Post-IDFT Multidimensional Beamforming for STC-OFDM Systems
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摘要: 提出了适用于空时编码-正交频分复用(OFDM)系统的后-逆离散傅立叶变换(post-IDFT)多波束形成技术.该技术通过对空频信道相关矩阵进行特征分解获得多个特征模式,再利用空时分组码(STBC)各发射分支信号的正交性使OFDM系统形成多个post-IDFT波束.接收端根据STBC传输矩阵的正交性对多波束解码.系统获得的空间分集增益为空频信道相关矩阵的特征值之和,最大空间分集增益与子载波波束形成方案相同,误码率比STC-OFDM的低.该技术将复杂度降低到子载波波束形成方案的1/S(S为OFDM系统的子载波数目),而且当波束维数(m)小于发射天线数目(M)时,可进一步减少M-m个IDFT模块Abstract: A post-inverse discrete Fourier transform(post-IDFT) multidimensional beamforming scheme was proposed for space-time coded-orthogonal frequency division multiplexing(STC-OFDM) systems.This scheme obtains multiple eigen mode by decomposing cross-matrix of space-frequency channels,and forms multidimensional post-IDFT beamformings for STC-OFDM systems based on the orthogonality of the STBC transmission matrix.The space-diversity gain achieved by the scheme is the sum of the multiple eigen values,and is the same as that of the sub-carrier beamforming,with a lower symbol error rate(SER) than a STC-OFDM does.The proposed scheme reduces the complexity to 1/S(S is the number of subcarriers of an OFDM system) compared with the sub-carrier beamforming;moreover,when the dimension of the post-IDFT beamforming(m) is less than the number of the transmit antennas(M),the system reduces M-m IDFT blocks.
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Key words:
- OFDM /
- space-time coding /
- beamforming /
- space-diversity
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