Practical, Real-time, Full Duplex Wireless

Mayank Jain, Jung Il ChoiTae Min Kim, Dinesh Bharadia, Sid-

dharth Seth, Kannan Srinivasan, Philip Levis, Sachin Katti, Prasn Sinha

MobiCom 2011

Single channel full-duplex

Antenna Cancellation

• Achieving Single Channel, Full Duplex Wireless Communication [Mobicom’10]

Contributions

• New full-duplex radio design:signal inversion cancellation

• Wideband, frequency independent• One transmit antenna design• Real-time full-duplex MAC layer im-

plementation

Signal Inversion vs. Phase Offset

Phase Offset

Signal Inversion

Signal Inversion vs. Phase Offset

Balun passive cancellation

Balun active cancellation

Balun active cancellation

Balun active cancellation

Digital cancellation

• Three novel achievements:- Real-time cancellation implementation that runs in hardware- Cancellation implementation can operate on 10MHz signals- Digital cancellation that operates on OFDM signals

• Digital cancellation has two components:- Channel Estimation >> least squares algo-rithm- Applying Digital Cancellation>>

ˆ[ ] [ ] [ ]r n r n i n

Balun + Digital cancellation

Implications to Wireless Net-works

• Breaks basic assumption in wireless• Can solve some fundamental prob-

lems with wireless networks today:- Hidden terminals- Network congestion and WLAN fair-ness

Hidden Terminals

Network Congestion and WLAN Fair-ness

Performance

• Balun Passive/Active Cancellation

Performance

• 1 AP with 4 stations without any hid-den terminals

Summary

• Design for real-time full-duplex wire-less- Makes full-duplex WiFi possible

• Made practical using adaptive tech-niques

• Rethinking of wireless networks- WiFi: hidden terminals and fairness