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