Research On Channel Estimation Based Onindex Modulation Orthogonal Frequency Division Multiplexing System

In recent years,the 4^th generation mobile communication technology has been gradually realized large-scale commercial applications;however,due to the rapid development of industries such as the Big Data,the Artificial Intelligence and the Internet of Things etc.,people are increasingly demanding data transmission rates,communication quality and user experience,so the 5^th generation mobile communication technology has become the main development direction of the new generation mobile communication technology.At present,the development of 5G technology is still in the initial stage of commercial application,and major research institutes and universities etc.are striving to study new physical layer transmission technologies applicable to 5G standards.The index modulation technology is one of them.Compared with the traditional orthogonal frequency division multiplexing technology,the index modulation technology has been rapidly developed in recent years due to its advantages of higher spectrum utilization,higher energy efficiency,stronger anti-subcarrier interference capability,and higher system configuration flexibility.This paper mainly researches the channel estimation based on index modulation OFDM system.Analyzing the performance of index modulation technique,sequential pilot structure,and three classical channel estimation algorithms in this system,and simulating verification under frequency selective fading channel.In order to eliminate the influence of noise on system performance,the existing channel estimation algorithm is improved.The paper briefly introduces the basic characteristics of wireless channel and the system model of OFDM technology,leads into the index modulation technology,combines it with OFDM technology to construct OFDM-IM system model,and presents the basic principle of the system in detail.Two different index modulation techniques and their corresponding detection algorithms are elaborated.Then,the method of pilot placement,the principle of channel estimation algorithm and the principle of common interpolation algorithm for OFDM-IM system are introduced,the model simulation are carried out by MATLAB software,and the performance of various algorithms are compared.The simulation results demonstrate that the bit error rate of DFT algorithm is lower than LMMSE algorithm,and the bit error rate of LMMSE algorithm is lower than LS algorithm;at that time ofBER=10^-3,the SNR of DFT algorithm obtains about 2 dB gain than LMMSE algorithm,and obtains about 5 dB gain than LS algorithm.When the value of SNR is greater than 25 dB,the bit error rate of each channel estimation algorithm in the OFDM-IM system is reduced by about one order of magnitude relative to the bit error rate of the corresponding algorithm in the OFDM system.For the problem that LS algorithm is susceptible to noise interference in channel estimation,an improved LS algorithm based on adaptive noise cancellation technique is proposed.The simulation results indicate that the improved LS algorithm has lower bit error rate than the original LS algorithm;at that time ofBER=10^-4,the SNR of the improved LS algorithm achieves a gain of about 5 dB over the original LS algorithm.In addition,for the problem that DFT algorithm still contains noise before the cyclic prefix or the maximum delay during the channel estimation,an improved DFT path-finding algorithm for OFDM-IM system is proposed.The simulation reveals that the improved DFT path-finding algorithm has lower bit error rate than the DFT path-finding algorithm under the same number of channels;at that time ofBER=10^-4,the SNR of the improved DFT path-finding algorithm with 9 channels of multipath transmission can obtain about 1 dB gain,and it receives a gain of about 2 dB when the number of channels for multipath transmission is 19.