Practical, real-time, full duplex wireless

TLDR

The paper aims to introduce a full‑duplex radio employing signal inversion and adaptive cancellation, along with a full‑duplex MAC protocol evaluated on a testbed of five prototype nodes. The radio uses a Balun‑based signal inversion for analog cancellation, supplemented by digital domain cancellation, while the MAC design is implemented and tested on the prototype nodes. The design achieves at least 45 dB cancellation over 40 MHz, up to 73 dB with digital cancellation on a 10 MHz OFDM signal, supports wideband and high‑power operation, and experimentally reduces hidden‑terminal packet loss by 88 %, improves fairness from 0.85 to 0.98, boosts downlink throughput by 110 % and uplink by 15 %, demonstrating that a full‑duplex stack redesign yields substantial network performance gains.

Abstract

This paper presents a full duplex radio design using signal inversion and adaptive cancellation. Signal inversion uses a simple design based on a balanced/unbalanced (Balun) transformer. This new design, unlike prior work, supports wideband and high power systems. In theory, this new design has no limitation on bandwidth or power. In practice, we find that the signal inversion technique alone can cancel at least 45dB across a 40MHz bandwidth. Further, combining signal inversion cancellation with cancellation in the digital domain can reduce self-interference by up to 73dB for a 10MHz OFDM signal. This paper also presents a full duplex medium access control (MAC) design and evaluates it using a testbed of 5 prototype full duplex nodes. Full duplex reduces packet losses due to hidden terminals by up to 88%. Full duplex also mitigates unfair channel allocation in AP-based networks, increasing fairness from 0.85 to 0.98 while improving downlink throughput by 110% and uplink throughput by 15%. These experimental results show that a re- design of the wireless network stack to exploit full duplex capability can result in significant improvements in network performance.