Software-Defined Radio
Chang Chung-Liang
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Content
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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
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1970`s late ICNIA
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?
PHS
PACS
WCDMA
GSM
DECT
AMPS
CDMA2000
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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 with
 Multi-band antenna(s) and RF conversion
 Wideband A/D and D/A
 Digital signal processing(using software )
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Function Definition of Software
Radio
•Transmit
characterize the available transmission
probe propagation path
construct an appropriate channel modulation
electronically steers its transmit beam in the
right direction
select the appropriate power level
transmit
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Function Definition of Software
Radio
•Receiver
characterize the energy distribution in channel
and adjacent channel
recognizes the mode of the incoming transmission
adaptively nulls interferers
estimates the dynamic properties of the desiredsignal multipath
coherently combines desired-signal multipath
decodes the channel modulation
corrects 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, Source Coding,
Baseband MODEM and IF(RF) by Software
Processing Channel Coding, Source Coding and
Baseband MODEM by Software
Processing Channel Coding and Source Coding
by Software
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Software Radio Architecture
RF
conversion
Wideband
A/D/A
High-Speed
DSP
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Wideband Software
Transmitter Architecture
Channel 1
Channel 2
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.
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Baseband
Processing
Digital
Channelization
Single
DAC
RF-IF
upconverter
Wideband
transmit
filter
HPA
Channel M
Operator’s Licensed Band
1 2 3 4
5
6
N
Frequency
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Wideband Software
Receiver Architecture
Channel 1
Channel 2
.
.
.
Baseband
Processing
Digital
Channeliztion
Single
ADC
Wideband
receive
filter
RF-IF
down
converter
LNA
Channel M
Received PSD
Operator’s Licensed Band
1 2 3 4
5
6
N
Frequency
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RF conversion and A/D
Architecture 1:
LO
A/D
RF-BF LNA
LF-BF
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Architecture 2:
LO
A/D
RF-BF LNA
LF-BF
A/D
RF-BF LNA
LF-BF
A/D
RF-BF LNA
LF-BF
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Architecture 3:
A/D
RF-BF LNA
RF-BF LNA
RF-BF
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Evolution of RF Transceiver
Architecture
source:TI semiconductor
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High-Speed Digital Signal
Processor
Typical DSP Function:
I
Q
cos
sin
Number
Controlled
Oscillator
Low-pass
Decimating
Filter
Digital Signal
Processor
(Demodulation)
Error signal
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Phase I
(Dedicated digital HW)
RF
Front
End
Analog
IF
Processing
A/D
D/A
Baseband
MODEM
Processing
Can introduce new functions
into the same system easily
Software processing
(DSP, CPU, Programmable logic)
Data
Bitstream
terminal
I/F
Processing
(MUX,
De-MUX,
CODEC
FEC
D/A
A/D
MMI
Control
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Phase II
(Dedicated digital HW)
RF
Front
End
Analog
IF
Processing
A/D
D/A
Software processing
(DSP, CPU, Programmable logic)
Baseband
MODEM
Processing
Bitstream
Processing
(MUX,
De-MUX,
FEC
Data
terminal I/F
D/A
CODEC
A/D
Control
MMI
Can realize adaptive modulation
and adaptive reception scheme etc.
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Phase III( Ideal Soft Radio)
Software processing
(DSP, CPU, Programmable logic)
(Dedicated digital HW)
Wideband
RF
Front
End
A/D
D/A
Digital
IF
Processing
Baseband
MODEM
Processing
Data
Bitstream
Processing terminal I/F
(MUX,
De-MUX, CODEC
FEC
Control
Will enable single terminal to adapt to
multiple air interface standards
D/A
A/D
MMI
Software
Reconfigure a radio by changing software
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Smart Antenna
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Smart Antenna TechnologyPrecursors
 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
recover 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 Challenges
Module level Challenges
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Technology Challenges
 Architecture challenges
Partitioning between analog and digital
Partitioning between DSP/RSIC, PGA etc.
SW architecture: modularity
Dynamic processing capacity allocation between similar
 (and different) units
Required duplication of frequency-dependent parts
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Transceiver Architecture
 Sampling at 1st IF
Filtering easier when divided to several stages
IF filters hard to integrate
 Direct Conversion
No large IF filters
Spurious leakage and DC offset
 Direct Sampling
Highest 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 operation
Low 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 I
Objects
Robust Electronic Counter-Counter
Measures(ECCM)
Low Probability of Intercept(LPI) Waveform
Open architecture
Modular, Reprogrammable, Modem
Develop The Addition of New Waveform
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Speakeasy Project
• Speakeasy Phase I
Advance Designs
Fast fourier Transform(FFT)
ADC
High-Speed Sampling and Large Dynamic Range
A Quad-DSP Module
RF Up- and Downconversion with instantaneous
bandwidth
A Programmable Information Security(INFOSEC)
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Speakeasy Project
• Speakeasy Phase I
 Results
Four Channel
High-Speed Frequency-Hopped
Pseudorandom Spread-Spectrum Waveforms
Over The Military HF, VHF, UHF Bands
 Unfortunate
Modem Software
User Interface
Waveform Development Enviroment
Only Midband 30 to 400MHz Demonstration
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Speakeasy Project
• Speakeasy Phase II
Objects
Expand The Modem to The Entire Radio System
Open, Modular, Reprogrammable
Lower Life-Cycle Costs
Emphasized Commercial Off-The-Shelf(COTS)
Commercial Communication Standards
Coverage from 2MHz to 2GHz
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Speakeasy Phase II Architecture
RF FRONT END
Ext
RF
Ref
Gen
TX/
RX
Cellular
MODEM
A/D
D/A
PreProc
INFOSEC
Wave
-form
Proc
INFOSEC
MMI/
CONTROL
NETWORKING
Multi- Router
media
Control
Proc
I/O
GPS
MMI
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Speakeasy Phase II
HAVE QUICK(UHF)
Voice and data
HAVE QUICK(UHF)
Voice and data
SDR
wire
Air Force Tactical Air Control Parties
California
LMR
SINCGARS(VHF)
Arizona
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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
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