接入信道中，导频信道的开环输出功率为mean pilot channel output power，数据信道的开环输出功率为meandatachanneloutputpower，则接入信导前缀中的导频信道输出功率为（）

A.mean pilot channel output power-mean data channel output power
B.mean pilot channel output power+mean data channel output power
C.mean pilot channel output power-0.5*mean data channel output power
D.mean pilot channel output power+0.5*mean data channel output power