SoftNull: Many-Antenna Full-Duplex Wireless via Digital Beamforming

TL;DR

SoftNull introduces a digital beamforming approach for full-duplex wireless with many antennas, effectively reducing self-interference without relying on analog cancelers, and demonstrating significant performance gains in practical environments.

Contribution

This paper presents SoftNull, a novel digital beamforming method enabling full-duplex operation in many-antenna systems, diverging from traditional analog cancellation techniques.

Findings

SoftNull significantly outperforms half-duplex in small-cell scenarios.

The method effectively reduces self-interference in large antenna arrays.

Performance validated with real-world measurements from a 72-element array.

Abstract

In this paper, we present and study a digital-controlled method, called SoftNull, to enable full-duplex in many-antenna systems. Unlike most designs that rely on analog cancelers to suppress self-interference, SoftNull relies on digital transmit beamforming to reduce self-interference. SoftNull does not attempt to perfectly null self-interference, but instead seeks to reduce self-interference sufficiently to prevent swamping the receiver's dynamic range. Residual self-interference is then cancelled digitally by the receiver. We evaluate the performance of SoftNull using measurements from a 72-element antenna array in both indoor and outdoor environments. We find that SoftNull can significantly outperform half-duplex for small cells operating in the many-antenna regime, where the number of antennas is many more than the number of users served simultaneously.