency • PAPR • envelope statistics • energy efficiency • Doppler intolerance • demodulation principles • introduction to noise performance

Antennas and Wireless Propagation

 • Path Loss • Transmit Power • Antenna Gain • Antenna Directivity • Near and Far Fields • Polarization • Receive Sensitivity • Range Expectations • Level Diagrams • Delay Spread • Diversity • Correlation

Shannon’s Capacity Limit

 • Shannon’s Fundamental Theorem on Information Theory • Shannon-Hartley equation • capacity density • SNR vs. Eb/No forms • finite available power • power vs. bandwidth • signal design region

Principles of Coding

 • Motivations • definitions • coding for bandwidth efficiency • coding for spectrum control and link operation • coding for error control - block codes, convolutional codes, turbo codes • coding to manage error bursts • coding for channel throughput (MIMO) • equalization

Spread Spectrum

 • Direct Sequence and Frequency Hopping • cyclic cancellation • synchronization • interference suppression • process gain • jamming margin • chips and spreading codes • frequency hopping details • direct sequence details • DS vs. FH comparison

Cost Comparisons among Signal Implementations

 • The Keep-It-Simple (KIS) Procedure

Subject Areas:

• Antennas
• Wireless Digital Communications Fundamentals
• Modulation Techniques