STC-OFDM系统的post-IDFT多波束形成技术

Post-IDFT Multidimensional Beamforming for STC-OFDM Systems

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。

A post-inverse discrete Fourier transform scheme was proposed for space-time coded-orthogonal post-IDFT ） multidimensional beamforming quency 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-lDFF beamforming （m） is less than the number of the transmit antennas （M）, the system reduces M -m IDFF blocks.