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Software Defined Radio Testbed
Team may11-18Members: Alex Dolan, Mohammad Khan, Ahmet Unsal
Adviser: Dr. Aditya Ramamoorthy
Presentation Overview Background Information
Requirements Deliverables
System Design
Implementation
Testing & Analysis/ Error Calculations
Image File Transfer
Conclusion
Background Information
Problem• MATLAB Simulink is a
relatively new platform for Software Defined Radio.
• Very little work has been done to build a communication system of SDR using this platform.
Solution• Build a Digital
Communication System using MATLAB Simulink and USRP2.
• Implement the Physical Layer in MATLAB Simulink environment.
• Utilize the Universal Software Radio Peripheral-2 (USRP2) to send and receive the physical packet over the air.
• Test the communication System using data packets.
Functional Requirements
Use of Universal Software Radio Peripheral 2 (USRP2) & MATLAB
Simulink
Non Coherent schemes like FSK, DBPSK modulation schemes must
be implemented
Build point to point digital communication system
Maximum bandwidth utilization
Transmission rate of 100-125 kbits/sec
Test limitations of MATLAB & Simulink as a platform for SDR
System must be reusable for academic purposes and further
research
Resource Requirements• USRP2
Daughter boards (RFX2400, RFX400 etc.) (80 MHz-2.9 GHz)Connection Cables (Ethernet cable)Data transmission and receptionA/D and D/A conversionUp Conversion and Down Conversion
• ComputersMATLAB/ Simulink
Data generation, digital modulation, demodulation, filtering, error control, synchronization etc. to make data usable.
Very High speed computers needed to process data (e.g. Intel i7) Windows Operating System
Deliverables • Functional Digital Communication System
Using USRP2 and MATLAB / SimulinkSimulink will be used to generate and process signals on
transmitter side.USRP2s on both sides will transmit and receive signalsSimulink on the receiver side will process received signalsData packets should be transferrable using the system
• Complete documentationReports (Weekly + Final)Commented Models & CodeBuild instructionsRepository Access
Schedule
System Design Process
Build & test models in Simulink
environment
Simulate with/without white
Gaussian noise
Use simulation results to create
models for over the air
transmission
Test models and document
results
System Decomposition• CPU1 generates data from MATLAB & passes to USRP2
• USRP2 on the transmitter side transmits the data over the air
• USRP2 on the receiver side receives the data & passes to MATLAB on CPU2
• MATLAB receives the data from USRP2 & analyzes it to make it usableCPU1 / MATLAB
USRP2 / Data TX
USRP2 / Data RX
CPU2 / MATLAB
System Decomposition• Physical layer:
• MATLAB Simulink• FSK, DBPSK modulation / demodulation, signal processing• Synchronization and packetization
• USRP-2• Ethernet interface with 100 MSamples/s, A/D & D/A conversion
• Testing and Logging:• Tools used to test the system• Tracks progress and successTesting & Logging
PHY
RF Daughterboard (USRP2)
Rx / Tx
Implementation
Built models of physical layers inside MATLAB environment
Focused on two schemes:
DBPSK (Differential Binary Phase Shift Keying)
FSK (Frequency Shift Keying)
Tested models with/without noise induced environment
Next phase: Built over the air models using USRP2s
MATLAB SimulationMATLAB models of DBPSK & FSKSimulated with and without noise
Fig: A preliminary binary FSK model for MATLAB
Over the Air Physical LayerDesign FSK & DBPSK models, fit for over the air transmissionSampling time, center frequency becomes importantSampling time has to be consistent throughout the whole
system
Over the Air Physical Layer
More signal processing needed to be added
Timing recovery, filters, etc.
There was no synchronization between USRP2s, so
recovery of data had to be designed
Testing & Analysis• Tested primarily in three phases.
Single bit Transmission ReceptionKnown Binary Sequence Transmission Reception Image File Transfer
• Single Bit Transmission Continuously transmitting one bit over the air Looking at the scope on the receiver end to verify
Testing & Analysis • Known Binary sequence transmission
Encoded data to add headers and footers, creating a frame ready for transmission
Receiver side, sent the data to MATLAB workspace for analysis Created a script file to analyze the workspace data using
autocorrelation techniques
Fig: FSK transmitter with known binary sequence
Error Rate Calculation • Transmitted 128-bit sequence
(including header, data, footer) & calculated bit errors
• Exported data from Simulink model to Workspace and processed the data from there
• The xcorr function was used to determine the location of frames, headers and footers
• Plotted this function to observe trends Fig: Plot of xcorr function on received data
Testing & Analysis
• Tested both systems for continuous single bit & known
sequence
• FSK showed better performance
• DBPSK had errors not suitable for data transmission
• Proceeded to image file transfer for FSK
Image File Transfer
Transmitter Side• Image files needed to be encoded to packets for use on the
system• Encoded the image files to become a binary matrix, utilizing a
colormap that is known on both sides• A typical frame would include:
Header CRC (Cycling Redundancy Check) bitsPosition indicating bits Payload dataFooter
• Once encoded, the image file is ready for transmission
Image File Transfer
Receiver Architecture• Received data is sent to workspace
• Each frame is defined, and analyzed
• CRC bits are used to check for accuracy
If CRC check passes, the payload data of the frame is placed
where the position indicating bits indicate
If CRC check fails, the program moves on to the next frame
• When all the frames pass CRC checks, and are assembled, image
transfer is complete
Image File Transfer
• Started with small binary images
• Finally worked with .gif format
• Each pixel is composed of 8 bits, then converted to an integrer.
• Successfully transferred small image
Conclusion
Lessons Learned How to manage our time
requirements How to manage focus in
a research based project.
Gained experience working on an application of our area of study.
Results Achieved Discovered capabilities
and shortcomings of a point to point data communication system in Simulink.
Application Image file transfer
successful Potential for more
applications
Thank you for your patience.
Questions?