Thursday, August 15, 2013

SIGCOMM2013: Full Duplex Radios

Presenter: Dinesh Bharadia
Co-authors: Emily McMilin and Sachin Katti

Achieving full duplex radio is difficult because self-interference is a hundred billion times stronger than the received signal. Canceling the transmitted signal is difficult because the signal transmitted is actually quite different from what you think you are transmitting, due to noise and non-linear affects called harmonics. You need 110 dB (at least 70 dB of which is analog) in order to eliminate the transmitter noise.

This paper presents the first full duplex radio, which uses a new cancellation technique that eliminates all self-interference. Their approach is a hybrid design, with both analog and digital components.

Using commodity radios, this work is able to reduce self interference to within 1 dB of the noise floor. This approach significantly outperforms previous works in reducing the self-interference residue. This design achieves a 1.97x increase in throughput over non-duplex designs, which is very close to the optimal 2x throughput increase.

Q: How does this compare with a previous work from Waterloo?
A: They acheived 50 dB of cancellation, but they didn't do any non-linear cancellation.

Q: You are suggesting that your own work from SIGCOMM 2011 does worse than half-duplex?
A: That wasn't our work.

Q: Would this scale?
A: I still believe this would scale.