Software Defined RadioMentor: Dr. Brian Banister Sponsor: Comtech AHA

Team: Brad Eylander, Dylan Kievit, Jeff Chang, Ted Storms

Acknowledgements:Dr. Brian Banister, Comtech AHADr. Thomas Fischer, WSUJohn Yates, WSU Team Seal

BackgroundSoftware defined radio (SDR) is a communication system that replaces certain dedicated hardware functions with software. This software can be modified in real time to implement arbitrary communications protocols. Comtech AHA is sponsoring the design of an SDR to demonstrate the effects of forward error correction and data compression technologies on data transmission.

QPSK

Equipment

(Quadrature Phase-Shift Keying)Phase-shift keying (PSK) is a modulation technique that encodes data by changing the phase of a carrier signal. QPSK has two bits per symbol for a total of four possible symbols. A QPSK symbol is made up of a quadrature (Q) component and an in-phase (I) component.

Universal Software Radio Peripheral• Software Radio Platform• Receive and Transmit Data - OTA or Cable• A/D and D/A Conversions• Interpolation and Decimation

GNU Radio• Software Radio Toolset• Digital Data Manipulation• Visualization of Data Flow• Signal Processing Blocks in C++• Systems Described using Python

• Display Signal-to-Noise ratio• Calculate bit error rate / signal to noise ratio• Wireless transmission• Communication between multiple USRP boards• Analysis of external transmission noise

Future Work

• Produced documentation for use of GNU Radio and USRP• Data transmission at desired frequency using the USRP• Able to detect set frequencies using the USRP Board• Modulation and Demodulation of QPSK• QPSK Phase ambiguity resolution• Data packetization encoding and decoding• Data transfer rate of 213 kbps

Work Completed

Impact

Project Overview• Implementation of QPSK modulation and demodulation.

Transmission and reception of data reliably over a clean channel.

• Data Packetization Phase ambiguity resolution.

• Soft Output Helps with error correction and SNR.

• Multiple Stage Project Documentation will be produced for easy transition to the next phase.

Data PacketizationBinary data is bundled together in a set number of bits, and then packed with a unique word at the beginning. The unique word enables the receiver to determine where each packet begins. This enables the receiver to quickly recover from temporary signal loss. The unique word also facilitates phase ambiguity resolution.

Soft Output• Passes in-phase and quadrature components of the received symbol.

• Used to calculate signal-to-noise ratio.

Combined, the I/Q components can be used to describe the signal constellation (right). The block diagram below describes the modulation and demodulation of QPSK.

•Customizability GNU Radio allows for on-the-fly customizability. After the tsunami disaster of 2004, countries sent relief teams to aid in search and rescue. However, different broadcast frequencies made it difficult for the groups to coordinate efforts. GNU Radio could have aided in receiving and rebroadcasting transmissions to aid in rescue efforts.

Spectrum Analysis

The frequency spectrum confirms our expected bandwidth of 144 kHz.

•Education GNU Radio allows students to learn and experiment with different technologies such as Communications, RF, DSP, Programming, Mod/Demod Techniques, and Cryptography.