3. LITERATURE SURVEY
 An IEEE 802.11 MAC Software Defined Radio
implementation for experimental wireless
communications and networking research.
AUTHORS:- Gutierrez-Agullo, J.R.; Coll-Perales,
B.; Gozalvez, J.
Wireless Days (WD), 2010 IFIP Year: 2010

4. CONTENTS
 DEFINATION
 WHY SDR.?
 TECHNICAL OVERVIEW
 SOFTWARES OF SDR
 APPLICATIONS
 ADVANTAGES
DISADVANTAGES
 BENEFITS
 CONCLUSION
REFERENCES

5. DEFINITION
What’s SDR.?
Software-defined radio (SDR)
Is a radio communication system where components that have
been typically implemented in hardware (e.g. mixers ,filters
, amplifiers , modulators /demodulators , detectors , etc.) are
instead implemented by means of software on a personal computer
or embedded system.

6. SDR IN EASY WORDS
 Refers to a technique in which all the processing
is done in software.
 The processing mentioned include mixing,
filtering,demodulation etc.
 The software can be used to implement different
demodulation scheme and different standards
can be implemented in the same device.
 The software can be updated so the device doesn’t
become obsolete with time.

7. WHY SDR.?
 To produce a radio that can receive and transmit a new form of
radio protocol just by running new software.
 A technique in which all the processing is done in software i.e.,
mixing, filtering, demodulation etc.
 Used to implement different demodulation scheme and
different standards can be implemented in the same device.
 Can be updated so that device doesn’t become obsolete with
time.

8. SDR EXPLAINED

9. TECHNICAL OVERVIEW
• IDEAL SDR
• IDEAL RECEIVER
• IDEAL TRANSMITTER
• PRACTICAL RECEIVERS
• TYPICAL COMPONENTS

10. Ideal SDR
 The ideal SDR will cover all frequencies from 9kHz
to 300GHz.
 •It will receive/transmit and modulate/demodulate all
modulation modes and bandwidths
 •It will configure itself automatically.
•

11. IDEAL TRANSMITTER &
RECEIVER
 The ideal receiver scheme would be to attach an analog-to-digital
converter to an antenna to directly convert RF to digital.
 A digital signal processor would read the converter, and then its
software would transform the stream of data from the converter to
any other form the application requires.
 An ideal transmitter would be similar.
 A digital signal processor would generate a stream of numbers.
These would be sent to a digital-to-analog converter connected to
a radio antenna.

12. Practical receivers
Current digital electronics are too slow
to receive typical radio signals that
range from 10 kHz to 2 GHz.
Problem solved by using a mixer and a
reference oscillator to heterodyne the
radio signal to a lower frequency.
Digital IQ modulator used.
Real analog-to-digital converters lack
the discrimination to pick up sub-
microvolt, nano watt radio signals.
A low noise amplifier must precede
the conversion step.

13. Typical Components of SDR
 Analog Radio Frequency (RF) receiver/transmitter in the 200 MHz to
multi-gigahertz range.
 High-speed A/D and D/A converters to digitize a wide portion of the
spectrum at 25 to 210 Msamples/sec.
 High-speed front-end signal processing including Digital Down
Conversion (DDC) consisting of one or more chains of mix + filter +
decimate or up conversion.
 Spread spectrum and ultra wideband techniques allow several
transmitters to transmit in the same place on the same frequency with
very little interference
 PC equipped with sound card

14. Architectures of SDR
DUC: Digital
upconverter
DDC: Digital
downconvert
er
CFR: Crest
factor
reduction
DPD: Digital
predistortion
PA: Power
amplifier
LNA: Low
noise
amplifier

15. RF Front End
 The principle of operation depends on the use
of heterodyning or frequency mixing.
 The signal from the antenna is filtered sufficiently at least to reject
the image frequency and possibly amplified.
 A local oscillator in the receiver produces a sine wave which mixes with
that signal, shifting it to a specific intermediate frequency (IF), usually
a lower frequency.
 The IF signal is itself filtered and amplified and possibly processed in
additional ways.

