Software-Based Real-Time Full-Duplex Relaying: An Experimental Study

Relaying in wireless networks is one of the most important concepts to improve the overall communication performance and to increase coverage. Relay systems can work in either half or full-duplex mode. Half-duplex relaying unfortunately increases the overall latency and also causes spectral losses. On the other hand, in-band full-duplex relaying helps to overcome such issues by simultaneously receiving packets from the source and forwarding them towards the destination. We present a software-based real-time full-duplex relaying system, which we implemented in GNU Radio. The system supports running simulations using an abstract channel model as well as over-the-air experiments using Software Defined Radios (SDRs). A major challenge in developing such a system is dealing with self-interference. For this, we constructed a new looped self-interference cancellation system and integrated it with the GNU Radio implementation. In an experimental study, we validated and evaluated our system to characterize the practical performance of the proposed full-duplex relay system. Our main focus is on the impact of the residual looped self-interference, for which we show analytical and simulation results to confirm the experimental study.