OFDM中导频相位连续指的是什么意思？

12-16

最近看DRM系统，提到导频是相位连续的（tone are continous），可以使频率同步独立于码元同步，但是不太明白相位连续的具体定义，有知道的请指教一下。谢谢！

"Fundamentals of WiMAX"这本书里的，wimax的ranging code，就是相位连续的:
"During a ranging process, the BS determines the parameters of ranging by correlating the received signal with an expected copy of the signal, which is known by the BS a priori. In order for the correlation process to work over the entire ranging signal, which spans multiple OFDM symbols, there
must be no discontinuity of the signal across OFDM symbols."
更多的你上网下这本书看看就知道了。