多输入多输出(MIMO)正交频分复用(OFDM)雷达通常采用等间距子载频交错(ESI),实现不同发射天线信号在频域的正交。然而,ESI存在距离依赖性的角度误差问题。针对该问题,文中提出一种基于距离分复用(RDM)MIMO OFDM雷达的目标参数估计方法...多输入多输出(MIMO)正交频分复用(OFDM)雷达通常采用等间距子载频交错(ESI),实现不同发射天线信号在频域的正交。然而,ESI存在距离依赖性的角度误差问题。针对该问题,文中提出一种基于距离分复用(RDM)MIMO OFDM雷达的目标参数估计方法。首先,建立RDM MIMO OFDM雷达信号模型,获得发射端在距离维的正交波形,使得雷达接收机的天线孔径得到明显扩展,提升角度分辨率;其次,在距离-速度处理和角度估计之间,提出一种二值掩码方法分离不同发射波形,代替了传统的带通滤波器,同时抑制噪声干扰,改善成像质量;最后,仿真验证所提方法的正确性和有效性,结果表明,与ESI相比,所提方法可以有效去除距离依赖性的角度误差,提升成像分辨率和角度参数估计精度。展开更多
多输入多输出(MIMO)正交频分复用(OFDM)雷达通常采用等间距子载频交错(ESI)方式,实现不同发射天线信号在频域的正交。然而,ESI存在距离依赖性的角度误差和距离模糊问题。针对该问题,提出了一种基于距离分复用(RDM)的MIMO OFDM雷达距离...多输入多输出(MIMO)正交频分复用(OFDM)雷达通常采用等间距子载频交错(ESI)方式,实现不同发射天线信号在频域的正交。然而,ESI存在距离依赖性的角度误差和距离模糊问题。针对该问题,提出了一种基于距离分复用(RDM)的MIMO OFDM雷达距离和角度联合估计方法。首先,建立RDM MIMO OFDM雷达信号模型,获得发射端在距离维的正交波形,同时消除了距离依赖性的角度误差;其次,在距离-速度-角度成像处理中采用改进DFT,代替传统DFT实现多普勒估计和校正;此外,在某些发射天线上额外添加相位偏移,打破目标峰值在距离维的等间距分布特性,通过搜索目标峰值距离索引差来确定模糊数,从而求解距离模糊问题。仿真结果验证了所提方法的有效性。展开更多
Based on the frequency domain training sequences, the polynomial-based carrier frequency offset （CFO） estimation in multiple-input multiple-output （ MIMO ） orthogonal frequency division multiplexing （ OFDM ） sys...Based on the frequency domain training sequences, the polynomial-based carrier frequency offset （CFO） estimation in multiple-input multiple-output （ MIMO ） orthogonal frequency division multiplexing （ OFDM ） systems is extensively investigated. By designing the training sequences to meet certain conditions and exploiting the Hermitian and real symmetric properties of the corresponding matrices, it is found that the roots of the polynomials corresponding to the cost functions are pairwise and that both meger CFO and fractional CFO can be estimated by the direct polynomial rooting approach. By analyzing the polynomials corresponding to the cost functions and their derivatives, it is shown that they have a common polynomial factor and the former can be expressed in a quadratic form of the common polynomial factor. Analytical results further reveal that the derivative polynomial rooting approach is equivalent to the direct one in estimation at the same signal-to-noise ratio（SNR） value and that the latter is superior to the former in complexity. Simulation results agree well with analytical results.展开更多
A new preamble structure is designed for wireless LAN based on MIMO OFDM systems, which can be used for both synchronization and channel estimation. Modulatable orthogonal polyphase sequence is utilized in training sy...A new preamble structure is designed for wireless LAN based on MIMO OFDM systems, which can be used for both synchronization and channel estimation. Modulatable orthogonal polyphase sequence is utilized in training symbol design regarding its correlation properties. The time synchronization and channel estimation are achieved by measuring the correlation between the received training sequence and the locally generated training sequence. Repeated training symbols are used to get carrier frequency offset （CFO） estimation. It is shown from the analysis that the accuracy of frequency synchronization is close to the Cramer-Rao lower bound. The training sequences are optimal for channel estimation based on the minimum mean square error （MMSE）.展开更多
