Software Defined Radio and Cognitive Radio:

Software Defined Radio and Cognitive Radio: Implementations & Test-Beds Alexander M. Wyglinski,

Ph.D.

Associate Professor of Electrical and Computer Engineering IEEE Vehicular Technology Society Distinguished Lecturer

Presentation Outline • Introduction • The Information Age • Wireless Innovation Laboratory • Spectrally Agile Waveforms • SDR and CubeSats • Concluding Remarks • More Information

Worcester Polytechnic Institute

Introduction

Definition: Cognitive radio A cognitive radio, radio is asadefined kind ofby twothe way radio that researchers at Virginia automatically Polytechnic changes its transmission Institute and State or University, reception is "a parameters, software defined in such radio a way with that a the entire wireless cognitive enginecommunication brain". network - of which it is a node communicates efficiently, while avoiding interference with licensed or unlicensed users. http://en.wikipedia.org/wiki/Cognitive_radio


So what is Cognitive Radio?

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? Worcester Polytechnic Institute

Cognitive radio means …

Opportunistic

Adaptation

Environmental Awareness

Agile Flexible

Cooperative

Spectrally Efficient

Optimization

Intelligence

Learning Autonomous

Dynamic Spectrum Access Worcester Polytechnic Institute

The Information Age

Several Key Innovators

Marconi

Shannon

Wireless Digital Transmission Communications

Bardeen

Brittain

Shockley

Transistors Source: Wikipedia


Evolution of Wireless Systems


“Cognitive Radio Communications and Networks: Principles and Practice” By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)

Progress of Technology


Quick Survey How many of you: ─Own a cell phone? ─Use a laptop with WiFi? ─Use an ATM? ─Fly on a plane? ─Traveled in a car?

11


Increasing Demand 262 Million Subscribers!

Source: CTIA


Increasing Demand 1.1 Trillion Minutes!

Source: CTIA


Source: NTIA

US Spectrum Scarcity!


Source: Roke Manor

Across the Pond in the UK!


Source: Industry Canada

Oh Canada!


Apparent Scarcity • Measurement studies have shown that in both the time and frequency domains that spectrum is underutilized Spectrum Holes

Spectrum measurement across the 900 kHz –1 GHz band (Lawrence, KS, USA)


Potential Solution • Dynamic Spectrum Access (DSA) Fill with secondary users

Spectrum measurement across the 900 kHz –1 GHz band (Lawrence, KS, USA)


Enabling Transmission Agility

PROGRAMMABLE

FIXED


Sample SDR Platforms

Universal Software Radio Peripheral 2 (USRP2) Unit.

COSMIAC FPGA board currently being retrofitted for better memory access, to add USB functionality and to make the board SPA compatible.


Mitola & Cognitive Radio

Mitola


Cognitive Radio: A Black Box Model What you want What you see

What you can do

What you can tune


Flexible RF Front Ends Needed

Can I do this with just one RF front end? 88 MHz

5.8 GHz


RF MEMS Can Help! • A single RF front end would not normally be able to support a very wide frequency range of operations

─ Radio Frequency Micro-ElectroMechanical Systems (RF MEMS) can be used to “tune” the RF front end to the corresponding frequency

Capacitor Inductor

Close-Up of MEMS Tunable LC Filter.

Source: Wireless ICs and MEMS Laboratory, McGill University


RF MEMS • RF MEMS can be used to implement: ─ Antennas (e.g., fractal antennas) ─ Filters (e.g., tunable RF bandpass filters) ─ Oscillators

• Real-time operations very difficult to support ─ Time needed to physically change configurations on the order of seconds  Compared to the rate at which data is transmitted, this is considered to be ages!


