Adaptive Spectrum Utilization with Software Defined · PDF fileMITRE Adaptive Spectrum Utilization with Software Defined Radios Dr. Daniel Schaefer 703-883-3664 • [email protected]

MITRE

Adaptive SpectrumUtilization with Software

Defined RadiosDr. Daniel Schaefer 703-883-3664 •

[email protected]. Steve Cox 703-883-6269 •

[email protected] MITRE Corporation

October 2, 2002

2

MITRE © 2002, The MITRE Corporation

AgendalProject Overview

- What is it?- Key components and technology used

lWhat Capabilities and Resources were developed- Spectrum and Research community

lTechnology Transfer to Real World Applications

lOngoing Research & Development Opportunities

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Approach: Adaptive System Operation

Radio Frequency (MHz)

Not all spectrum used 100% of time

See what’s free

Spectrum Picture at T1

Occupied SpectrumOccupied Spectrum

Create waveform touse free spectrum

Multiple Componentsto waveform

• form of disjoint OFDM

Transmit Waveform

Monitor channels &repeat processwhen environmentchanges

Waveform compatible with existing spectrum channelization plans and scalableto support wide range of user data rates using non-contiguous spectrum

Waveform compatible with existing spectrum channelization plans and scalableto support wide range of user data rates using non-contiguous spectrum

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Implementation Considerations•What frequencies to use ???•What’s available ?•Don’t Interfere with others

What frequency do I listen on ???

Coordination & Control

Connectivity !!

How do I connect ???

Adaptive Radio

Implementation Needs• Not interfere with primary users• Close the RF links• Coordinate frequency innetwork - no dedicated controlchannels• Connect all network users• Must share spectrum picturesamong users (Hidden Tx & Rx Solutions)

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What’s Differentl Many sharing applications use compatible waveforms to

simultaneously share spectrum- Overlays such as spread spectrum- Avoidance by proper frequency selection- simultaneous operation limits performance of all systems

l Adaptive Spectrum concept shares spectrum in both time andfrequency

- minimize interference to primary users- allow higher transmit energy using transmit burst

operation avoiding other primary users.

Time Frequency

Tx Spectrum

Tx-3Tx-1 Tx-2

Transmit Packets TransmitWaveform

packet

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Potential Advantagesl Technology provides opportunity for secondary sharing of

frequency channels with both cooperative and uncooperativeusers

l Use of smart protocols internal to radio minimizes the needfor spectrum assignment pre-planning

- Reduced spectrum related mission preplanning- Increased abilities to rapidly adapt to changing missions

l Technology and protocol implementations are hierarchical instructure

- Totally automatic with no dedicated control channels- Dedicated control channel infrastructures for more

positive regulationl for range use can employ additional scheduling

- Distributed control architectures to accommodate uniquemission needs

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Adaptive Spectrum Communication SystemRF Processing

Diplexer orT/R switch

Synthesizer

PreselectFilter

LNA Filter Gain A/D

PA Gain Filter D/AFilterTxFilter

12 - bits

14 - bits

100 MHz

100 MHz

BandbandProcessor

AGC

Transmit Power Control

Frequency

Operating Band RF ProcessingDetermines

Frequency Band ProcessesSub-channels

Analog Digital

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Adaptive Spectrum MOIEDevelopment Environment

Block RFUpconverter

Block RFDownconverter

RF Signals

D/A, digital UpconvertBoard

Quad DSP ProcessorBoard

A/D, digital DownConvert Board

Interface Board

DSP Hardware Platform

Ethernet

Software Tools• TI Code Composer• Pentek DSP tool set

Includes FPGA’s, DSPs,& Configurable ASICS

MOIE has TWO Complete Platforms

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Adaptive Spectrum Use Measurements

Reston BuildingWest Whip Antenna

HP 8591ESpectrum Analyzer

Laptop with LabViewprogram records snapshotsof spectrum use

Workstation withMATLAB analyzes spectrum use

GPIB bus

•Need high time resolution, long term data to determine adaptive systemperformance potentials ~ 1 sec with spectrum analyzer

•Must develop occupancy statistics to optimally design adaptive systemperformance requirements

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l Variation on Orthogonal Frequency Division Multiplex

- Note: Standard OFDM gives gives contiguous set of subcarriers

- MOIE NEEDS ARBITRARY SETS OF NON_CONTIGOUS Transmit Carriers

l NEW Signal Processing Implementation Approaches

- Extensive wave shaping for out-of-band rejection and non-contiguouscarrier implementation

Adaptive Waveform Generation

-250e+3

-250e+3

0

0

250e+3

250e+3

-80

-100

-120

-140

-160

Mag

in d

B

Frequency in Hz (dF = 29.3 Hz)

Conventional OFDMprofile

MOIEImplementation

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Adaptive Waveform Demonstration

