Research On ICI Cancellation Algorithm For OFDM System

OFDM(Orthogonal Frequency Division Multiplexing)technology has been widely used in many fields because of its inter-symbol interference(Inter-Symbol Interference,ISI)and spectrum utilization advantages in anti-multipath fading channels.However,the largest "hero" that makes the contribution is the orthogonality between the subcarriers of the technique,and the orthogonality occurs so that different subcarriers overlap each other in the spectrum.In recent years,with the growth of related technologies,OFDM technology has become more and more widely used,it has become the fourth generation(4G)of mobile communication key technology.However,every technology will have its own shortcomings,OFDM technology is no exception,it also has some shortcomings: the OFDM system in the subcarriers are overlapping between each other,so this system is very feared to CFO.In other words,if the orthogonal between subcarriers does not get 100% satisfied,it may lead to the existence of inter-carrier interference(ISI).With the increasing communication and technology in various fields in recent years,the demand for communication technology has been continuously improved,and the demand for spectrum resources has been increasing,resulting in a continuation of the interval between subcarriers.It is conceivable that orthogonality becomes more fragile and ICI is more severe.Therefore,it is necessary to study the inter-carrier interference cancellation technique.In this paper,the OFDM system is the main research background,through the study of the inter carrier interference cancellation algorithm as the core,based on the cancellation algorithm proposed by the predecessors.The main contents of the thesis include:1.This paper studies the inter-carrier interference(ICI)problem of OFDM system,analyzes the main causes of ICI,and from the mathematical formula derivation on the specific impact of ICI on the system..2.This paper introduces the research on ICI cancellation algorithm at home and abroad,and compares the performance of the algorithm from two aspects: theoretical analysis and simulation.Among them,the main research algorithms are: self-elimination algorithm based on frequency domain coding technology,CC(conjugate cancellation)algorithm based on dual path.3.For the frequency domain coding technology from the elimination algorithm,to do two aspects of improvement.First,the lack of spectrum utilization for this technology has been improved,bringing the efficiency of the traditional 50% to 75%.The main idea of this method is that the transmission channel is sent by the signal processing knowledge after passing the IFFT,so that the frequency offset factor of the odd carrier transmitted by the first half is only the second half of the carrier Half of the frequency offset factor,and the second half of the carrier and then the traditional coding self-elimination technology.Second,improvements in performance and spectrum utilization have been further improved,resulting in a significant improvement in bit error performance compared to conventional coding techniques that did not decrease.The main idea of this method is: on the basis of the first method,at the sending end,transmit three sections of data namely: odd carrier data,even carrier data,even carrier data.Due to the retransmission of the latter two data,they can be used to roughly estimate the corresponding frequency offset factor and compensate at the receiving end.