移动OFDM CFOs估计的步长算法实现

Realization of step-size algorithm of CFOs estimation for mobile OFDM

为了保持移动中正交频分复用（OFDM）技术子载波间的正交性,避免载波间的干扰（ICI）引起的系统性能退化,建立了载波频率偏移（CFOs）的步长估计模型,对模型的稳定性、步长参数和CFOs的估计误差等进行研究,并进行了MATLAB仿真。VHDL程序在电路板上运行的实验结果表明：在±3σ估计变化区间内,移动速度为400和800 km/h时,CFOs的误差分别近似为0.010和0.017,符合CFOs估计误差必须精确的在子载波空间1-2%范围内的衡量标准,同时程序在电路板上能够正确执行。

In order to maintain orthogonality among subcarriers for mobile OFDM,a CFOs step-size estimation model is established to avoid severe performance degradation caused by ICI,and algorithmic stability,step-size parameters,and the errors of CFOs estimation are investigated.First,after an averaging window algorithm is introduced,the mathematic model of step-size estimation algorithm is obtained through step-size parameter and time-varying CFOs.Then,based on the results of simulation referred to MATLAB,the determination of step-size parameter,the advantages of step-size algorithm and precision are presented.Finally,the procedure is implemented with VHDL.Experimental results indicate that the CFOs errors are approximately 0.01 and 0.017 in ±3σ variance interval,when mobile velocity are 400 km/h and 800 km/h,respectively,which accords with the verdicted principle that the error of CFOs estimation must be accurate within 1～2% of the subcarrier spacing,and the procedure can be correctly implemented on circuit board.