上行正交频分多址接入系统快速盲频偏估计算法

A Fast Blind Carrier Frequency Offset Estimation Algorithm for Uplink Orthogonal Frequency Division Multiplexing Access Systems

为了提高上行正交频分多址接入(OFDMA)系统多用户频偏(CFO)估计收敛速度,提出了一种基于重复因子的快速盲CFO估计算法。在窄带信号的假设条件下,利用直线阵接收信号的自相关、互相关矩阵特征值完成波达方向(DOA)估计,进而根据DOA与子载波以及CFO的对应关系建立子空间,并利用子空间之间的正交性完成CFO估计;通过引入信号重复因子,以循环移位的方式重复使用同一OFDMA符号的数据,大大减少了建立子空间时所需要的OFDMA符号数。另外,以多项式求根代替一维搜索完成最终CFO的求解,使得算法性能不受搜索步长的限制。仿真结果表明,该算法在保证估计精度的同时,能够有效减少算法所需的符号数,当子载波数为64、用户数为4时,在理想情况下所需符号数仅为原来的1/10。

A fast blind carrier frequency offset （CFO） estimation algorithm based on repetition factor is proposed to accelerate the multi-user~ s CFO estimation for the uplink of orthogonal frequency division multiplexing access （OFDMA） systems. Under the hypothesis of narrow band signal, the direction of arrival （DOA） is estimated via the eigenvalues of the auto-correlation and cross-correlation matrixes of received signals from a uniform linear array, and subspaces are set up based on the relationship among DOA, subcarriers and CFO. The orthogonal property of the resulting subspaces is exploited to estimate the CFO. A repetition factor is introduced and data of the same OFDMA symbols are repeatedly used in a cyclic shift manner, so that the number of OFDMA symbols is greatly reduced. The rooting method is used to replace the one-dimensional search for calculating the CFO, which makes the performance of the algorithm independent of the searching step size. Simulation results show that the proposed algorithm reduces the OFDMA symbols exponentially and has a considerable performance. Theoretically, it can reduce the symbols to a tenth part of the original number when there exist 64 subcarriers and 4 users.