SOFTWARE RADIO

By

Sanjana Prasad

1601RL01

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What is a Software Radio??? Characteristics and benefits of Software

Radio Model of a Software Radio Factors required for wider acceptance of a

Software Radio Design principles of a Software Radio

TOPICS

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The term Software Radio was coined by Joe Mitola in 1991

Class of reprogrammable or reconfigurable radios

Same piece of hardware can perform different functions at different times.

SDR forum definition(USR) Radio that accepts fully programmable traffic

and control information supports a broad range of frequencies, air-

interfaces and applications software

WHAT IS A SOFTWARE RADIO???

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The piece of hardware can be modified to perform different functions at different times ,allowing the hardware to be specifically tailored to the application at hand

Software radio can be used to encompass soft radios as well. Software is confined to controlling the interface with the network

Hardware Amplifiers Filters Mixers

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Software Confined to controlling the interface with the

network, stripping the headers and error correction

codes from the data packets and determining where the data packets need to

be routed based on header information.

Represent a paradigm shift from fixed ,hardware –intensive radios to multi-band, multi mode,software – intensive radios

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The user can Switch from one interface to another in

milliseconds Use GPS for location Store money using smartcard technology Watch a local broadcast station Receive a satellite transmission

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Implementation of software radio requires The digitization at the antenna ,allowing flexibility at

the digital domain Design of a completely flexible radio frequency

(RF)front end for handling a wide range of carrier frequencies and modulation formats.

CHARACTERISTICS AND BENEFITS OF SOFTWARE RADIO

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MODEL OF A SOFTWARE RADIO

Flexiblle RF

Hardware

ADC

DAC

Channelization and

sample rate

conversion

P Hardware•FPGA•DSP•ASIC

Software•Algorithms•Middleware •Corba•Virtual radio machine

Processing

Smart antenna

IF

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Smart Antenna Provides a gain vs direction characteristic to

minimize interference,multipath and noise. Provides similar benefits for the transmitter

Rxr(Superheterodyne)-digitization-as early-IF BAND Digital->analog->as late at transmitter using a DAC

Superheterodyne reciever: Rf signal picked up by the antenna along with other

spurious/unwanted signals filtered ,amplified with a LNA and mixed with a LO to an IF.

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No of stages-vary IF- mixed exactly to baseband Digitizing the signal with an ADC in the IF

range-eliminates the last stage

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Multi-functionality Global Mobility Compactness And Power Efficiency Ease Of Manufacture Ease Of Upgrades

FACTORS OF SOFTWARE RADIO

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Multi-functionalitysupport infinite variety of service capabilities in a system

Bluetooth IEEE 802.11

Global mobility 2G

IS-136 GSM IS-95/CDMA 13G:HARMONISE ALL

THE STANDARDS TRANSPARENCY HAS

FOSTERED THE GROWTH OF THE

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Compactness And Power Efficiency

Velcro approach Separate silicon for each

system Bulky,inefficient as number

of systems increases Used in multifunction,multi-

mode radios Software Radio Approach: Compact Power Efficient Design- as

number of systems increases Since same piece of

hardware reused to implement multiple systems and interfaces

Ease Of Manufacure

RF components hard to standardise /varying

performance characteristics Optimization

few years/delay product information

Digitisation of the signal –result in fewer parts,reduced inventory for the manufacturer

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• Current services-need to be updated/new services need to be updated

• Enhancements have to be made without disruption of current infrastructure

• flexible architecture->allows improvments/additional functionality

• Eg:VOCODER –High quality at low bit rates

Ease Of UpgradesUsers /Customers – -expect services regardless of geographical area-Expect one device to utilize services in all regions(reconfiguring the rxr to air-interface standards used in the respective regions)-Over the air updates-

allow for speedy implementation of software upgrades and new features

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Systems Engineering RF Chain Planning Analog To Digital Conversion and Digital To

Analog Conversion Selection Software Architecture Selection Digital Signal Processing hardware

architecture selection Radio validation

DESIGN PRINCIPLES OF SOFTWARE RADIO

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Understanding the constraints and requirements of the communication link and the network protocol

->allocation of sufficient resources to establish the services given the system s constraints and requirements

Modulation and data type ->depends on range and transmit power

Well defined standard:routing protocol predetermined In a ideal software radio

System parameters-change in real time Optimizing the active communications sessions-major

challenge

STEP 1-SYSTEMS ENGINEERING

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Ideal RF chain Incorporate simultaneous flexibility in selection

of power gain,bandwidth,center frequency,sensitivity,and dynamic range

Strict flexibility-impractical Trade-off s must be made Communication system constrained to selected

military or commercial bands->optimization problem simplified

Compensation for power amplifier distortion or power management of RF circuitry- digital domain

STEP-2 RF CHAIN PLANNING

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Difficult Selection-requires trading power

consumption ,dynamic range and bandwidth Tied to rf reqirements for dynamic range and

frequency translation Channelisation requirements->selection of

adc and dac Post digitization techniques(based on

multirate dsp)-improve flexibility on the digitization stage

STEP 3-ADC AND DAC SELECTION

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Ensure maintainability,expandability,compatibility and scalability for swr

Consider latency and timing for the whole protocol stack

Architecture-allow for hardware independence through the use of middleware

Middleware-Interface between application oriented software and the hardware layer

SOFTWARE aware of capabilities of the hardware(DSP and RF) at

both ends of the communications link to ensure compatibility /maximum use of hardware resources

STEP4:SOFTWARE ARCHITECTURE SELECTION

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Software Radio in a existing data infrastructure: Interface quickly and efficiently Security-important issue-to ensure software

downloads-legitimate Need to control issues regardless of protocol

Attribute naming Error management Addressing Partioning radio functions -> objects help in

portability , maintainence of the software

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Core DSP hardware –implemented through MicroprocessorsFPGA’S and/or

ASIC’s Microprocessors

maximum flexibility, power consumption and lowest computational rate

ASIC minimal flexibility lower power consumption highest computational rate

STEP 5:DSP HARDWARE ARCHITECTURE SELECTION

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FPGA-lie between ASIC and a DSP Selection Of Core Computing Elements Depends

On Algorithms Computational Throughput Requirements

Software radio will use all three core three core computing requirements

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Most difficult step Ensure not only communication units operate

correctly but also that a glitch does not cause system-level failures

Eg: interference caused by a software radio mobile unit-adjacent bands

Testing and validation steps -> minimize risk Structuring the software to link various modules with

limitations and deficiencies help in testing compatability of software modules

STEP7:RADIO VALIDATION

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Military radio Cellular services HF Transceivers FPGA

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APPLICATIONS OF SOFTWARE RADIO

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