Presentation Outline. Advisors: Dr. In Soo Ahn Dr. Thomas L. Stewart. Team Members: Luke Vercimak Karl Weyeneth

Transcription

1 Bradley University Department of Electrical and Computer Engineering Senior Capstone Project Proposal December 6 th, 2005 Team Members: Luke Vercimak Karl Weyeneth Advisors: Dr. In Soo Ahn Dr. Thomas L. Stewart Presentation Outline Karl Project Background Project Summary Applicable patents and standards Detailed Project description Functional Description Block Diagram Luke Project Specifications Preliminary lab work QAM Theory and Design QAM Results OFDM Theory and Design OFDM Results Equipment List Completion timeline

2 Digital Radio Transmission Purpose Desire to transmit data over a distance using electromagnetic radiation (radio waves) Computer s representation of digital data (pulse train) does not have dominant harmonics in convenient and/or available frequencies in the electromagnetic spectrum Need to transmit this data as efficiently as possible over available frequencies Hardware to Software Radio Modulation has traditionally been done with hardware. Recent advances in digital signal processing technology allows this to be done with a computer rather than electronics This allows generic radio hardware to be used and more powerful modulation techniques to be used. 2

3 Project Strategy By drawing upon the IEEE 802.a standard a general structure for transmitting the data was decided:. Demultiplexing The incoming binary stream will be buffered and split into 4 simultaneous channels. 2. Each data channel will then be modulated onto a subcarrier. This project will use four level quadrature amplitude modulation (QAM). 3. Each subcarrier will then be multiplexed onto one carrier. This project will use orthogonal frequency division multiplexing (OFDM). Digital Data 000 Demultiplexing QAM QAM QAM QAM OFDM Carrier Modulation Potential Problems The space through which the radio signal will be transmitted (channel) and imperfections in the transceivers will have adverse effects on the signal: Random attenuation at different frequencies Wide band and narrow band noise Multi-path interference Phase delay caused by distance of transmission Small frequency deviation and drift from oscillator imperfections. 3

4 Project Goals Successful modulation and demodulation of digital data at radio frequencies. Reasonable compensation for channel and transceiver problems. Carrier, symbol, and frame synchronization will be focused on. Related Patents and Standards Standard 802.a Patents Patent Number 6,09,765 6,353,640 6,937,877 6,954,628 Patent Application Description Reconfigurable radio system architecture Reconfigurable radio frequency communication system Wireless communication with a mobile asset employing dynamic configuration of a software defined radio Radio receiver Methods for processing a received signal in a software defined radio (SDR) system, a transceiver for an SDR system and a receiver for an SDR system Modulation/demodulation apparatus for the encoding and decoding of data and method for encoding and decoding data 4

5 Functional Description Input Digital Data (text / computer data file) Output Digital Data (text / computer data file) Modes of Operation Transmitter Receiver Channel Simulation (when actual channel is not being used) Block Diagram Parts of Software Radio: Transmitter Changes the data from the file into a signal that can be transmitted over the channel. Channel The path or medium that the transmitter and receiver are designed to transmit through. Receiver Recovers the data from the signal that was transmitted over the channel and converts it back into data. 5

6 Transmitter Demultiplexing Quadrature Amplitude Modulation (QAM) Orthogonal Frequency Division Multiplexing (OFDM) Local Oscillator and Mixer Channel Channel Attenuation Multi-path Noise 6

7 Receiver 4 Level QAM Demodulation From Channel Down Mixer Carrier Synchronization Automatic Gain Control OFDM Demodulation 4 Level QAM Demodulation 4 Level QAM Demodulation Symbol Synchronization 2:8 Multiplexer Frame Synchronization Output Bin Stream 4 Level QAM Demodulation Local Oscillator Carrier Synchronization Automatic Gain Control (time permitting) OFDM Demodulation QAM Demodulation Symbol Synchronization Multiplexing Frame Synchronization Presentation Outline Karl Project Background Project Summary Applicable patents and standards Detailed Project description Functional Description Block Diagram Luke Project Specifications Preliminary lab work QAM Theory and Design QAM Results OFDM Theory and Design OFDM Results Equipment List Completion timeline 7

8 Datasheet The following specifications were chosen for the software radio: The A/D converter s maximum sampling rate was 200KHz. 00KHz was used to avoid problems with the hardware and can be increased later to improve performance Limits Parameter Sampling Rate Modulation Frequency Data Rate F samp F mod R Symbol Min Typical 00 0 Max Units KHz KHz Kbps Preliminary lab work Simulink interface with board explored C S functions working with 673 DSK board. Will be useful in implementing the device drivers for the A/D and D/A boards QAM modulation and demodulation working OFDM modulation and demodulation working 8

9 QAM Theory Binary Input Data Stream translated into 2 n symbols Symbols assigned a position in the complex plane. Coordinates of symbols specify amplitude of Inphase & Quadrature components QAM Continued QAM Transmitter s(t) = x(t)cos(ω c t) y(t)sin(ω c t) 9

10 QAM Continued QAM Receiver Preliminary Lab Results ( QAM) Inphase input bit stream Inphase receiver signal Quadrature input bit stream Quadrature receiver signal 0

11 OFDM Theory Frequencies /Td apart so that they are orthogonal when carrying pulses OFDM uses the IFFT algorithm to generate orthogonal carrier frequencies. Normalized Power Relative Frequency OFDM Block Diagram w Zero Pad IFFT IFFT Unbuffer Re(u) Im (u) Complex to Real-Im ag x(t) 2 y(t) Matrix Viewer IFFT _OUT Matrix Viewer To Workspace Transmitter Diagram x^(t) 2 y^(t) Re Im Real-Imag to Com pl ex Buffer In FFT _IN FFT Out M atrix Viewer Select Rows M ulti port Selector w0 2 w 3 w2 4 w3 To Workspace Receiver Diagram M atrix Viewer

12 0.8 OFDM Results The power spectrum of the OFDM transmission matches theory. Input waveform recovered Carriers of OFDM transmission Power spectrum of OFDM transmission Equipment and Parts List DSP Starter Kit (TMDSDSK673) 5-6K Interface Board 6-bit 200KSPS ADC Serial Out 6-bit serial input, multiplying D/A converter with 0.5uS settling time 2

13 Completion Timeline & Milestones Task Test & Integrate QAM & OFDM Transmitter Develop & Integrate Carrier Synchronization Develop Symbol Synchronization Develop Message Encoder/Decoder Integrate Symbol Synchronization Develop & Integrate Message Synchronization Develop Channel Model & Test Message Encoder Test Message Synchronization Integrate Channel Model & Develop Device Drivers Test Performance of Software Radio Final Demonstration, Presentation & Report Date Jan 9 Jan 26-Feb 2 Feb 9-6 Feb 23-Mar 2 Mar 9 Mar 23 Mar 30-Apr 6 Apr 6-May 4 Questions, Comments? 3