Research On Channel Equalization Technology And FPGA Implementation For Broadband Satellite Communication

Satellite communication has developed from mobile communication to broadband communication,broadband satellite communication is a hot spot in the high throughput satellite(HTS)application industry,the DVB-S2 X standard is used for the general HTS's front channel.On a satellite transponder,the signal is amplified by an input multiplexer(IMUX),amplified by a high-power amplifier(HPA),and finally transmitted by an output multiplexer(OMUX).The IMUX-OMUX filter on the satellite introduces linear distortion in the form of inter-symbol interference(ISI),and HPA introduces nonlinear distortion.As the amount of information in satellite communications increases,high-speed data transmission will lead to further aggravation of ISI,the most common technology to overcome satellite channel distortion is adaptive equalization technology,in addition,The frame structure and high-order modulation methods supported by the DVB-S2 X standard also put forward higher requirements for the realization of the equalizer.This paper focuses on the equalization algorithm for DVB-S2 X system against linear distortion and nonlinear distortion,the low-complexity parallel equalization for high-speed data transmission and other key technologies,the main results of which are as follows:First,the equalization technology of the DVB-S2 X system against linear distortion under satellite channel is studied.First of all,the linear distortion of the satellite channel is modeled,the existed linear equalization algorithms applicable to DVB-S2 X system is analyzed,and obtain its advantages and disadvantages through the analysis of complexity and scope of application.Secondly,based on the time-domain symbol spcaed equalization algorithm,a variable-tap time-domain symbol spcaed equalization algorithm is proposed.Finally,the simulation verifies the effectiveness of the proposed algorithm and the traditional equalization algorithms suitable for DVB-S2 X system when there is linear distortion in the channel,it can be obtained that the proposed algorithms has the advantages of low complexity,small mean square error and applicable to all M-APSK modulations.Second,the equalization technology of DVB-S2 X system against nonlinear distortion under satellite channel is studied.First of all,the nonlinear distortion of satellite channels is modeled and the reported nonlinear equalization algorithm for DVB-S2 X system is analyzed.Secondly,based on the conventional volterra equalization algorithm,a low-complexvity volterra equalization scheme that can compensate for nonlinear distortion and can be used for all M-APSK modulation methods of DVB-S2 X system is proposed,which solves the problem of high complexity caused by the nonlinear terms of volterra equalizer.Then,the simulation verifies the validity of the proposed scheme and the traditional equalization algorithms suitable for DVB-S2 X system when there is nonlinear distortion in the channel.It can be seen that compared with the traditional volterra equalizer,the proposed scheme has the advantages of low complexity,similar convergence speed and applicable to all M-APSK modulations.When the proposed volterra equalization scheme for compensation of nonlinear distortion is added to the channel,the best backoff value can be obtained at a lower signal-to-noise ratio,which improves the overall link backoff performance.Finally,when the channel linear distortion and nonlinear distortion exist at the same time,the nonlinear equalization structure of time domain symbol spaced equalizer and volterra equalizer is proposed,and the MSE performance of the proposed nonlinear equalization structure is better than that of the traditional volterra equalizer.Third,the time and frequency domain parallel equalization technology and FPGA implementation of the DVB-S2 X system against linear distortion under the satellite channel are studied,analysis of traditional time domain,frequency domain parallel fractional spaced equalization algorithms and implementation of complexity.Aiming at the problem of excessive use of multiplier resources when the existing parallel equalizer technology is applied to high-speed data transmission,this paper proposes low-complexity parallel fractional-interval equalization schemes in the time domain and frequency domain.The simulation shows that the two proposed equalization schemes can effectively compensate the linear distortion caused by IMUX-OMUX with low complexity.