Wireless Innovation Laboratory

Who is Alex Wyglinski? • Associate Professor, WPI ECE • Director, Wireless Innovation Laboratory ─ 8 Ph.D. students, 5 M.S. students

• Distinguished Lecturer, IEEE Vehicular Technology Society (2012-2014) • Technical Editor, IEEE Communications Magazine • Editor, IEEE Transactions on Wireless Communications • General Co-Chair, IEEE VTC 2015-Fall (Boston, MA, USA) • ~35 journal publications, ~75 conference papers, 9 book chapters, 2 books • Served or is serving as PI/co-PI for several federal and industrial grants


Where is WPI?

~60 km


What is WPI? • Founded in 1865; 3rd oldest US polytechnic ─ Model for most engineering schools in US ─ Nationally ranked as 64th Best College in U.S. (2011 US News Rankings)

─ Voted one of the Top 10 Best U.S. Colleges for “Young Einsteins” by Unigo

(together with MIT, CalTech, Princeton, Dartmouth, Stanford, Johns Hopkins, Case Western, Georgia Tech, and Cornell)

• 3800 students & 220 faculty ─ ECE: 318 undegraduate, 250 graduate, 21 faculty


What is “Lehr und Kunst”? • Project-based education at the core of “The WPI Plan” • Many ECE students conduct their senior capstone design projects (called “Major Qualifying Projects” or MQPs) at off-campus locations: ─ ─ ─ ─ ─ ─

MIT Lincoln Laboratory MITRE (Bedford Campus) General Dynamics (Groton Campus) Silicon Valley Wall Street Etc … Worcester Polytechnic Institute

Wireless Innovation Laboratory •

2 USRP (Version 1) software-defined radio platforms

•

14 USRP (Version 2) software-defined radio platforms

•

15 USRP (Version N210) software-defined radio platforms

•

1 Agilent CSA N1996A 0-3 GHz spectrum analyzer (with battery packs)

•

1 Mini-discone antenna (100 – 1600 MHz, with 3’ tripod)

•

1 WG horn antenna (0.7 – 18.0 GHz, with tripod)

•

1 Xilinx Virtex 5 HW-V5-ML506-UNI-G Prototyping Board

•

25 complete licenses of MATLAB and Simulink with associated toolboxes and blocksets

•

2 OPNET licenses


WI Lab External Sponsorship


SDR Activities at WPI

Photograph of a supervised laboratory session for ECE4305 “Software-Defined Radio Systems and Analysis” during February 2011.

Screen capture of a functioning ECE4305 course design project in MATLAB showing four SDR units forming an ad hoc wireless network.

http://www.sdr.wpi.edu/ Worcester Polytechnic Institute

Spectrally Agile Waveforms

Opportunistic Spectrum Access • Opportunistic spectrum access (OSA) is a significant paradigm shift in the way wireless spectrum is accessed ─ Instead of PUs possessing exclusive access to licensed spectrum, SUs can temporarily borrow unoccupied frequency bands ─ SUs must respect the incumbent rights of the PUs with respect to their licensed spectrum

• OSA enables greater spectral efficiency and facilitates greater user and bandwidth capacity


OSA Motivation • The utilization efficiency of “prime” wireless spectrum has been shown to be poor

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A snapshot of PSD from 88 MHz to 2686 MHz measured on July 11th 2008 in Worcester, MA (N42o16.36602, W71o48.46548) A. M. Wyglinski, M. Nekovee, Y. T. Hou (Eds.). “Cognitive Radio Communications and Networks: Principles and Practice.” (Chapter 6) Academic Press, December 2009.


Several dimensions of the electrospace include space, time, and frequency, although there do exist others such as code, polarization, and directional.


Several Possible Approaches • Secondary transmission in licensed spectrum can be classified into three categories: – Cooperative Approach • Primary and secondary users coordinate with each other regarding spectrum usage

– Underlay Approach • Secondary signals transmitted at very low power spectral density; undetected by primary users • e.g., ultra wideband (UWB)

– Overlay Systems • Secondary signals fill in the spectrum unoccupied by primary users Worcester Polytechnic Institute

“Cognitive Radio Communications and Networks: Principles and Practice” By A. M. Wyglinski, M. Nekovee, Y. T. Hou (Elsevier, December 2009)

Leveraging the Electrospace

Spectral Opportunities!

