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Software-Defined Radio

Chang Chung-Liang

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Content

• Why is “Soft Radio”?

• What is “Software Radio”?

• Software Radio Architecture

• Benefits of Software Radio

• Technology Challenge

• Speakeasy Project

• Conclusions

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Software-Defined Radio History

• 1970`s lateICNIA U.S.A.F

• 1983 Grenada Conflict

• 1991 Desert Storm

• 1992 Speakeasy Phase I

• 1995 Speakeasy Phase II

• 1996 MMITS

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Evolution of Wireless Standards

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Panacea for All Standards?

CDMA2000

PACS

GSM

DECT

AMPS

WCDMA

PHS

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Hardware/Software Mixture

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What is Software Radio?• A radio that is substantially defined in software

and whose physical layer behavior can be significantly altered through changes to its software

• Convergence of digital radio and software technology

• Dynamic radio equipment reconfiguration by downloadable software

• A device withMulti-band antenna(s) and RF conversionWideband A/D and D/ADigital signal processing(using software )

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Function Definition of Software Radio

•Transmitcharacterize the available transmissionprobe propagation pathconstruct an appropriate channel modulationelectronically steers its transmit beam in the

right direction select the appropriate power leveltransmit

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Function Definition of Software Radio

•Receivercharacterize the energy distribution in channel and adjacent channelrecognizes the mode of the incoming transmissionadaptively nulls interferersestimates the dynamic properties of the desired- signal multipathcoherently combines desired-signal multipathdecodes the channel modulationcorrects residual errors via forward error control (FEC) decoding to receive the signal with lowest possible BER.

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The Evolution of Software Radio Terminal Structure

Processing Channel Coding and Source Coding by Software

Processing Channel Coding, Source Coding and Baseband MODEM by Software

Processing Channel Coding, Source Coding, Baseband MODEM and IF(RF) by Software

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Software Radio Architecture

RFconversion

WidebandA/D/A

High-SpeedDSP

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Wideband Software Transmitter Architecture

BasebandProcessing

.

.

.

Channel 1

Channel 2

Channel M

Digital Channelization

SingleDAC

RF-IFupconverter

Widebandtransmit

filter

HPA

1 2 3 4 5 6 N

Frequency

Operator’s Licensed Band

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Wideband Software Receiver Architecture

BasebandProcessing

.

.

.

Channel 1

Channel 2

Channel M

Digital Channeliztion

SingleADC

RF-IFdown

converter

Widebandreceive filter

LNA

1 2 3 4 5 6 N

Frequency

Operator’s Licensed BandReceived P

SD

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RF conversion and A/D

RF-BF LNA

LO

LF-BF

A/D

Architecture 1:

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RF-BF LNA

LO

LF-BF

A/D

RF-BF LNA LF-BF

A/D

RF-BF LNA LF-BF

A/D

Architecture 2:

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RF-BF LNA RF-BF

A/D

RF-BF LNA

Architecture 3:

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Evolution of RF Transceiver Architecture

source:TI semiconductor

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High-Speed Digital Signal Processor

NumberControlledOscillator

Low-passDecimating

Filter

Digital SignalProcessor

(Demodulation)

Typical DSP Function:

I

Q

sincos

Error signal

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Phase I

RF Front End

AnalogIF

Processing

A/D

D/A

Baseband MODEM

Processing

BitstreamProcessing

(MUX, De-MUX,

FEC

Dataterminal I/F

CODEC

Control MMI

D/A

A/D

(Dedicated digital HW)

Software processing(DSP, CPU, Programmable logic)

Can introduce new functions into the same system easily

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Phase II

RF Front End

AnalogIF

Processing

A/D

D/A

Baseband MODEM

Processing

BitstreamProcessing

(MUX, De-MUX,

FEC

Dataterminal I/F

CODEC

Control MMI

D/A

A/D

(Dedicated digital HW)Software processing

(DSP, CPU, Programmable logic)

Can realize adaptive modulationand adaptive reception scheme etc.

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Phase III( Ideal Soft Radio)

WidebandRF

Front End

DigitalIF

Processing

A/D

D/A

Baseband MODEM

Processing

BitstreamProcessing

(MUX, De-MUX,

FEC

Dataterminal I/F

CODEC

Control MMI

D/A

A/D

(Dedicated digital HW)Software processing

(DSP, CPU, Programmable logic)

Will enable single terminal to adapt to multiple air interface standards Software

Reconfigure a radio by changing software

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Smart Antenna

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Smart Antenna Technology-Precursors

Sectorization

Microcell

Diversity

More antennas provide increased

ability to control power

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Smart Antenna To increase the user capacity is the key motivation of smart antenna

development.