针对慢时变频率选择性MI MO OFDM(Multiple Input Multiple Output Orthogonal Frequency Division Multi-plexing)系统,提出一种低复杂度的信道估计算法。文中所用方法是STBC(space-ti me block coded)MI MO OFDM系统中一种基于EM(Expe...针对慢时变频率选择性MI MO OFDM(Multiple Input Multiple Output Orthogonal Frequency Division Multi-plexing)系统,提出一种低复杂度的信道估计算法。文中所用方法是STBC(space-ti me block coded)MI MO OFDM系统中一种基于EM(Expectation Maxi mization)的自适应信道估计技术。仿真结果显示在慢衰落环境下,随着用户数的增加,最小均方误差性能没有损失。与RLS(Recursive Least-Squares)算法比较,本文所提出的方法利用了Alamouti STBC编码结构,从而降低了计算复杂度。展开更多
文摘多输入多输出(MIMO)正交频分复用(OFDM)雷达通常采用等间距子载频交错(ESI),实现不同发射天线信号在频域的正交。然而,ESI存在距离依赖性的角度误差问题。针对该问题,文中提出一种基于距离分复用(RDM)MIMO OFDM雷达的目标参数估计方法。首先,建立RDM MIMO OFDM雷达信号模型,获得发射端在距离维的正交波形,使得雷达接收机的天线孔径得到明显扩展,提升角度分辨率;其次,在距离-速度处理和角度估计之间,提出一种二值掩码方法分离不同发射波形,代替了传统的带通滤波器,同时抑制噪声干扰,改善成像质量;最后,仿真验证所提方法的正确性和有效性,结果表明,与ESI相比,所提方法可以有效去除距离依赖性的角度误差,提升成像分辨率和角度参数估计精度。
文摘多输入多输出(MIMO)正交频分复用(OFDM)雷达通常采用等间距子载频交错(ESI)方式,实现不同发射天线信号在频域的正交。然而,ESI存在距离依赖性的角度误差和距离模糊问题。针对该问题,提出了一种基于距离分复用(RDM)的MIMO OFDM雷达距离和角度联合估计方法。首先,建立RDM MIMO OFDM雷达信号模型,获得发射端在距离维的正交波形,同时消除了距离依赖性的角度误差;其次,在距离-速度-角度成像处理中采用改进DFT,代替传统DFT实现多普勒估计和校正;此外,在某些发射天线上额外添加相位偏移,打破目标峰值在距离维的等间距分布特性,通过搜索目标峰值距离索引差来确定模糊数,从而求解距离模糊问题。仿真结果验证了所提方法的有效性。
基金The National Natural Science Foundation of China(No.60702028)the National High Technology Research and Development Program of China(863Program)(No.2007AA01Z268)
文摘Based on the frequency domain training sequences, the polynomial-based carrier frequency offset （CFO） estimation in multiple-input multiple-output （ MIMO ） orthogonal frequency division multiplexing （ OFDM ） systems is extensively investigated. By designing the training sequences to meet certain conditions and exploiting the Hermitian and real symmetric properties of the corresponding matrices, it is found that the roots of the polynomials corresponding to the cost functions are pairwise and that both meger CFO and fractional CFO can be estimated by the direct polynomial rooting approach. By analyzing the polynomials corresponding to the cost functions and their derivatives, it is shown that they have a common polynomial factor and the former can be expressed in a quadratic form of the common polynomial factor. Analytical results further reveal that the derivative polynomial rooting approach is equivalent to the direct one in estimation at the same signal-to-noise ratio（SNR） value and that the latter is superior to the former in complexity. Simulation results agree well with analytical results.
文摘A new preamble structure is designed for wireless LAN based on MIMO OFDM systems, which can be used for both synchronization and channel estimation. Modulatable orthogonal polyphase sequence is utilized in training symbol design regarding its correlation properties. The time synchronization and channel estimation are achieved by measuring the correlation between the received training sequence and the locally generated training sequence. Repeated training symbols are used to get carrier frequency offset （CFO） estimation. It is shown from the analysis that the accuracy of frequency synchronization is close to the Cramer-Rao lower bound. The training sequences are optimal for channel estimation based on the minimum mean square error （MMSE）.
文摘针对慢时变频率选择性MI MO OFDM(Multiple Input Multiple Output Orthogonal Frequency Division Multi-plexing)系统,提出一种低复杂度的信道估计算法。文中所用方法是STBC(space-ti me block coded)MI MO OFDM系统中一种基于EM(Expectation Maxi mization)的自适应信道估计技术。仿真结果显示在慢衰落环境下,随着用户数的增加,最小均方误差性能没有损失。与RLS(Recursive Least-Squares)算法比较,本文所提出的方法利用了Alamouti STBC编码结构,从而降低了计算复杂度。
