New Technologies - Software Radios
An Easy Definition
A software-defined radio (SDR) system is a radio communication
system which uses software for the modulation and
demodulation of radio signals. (Wikipedia)
The Industry Definition
A software radio is a wireless communications device
in which all of the signal processing is implemented in
software. By simply downloading a new program, a
software radio is able to interoperate with different
wireless protocols, incorporate new services, and
upgrade to new standards.
(An Introduction to Software Radio, Vanu Inc.)
Technical Definition.
Software defined radios are elements of a wireless
network whose operational modes and parameters can
be changed or augmented, post-manufacturing, via
software. Software defined radios are a collection of
hardware and software technologies that enable
reconfigurable system architectures for wireless
networks and user terminals.
(Software Defined Radio Forum, “Overview and Definition of Software
Download for RF Reconfiguration”, Aug 2002,www.sdfforum.org)
Regulatory Definition
A radio that includes a transmitter in which the
operating parameters of frequency range, modulation
type or maximum output power (either radiated or
conducted) can be altered by making a change in
software without making any changes to hardware
components that effect the radio frequency
emissions.
(US, Federal Communications Commission, First
Report And Order, “Authorization and Use of
Software Defined Radios”, Sep 2001, www.fcc.gov )
Keywords
• Modulation, Demodulation – Signal Processing in software.
• Interoperability between different wireless protocols,
different frequencies.
• Upgradeable and reconfigurable via software
What are we looking for:
Flexible
Software
Architecture
Generic
Hardware
Interoperable
Upgradeable
Multiple
Protocols
Reconfigurable
Multiple
Frequencies
Wireless Devices in Use
•
Cell Phone – GSM,
CDMA etc.
•
GPS navigation
system
•
Cordless Phone
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Car Phones
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Wireless PDA
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Ham radios
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Wireless Email
device
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FM Radios
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Walkie-Talkies
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Pager
Need for Software Radios
Scenario 1:
Communication required between personnel from different departments
of Public Safety and Emergency Services at a disaster recovery area.
Police – use 800 MHz 2-way analog radio
Firefighters – use Digital VHF band radios
Problem: Incompatibility between communication devices
Solution:
Bring in thousands of new radio devices and distribute to all
departments?
Better Solution:
Software patch – download a patch and reconfigure all radios to
communicate with each other.
Need for Software Radios
Scenario 2:
Commercial wireless network standards continuously evolving from
2G to 2.5G/3G and then further onto 4G. Significant difference in
link-layer protocol standards. Cellular Service Provider – needs to
upgrade to new technology.
Problem:
Customer base using 2G. As need for data services arises among
customers – provider needs to upgrade to 2.5 or 3 G.
Solution :
Providers -Spend millions and billions to replace expensive equipment.
Subscribers – buy new handsets.
Better solution :
Software upgrade – software changed to upgrade from old to new
technology.
Need for Software Radios
Scenario 3:
A day in the life of an ordinary individual
– cell phone, cordless phone, pager, internet enabled PDA, Navigation
System in car, TV Remote, Music System remote, FM Radio, Garage
Door opener.
So many wireless devices !!!!!
A single Software radio device could
• Act as a cell phone when he is traveling.
• Switch to performing as a cordless phone from his office desk.
• Accept GPS (global positioning system) signals in his car.
• Act as a wireless Internet device to download e-mail.
• Act as a garage-door opener when the user gets home.
Brief History
•
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SDR technology was first demonstrated in a Department of Defense
project in 1995.
SpeakEasy Phase I
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2 MHz to 2 GHz
Ground force radios (frequency-agile VHF, FM, and SINCGARS)
Air Force radios (VHF AM),
Naval Radios (VHF AM and HF SSB teleprinters)
Satellites (microwave QAM).
SpeakEasy Phase II
–
–
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4 MHz to 400 MHz range
more quickly reconfigurable architecture (i.e. several conversations at once)
cross-channel connectivity (i.e "bridge" different radio protocols).
Air ForceTactical Air Control Party (TACP) Personnel, using a VHF/AM Radio
communicated with an F-16 operating on a UHF Radio.
Brief History … contd.
• Joint Tactical Radio Systems - 1998
– based on an internationally endorsed open Software Communications
Architecture (SCA).
– CORBA on POSIX operating systems to coordinate various software
modules.
– First known use of FPGAs
• Amateur Software Radio
– GNU Radio - free software toolkit for learning about, building, and deploying
Software Defined Radios. (1998)
– The goal is to give ordinary software people the ability to 'hack' the
electromagnetic spectrum - to understand the radio spectrum and think of
clever ways to use it.
Quick Recap - Radio
Source - Wikipedia
The Superheterodyne Receiver
Source - Wikipedia
Software Radio
Change from Hardware to
Software Radio
•
Move analog/digital (A/D) conversion as close to the receiving antenna
as possible.
