正交频分复用无线局域网系统的帧信号检测

Frame detector suitable for orthogonal frequency division multiplexing based WLAN system

为了能够在大载波频偏、多径信道下快速可靠地捕获频分复用(OFDM)无线局域网(WLAN)系统帧信号,提出了一种低复杂性帧检测器.帧检测被等效为一个含未知参数(噪声功率、信道响应和载波频偏)的假设检验模型,对它应用广义似然比检验原理,导出了最大似然检测统计量,然后根据帧前导字周期性的特点进行简化,得到帧检测器.该检测器具有恒虚警、与载波频偏无关、结构简单等良好特性.仿真结果显示,该检测器和常规的自相关检测器相比在漏警概率为10-4时有大于1 dB的性能改善.

This work presents a low complexity frame detector to rapidly and reliably detect frame signal of orthogonal frequency division multiplexing （OFDM） wireless LAN （WLAN） system over multipath channel with large carrier frequency offset （CFO）. Frame detection was taken as a hypothesis test model with unknown parameters, including noise variance, channel impulse response and CFO. Application of generalized likelihood ratio test to this model yielded maximum likelihood test statistics. The periodic structure of the transmitted frame preamble was exploited to simplify the test statistics of the expected frame detector, which was a constant false-alarm rate （CFAR） detector and insensitive to CFO. Simulation results showed that the proposed detector can provide above 1 dB improvement over the conventional autocorrelation-based detector at a miss probability of 10^-4.