Timeslot Arrangement on the Abis Interface

During the operations involving timeslot assignment on the BSC6000 Local Maintenance Terminal, if timeslot assignment fails, the LMT prompts you to arrange timeslots. With your confirmation, the BSC automatically arranges timeslots.

The operations related to timeslot assignment are as follows:

• Changing the BTS multiplexing mode
• Adding a BTS
• Adding a cell
• Adding a TRX
• Adding an idle timeslot
• Adding a monitoring timeslot
• Manually assigning Abis timeslots
• Deleting a site chain
• Moving a BTS
• Blocking a timeslot

Assume that there are two cascaded BTSs. Level 1 BTS uses timeslots 4-59, and level 2 BTS uses timeslots 68-127. Four idle timeslots of level 1 BTS are deleted, and timeslots 6, 7, 8, and 9 are released. A new TRX is added to level 2 BTS. The TRX carries six TCHs. Only two complete 64 kbit/s timeslots and two 32 kbit/s timeslots are available. The RSLs cannot be multiplexed onto the TCHs and the timeslots of different BTSs also cannot be multiplexed. Therefore, timeslot resources are insufficient.

The LMT prompts you to decide whether to allow automatic timeslot arrangement by the BSC.

• If the existing timeslot distribution meets the requirements for BSC automatic arrangement, the BSC starts to arrange timeslots.
• If the existing timeslot distribution does not meet the requirements for BSC automatic arrangement, you need to add physical E1 links and add the corresponding site chains on the LMT.

You can use the following methods to arrange timeslots to meet the requirement of the newly added TRX for timeslots.

• Arrange the timeslots of level 1 BTS. Move the services on timeslots 4 and 5 to timeslots 8 and 9. Therefore, an E1 contains three complete 64 kbit/s timeslots. There are sufficient timeslot resources to add a TRX.
• The RSL of the added TRX can use timeslots 4, 5, 6, and 7. The remaining two complete 64 kbit/s timeslots can be assigned to six TCHs.

Table 1 shows the timeslot distribution on the Abis interface before timeslot arrangement by the BSC.

Table 2 shows the timeslot distribution on the Abis interface after timeslot arrangement by the BSC.

The process of timeslot arrangement by the BSC is as follows:

• The BSC releases all the timeslots that are used by the cascaded BTSs except for the timeslots assigned manually.
• The BSC reassigns timeslots for each object.
• If the reassignment of timeslots fails, a timeslot arrangement failure message is displayed.
• The manual assignment of Abis timeslots does not involve timeslot arrangement.
• If the timeslot arrangement fails, the timeslot distribution before the timeslot arrangement is restored.