16. DIGITAL IQ modulator
 Two carriers of same frequency but 90 deg out of phase
are used, which are combined at transmission.
 Message too is modified to consist of two separate
signals 90 deg phase shifted version
original 90 deg phase shifted version

17. ADC & DAC
 ADC- Sampling ( Nyquist theorem)
Quantisation
Flash ADC is the fastest of all.
 DAC- weighted resistor
R-2R ladder V(out)= V( ref)* (D/2^N)
The main problem in both directions is the difficulty of
conversion between the digital and the analog domains
at a high enough rate and a high enough accuracy

18. SOFTWARE
Windows , Mac and Linux (Cross Platform)
 GNU Radio: Toolkit used by most SDR
(includes GNU Radio Companion)
 Linard: Library used to interface with hardware
Windows
 SDR# :spectrum viewer (Open Source)
 HDSDR: spectrum viewer (Open Source)

19. SOFTWARE
COMMUNICATION
ARCHITECTURE
 “Software communications architecture” (SCA) provides a
real-time software
 operating-system environment to support the dynamic
waveform generation and signal processing aspects of a radio
. as well as the administrative aspects for radio installation
and change control.
 Such an example of standardized architecture of hardware
and software will lead to generic, flexible radio systems which
may be loaded with applications to suit particular operating
scenarios.
 SDR may be flexible enough to operate in several modes at
the same time and some may be capable of changing or
adding modes while continuing operation in other modes

20. Fig: SCA interfaces used in
the SDR design

21. COBRA(Common Object
Request Broker Architecture)
 CORBA is the Object Management Group’s open
architecture that provides the infrastructure for computer
applications to work together over a network.
 CORBA has been chosen as the middleware layer of the
Software Communications Architecture, because of the
wide commercial availability of CORBA products and its
industry acceptance.
 CORBA is used to provide a cross-platform middleware
service that simplifies standardized client/server
operations in this distributed environment by hiding the
actual communication mechanisms under an Object
Request Broker software bus.

23. Applications Of SDR Technology
 SDR use in public safety
 SDR use in the military
 Commercial use of SDR

24. The advantages of SDR
• Highly reconfigurable
• Software upgrades of commercial radios
• Generic hardware can be used for a variety of applications
• Software prototyping faster and cheaper than hardware
prototyping
• Mathematically sophisticated signal processing techniques can be
performed in the “digital domain” (software)
• Libraries of software radio components are easily created and
shared
• Digital manipulation of signals is ideal, unencumbered by the
non-linearities that plague hardware
Technical aspects of SDR

25. DISADVANTAGES
For very wide frequency coverage, the RF hardware may need to be built
in separate portions of circuitry dedicated to particular frequency ranges
Two tone Inter Modulation There are technology limits on achievable RF
performances
Distortion(IMD)
The choice of architecture depends on the available technology
Complexity in using the software
Software reliability may define overall radio reliability, rather than
hardware limitations

26. Benefits of SDR
 Manufactures
 Grouping of H/W platform sets
 Cost reduction
 Ability to S/W improvements
 Operators
 New services
 Services upgrades on existing systems
 Flexible coverage / Dynamic Frequency Allocation
 Customers
 Services personalization
 Improve roaming
 Reduction of CPE Obsolescence

27. Conclusions
• SDR means:
• Reconfigurable radios
• More generic hardware
• Reduced rate of hardware obsolescence
• Lower cost of entry to radio development
• Excellent tool for the experimenter
• Simple transition between computer simulation and
implementation
• Becoming increasingly popular in industry
• A technology to watch!
Software-Defined Radio
Technical aspects of SDR

28. REFERENCES
[1] Software Defined Radio- A brief overview :Matthew N. O. Sadiku and Cajetan
M Akujuobi . IEEE potential OCTOBER/NOVEMBER 2004
[2] Software-defined GPS receiver on USRP-platform : Elizabeth A. Thompson
a,n, Nathan Clem a, Isaac Renninger a, Timothy Loos b . Journal of Network and
Computer Applications 35 (2012) 1352–1360
[3] Software Defined Radio , Brad Brannon, Analog Devices, Inc.
[4] Software defined radio in the land mobile, amateur and amateur satellite
services .
[5] A SOFTWARE DEFINED BY RADIO : Nark W. Chamberlain Harris
Corporation, RF Communications Division Rochester, New York.
[6] Introduction to the Software-defined Radio Approach : A. F. B. Selva, A. L. G.
Reis, K. G. Lenzi, L. G. P. Meloni, Member, IEEE and S. E. Barbin, Member,
IEEE.