•
Substitute software for hardware processing
•
Transition from dedicated to general-purpose hardware – from ASICs
to FPGAs and DSPs and even general purpose processors.
Software functions
•
•
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Signal generation
Waveform modulation and demodulation
Baseband and digital signal processing functions
Use of intermediate frequencies (such as for frequency hopping)
Use of multiple link-layer protocols
Security and encryption
Dynamic selection of parameters.
Components
Software collected in libraries:
• Signal processing modules:
– Basic functions such as coding and modulation.
• Real-time control modules:
– Supervise the processing flow, perform the scheduling of the signal
processing and hardware interface modules.
• Hardware interface modules:
– Manage the data input/output flow from and toward the IF stage.
Difficulties
•
Antennas and LNAs serving bandwidths ranging from 100s of MHz to
10s of GHz
•
Jitters in A/D conversion at RF
Software Architecture of SDR
Software Download
SMART CARD LOADING
(SIM)
• Advantages
– Error free, faster, no
overhead on network
• Disadvantages
– Memory and processing
power
– Sale points of smart cards
AIR INTERFACE
DOWNLOAD
• Advantages
– Easy for user.
– Better managed
• Disadvantages
– Network overhead –
dedicated channel,
defined download
procedure.
– Error control
– Speed
– Security
Software Radios in Wireless
Networking
•
Mobile computing device with wide range of connectivity options.
–
–
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Cellular
Wireless LAN
Satellite systems
• Spectrum Ware software radio system
–
All physical layer functions implemented in software.
–
Flexible easy to use software radio research platform/ testbed.
•
Contribution
•
Components
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–
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Signal acquisition
I/O subsystem – A/D/A converter to memory and vice versa
Programming environment – Signal Processing Environment for Continuous Real-Time
Applications (SPECTRA)
Radio Specification model – Next slide
Data link - Link Framing, MAC, Coding, Modulation,
Software Radio Layering Model
Virtual Radios
•
Does all the Digital Signal Processing in off-the-shelf workstation (e.g
PC).
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•
Experimentation
Integration with other applications.
Rapid deployment
Current work stations have enough processing power
Implemented as
– A software cellular receiver
– A software network interface “card”.
Flavours of Software Radio
•
Tier 1 - Software-Controlled Radios (SCR).
– multiple transceivers
– software control functions activate transceiver as required
– e.g. dual mode cell phones – support CDMA and GSM
•
Tier 2 – Reconfigurable Software Defined Radios (SDR)
– what is available now
– software controls modulation techniques, wideband and narrowband
operation, security, and the waveform requirements.
– Software starts from IF processing
•
Tier 3 – Ideal Software Radio
– The future
– A/D conversion at antenna
– Software starts from RF onwards
•
Tier 4 – Ultimate Software Radio
– Hypothetical – only for comparisons.
Advantages
•
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Reconfigurability
Interoperability
Low cost solutions – software cheaper than hardware, mass production
Time to market
Easy to fix bug – once shipped.
Quick evolution of end user equipment, communication and network
infrastructures.
Easier upgrade for evolving link-layer communication protocol
standards.
Increase product lifetime – reduce obsolescence.
Future-proof!!
Issues
•
Security – of downloading an upgrade.
•
Fast, easy to perform, error-free download despite mobility of end user
terminals
•
Higher processing power required.
•
Battery/power consumption – with all the increased processing load.
•
Licensing issues with FCC
Some bits of info…..
• Industry support for SDR on the network/base station side.
– Cost and battery power of handset are limitations.
• FCC introduced special licensing process for software radio –
“permissive change” – Sep 2004
• FCC approved the Vanu Software Radio GSM Base Station
– Supports multiple cellular technologies and frequencies at the same
time.
– Can be modified in the future without any hardware changes.
– Runs on an off-the–shelf server and standard OS.
Cognitive Radios On the Horizon
• “Cognitive" - being aware of and making judgments about
something.
• A cognitive radio will be able to sense its surroundings and the
presence of other signals.
• Use that information, and adapt, without user intervention, to
its user’s communication needs.
• Sense unused range of the unlicensed spectrum and switch to a
frequency that will give better performance.
• Select the correct radio interface, channel, data rate, etc., to
provide maximum data throughput to the user's application
Discussion
What could be the possible impact on higher layers of networking?
• Adverbs and adjectives.
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Links of interest
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SDR Forum -http://www.sdrforum.org/faq.html
SDR resources page – http://www-sop.inria.fr/planete/SoftwareRadio/
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GNU software radio project - http://www.gnu.org/software/gnuradio/
SDRadio - http://www.sdradio.org/
Vanu Inc. - http://vanu.com/
Thank You.