hij is a complex channel gain for data symbol xi at receive antenna j ,
hij是接收天线j上对数据码元xi的复信道增益，
in particular , complex channel gain hij represents the amplification ( or atte nuation ) that a transmitted signal undergoes in the wireless channel .
具体而言，复信道增益hij表示发送的信号在该无线信道中经历的放大量（或衰减量）。
Hat matrix has special effect in regression diagnostics and residual analysis . It important to discuss the nature of the Hat matrix H = ( hij ) .
帽子矩阵在回归诊断，残差分析中有着特殊的作用，讨论帽子矩阵H=（hij）元素的性质非常重要。
in a frequency division duplex ( fdd ) system such as ofdma , the complex channel gain hij is usually estimated at the ue end .
