On Phase Noise Suppression Technology In Co-Time Co-Frequency Full-Duplex Systems

The needs of wireless communication on traffic transmission to promote innovation and development of new communication technologies. The traditional half-duplex transmission system based on time division multiplexing or frequency division multiplexing with limited spectrum efficiency. As the sending and receiving equipment can work at the same frequency simultaneously in a full duplex communication system, and the spectrum resource utilization is double that of half duplex communication systems.Co-frequency Co-time full duplex system is sensitive to phase noise. Transceiver introduce a phase noise with up-converting and down-converting. The phase noise leads to common phase error and inter-carrier interference which destroys self-interference signal. While the common phase error can be suppressed with the channel estimate, but inter-carrier interference is random between sub-carriers, which is difficult to eliminate and expect a strong interference in intended signal. At present, new technologies to suppress phase noise are divided into two aspects, one is architecture, the other one is about algorithm which is divided into the time domain phase noise suppression algorithm and frequency domain phase noise suppression algorithm. Phase noise suppression in full duplex is mainly researched in this paper. In this paper, phase noise suppression technology is studied and improved based on the existing literature, which committed to improve the self-interference suppression gain and the signal to interference plus noise ratio.First of all, traditional phase noise suppression algorithms in frequency-domain and time-domain are researched. The main procedures include signal model, estimating the phase noise, reconstructing and suppressing the self-interference signal. Simulation with Simulink to verify the phase noise suppression performances about traditional algorithms. Following conclusions can be obtained from the simulations: under the conditions of ISR equaling 40 dB and phase noise 3dB bandwidth equaling 6Hz, the SINR of algorithms in time-domain and frequency-domain are respectively 8.3d B and 8.0dB.Secondly, based on the traditional self-interference suppression architecture, this paper proposes a phase noise self-inhibiting architecture with feedback path, and discusses the phase noise suppression performance of the architecture in detail. Derive conclusions proved that, under ideal channel estimation, this architecture can be completely inhibited the phase noise interference. Following conclusions can be obtained from the simulations: under the conditions of ISR equaling 40 d B and phase noise 3dB bandwidth ranging from 0.6Hz to 600 Hz, the new architecture can ensure the ratio of signal to interference plus noise up to 1.6dB at least and 7.6dB at most than the traditional architecture.Finally, BEM estimate based on complex exponential in full-duplex system is discussed, and presented a phase noise suppression algorithm based on iterative. Some measurements(i.e., signal to interference plus noise rate, self-interference suppression gain) are made. Results indicate that the new method can effectively suppress phase noise interference. When the BEM extended order is 18, SNR of 20 dB, and Rice channel of three-path, after 10 iterations, the self-interference channel MSE approximate to 210-. When the phase noise 3dB bandwidth equaling 6Hz, the new algorithm can ensure the self- interference suppression gain is 42.5dB and 54.6dB while ISR equaling 30 dB and 40 dB, the improvements achieve to 5dB and 4.1dB.When the ISR equaling 40 dB and the phase noise 3dB bandwidth ranging from 6Hz to 600 Hz, the algorithm can ensure the ratio of signal to interference plus noise of 13.6d B to 4.3dB,which up to 0.4dB at least and 3.3dB at most than the traditional algorithm.