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Underlay Solution underlay transmissions



Overlay Solution overlay transmissions



Multicarrier-Based OSA • Multicarrier modulation is a variant of the conventional frequency division multiplexing (FDM) ─ Orthogonal Frequency Division Multiplexing (OFDM) an efficient form of multicarrier modulation

• In order to utilize unused portions of licensed spectrum, several subcarriers can be turned OFF to avoid interfering with the primary signals • Each subcarrier experiences flat-fading and hence high data-rates are possible if several unused bands of secondary spectrum are available


Multicarrier Overlay Solution multicarrier overlay transmissions



Spectral Agility In Action! PU signal!

As seen in this closeup of the multicarrier overlay transmission, subcarriers located within the vicinity of a PU can be deactivated in order to avoid interference with that signal.

multicarrier overlay SU transmission wraps around PU


H. Bogucka, A. M. Wyglinski, S. Pagadarai, A. Kliks. “Spectrally Agile Multicarrier Waveforms for Opportunistic Wireless Access”. IEEE Communications Magazine, June 2011.

Spectrally Agile Multicarrier


Major Issue: Out-of-band Emission • Out-of-band (OOB) interference problem with OFDM-based cognitive radios • Power spectral density of the transmit signal over one subcarrier:

• Mean relative interference to a neighboring legacy system subband:


Sinc Pulses Have High OOB Levels! 5 Normalized power spectrum (in dB) Normalized power in dBm Normalized amplitude

0

1 Other

-5

-10

0.5

Other

Transmissions

Transmissions OOB

-15 0 -20

−10

−5

0

5

-25

Other

OFDM carrier spacing Transmissions

10 15 Subcarrier index

Interference power to the first adjacent sub-band 20

25

30

-30 0 Other

Other Transmissions

-35−20 Transmissions

Other Transmissions

-40 −40

-45 −60

-50 -6

OOB −10

-4 −5

-2 0

0 101 215 5 Subcarrier Subcarrier Index index

20 4

25

6 30


Several Solutions • Cancellation Carriers ─ Non-data bearing subcarriers whose phase and amplitude values cancel OOB

• Modulated Filter Banks ─ Attenuates OOB in stopband region

• Combine cancellation carriers (CCs) with modulated filter banks (MFBs) to attenuate OOB emissions


Cancellation Carriers


Filtering with CCs Raised−Cosine Filter 1

Normalized Amplitude

0.8

0.6 CC1

CC2

0.4

0.2

0

−0.2 −4

−2

0

2

4 6 8 Subcarrier Index

10

12

14

16


Hardware Experimentation

Photograph of a spectrally agile wireless transceiver test-bed at Poznan University of Technology, Poznan, Poland.

Photograph of a spectrally agile wireless transceiver test-bed at Worcester Polytechnic Institute, Worcester, MA, USA.


P. Kryszkiewicz, H. Bogucka, A. M. Wyglinski. "Protection of Primary Users in Dynamically Varying Radio Environment: Practical Solutions and Challenges." Accepted for publication in the EURASIP Journal on Wireless Communications and Networking December 23 2011

Spectrally Agile Waveform Results


Performance with notches of different size

53


Performance with different number of notches

54


Digital Pre-Distortion Results 20

1 Nonlinear PA model Linearized PA model

0.8 0.7 0.6 0.5 0.4 0.3 0.2

−20 −40 −60 −80 −100 −120 −140

0.1 0

1st ILA iteration 2nd ILA iteration 3rd ILA iteration

0

Power Spectral Density [dB]

Normalized Output Magnitude

0.9

0

0.05

0.1

0.15

0.2

0.25

PA Input Magnitude

AM/AM

−160 −1

−0.5

0

0.5

Normalized Frequency (x π rad/sample)

1

Output PSD of PA model

Zhu Fu, Lauri Anttila, Mikko Valkama and Alexander M. WyglinskiA. M. Wyglinski. "Digital Pre-distortion of Power Amplifier Impairments in Spectrally Agile Transmissions." Proceedings of the 2012 IEEE Sarnoff Symposium, Newark, NJ, USA, May 2012.

