DBF Based Channel Estimation for Self-interference Cancellation in Full-Duplex Communications

The full-duplex technology can achieve higher spectrum utilization than the traditional half-duplex technology, which has attracted widespread attention in both academia and industry. Since the performance of the full-duplex system is severely restricted by the self-interference (SI) signal, the influence of the SI signal must be eliminated to give full play to the advantages of the full-duplex technology. Restricted by device performance and circuit structure, traditional analog domain SI cancellation technology has disadvantages such as low accuracy, poor flexibility, and high hardware overhead. In order to avoid the above-mentioned problems, we investigate the SI cancellation technology in the digital domain, and uses digital beamforming (DBF) algorithm for high-precision SI channel estimation. Relying on the auto-correlation characteristics of spread spectrum sequences, SI channel parameters can be quickly obtained by implementing both amplitude and phase tests. It is shown in both simulation and hardware experiment that the adjustment accuracy of amplitude and phase can be better than 0.05dB and 0.05° which is far better than that of the commonly used 8-bit controlled phase shifter, with the accuracy of 1.4° and adjustable attenuator, with the accuracy of 0.5dB. The improvement of accuracy makes the SI cancellation capability of the proposed algorithm 13.49 dB higher than that of the traditional method. The proposed algorithm can be implemented with high enough accuracy and better performance which has a wide range of applications.