UNDERSTANDING WIRELESS MODULATIONS
DATES: DEC. 1, 2019 - JAN. 1, 2020
This five-day course will give participants the technical background, modeling tools, and practical experience to predict and evaluate performance of RF links using a variety of modulations, operating in ideal and real-world conditions with noise, interference, and jammers.
All RF communications systems use some type of carrier modulation or waveform to transmit signals, data, and information. Familiar modulations include amplitude modulation, for AM broadcast radio, frequency modulation, for broadcast FM radio. Simple digital systems, such as remote controls, use carrier on-off-keying (OOK), amplitude shift keying (ASK), and frequency shift keying (FSK), whereas cellular and wireless systems use combinations of phase shift keying (PSK), Quadrature AM (QAM) and Quaternary PSK (QPSK). Complex commercial and military communication systems also use frequency hopping (FHSS) and direct-sequence spread spectrum (DSSS) waveforms.
Using both presentations, simulations, and hands-on, lab based exercises, participants will study, measure, and characterize the time/frequency domain signatures of each of the modulations outlined. Leveraging the principle that communications is the transmission of information and signals in the presence of noise, participants will estimate channel models and capacity limits under typical real-world impediments such as noise, multi-path, Doppler, interferers, and jammers; lab demonstrations will give participants an opportunity to experiment with real waveforms*. Examples and exercises will demonstrate how modulations are selected based on overall system requirements such as data rate, available bandwidth, channel signal-to-noise, operating range, implementation complexity, and available power budget.
Participants will learn:
Describe the characteristics and system trade-offs of modern wireless modulations including ASK, FSK, PSK, QAM, and QPSK.
Describe how FSHH and DSSS waveforms extend modulation techniques.
Using oscilloscopes and spectrum analyzers, Identify and measure actual modulation waveforms used in remote controls, WiFi, cellular, satellite, and other commercial and military systems.*
Understand and evaluate the performance metrics of modern communications systems including link budget, Nyquist sampling, and Shannon channel capacity.
Identify real-world wireless impediments, eg interferers and jammers, and how they are mitigated by different modulations.
Understand and use hardware and software tools to estimate and characterize wireless system performance.
* To tailor the course to participants requirements, with prior coordination, participants may bring devices for analysis, characterization, and discussion.
This course is intended for professionals who use wireless communications devices and systems but want a deeper understanding of the principals and actually engineering of these systems. The class is intended for those with some basic mathematics background (basic spreadsheet calculations), participants will be given spreadsheets and software tools for analysis and lab exercises, to give insight to communications and modulation mathematics and theory. The course format combines lectures, readings, discussions, and hands-on exercises; participants are given opportunities to use class room material to make measurements in practical lab exercises. The goal of this class is to give deeper understand and practical field skills to understand, characterize, and use modern communications systems.
Provided texts: Schaum’s Analog and Digital Communications
Recommended reference texts: Stemler, Communications Systems; Peebles, Digital Communications Systems; Siebert, Circuits, Signal, Systems.
GNU Radio, Gqrx and alternatives, Octave/Matlab
Demo instruments: Analog Devices PlutoSdr