基于阵列导频的正交时频空调制信道估计算法

Channel Estimation Algorithm for Orthogonal Time Frequency Space Modulation System Based on Array Pilot

正交时频空调制(orthogonal time frequency space modulation,OTFS)系统中,发送端嵌入少量高能量导频,并在导频周围预留保护符号的导频结构,会导致OTFS信号峰均比(peak-to-average power ratio,PAPR)高。基于导频和数据叠加的导频设计结构,可以降低发送端信号峰均比,但接收端信道估计复杂度高。为降低OTFS信号峰均比和信道估计复杂度,设计了一种基于最佳二进制阵列(perfect binary array,PBA)的导频结构和信道估计算法。在发送端,通过将导频能量均匀分布在一个阵列的多个导频中,降低了OTFS信号峰均比。在接收端,利用最佳二进制阵列导频的理想自相关特性,通过移位相关操作,分离信道多径和聚集每条信道径的能量,并抑制噪声和残留多径间干扰,以较低的计算复杂度实现较高精度的信道估计。相较于现有的一些导频结构及其信道估计算法,在牺牲一定的信道估计精度情况下,所提方案有效降低了OTFS信号的PAPR和信道估计复杂度。

In orthogonal time frequency space modulation(OTFS)system,a pilot structure with a small amount of high-energy pilots embedded in the transmitter and protection symbols reserved around the pilots would lead to high peak-to-average power ratio(PAPR)of OTFS signals.The pilot design structure based on pilot and data superposition can reduce the signal PAPR at the transmitter,but the complexity of channel estimation at the receiver is high.In order to reduce the PAPR of OTFS signal and the complexity of channel estimation,a pilot structure and channel estimation algorithm was designed based on perfect binary array(PBA).At the transmitter,the PAPR of OTFS signals was reduced by uniformly distributing the pilot energy among multiple pilots of an array.At the receiver,by using the ideal autocorrelation characteristic of the PBA,the channel multipath were separated and the energy of each channel path was aggregated through the shift correlation operation,and the noise and residual interference among multipath were suppressed.In such way,the high precision channel estimation was achieved with low computational complexity.Compared with some existing pilot structures and channel estimation algorithms,the proposed scheme effectively reduces the PAPR of OTFS signal and the complexity of channel estimation at the expense of certain channel estimation accuracy.