Research On Adaptive Technology Based On Index Modulation Orthogonal Frequency Division Multiplexing System

With the continuous development of mobile communication technology,future communication systems will continue to increase the requirements for data transmission rates,system spectral efficiency,energy efficiency,and transmission stability.The communication system based on OFDM technology has many advantages including: high spectrum utilization,effective response to frequency selective fading channel environment,fast transmission rate,etc.,but OFDM system also has its inherent defects such as sensitivity to frequency offset,signal The peak-to-average power ratio?PAPR?is larger.The index modulation technology can increase the sparseness of the subcarriers,improve the anti-interference performance of the system,and reduce the sensitivity of the system to frequency offsets.Therefore,this paper introduces the index modulation technology into the OFDM system,and then improves the channel estimation technology and transmission structure of the system Then,an improved adaptive transmission algorithm is proposed to improve the overall performance of the system.1)This paper analyzes the basic characteristics of the wireless channel and the transmission model and basic principles of the OFDM system.Based on the OFDM system,the index modulation technology is introduced.The simulation shows that the index error modulation performance of the OFDM system based on index modulation is better than that of the original OFDM system;2)At the receiving end,a channel estimation algorithm based on DFT path finding is used,and the channel response function obtained by this algorithm is used to optimize the adaptive modulation algorithm Chow algorithm and Fisher algorithm suitable for multi-carrier communication,and is applied to OFDM In the-IM system,it can be seen from the simulation results that the optimized Chow algorithm can obtain a signal-to-noise ratio gain of 3.5 dB when the bit error rate is 10^-3 compared with the previous Chow algorithm.Compared with the previous Fisher algorithm,the optimized Fisher algorithm can obtain a signal-to-noise ratio gain of 5dB when the bit error rate is 10^-3;3)By finding the combination of subcarrier block modulation methods that maximizes the minimum Euclidean distance,the system's bit error rate performance is optimized.From the simulation results,it can be seen that when the bit error rate is10^-3,compared with the optimized Chow It has a 3dB SNR gain,which has a 5dB SNR gain compared to the original Chow algorithm;4)A dual-mode constellation modulation method is used,and a new index mode lookup table and a dual-mode mapping method of the constellation points are updated.This method can improve the spectral efficiency compared to the original index modulation system,and then the simulation finds that the system can use [20,30] dB adaptive modulation of the SNR threshold interval to obtain the best bit error rate performance,and then the dual-mode system uses an adaptive modulation algorithm based on a fixed SNR threshold interval,which can be seen through simulation When the bit error rate is 10-4,the signal-to-noise ratio gain of 5dB can be improved compared with the dual-mode index modulation system without adaptive modulation.Compared with OFDM and OFDM-IM systems using QPSK,when the signal-to-noise ratio interval exceeds 4dB,it still provides better BER performance;5)Finally,the adaptive modulation method of the fixed SNR threshold interval is improved,and an adaptive modulation algorithm based on the dynamic SNR threshold interval is proposed.From the simulation results,it can be seen that when the bit error rate is 10^-3,the adaptive modulation method has a signal-to-noise ratio gain of 3dB.Compared with the dual-mode index modulation system without adaptive modulation,it has a signal-to-noise ratio gain of 5dB.The OFDM system without adaptive transmission technology has a signal-to-noise ratio gain close to 10 dB.