SpectrumAnalyzer

Test SignalSource

Optional SingleFreq Tx

SpectrumEstimator

AdaptiveSystem

Controller

Transmitter /Modulator

ReceiveSubsystem

Tx/Rx Chassis Assy

Combined Rx spectrumenvironment

Rx Subsystem in final implementation

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Test Signal Sourcel Test Source represents

assigned user’s signalactivity within afrequency band

l Signal bandwidths aremultiples of thespectrum channelband plan

l Duration and specificchannel combinationsare selected on apseudo random basis

SignalPower(dB)

Frequency (MHz)Note: incremental changes are inkHz increments corresponding toindividual channel assignments

Activesignal

InactiveActivechannel (s)

Click to run movie

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Adaptive Waveform with Test Signal

l Adaptivewaveform andtest signalsuperimposed

l Lower power signal

is test signal

l Higher power signal

is adaptive

waveform

transmission

l Adaptation rateis reduced forviewing onspectrumanalyzer

SignalPower(dB)

Frequency (MHz)Note: incremental changes are in kHz incrementscorresponding to individual channel assignments

Adaptivewaveformsignal

Testsignal

Click to run movie

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System Demonstration Goal

l Complete End-to-End System Demonstration- Two independent radio sets- Channel and traffic simulator

Adaptive Radio Transmit/Receive

Pair 1 (DSP Chassis -1)

Adaptive Radio Transmit/Receive

Pair 2(DSP Chassis -2)

Traffic Simulator

Traffic Simulator

Channel Simulation

Rx-2

Tx-2

Tx-1

Rx-1

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Generic Application Scenario Example

Airborne Collector

Surface Sensor

Non-CooperativeInterferers

Non-CooperativeInterferers

“Occupancy”Command

CommandedFrequencies

•Monitors 256 30 KHzfrequency binssimultaneously•Commands surfacesensor to transmit on openfrequencies

MITRE

BACKUPS

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Link Negotiation & Establishment(Point-to-Point Case Illustrated Here)

l Since each node makes an independent, local measurementof the radio spectrum some coordination is required beforecommunication can occur:

- spectrum pictures shared between users- optimum picture sharing dependent on environmentNode #1’s Choice of Channels

(AOFDM approach)

PS

D (a

rb. s

cale

)

frequency (arb. scale)

Common Channel Assignments

PS

D (a

rb. s

cale

)


Node #2’s Choice of Channels(AOFDM approach)

PS

D (a

rb. s

cale

)


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Summary of Link Negotiation via anExtended RTS/CTS Process

Generate ERTS

Create Waveform

TX ERTS

Tprop

RX & DecodeCompute Link Vars.

(ECTS assumed)

Create Waveform

TX Data

Tprop

RX & DecodeProcess (N)ACK

Tprop.

RX & Decode

Compute (N)ECTS

Create Waveform

TX (N)ECTS

Tprop

RX & Decode

Compute (N)ACK(if explicit)

Create Waveform

TX (N)ACK

Node BNode A Time(not to scale)

Bounds onAdaptation Rates !• Environment•Implementation

Return

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Adaptive Spectrum Communication SystemBaseband Processing

Serial toParallelModulatorIFFTCyclic

ExtensionPulse

ShapingSerial BitStream

OFDM Transmitter

0

N-1

::

ComplexData

Channel Assignmentand

Moduation Index

14-bitD/A Complex

Upconverter

0

N-1

::

ReceiveData

Parallelto SerialDeModFFTOFDM

BaudBuffer

OFDM Receiver

ComplexData

::

0

N-1

::

ComplexDown

Converter

Correlators Valid Probe (K) channelsTiming

Frequency

ComplexNCO

ChannelSelection,Correction,

andPower

Monitor/Control

::

ChannelResevation

Transmit Power Control

Channel Assignment&

Moduation Index

A/D data

AGC

K K

FFT output

Channel Quality

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Pentek Quad Processor Board

l Four TMS320C6701 floating-point DSP’s

- operating at 167 MHz

- 4 GFLOPS performance

- SDRAM

- serial full-duplex ports

- zero-wait sync burst & dualport SRAM

- flash memory

- Data transfer rates up to 400MB/sec

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Pentek Upconverter Board

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Pentek Downconverter Board

80 MHzclock rate

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Additional Enhancements

•Transition work togovernmentprogram activities

•Enhance controlinfrastructure

• Add directionalantennas

• Enhanceconnectivity bynetwork relay

• Model operationalscenarios

Coordination & Control

Connectivity !!

Directionalantennas

NetworkData Forwarding

Documents

Adaptive Spectrum Utilization with Software Defined · PDF fileMITRE Adaptive Spectrum Utilization with Software Defined Radios Dr. Daniel Schaefer 703-883-3664 • [email protected]