Working with programmable radios

Hariharan Rahul

Our Group’s Experience

• USRP

• USRP2

• WiGLAN

• WARP

• Lyrtech

What have we used programmable radios for?

• Network-oriented PHY design– Flexible layering• SOFT, MIXIT, Softcast

– New technologies: UWB, MIMO• SWIFT, FARA, IAC

– Dealing with Interference• ANC, ZigZag

Peeling the Onion• Changing the PHY interface– Soft information

• Changing the PHY algorithms– Interference cancellation and Interference

alignment• Timing-sensitive PHY algorithms– Adaptive sensing

• Bandwidth limited– Wide frequency bands

Host

FPGA

USRP and USRP 2• What’s good?– Affordable– Stable algorithms– Large community– Easy to use– USRP had narrow bandwidth; better with USRP2

• What’s bad?– No room for additional FPGA logic– Bandwidth only up to 20 MHz even in USRP2– High latency

WARP• What’s good?– Close to our ideal board– Large FPGA– Relatively fast host interface– Rich development platform • Onboard processor cores

• What’s bad?– Cost– Relatively narrow bandwidth (FPGA code does 10 MHz,

radio can support 40 MHz)– Calibration

WiGLAN• What’s good?– Very high bandwidth (128 MHz)– Large FPGA to deal with high bandwidth– Calibrated

• What’s bad?– Development process• Form factor

– Out of print

Learnt Lessons• A programmable radio is a package– Hardware– Software

• SNR-BER curve is the proof of the pudding

4 5.5 7 8.5 1011.5 13

14.5 1617.5 19

20.5 2223.5 25

26.5 2829.5

00.5

11.5

22.5

33.5

44.5

5BPSK,1/2BPSK,3/44-QAM,1/24-QAM,3/416-QAM,1/216-QAM,3/464-QAM,2/364-QAM,3/4

SNR (dB)

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