using sdr for hands-on digital communication...

USING SDR FOR HANDS-ON DIGITAL COMMUNICATION SYSTEMS ENGINEERING EDUCATION

Alexander M. Wyglinski, Di Pu, Daniel CullenWorcester Polytechnic Institute, Worcester, MA, USA

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Using SDR for Hands-On Digital Communication Systems Engineering Education

Acknowledgements

We would like to express our sincere gratitude to The Mathworks for their financial and technical support during the development of the SDR-based undergraduate digital communications course

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Presentation Overview

Motivation What is SDR? Different SDR Experimentation Tools ECE4305 “SDR Systems and Analysis” Next Steps More Information

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Motivation

Software-defined radio represents a significant paradigm shift in how data transmission is performed SDR rapidly becoming prevalent technology in

commercial, defense, and public communication sectors Although fundamental concepts in digital

communications and digital signal processing are unchanged, algorithm implementation on SDR platforms revolutionary

Interdisciplinary Computer engineering

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What is SDR?

Figure 1: The structure of a typical software defined radio communication system.

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USRP2 Platform

Figure 2: Front panel of a Universal Software Radio Peripheral, Version 2 (USRP2) SDR platform.

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GNU Radio & GRC

Figure 3: Screen capture of the GNU Radio Companion software employed in a digital communications experiment using the USRP2 as an actual wireless receiver.

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Simulink USRP2 Interface (1)

Figure 4: Properties window for the Simulink USRP2 transmitter interface block.

Figure 5: Properties window for the Simulink USRP2 receiver interface block.

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Simulink USRP2 Interface (2)

Figure 6: Sample Simulink implementation of a DBPSK transmitter employed in Laboratory 1 of the digital communications course. Notice the use of the Simulink USRP2 transmitter interface block.

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Course Format & Evaluation

WPI undergraduate course format 7-week terms Lecture: MTRF 1:00 PM – 1:50 PM Supervised Laboratory: W 2:00 PM – 4:50 PM

Evaluation No class tests of final exams Course entirely project driven (team size = 2 students) Pre-lab, lab demo, lab report, course design project

Significant amounts of contact hours between instructor/teaching assistant and students

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Linkage Between Theory & Practice

Topics covered over the duration of this course, each via a laboratory experiment: Digital Signaling and Data Transmission Error Performance of Digital Communications in Noise Receiver Structures Spectrum Sensing and Identification

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Project Driven Learning

Figure 7: Photograph of a supervised laboratory session for the proposed digital communication systems course. Note the availability of a USRP2 platform at each lab workstation.

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“Getting Started” Phase

MATLAB Refresher and Simulink Introduction USRP2 Hardware Experimental Preparations Interaction between Simulink and USRP2 Hardware

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Open-Ended Design Component

In addition to some guided experimentation and laboratory work, every laboratory assignment possessed an open-ended design component to synthesize concepts Four open-ended design components

Automatic Frequency Offset Compensator Frame Synchronization Duplex Communication Carrier sense multiple access with collision avoidance (CSMA/CA)

Students found this to be the best part of each experiment Open-ended design components chosen to prepare students

for course design project

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Course Design Project (1)

Design and implement a software-defined radio (SDR) communication system capable of performing ad hoc wireless networking Project synthesizes open ended design components from

each laboratory experiments Students progressively build up their final prototype

The prototype SDR communication system must be able to either join an existing ad hoc wireless network or establish an ad hoc wireless network of its own when no such network is present

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Progressive monitoring and evaluation of student course design project activities Design Proposal: 5% Due at end of Week 2

Mid-term Progress Review: 5% During Week 4

Final In-Class Demonstration: 10% During Week 7

Final Project Report: 10%

Total Grade: 30%

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Figure 8: Example of the final prototype for the course design project.

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Real-World Experience (1)

Figure 9: Experimental results using correlation of incoming signal (Barker sequence embedded) showing change in sampling delay.

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Real-World Experience (2)

Significant design decisions encountered during course Trade-offs between computational complexity and

system functionality performance SDR prototypes heavily dependent on computational

horsepower of available processing resources

Understanding resource constraints became apparent throughout course “358” frame size Decimation rate of 512

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Student Feedback is Essential!

Figure 10: For each laboratory, there is a online survey to collect the feedback from students.

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Feedback Summary (1)

Q1: Difficulty level of this lab. Too Easy = 0

Easy = 0

Reasonable = 9

Difficult = 18

Too Difficult = 4

Q2: Which aspects of this lab did you find interesting? Theoretical Prep = 0

MATLAB Simulations = 8

Simulink Simulations = 7

Simulink SDR Experimentation = 12

Open-Ended Design Problem = 24

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Q3: Which aspects of this lab do you think need to be improved? Theoretical Prep = 9

MATLAB Simulations = 4 Simulink Simulations = 9 Simulink SDR Experimentation = 10

Open-Ended Design Problem = 6

Q4: What modifications and/or additions would you suggest for future offerings of this lab? Better linkage between pre-labs (math!!) and experiments

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Q5: How did you find the Simulink software employed in this lab? Unsatisfactory = 0

Needs Improvement = 14

Reasonable = 8

Good = 9

Excellent = 0

Q6: How did you find the clarity and level of detail for this lab handout? Very Poor = 0

Poor = 2

Reasonble = 12

Good = 13

Excellent = 4

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Q7: What was your level of interest regarding the experiments conducted in this lab? Very Low = 0

Low = 0

Indifferent = 6

High = 21

Very High = 4

Q8: What was the level of reliability and accessibility of the lab hardware and computer workstations? Very Low = 1

Low = 8

Reasonable = 10

High = 9

Very High = 2

Q9: Any other comments? Why Linux? Better computers needed!! More SDR platforms available for the lab (14 radios for 10 lab

teams!!)

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Next-Generation USRP Hardware

Figure 12: The USRP E100 software defined radio is an embedded stand-alone system.

Figure 11: The USRP N210 software defined radio builds on the USRP2 platform, offering higher performance and increased flexibility.

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UHD Interface

Universal Hardware Driver Current Simulink interface uses User Datagram

Protocol (UDP) UDP requires packet length = 358 UHD will enable a flexible packet length

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SDR Textbook to be Published

An SDR textbook based on this course and using Simulink expected to be published in 2012

Tentatively consists of the following chapters: Signals and Systems

Random Variables and Processes

Digital Modulation and Demodulation

Receiver Structure & Waveform Synthesis

Synchronization

Equalization

Multicarrier Modulation

Spectrum Sensing Techniques

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For More Information

Professor Alexander WyglinskiDepartment of Electrical and Computer Engineering

Worcester Polytechnic InstituteAtwater Kent Laboratories, Room AK230

[email protected]

http://www.wireless.wpi.edu/

Thank You!

using sdr for hands-on digital communication...

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