OFDM Weekly Progressback to main

Weekly Updates:4/19/2001

MATLAB code updateso Add channel magnitude response to frequency spectrum plotso Revised binary error checkingo Corrected memory allocation in QAM codeo Corrected QAM transmission size for input less than one OFDM

symbol long GUI Implementation - SoundGUI

o Axis handlers and GUI technique learningo Integrate GUI code with Steve's versiono BER, good channel for EXPO, Long sound file interface

EXPO Planningo Main Pointso Sketch of poster board layout

User Testingo Greg & Dawno Wording and layout suggestions

4/18/2001

Analysis Codeo Changed frequency plots to digital frequencyo Improved labeling of all plots

GUI Implementation - SoundGUIo Added appropriate graphs for each stringo Developed UI flowo Speed improvemet: use output files - don't re-run simulation codeo Hide/Show different UI elements depending on current demo state

4/17/2001

OFDM Decoding - Now intelligento 'Unpad' zeros from transmissiono Always receive same number of bits as transmitted

QAM vs OFDMo Utilized MATLAB FIR filter design techniques, i.e., 'fir1()' and 'fir2()'

BER for both schemes ~50% Conclusion: MATLAB FIR filter not appropriate for this

applicationo New multipath simulation - user specifies 2-tap FIR filter

Revised OFDM decoding allows practical comparision OFDM has higher multipath tolerance with ANY parameter

setup! Analysis Code

o Improved labeling of all plotso Plot multipath frequency response - allows user to target QAM

frequencieso MATLAB command window display more user friendly

Spacing between major sections of feedback BER displayed as the actual number of errors and percent error

GUI Implementationo BasicGUI

Initialized "setup.m" variables with new function: "SetupGUI.m"

Added corresponding graphs to text strings Finished interface functionality

o SoundGUI Paper design of interface Implemented simple version of interface layout Wrote the text strings for the demo

4/12/2001

QAM vs OFDMo First resonable comparison between the two schemeso Compared channel effects

Noise - OFDM affected more because of the high peak to average signal power

Clipping - QAM affected more because of OFDM's high peak to average signal power

Multipath - No conclusive results GUI Implementation - BasicGUI

o Wrote the text strings that will lead the user through the demoo Used the global counter variable to step throught the strings

4/10/2001

Revised schedule of remaining tasks GUI Paper Design of main interface QAM Improvements

o Revised perameters for a reasonable comparison to OFDMo Changed to 16-level QAM - major code rewrite

GUI Implementationo Designed the graphical interfaceo Worked on the callback functions to integrate all of the GUI functions

into one m-file, "OFDMguiFn.m"o Global counter variable

4/5/2001

Channel Modelingo FIR filtero QAM periods added

QAM Code Speedup (zeros initializion forgotten) GUI Research

o Found many versions of 'buildgui.pdf', a guide to MATLAB GUI implementation

o Made simple example interface to learn design tool Windows Compatibility QAM Constellation Plotting

4/3/2001

Update presentation preparation New Plan

o MATLAB GUIo Improve MATLAB code

QAM Decoding

3/29/2001

MATLAB QAM Codeo Used OFDM variables to generate single carrier QAM equivalanto "Transmitter" portion of QAM code complete

3/15/2001

Much crashing and locking of the DSP boardo Searched through documentationo Found possible sampling rates of the audio codec

Repeated 16 point FFT data to fill 1 second of buffer to be played pack at 8kHz sampling rate

Revision of Student EXPO paper

3/13/2001

IFFT Amplitude Considerations Connected scope to Mini-plug audio output to view generated sinusoid Wrote paper for Student EXPO

3/8/2001

Audio Codec Exampleo Isolated tone generation portion of example codeo Documented the functions and main code

Began modifications to merge our IFFT routine into this example with a goal of generateing a tone using the IFFT

3/6/2001

Continued experiments with DSP example and finally was able to generate an example tone by setting the correct paths, including the right files, and thourghouly reading the documentation

3/1/2001

Planned simple DSP test to use the IFFT to generate sinusoidal outputs Experimented with running examples that use the printf() and line out

components of c60 DSP board

2/27/2001

MATLAB Codeo Documented each file's name, function and variables used/modifiedo Pasted in current code into notebook as a quick reference for

translation into C FFT Testing in C

o Worked on compiling and testing four1 algorithm using Microsoft compiler

o Compared C routine's output with Matlab The ordering of the output was opposite Matlab's Fixed ordering by defining DFT with EE conventional negative

sign (the algorithm used a mathematician's definition of the DFT with an e^+j... )

Planned Work Paths for C Translation

2/20/2001

FFT Algorithm research and reading to try to find short/simple FFT. Found "Numerical Recipes in C" FFT algorithm called "four1"

2/15/2001

Experimentation with Volume example - looping Found Line_In/Microphone example Tried compiling basic complex number and FFT routines in C on Codewarrior

2/13/2001

Project Progress Presentation One DSP TMS320c6x01 board Tutorial

o Set correct pathso File I/O - can now use a file as input and save to file output

DSP C code research - found basic fft/ifft routines written in C

2/8/2001

Channelo Fixed Noise and Multipath Simulationo Moved Parameters into setup.m

QAM comparisono Uses most of OFDM code to produce QAM signal with the same datao Necessary to compare ISI of OFDM (multicarrier) vs QAM (single

carrier) TI c60 DSP board - initial tool investigation

2/6/2001

Modified website to include weekly progress report Binary Inputs / Outputs

o Improved Write to reconstruct original data format Text Sound - also added scaling and fixed file output

o Converted all test inputs to binary Corrected Pol2Bin.m to discard trailing zeros from polar data Added symbol view to analysis window Determined fast method of converting Mac text files to Windows format

2/1/2001

Finished modifying transmission (TX) code to separate FFT points and # of carriers

Modified receiver (RX) code to separate FFT points and # of carriers Binary Inputs

o created conversion routines to convert 8-bit data to binary and backo implemented binary for the Sine and Random test inputs

Polar QAMo created conversion routines to convert from binary {0,1} to polar {-

1,1} and backo implemented polar routines into TX and RX code

1/31/2001

Modified web site to include 180k OFDMdemo movie

1/30/2001

Outline of 4 MATLAB goals:o Separate FFT points and # of carrierso Polar QAMo Binary Inputso Extra Features (phase estimation/correction)

Began modifying transmission code to separate FFT points and # of carriers

 

Projected Timeline:As shown in the timeline below, the main goals to accomplish in Spring 2001 includefinalizing MATLAB, generating the corresponding DSP code, and then testing the system.

MATLAB code will be improved to make a hardware implementation feasible. This will involve adding QAM and guard periods, as well as windowing, interleaving, and coding features.

The next phase will be to learn the DSP tools. By writing simple test simulations, the functionality of the DSP tools will be explored.

Once these tools are understood, the MATLAB code will be translated into the appropriate format for the DSP board. Simulink can be used with the dSpace board, but the TMSC60 board uses C.

The testing phase will involve verifying that the DSP board produces results consistent with the MATLAB code.

Once the OFDM system works correctly, the characteristics of the OFDM transmission will be examined. This may include phase shift and synchronization techniques.

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