Opt Express. 2023 Apr 10;31(8):13140-13153. doi: 10.1364/OE.486889.
Self-interference (SI) due to signal leakage from a local transmitter is an issue in an in-band full-duplex (IBFD) transmission system, which would cause severe distortions to a receiving signal of interest (SOI). By superimposing a local reference signal with the same amplitude and opposite phase, the SI signal can be fully canceled. However, as the manipulation of the reference signal is usually operated manually, it is difficult to ensure a high speed and high accurate cancellation. To overcome this problem, a real-time adaptive optical SI cancellation (RTA-OSIC) scheme using a SARSA(λ) reinforcement learning (RL) algorithm is proposed and experimentally demonstrated. The proposed RTA-OSIC scheme can automatically adjust the amplitude and phase of a reference signal by adjusting a variable optical attenuator (VOA) and a variable optical delay line (VODL) achieved through an adaptive feedback signal, which is generated by evaluating the quality of the received SOI. To verify the feasibility of the proposed scheme, a 5 GHz 16QAM OFDM IBFD transmission experiment is demonstrated. By using the proposed RTA-OSIC scheme, for an SOI at three different bandwidths of 200, 400, and 800 MHz, the signal can be adaptively and correctly recovered within 8 time periods (TPs), which is the required time of a single adaptive control step. The cancellation depth for the SOI with a bandwidth of 800 MHz is 20.18 dB. The short- and long-term stability of the proposed RTA-OSIC scheme is also evaluated. The experimental results indicate that the proposed approach could be a promising solution for real-time adaptive SI cancellation in future IBFD transmission systems.
自干扰（SI）是一种由于本地发射机信号泄漏而导致的问题，在带内全双工（IBFD）传输系统中，它会严重扭曲感兴趣的接收信号（SOI）。通过同相叠加一个幅度相同、相位相反的本地参考信号，可以完全消除 SI 信号。然而，由于参考信号的操作通常是手动完成的，因此很难确保高速和高精度的消除。为了解决这个问题，提出并实验验证了一种使用 SARSA(λ)强化学习（RL）算法的实时自适应光学 SI 消除（RTA-OSIC）方案。所提出的 RTA-OSIC 方案可以通过自适应反馈信号自动调整参考信号的幅度和相位，该反馈信号是通过评估接收 SOI 的质量来生成的。为了验证所提出方案的可行性，进行了 5GHz 16QAM OFDM IBFD 传输实验。通过使用所提出的 RTA-OSIC 方案，对于三个不同带宽（200MHz、400MHz 和 800MHz）的 SOI，可以在 8 个时间周期（TP）内自适应且正确地恢复信号，这是单个自适应控制步骤所需的时间。对于带宽为 800MHz 的 SOI，消除深度为 20.18dB。还评估了所提出的 RTA-OSIC 方案的短期和长期稳定性。实验结果表明，该方法可能是未来 IBFD 传输系统中实时自适应 SI 消除的一种有前途的解决方案。