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CubeSat SDR

56

Motivation • Challenges associated with timevarying satellite communication links • Leverage existing technologies in order to enhance transmission quality via an efficient, low-cost approach ─Software-defined radio (SDR) employed to achieve highly responsive space platforms


Proposed Solution • CubeSat-based SDR platform prototype developed ─ Custom designed FPGA board possessing Spartan 3A XC3S1400A device incorporated into CubeSat platform ─ Contains customized variant of commercially available Universal Software Radio Peripheral (USRP) SDR platform

• Several satellite communication baseband modules implemented for FPGA ─ Migrated to COSMIAC Small Form Factor CubeSat FPGA Board (CCFB) possessing customized USRP SDR


Project Vision • Creation of adaptive satellite communications link based on a combination of reconfigurable FPGA-based software-defined radio (SDR) platforms and cognitive radio concept ─ Enables “data throttling” for maximizing data throughput ─ CubeSat SDR platforms aware of environmental conditions


COSMIAC FPGA

1”

COSMIAC Xilinx Spartan 3A FPGA Worcester Polytechnic Institute

COSMIAC CubeSat Modules Power Board

Optical Sensor Board

FPGA Board

COSMIAC CubeSat FPGA Board with Sensor and Power Daughtercards (no RF daughtercards are present in this photo) Worcester Polytechnic Institute

FPGA-Based Embedded Controller Board 4 Gb NAND Flash Memory

2 Gb DDR2 SDRAM Memory

LEDs & Switch

Ethernet LAN8700

RS232 Level Shift

USB2 USB3300

Spartan 3A FPGA

Connectors to Daughter Card

AT90 (SPA-U) Microcontroller

1 Mb NOR Flash Config Memory JTAG

SPA-1 Header SPA-U Connector


RS232 UART (AT90)

RS232 UART

DDR2 Memory Controller

Ethernet Controller

SPI Controller RF Daughte Card

MicroBlaze Flash Memory Controller

I2C Controller

USB2 Controller

USB Data

Modified USRP


Laboratory Testing

Current SatCom laboratory setup at COSMIAC


Concluding Remarks

These are interesting times! • Numerous advances in cognitive radio, dynamic spectrum access, and software-defined radio have recently occurred ─ Secondary access of digital TV spectrum ─ Ratification of IEEE 802.22, IEEE 802.11af standards

• Today’s wireless landscape is quickly changing due to new capabilities of wireless transceiver devices ─ Largely due to smaller, faster processing devices resulting from applications such as smart phones


Still room for improvement • There still exists a substantial amount of research that is needed to make future wireless devices such as cognitive radio more reliable ─ Ensuring minimal interference to other wireless transmissions ─ Enabling real-time decision-making and transmission operations ─ Making RF spectrum access more reliable for everyone involved


More Information

Contact Info Professor Alexander Wyglinski Department of Electrical and Computer Engineering Worcester Polytechnic Institute Atwater Kent Laboratories, Room AK230 508-831-5061

[email protected] http://www.wireless.wpi.edu/


Cognitive Radio Textbook  Available since December 2009 (Academic Press)  20 chapters  End-of-chapter problems (with solutions guide)  Presentation slides for most chapters  Covers physical and network layers, in addition to current platforms and standards


New SDR Textbook • January 2013 Publications Date (Artech House Publishers) • 9 comprehensive chapters ─ Fundamentals in signals & systems, probability, and digital communications ─ “Hands on” approach to learning digital communication concepts using SDR and Simulink ─ End-of-chapter problems ─ Corresponding course lecture slides

http://www.sdr.wpi.edu/ Worcester Polytechnic Institute