Sdr

Technical Aspects of SDR

JUNAID IQBAL

08TL27

Technical aspects of SDR

Introduction to SDR What is SDR?

What is SDR?

• Software- Defined Radio

• Signal manipulation (e.g. modulation, demodulation, filtering)performed in software

• A digital signal processor (DSP) replaces analogue hardware oftraditional radios

) Technical aspects of SDR

Where can we use SDR ?Where can we use SDR ?

Base stations◦ Weak constraints on power and area ◦ Support several hundred subscribers◦ Will be commercialized first

Wireless terminals◦ Tight constraints on power and area.◦ Will be commercialized next

A Typical SDR Block diagram

Block diagram of a typical SDR

Receiver Transmitter

BPF BPF

LPF ADC DSP DAC LPF

Analogue Front-End Analogue Front-End

Technical aspects of SDR

A Typical SDR The digital processor

The digital processor and its software

• Signal processing (modulation, demodulation, etc.) is performedinside the digital processor

• Variety of suitable devices:• DPSs

••••

Digital Signal Processor ICs.Highly specialised number-crunchersLow power consumptionExcellent SDRs, especially for mobile applications

• General-purpose microprocessors• e.g. a personal computer (PC)• Very flexible• Radio functionality can share resources with other applications• Very cost-effective for static installations, e.g. cellphone base stations

• FPGAs• Reconfigurable at the digital logic level• Can be used to create custom digital processors for SDR• Extremely high processing speeds possible• Less flexible than DSPs or µPs

Technical aspects of SDR

A Typical SDR Signal theory and DSP software

Signal theory and DSP software

• Modulation is performed using software techniques such asdirect-digital synthesis.

• Demodulation is done using software techniques such as digitalfiltering, digital phase-locked loops and coherent demodulation.

• One part of SDR software design is concerned with signalprocessing algorithms

• Another part of SDR software design involves architecturalconsiderations:

• scheduling• reusability• data flow

Technical aspects of SDR

A Typical SDR Signal conversion

Signal conversion

• In any SDR, digital-to-analogue or analogue-to-digital conversionis required at some point

• Signal conversion must be higher than twice the highest frequencyin the signal [Nyquist’s Theorem]

• High-resolution converters only available up to a few hundred MHzsampling rate

• Signal quality often deteriorates at high sampling rates

• Advantageous to let software work at low IF, and perform signaltranslation in hardware

• SDR’s signal translation hardware: RF front-end

Technical aspects of SDR

Introduction to SDR The advantages of SDR

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 hardwareprototyping

• Mathematically sophisticated signal processing techniques can beperformed in the “digital domain” (software)

• Libraries of software radio components are easily created andshared

• Digital manipulation of signals is ideal, unencumbered by thenon-linearities that plague hardware

Technical aspects of SDRio

Benefits of SDRBenefits 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

Conclusions

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 andimplementation

• Becoming increasingly popular in industry

• A technology to watch!

Software-Defined Radio

Technical aspects of SDR

Conclusions

Thank You