1. Software Defined Radio
Advisors: Prof. Chih-Chun Wang
Prof. J. V. Krogmeier
Graduate Mentor: A. W. Layton
Members: Shannon Sremac, Kevin Choi, Zi Jin Lu, Jack O’Reilly
Software Defined Radio
Department of Electrical and Computer Engineering
System Diagram (GNURadio)
Differential Phase Shift Keying
(DBPSK)
Software Defined Radio
Software-defined radio (SDR) is a radio communication technology that is based on software defined wireless communication protocols instead of hardwired implementations.
We aimed to continue the work from last semester’ team and develop a walkie-talkie system implemented with software defined radios.
Simplified waveform utilizing DBPSK
Information is carried in a change in phase. Demodulation consists on comparing the previous wave with the current wave.
Signal Processing Overview:
Encode audio data
Package data into bytes
Transmit data over free space from one computer
Receive data from free space to second computer
Decode data, convert to audio signal
Components in a Typical Packet
Packet Encoder/Decoder
Conversion of Audio: CVSD
Discussion & Future Work
Preamble
(Default = 2 Bytes)
Access Code
(Default = 8 Bytes)
Whitener Offset
(4 bits)
Payload Length
(12 bits)
512 Bytes payload
(512 Bytes)
CRC
(4 Bytes)
Padding
(Making the packet multiple of 512 Bytes)
Continuously variable slope delta modulation
Encoder reads input sample and compares to reference value. Will output 1/0 bit and change step size of bit accordingly.
“Compromise between simplicity, low bitrate, and quality”
Similar methods: Pulse Code Modulation (PCM), etc.
Continue testing and implementing the system.
Research ways to improve upon system performance.
1. Preamble and Access code are important in identifying the data as a packet by the receiver. Receiver will check for Preamble and Access code before processing the packet.
2. The whitener offset is important for the receiver to dewhiten the packet. It takes 4 bits in packet space.
3. Payload length records how much bytes of actual data occupies the packet. By default it is 512 bytes.
4. The CRC32(4 Bytes) will check for the correctness of the packet.
5. If we open the option “Pad for USRP”, the packet encoder will automatically pad the data to be a multiple of 512 bytes.
Design and develop model to compete in DARPA Spectrum challenge.
Relevant Experience
Experience with communication systems and digital signal processing is preferred.
ECE 264, ECE301, ECE438, and ECE440 are all used in this SDR project.
Skilled in Linux operation.