OFDMA系统上行链路的符号定时估计

Symbol Timing Estimation of the Uplink for OFDMA Systems

在多径信道中,任何符号定时的变化,都会增加OFDMA系统对时延扩展的敏感程度,为了获得最佳的系统性能,需要尽量减小符号定时同步的误差。已有的符号定时估计算法多是基于特定训练序列的,其优点是实现简单且较为准确,但需要占用额外的频谱资源,且时间偏移量需小于循环前缀的长度。文中提出的基于子载波相位差分的符号定时估计算法是一种盲估计算法,不需要额外发送训练序列,节省了资源,且对时间偏移量大于循环前缀的情况同样适用。

In muhi-path channels, any change of symbol timing will increase the sensitivity to delay spread for OFDMA systems. In order to obtain optimum performance of systems, the error of symbol timing synchronization should be reduced as much as possible. Currently, most of the symbol-timing-estimation algorithms are based on training sequences. The advantages of these algorithms are that their implementations are simple, and relatively accurate. However, they also need more spectrum resources, and the timing offset should be no longer than cyclic prefix. In this paper, a blind symbol timing estimation algorithm based on the phase differ- ence between sub-carriers is proposed. This algorithm saves resources because it does not need to transmit extra training sequences. And it also can be applied to the case of timing offset be longer than cyclic prefix.