快变信道环境下OFDMA系统的信道估计算法

Channel estimation method for OFDMA systems over fast time-varying channels

现有OFDMA系统时变信道估计方法仍需假设信道在一个符号内平稳,而在高速移动环境下,信道在符号内的时变将造成OFDMA系统子载波间干扰(ICI).经典的OFDM系统中的时域快时变信道估计方法可以较好地估计出信道在一个符号内的时变,但需要理想等间隔均匀分布于整个频域的导频.针对OFDMA频分多址系统中某一用户占用的频域非均匀导频样式,提出一种适用于OFDMA系统的频域快时变信道估计方法.该方法在频域进行,避开时域处理对等间隔导频的要求,利用频域时变传输函数辅助跟踪估计信道在一个符号内的时变,最终得到信道频域传输矩阵,估计出快变信道符号内时变对系统造成的ICI影响系数.仿真实验从误码率、均方误差两方面验证了该方法的有效性.

Current channel estimation（CE） schemes for OFDMA systems track channel variations symbol by symbol result in ICI when the channel is Time-varying（TV） in one symbol period.However,conventional TV CE methods for OFDM systems need optimal even-pilots to track channel time variations in one symbol period.For practical OFDMA systems,the required even pilot tone is not satisfied.In this paper,we present a pilot-assisted CE method for practical OFDMA systems in TV channels,which is performed in the frequency-domain,avoiding time-domain transformations and does not need even-spaced pilots.The frequency-domain transmission function is employed to estimate channel variations over one OFDMA symbol period.Simulation results show that the proposed method outperforms current OFDMA CE schemes in terms of the symbol-error-rate（SER） and Mean Square Error（MSE）.