快时变环境下OFDM系统中的信道估计

Channel Estimation of Rapidly Time-Varying Channels for OFDM Systems

在OFDM系统中,怎样对快时变信道进行较为准确的估计是一个具有挑战性的课题。该文在利用信道基扩展模型的基础上,提出了一种适合于快时变环境下OFDM系统的信道估计方法,并且依据使估计的均方误差最小的准则,推导了相应最优的导频序列,包括最优的导频取值和最优的导频分布。可以证明,最优的导频序列是由一些相邻的等间隔等能量的子序列构成,每个子序列的导频之间满足一定的相位关系。仿真结果表明了所提估计算法在快时变环境下的有效性和采用所推导的最优导频序列进行估计的优越性。

In Orthogonal Frequency-Division Multiplexing （OFDM） systems, how to estimate rapidly time-varying channels exactly is a challenge issue. In this paper, relying on a basis expansion channel model, a channel estimation scheme of rapidly time-varying channels is proposed for OFDM systems. Along with the channel estimation scheme, the optimal pilot sequence and optimal placement of the pilot tones are also derived with respect to the mean square error （MSE） of the channel estimate. It is shown that the optimal pilot sequence consists of some adjacent equipowered and equispaced subscquences, and each of them is constrained by certain phase conditions. Simulation results demonstrate the effectiveness of the proposed channel estimation scheme in rapidly time-varying scenarios and the superiority of using the derived optimal pilot sequences.