摘要
针对目前正交频分复用系统时频同步算法中整数频偏估计大多在频域进行从而导致同步模块实现复杂、同步时间较长的问题,提出了一种时域时频同步方案。该方案用CAZAC序列构造了一个具有前后重复结构的训练序列,并用伪随机序列对其中部分数据进行加权,利用数据的重复性和伪随机序列的相关性来完成定时同步;然后通过计算训练序列中未被加权的数据块之间的相位差来估计小数频偏,估计结果具有很高的精度;通过分析频偏对CAZAC序列时域相关特性的影响,设计了相应的整数频偏判决函数,在时域完成整数频偏估计,估计范围较大,且实现复杂度低。仿真结果表明,无论是在AWGN信道还是在多径衰落信道下,该方案中定时同步都具有极高的准确率,与已有算法相比,频偏估计性能也有明显的改善。
To reduce the complexity and operation time of synchronization due to the operations of integer frequency offset estimation in the frequency domain in orthogonal frequency division multiplexing systems, a time-domain time and frequency syn- chronization scheme is proposed. A constant amplitude zero auto correlation （CAZAC） sequence is used to construct a training sequence which contains the same two halves, part of which is then weighted by a pseudo-noise （PN） sequence. The time syn- chronization is accomplished by utilizing the repeatability of the training sequence and the correlation of the PN sequence. Then the fractional frequency offset is estimated with high accuracy by calculating the phase difference between the two parts of the training sequence which have not been weighted by the PN sequence. By analyzing the effect of frequency offset on the correla- tion of CAZAC sequence in the time domain, a decision function for integer frequency offset estimation is designed. The integer frequency offset is estimated in the time domain with a wide estimation range and low complexity. The simulation results show that the proposed time synchronization method has a robust performance in both AWGN channel and multi-path fading channel, and the performance of frequency offset estimation is remarkably improved compared with other methods.
出处
《现代电子技术》
2013年第5期52-56,62,共6页
Modern Electronics Technique
基金
中国科学院战略性先导专项"面向感知中国的新一代信息技术研究资助项目"(XDA06020301)
关键词
正交频分复用
定时同步
频偏估计
CAZAC序列
伪随机序列
orthogonal frequency division muhiplexing
timing synchronization
frequency offset estimation
CAZAC se-quence
pseudo-noise sequence
