Software Defined Radio: Radios of Tomorrow Behrouz Farhang ECE Department, Univ of Utah

Organization 1.A Brief History of Radio Communication 2.Background: Fourier Series Expansion 3.Important Concepts: Filtering and Modulation 4.MATLAB Demos 5.From Analog to Digital 6.Cognitive Radios 7.Research Activities at Wireless Communications

History of the Radio: James C. Maxwell : James Clerk Maxwell experiments with electromagnetic waves 1873: describes the propagation of electromagnetic waves in his paper “A Dynamical Theory of the Electromagnetic Field”

Wireless Radio Begins: Nikola Tesla 1893: Tesla gives public demonstration of wireless radio communication at St. Louis, Missouri. He describes in detail the principles of radio communication.

Wireless Radio Begins: Guglielmo Marconi and K. F. Braun 1896: G. Marconi is awarded a patent for radio: Improvements in Transmitting Electrical Impulses and Signals and in Apparatus There-for 1897: Marconi establishes a radio station on the Isle of Wight (England) 1909: Marconi and Karl Ferdinand Braun win Nobel Prize in Physics for "contributions to the development of wireless telegraphy"

The History of the Radio

Better Sound Quality: FM Radio 1933: Edwin H. Armstrong patents FM radio (better quality than AM)

Television 1940s: analog television transmissions start in North America and Europe.

Television 1940s: analog black and white television transmissions start in North America and Europe. 1950s: analog color television transmissions start in North America and Europe.

Other stuff Internet Digital Audio Broadcasting (DAB) Digital Video Broadcasting (DVB) HDTV Satellite Radio etc… Going from analog “payload” to digital “payload” However, radio itself still “analog” up to the decoder stage

The Fundamental Blocks in a Radio Move signal from RF to baseband (original signal) HOW? Remove frequency components HOW? Increase amplitude of signal multiply by constant Fourier Series Expansion

The Theory Behind Radio Technology: Fourier Series Jean Baptiste Joseph Fourier ( ) French mathematician and physicist Idea: “any” periodic function can be decomposed into an (infinite) sum of sines and cosines

How Radios Work? According to Fourier any signal f(t) can be expanded as a sum of sine-waves: This leads to the notion of signal spectrum

Example: Square Pulse, infinite # harmonics! With 250 harmonics: Gibbs phenomenon at discontinuity

Example: Sawtooth Wave

Example: Triangle Wave Some TD signals are suited better for transmission than others (less harmonics) Rect-wave: poor TD quality with 25 harmonics Sawtooth-wave: poor TD quality with 25 harmonics Triangle-wave: pretty good TD quality with 10 harmonics

Modulation Modulation is established by multiplying a signal with a carrier cos(  c t): The spectrum is shifted from frequencies  1,  2,  3, … to frequencies  c +  1,  c -  1,  c +  2,  c -  2,  c +  3,  c -  3, …

Demodulation Now let us take the modulated signal f(t)cos(  c t) and modulate it again with the same carrier. By passing this signal through a lowpass filter (a system that cancels the second term on the right hand side) and amplifying the result by a gain of 2, we get f(t).

Next let us consider the modulated signal And demodulated versions of it: and Demodulation

What is Filtering? Input Signal Filter Response Output Signal

A Radio?

A Conventional Radio: all in Analog

New Paradigm: Software Defined Radio (SDR) RX Signals are digitized immediately after the LNA and then processed entirely in software, flexible TX vice versa Software Defined Radio:

A Radio!

Cognitive Radios Have the capability to be aware of their surrounding environment Can change PHY depending on environment Can change PHY depending on traffic needs Can alter higher layer behavior as needed Learn from past experiences Capable of complex adaptation

Cognitive Radios: Primary and secondary users  Primary (licensed) and secondary (unlicensed) users coexist and share the same spectrum  PUs have priority and thus SUs must back-off as soon as PUs begin a communication  This requires channel sensing PU SU

SDR Activities at the Wireless Communications Lab 1.A course title “Software Radio” is offered (graduate level class) 2.We are actively involved in the SDR Forum, a nonprofit international industry association that supports the development and deployment of SDR technologies 3.A team of our students is finalist in the Smart Radio Challenge; a worldwide competition that challenges student teams to design, develop and test an SDR / a cognitive radio (CR) system. 4.We also develop MIMO Communication systems; a technology that promises data rates in order of Giga bits persecond.