Self-Interference Mitigation Based The Positive-Negative Array-Element And Fractal Geometry For Full-Duplex Communications

With the increasing demand for high-capacity and high-compatibility communications,how to achieve higher spectral efficiency and better mitigate intra/inter self-interference(intra-SI/inter-SI)in future wireless communications have been the key problem which next-generation wireless communications urgently need to solve.Co-time co-frequency full-duplex(FD)has been treated as one of the potential candidate techniques to enhance the spectral efficiency of wireless communications.How to efficiently mitigate the SI caused by the leakage of local signal corresponding to FD is the precondition for the application of FD.The existing intra-SI mitigation for FD require multiple antennas to cancel the intra-SI of single antenna.And the mitigation cannot ensure that transmitting and receiving data within one antenna,which leads to a huge waste of antenna resources.To solve this problem,the main work of this paper is listed as follows:1.This paper mainly studies the intra/inter-SI mitigation based the positive-negative array-element for FD communications.The main work of this part consists of two aspects:(1)For the case with one array-element,this paper establishes the expression of the auxiliary channel and designs a correlator.Then,by using the delay,phase and amplitude differ from the main part of the intra-SI,the auxiliary signal is weighted in the digital domain.Then,the main part intra-SI is cancelled through the RF domain adder.Data shows that the mitigation can cancel intra-SI effectively under the case where error of the line is low.With the same error,the capacity of the system is close to the optimal capacity in lower SNR.(2)For the case with two array-elements,the structure based positive-negative array-element of single antenna is proposed in the paper.In this structure,the transmit signal goes through the main transmit channel and then it is split into two paths through a coupler.The amplitudes of the two signals are same,but the phases of two signals differ by 180~?.Due to the phase difference,the combination after the two circulators can partially cancel the inter-SI between the positive array-element and the negative array-element.The inter-SI between the positive array-element and the negative array-element can be completely cancelled in the ideal case.It easily concludes that the fractal antenna can effectively mitigate inter-SI about50dB between different array-elements by using HFSS.However,the mitigation is 31dB through MegaBEE because of the errors of environmental factors.2.This paper mainly analyzes the inter-SI mitigation based fractal geometry for FD com-munications corresponding to the single antenna and multiple antennas,respectively.(1)For the scenario with single antenna,this paper analyzes many fractal models and stud-ies the layout of the positive-negative array elements by referring to the FD communications based positive-negative array-element above and fractal geometry for the FD communication based fractal geometry to effectively mitigate the inter-SI between different positive-negative array-elements.It easily concludes that the fractal antenna based rectangle and circle can effectively mitigate inter-SI between different positive-negative array-elements 43.23dB and45.45dB by observing antenna pattern through HFSS,respectively.Data shoes that the mit-igation is 36.5dB through MegaBEE.(2)For the scenario of Multiple antennas,an adaptive beam forming algorithm named adaptive diagonal loading(ADL)beam forming algorithm corresponding to multiple antennas based on fractal geometry is proposed.The adaptive beam forming algorithm based on fractal geometry and diagonal loading(DL)is proposed to mitigate the inter-SI between different antennas.The data shows that ADL can effectively mitigate the inter-SI between different antennas compared to the DL,which increases the Signal to Interference and Noise Radio(SINR)of the system.