Research Of A Cross-polarization Discrimination Compensation Algorithm For Polarization Modulation Signal

In order to promote green communication and realize energy conservation and emissions reduction, research on optimization of the power amplifier efficiency communication technology is necessary.Polarization modulation technology utilizes the signal state information and the property that polarization state is not affected by nonlinear power amplifier to improve the power amplifier efficiency effectively. However,the depolarization effect XPD in the wireless channel can cause cross leakage of the power of the polarization modulation signal component thus reduces the polarization modulation performance. Therefore, the effective compensation algorithm against XPD is very necessary.In view of the depolarization effect XPD can reduce polarization modulation performance, and thus affect the power amplifier efficiency, an XPD compensation algorithm against the polarization cross power leakage between the modulation signal components caused by XPD is proposed in this paper. According to whether the channel state information estimation is ideal, the XPD compensation algorithm is studied from two cases where the channel estimation is ideal and the channel estimation error exists. The main work of this paper is following three aspects:(1) This paper analyzes and summarizes the current research status of the polarization modulation, including the research content, primary uses and the main challenges. It pointed that the depolarization effect is the key factor that influences the properties of polarization modulation. In addition,this paper gives a brief introduction of the relevant theory and elimination algorithm of the depolarization effect, and points out that the research on compensation algorithm against the depolarization effect of XPD to improve the polarization modulation performance is necessary.(2) Aimed at the depolarization effects XPD in the wireless channel on the polarization modulation signal, this paper proposed an XPD compensation algorithm of polarization modulation signal under the conditions of the ideal channel state information estimation. In the first step,the system model confronting XPD polarization modulation effect is established, and the effect of XPD on polarization modulation is analyzed.In the second step, channel state information is estimated. Under the ideal estimation situation, using the channel state information obtained from the estimation the compensation factor is calculated, and the signal is processed in the receiver, polarization state of the received signal times the compensation factor, in order to counter the cross power attenuation between the two signal component brought by the depolarization effect of XPD, to improve BER performance of the polarization modulation.Theoretical analysis and simulation analysis show that the performance of compensation algorithm is 2.5 dB better than that before the compensation.(3) Considering the XPD effects on the polarization modulation, it is necessary to estimate the channel state information and compensate the influence of XPD. However, the actual channel estimation algorithm can introduce estimation error, so this paper researches the effects of the channel estimation error on the performance of the XPD compensation algorithm. First, set up the polarization modulation system model under the influence of channel estimation error affected by XPD, and through the analysis of the influences of channel estimation error on the receiving SNR,calculate the closed solution of polarization modulation BER when the estimated error exists, to assess the influence of channel estimation error on the performances of the XPD compensation algorithm. The results show that the size of the channel estimation error will degrade the performance of the compensation algorithm in different degrees, this conclusion has guiding significance on selection for high precision of channel estimation methods to improve the system performance.In the research of fighting against the depolarization effect XPD in wireless communication, an XPD compensation algorithm against the polarization cross power leakage between the modulation signal components caused by XPD is proposed in this paper, which provides a new idea of the polarization modulation performance research under the depolarization effect XPD.