问一下TD-SCDMA标准中一句话的解释

就是8.1.1 Modulation of the SYNC-DL中的
不知道下面这段说的什么意思，哪位给个明白的说法，谢谢，全文附后
The SYNC-DL sequences are modulated with respect to the midamble (m(1)) in time slot #0.
Four consecutive phases (phase quadruple) of the SYNC-DL are used to indicate the presence of the P-CCPCH in the
following 4 sub-frames. In case the presence of a P-CCPCH is indicated, the next following sub-frame is the first subframe
of the interleaving period. As QPSK is used for the modulation of the SYNC-DL, the phases 45, 135, 225, and
315° are used.
The total number of different phase quadruples is 2 (S1 and S2). A quadruple always starts with an even system frame
number ((SFN mod 2) =0). Table 8 is showing the quadruples and their meaning.

 25223-450.pdf

或者看看这段中文的，所谓以m(1)为基准进行相位调制是什么意思呢
先差分？
7.1.1    SYNC-DL的调制
SYNC-DL序列以timeslot 0 的m(1)为基准进行相位调制。
SYNC-DL的四个连续相位用于指出P-CCPCH在接下来的四个子帧中的存在。在指出P-CCPCH存在的情况下，紧接着的子帧即为交织周期的第一子帧。因为SYNC-DL 使用QPSK调制，相应的相位是45,135,225和315。
不同的相位quadruple总数是2（S1和S2）。一个quadruple总是从奇系统帧号开始((SFN mod 2) =0)。表2给出了quadruple和它们的含义。
表 2: 用于 SYNC-DL相位调制的序列
名字    4个连续相位    含义
S1    135, 45, 225, 135    在后续的四个子帧有P-CCPCH
S2    315, 225, 315, 45    在后续的四个子帧没有P-CCPCH