That is to enhance the voice channel in a given coverage area

Technical requirement: an array to increase C/I

Create gain on the array in the intended direction using antenna aperture.

Minimize the effects of destructive specular multipath combining to recove

r the fading margin.

The identification and nulling of interference

Few cell sites required

More efficient use of licensed RF spectrum

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Benefits of Software Radio

• Manufacturer– One hardware platform for all markets – Portability of software between platforms.

• Operator– Upgrade of terminals– Addition of new services– Correction of software bugs in terminals

• Consumer – Connect to any network and world wide roaming– Support for new services

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Benefits of Software Radio• Flexibility: multi-band, multi-mode, multi-protocol• Adaptability: Change modulation schemes for different environment.• Upgradability: Change for new emerging standards.• Universal accessibility: GSM, CDMA, IS-136, PDC, PHS, PACS, DECT, CDPD, Mobitex, GPS...• Cost Scalability:Silicon-based DSP implementation allows aggressive cost reduction• Feasibility: Radio functions can be implemented that cannot be implemented in analog hardware, ex. FIR filter, sharp rolloff & linear phase• Stability: Radio functions implemented with DSP don’t require tuning or tweaking typically required in analog hardware

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Technology Challenges

Common baseband (BB) and RF hardware for several different systems

Higher integration level Parameterized BB modules

Configurable RF architecture

Architecture ChallengesModule level Challenges

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Technology Challenges Architecture challenges

Partitioning between analog and digitalPartitioning between DSP/RSIC, PGA etc.SW architecture: modularityDynamic processing capacity allocation between similar (and different) unitsRequired duplication of frequency-dependent parts

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Transceiver Architecture Sampling at 1st IF

Filtering easier when divided to several stagesIF filters hard to integrate

Direct ConversionNo large IF filtersSpurious leakage and DC offset

Direct SamplingHighest digitalization level Extreme Requirement for RF filtering and DSP

processing

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RF Hardware Challenges Broadband, Multi-mode, Smart antennas Broadband, Low-distortion, high efficiency HPA

Cartesian feedback Digital predistortion Feedforward Accuracy and linearization requirement extremely high for multilevel modulation, multicarrier and CDMA systems

RF/IF filtering - different bands, different bandwidths Configurable (tunable/switched) filters

Wide dynamic range AGC in IF or RF Wide operation range synthesizers and VCOs Frequency-elimination duplexer to allow both FDD and TDD operationLow power consumption and small size

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Base Band Challenges High Speed Signal Processing Most Challenging

High speed instruction processor DSP

DSP plus multiple ASIC’s one for each service

DSP plus parameterized ASIC accelerators

Reconfigurable Logic

Multiple bandwidth A/D’s

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Speakeasy Project

• Speakeasy Phase IObjects

Robust Electronic Counter-Counter Measures(ECCM)

Low Probability of Intercept(LPI) WaveformOpen architecture

Modular, Reprogrammable, ModemDevelop The Addition of New Waveform

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Speakeasy Project

• Speakeasy Phase IAdvance Designs

Fast fourier Transform(FFT)ADC High-Speed Sampling and Large Dynamic RangeA Quad-DSP ModuleRF Up- and Downconversion with instantaneous ba

ndwidthA Programmable Information Security(INFOSEC)

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Speakeasy Project

• Speakeasy Phase IResults

Four ChannelHigh-Speed Frequency-HoppedPseudorandom Spread-Spectrum WaveformsOver The Military HF, VHF, UHF Bands

UnfortunateModem SoftwareUser InterfaceWaveform Development EnviromentOnly Midband 30 to 400MHz Demonstration

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Speakeasy Project

• Speakeasy Phase IIObjects

Expand The Modem to The Entire Radio System

Open, Modular, ReprogrammableLower Life-Cycle CostsEmphasized Commercial Off-The-Shelf(COTS)Commercial Communication StandardsCoverage from 2MHz to 2GHz

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ExtRF

TX/RX

RefGen

Cellular

A/DD/A

Pre-Proc

Wave-formProc

INFO-SEC

Multi-media

Router I/OControl

Proc

GPS MMI

Speakeasy Phase II Architecture

RF FRONT END MODEM INFOSEC NETWORKINGMMI/

CONTROL

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Speakeasy Phase II

Air Force Tactical Air Control Parties

HAVE QUICK(UHF)Voice and data

SINCGARS(VHF)

SDR

LMR

California Arizona

wire

HAVE QUICK(UHF)Voice and data

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Conclusion

• Software Radio concepts are being rapidly accepted for communication system

• There are still many bottlenecks having to be overcome to realize Software Radio, such as RF technology, DSP and Protocol

• Software Radio provides a very wide area for the playing of researchers.manufacturers, service providers in the future