Research On Self-Interference Cancellation Technology Based On Polarization Signal Processing In The Full Duplex Communications

It’s necessary to develop the communication technologies with high spectrum efficiency when there is a severe shortage of spectrum resources. In the wireless communication, full duplex permits the two-way data to be transmitted in a single channel at the same time, which has higher spectrum efficiency than the existing duplex modes, namely time division duplex and frequency division duplex. Among key technologies of full duplex, self-interference cancellation is the foundation of implementation of full duplex. It’s of great importance to the full duplex.The task of this paper is from the national major projects for science and technology development of research and verification of Cognitive Radio in TD-LTE, and also supported by the Postgraduate Innovation Fund of SICE, BUPT,2013. The main work of this paper is shown in the following three aspects:(1) This paper summarizes and analyzes the current related works of full duplex, especially the self-interference cancellation, and points out the disadvantage of them. Then it makes a brief introduction to polarization signal processing technologies, which has huge potential in the wireless communication.(2) The performance of baseband self-interference cancellation techniques are restricted by the performance of radio frequency self-interference cancellation techniques in existing schemes in time-frequency domain. To mitigate this problem, this paper proposes a non-restricted self-interference cancellation scheme in polarization domain (NRSCS_PD) based on the polarization filter technique, after analyzing the cause of this problem and considering the orthogonality between polarization domain and time-frequency domain. Then the cancellation performance of this scheme and the relationship between cancellation performance and signals’polarization states are analyzed, and the condition which should be met in this scheme is obtained. According to the simulation, the cancellation performance is verified that the scheme proposed in this paper has higher cancellation gain.(3) The cancellation performance of self-interference cancellation scheme based on the isolation of orthogonal single-polarized antennas (SCS_IOSA) is affected by the channel condition severely. To mitigate this problem, this paper proposed the channel-adapted self-interference cancellation scheme based on the polarization signal processing (SCS_PSP). This scheme estimates the polarization states of self-interference and desired signal firstly, then cancels the self-interference in the polarization domain and gets the desired signal. This paper analyzes the impact of ricean channel to the polarization signal and the cancellation performance of this scheme. According to the simulation and comparison, the performance of this scheme is verified that it has the better cancellation performance and less affected by the channel.This paper makes full use of advantage of polarization signal processing to solve problems in full duplex communication, which provide a novel method to cancel the interference. It is of great necessity.