Group Members: Surujlal Dasrath & Adam Truelove Advisors Dr. In Soo Ahn – Theory + Software Dr. Thomas Stewart – Theory + Software Dr. Anakwa – Hardware Software and Hardware Implementation of an Orthogonal Frequency Division Multiplexing (OFDM) System Software and Hardware Implementation of an Orthogonal Frequency Division Multiplexing (OFDM) System

The field of communications is a rapidly growing industry. OFDM is just a single area of this field. We plan to research this technique as well as implement a fully operational system primarily in software. Introduction

Presentation Outline Theory Background What is OFDM? OFDM Generation Software Implementation Matlab Matlab results

Presentation Outline Theory Background What is OFDM? OFDM Generation Software Implementation Matlab Matlab results

Telecommunications Background Necessary Definitions Digital Communications in its basic form is the mapping of digital information onto a waveform. A Carrier is a transmitted electromagnetic pulse or wave at a steady base frequency of alternation on which information can be imposed. A Channel is a separate path through which signals can flow such as: wires fiber-optic cables air

Presentation Outline Theory Background What is OFDM? OFDM Generation Software Implementation Matlab Matlab results

A Qualitative Description of OFDM OFDM stands for Orthogonal Frequency Division Multiplexing. An OFDM signal is composed of a collection of closely spaced carriers. Orthogonality is an implication of a definite and fixed relationship between all carriers in the collection.

Why use OFDM? In previous research, it has been proven that OFDM outperforms other transmission schemes in many aspects of multiple access transmission. Suppression of Inter-Symbol Interference (ISI) Allows many more users Flexible bandwidth allocation

Presentation Outline Theory Background What is OFDM? OFDM Generation Software Implementation Matlab Matlab results

OFDM Generation Even though OFDM has been around for a few decades now, a hardware solution using banks of oscillators was not very practical to realize. The advent of the Fourier Transform (FT)made OFDM possible today. The FT is simply a way to go from between the Time Domain and the Frequency Domain. Specifically, OFDM utilizes the: FFT – Fast Fourier Transform IFFT – Inverse Fast Fourier Transform

OFDM Generation Application of the FFT & IFFT simplified the initial complexity problem with OFDM. A simple system in indicated in Fig. 2. Fig. 2. Block Diagram of a simple OFDM System

Presentation Outline Theory Background What is OFDM? OFDM Generation Software Implementation Matlab Matlab results

Matlab Matlab is a very powerful and flexible software package. It is used in many engineering applications. Here are just a few examples. Hydraulics Aeronautics Global Positioning System (GPS) Signal Processing Communications All simulations will be done using the Matlab Software Package Note: © MATLAB is made by MathWorks (

Matlab Block Diagram A/D PCMQPSKIFFTFFTQPSKISID/A PCM OFDM Analog in Analog out Software will follow several algorithms to realize the block diagram given in Fig. 3. Fig. 3. Overall software block diagram

Definition of Terms in Block Diagram A/D–Analog to Digital PCM–Pulse Code Modulation QPSK–Quadrature Phase Shift Keying FFT–Fast Fourier Transform IFFT–Inverse Fast Fourier Transform ISI–Inter-Symbol Interference D/A–Digital to Analog

QPSK imag f 0 1 imag f 1 0 real f 1 real f

Inter Symbol Interference transmitterreceiver A B C D = A+B+C

Inter Symbol Interference A B C D = A+B+C A A is still present, only with some phase shift.

Inter Symbol Interference realimag ff real imag real imag realimag ff A A B B 80 ° rotation A A B B AA A = unknown signal B B = known signal If phase rotation is known, it can be compensated for.

Phase Shift Compensation original (real) original (imag) w/phase shift (real) w/phase shift (imag) phase shift compensated (real) phase shift compensated (imag)

OFDM Reception

real imag f f

OFDM Reception real imag f f 0

OFDM Reception real imag f f 0 0 1

OFDM Reception real imag f f

OFDM Reception real imag f f

OFDM Reception real imag f f

OFDM Reception Our original 8 bit sequence has been recovered successfully. This can be done to a code sequence of infinite length 8 bits at a time.

Presentation Outline Theory Background What is OFDM? OFDM Generation Software Implementation Matlab Matlab results

Text Transmission (phase shift compensated)

Text Transmission (phase shift uncompensated)

Sound Transmission (phase shift compensated)

Sound Transmission (phase shift uncompensated)

Image Transmission (phase shift compensated)

Image Transmission (phase shift uncompensated)