For Multi-Input Multi-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems with virtual subcarriers, conventional equispaced pilot tones are no longer applicable in some situations.

• 对于采用虚拟子载波的多输入多输出(MIMO)正交频分复用(OFDM)系统，传统最优的均匀分布导频序列在某些情况下是不可用的。