Principles of Configuring Clocks for the BSC (BM/TC Separated)

This describes the principles of configuring clocks for the BSC when the BM and TC are configured in different subracks.

GMPS/GEPS Clock

The GGCU in the GMPS traces the upper-level clock, and then provides clock signals for the GMPS and the GEPS.

The reference clock for the GGCU is of two types: the line clock and the BITS clock. The line clock is extracted from the Ater interface by the GMPS. The BITS clock is highly accurate and reliable and therefore the GGCU prefers the BITS clock.

GTCS Clock

The GTCS traces the clock from the A interface. Each GTCS extracts the line clock from the A interface. The configuration of the GTCS clock is the same regardless of whether the GTCS is configured on the BSC side or on the MSC side.

Principles of Configuring Clocks for the BSC

Table 1 lists the principles of configuring clocks for the BSC.

**Table 1** Principles of configuring clocks for the BSC
Clock	Configuration Principle
Line clock of the GTCS	If the GEIUA is configured in the GTCS, a maximum of two line clocks, line clock 0 and line clock 1, can be configured, and the line clock must be configured on the E1/T1 of the A interface. If the GOIUA is configured in the GTCS, only one line clock can be and must be configured on port 0 on the GOIUA. If the BSC is configured with more than one GTCS, the GTCSs extract clock signals from the A interface and use them as line clocks.
8 kHz reference clock of the GTCS	If the configured line clock signals are selected for the 8 kHz reference clock, do not delete any line clock.
Line clock of the GMPS	The line clock of the GMPS must be configured on the Ater connection path of the GMPS.
System clock	The principles of configuring the priority of the clock source are as follows: The BSC provides up to four clock source priorities: priority 1 to priority 4, from the highest to the lowest. The clock source and the clock source priority have a one-to-one mapping. By default, the priority of the BITS clock is higher than that of the line clock. By modifying the priority of the clock source, you can set the priority of the line clock higher than that of the BITS clock. The strategies of switching the clock source are as follows: The BSC in operation requires only one clock source. You need to select the strategy of switching the faulty clock source to a normal clock source. The clock source has three working modes: automatic, manual, and self-oscillation. In automatic mode, you do not have to specify a clock source as the current clock source. The BSC automatically selects a clock source with the highest priority. For example, if the current clock source of priority 3 is faulty, the BSC selects the clock source of priority 4. After the faulty clock source recovers, the BSC switches back to the clock source of priority 3. If all the clock sources are faulty, the BSC switches to the HOLD OVER mode. When the clock source recovers, the BSC switches to the self-oscillation mode. In manual mode, a clock source is specified as the current clock source. The BSC cannot automatically switch to another clock source even if this clock source fails. The self-oscillation mode is the default clock working mode of the BSC.