In this article, we present a real-time full duplex radio system for 5G wireless networks. Full duplex radios are capable of opening new possibilities in contexts of high traffic demand where there are limited radio resources. A critical issue, however, to implementing full duplex radios, in real wireless environments, is being able to cancel self-interference. To overcome the self-interference challenge, we prototype our design on a software-defined radio (SDR) platform. This design combines a dual-polarization antenna-based analog part with a digital self-interference canceller that operates in real-time. Prototype test results confirm that the proposed full-duplex system achieves about 1.9 times higher throughput than a half-duplex system. This article concludes with a discussion of implementationchallenges that remain for researchers seeking the most viable solution for full duplex communications.