ICI elimination of M-band wavelet multi-carrier modulation system

To solve the inter carrier interference （ICI） elimination problem of an M-band wavelet multi-carrier modulation system, this paper analyzes the principle of the ICI caused by the Doppler frequency shift and its mathematical expression based on the M-band wavelet multi-carrier modulation system model. Through the analysis of the mathematical expression and combining with the perfect reconstruction conditions of the filter banks, we propose the design conditions of an M-band filter to reduce and eliminate the ICI. The impulse response model of the filter design conditions and an iterative algorithm is also established. The simulation results show that the proposed ICI reduction and elimination methods can effectively improve the system performance.

Wireless channel estimation for high-speed rail communications:Challenges,solutions and future directions

With the development of High-Speed Rail(HSR),countries and individual passengers alike have enjoyed far ranging benefits as a result-economic,social,environment and in added convenience.One of the important parts of HSR construction is the signaling system,where wireless communications play a key role in the transmission of train control data.Channel estimation has a significant impact on the quality of the wireless communication,however,whose performance is degraded due to the fast mobility of HSR.This paper focuses on the channel estimation technology in HSR.We first summarize the key challenges for HSR channel estimation,especially the Inter-Carrier Interference(ICI)faced by Orthogonal Frequency Division Multiplexing(OFDM)systems.Then we provide a comprehensive review of existing pilot-aided channel estimation schemes from three points:channel model,estimation algorithm,joint channel estimation and ICI mitigation schemes.Lastly,we present the challenges of channel estimation for the Orthogonal Time Frequency Space(OTFS)system and Reconfigurable Intelligent Surface(RIS),which are promising techniques for HSR systems in the future sixth Generation(6G)wireless communication.

A novel energy-efficient ICI cancellation technique for bandwidth improvements through cyclic prefix reuse in an OFDM system

作为一项非常有前景的技术,正交频分复用(orthogonal frequency division multiplexing,OFDM)解决了频谱分配中的带宽不足问题,引领了无线移动通信领域的发展。然而,多普勒频移和本地振荡器频率同步误差的存在会导致载波间干扰(inter carrier interference,ICI),严重影响了正交频分复用。以往文献中提出了许多ICI消除技术,例如自消除法(self-cancellation,SC),最大似然估计法(maximum likelihood estimation,MLE)和加窗法,但需要在带宽冗余和系统复杂度之间权衡。本文基于接收端循环前缀(cyclic prefix,CP)再利用,提出了一种节能且具有有效带宽的新技术来消除ICI。自消除法和最大似然估计法在发送端发送整个OFDM符号数据时会产生冗余,而本文提出的技术仅使用循环前缀数据(仅占总符号带宽的20%)来估计信道,产生与前两者类似结果的同时节省了大量带宽。仿真结果表明,该技术在误差性能方面有显著的改进;并且在实现高带宽增益的同时,能效也得到了实质性的改善。因此,该技术优于传统ICI消除技术。