Changing Reciprocal Relations Between Cells

If some neighboring cells of a cell are redundant or missing, the services between cells may lose the balance. In this case, you need to delete or add neighboring cells of this cell. If call drops occur frequently when the MSs in a cell are handed over to a neighboring cell, you need to set the related parameters of reciprocal relations between cells.

Scenario	Network optimization
Impact	There is no impact on the BSC services.
NEs Involved	BSC and BTS

Redundant cell: If cell A is a neighboring cell of cell B, but the services in cell B are never or rarely handed over to cell A. In this case, cell A is a redundant cell.

Missing cell: If cell A needs to have cell B as its neighboring cell, so that it can hand over some services to cell B when necessary, but cell B is not configured as a neighboring cell of cell A. In this case, cell B is a missing cell.

Through the analysis of related performance measurement counters, you can determine whether a cell is a redundant cell or missing cell of the originating cell.

Through the analysis of the measurement counter Outgoing Internal Inter-Cell Handover Measurement per Cell, you can determine whether a cell is a redundant cell of the source cell.
Through the analysis of the measurement counter Neighbor Cell Level Measurement per Cell, you can determine whether a cell is a missing cell of the source cell.

Prerequisites

The LMT runs normally.
The communication between the LMT and the BSC is normal.
The communication between the BTS and the BSC is normal.

Preparation

Table 1 lists the data to be negotiated and planned before you change the reciprocal relations between cells.

**Table 1** Data to be negotiated and planned before changing the reciprocal relations between cells
Category	Description	Source
Bidirectional adjacent cell	Two bidirectional neighboring cells are neighboring cells of each other.	Network planning
Unidirectional adjacent cell	A unidirectional neighboring cell can use only the cells in its neighboring cell list as its neighboring cells.	Network planning
Inter-cell HO Hysteresis	Handover hysteresis of the neighboring cells in the same layer. Inter-cell HO Hysteresis is configured to reduce the ping-pong effect. If the cells are in different layers, this parameter is invalid. Inter-cell HO Hysteresis should be modified according to handover performance measurement and network conditions. A proper setting of Inter-cell HO Hysteresis can facilitate the handovers between neighboring cells.	Network planning
Min Access Level Offset	A neighboring cell is configured with Min Access Level Offset based on Min DL Level on Candidate Cell. The receive level of a candidate cell must be greater than Min DL Level on Candidate Cell plus Min Access Level Offset.	Network planning
PBGT HO Threshold	The PBGT handover to a neighboring cell occurs when the difference between the downlink level of the neighboring cell and that of the serving cell is greater than PBGT HO Threshold.	Network planning
BQ HO Margin	Set BQ HO Margin to approximately 69 in densely-populated urban areas. Set BQ HO Margin to approximately 72 in suburban areas. The handover to a neighboring cell occurs when the following condition is met: downlink level of the neighboring cell after filtering - downlink level of the serving cell after power control compensation > Inter-cell HO Hysteresis - BQ HO Margin + 64. The services in the serving cell can be handed over to the neighboring cell whose level is lower than that of the serving cell after power control compensation when the following condition is met: Inter-cell HO Hysteresis - BQ HO Margin + 64 < 0.	Network planning
Chain Neighbor Cell	This parameter determines whether the cell is a chain neighboring cell. YES: chain neighboring cell; NO: non-chain neighboring cell	Network planning
Adjacent Cell Inter-layer HO Hysteresis	This parameter determines the hysteresis of an inter-layer or inter-priority handover. This parameter is used to avoid inter-layer ping-pong handovers. Actual Inter-layer HO Threshold of a serving cell = configured Inter-layer HO Threshold - Inter-layer HO hysteresis. Actual Inter-layer HO Threshold of a neighboring cell = configured Inter-layer HO Threshold + Adjacent Cell Inter-layer HO Hysteresis - 64.	Network planning
Direct Retry Handover Level Range	This parameter determines the difference between the level of the neighboring cell and that of the serving cell in directed retry.	Network planning
IBCA Neighbor Cell Flag	When the neighboring cell of the serving cell is configured, this parameter is set to Yes if the IBCA algorithm needs to consider the interference of the serving cell and neighboring cell; otherwise, this parameter is set to No.	Network planning
IBCA Dynamic Measure Neighbor Cell Flag	When the neighboring cell is configured for the serving cell, this parameter is set to Yes if the information about the neighboring cell is not reported in the measurement report and the interference of the neighboring cell cannot be ignored; otherwise, this parameter is set to No. Usually, this parameter of the neighboring cell that the co-channel interference occurs is set to dynamic measurement cell. This parameter of the neighboring cell at layer 2 that the co-channel interference occurs must be set to Yes.	Network planning

NOTE:

Inter-cell HO Hysteresis, Min Access Level Offset, PBGT HO Threshold, BQ HO Margin, Chain Neighbor Cell, Adjacent Cell Inter-layer HO Hysteresis, Direct Retry Handover Level Range, IBCA Neighbor Cell Flag, and IBCA Dynamic Measure Neighbor Cell Flag are used as the supplementary parameters to reduce call drops during handovers. If call drops are not reduced after these parameters are set, you need to change the handover data of the related cells. You can use the default settings of these parameters or set them according to actual requirements.

Table 2 lists the example of the data negotiated and planned for changing reciprocal relations between cells.

**Table 2** Example of the data negotiated and planned for changing reciprocal relations between cells
Category	Original Configuration Data	Target Configuration Data
Bidirectional neighboring cells of cell 3012	3012-1, 3012-2	3012-1, 3012-3
Unidirectional neighboring cells of cell 3012	3012-4, 3012-5, 22-0, 11-0	3012-4, 3012-6, 22-1, 11-1

NOTE:

The cells under the same BSC can be set to unidirectional neighboring cells or bidirectional neighboring cells. The external cells can be set to only unidirectional neighboring cells.

Procedure

If there are redundant cells, delete them from the neighboring cell list.
1. On the BSC6000 Local Maintenance Terminal, right-click the target cell. Choose Configure Adjacent Cell. A dialog box is displayed, as shown in Figure 1.
  Figure 1 Configuring Cells Attributes dialog box
2. Add the cell from the Cell view list box to the Selected cells list box, as shown in Figure 2.
  Figure 2 Selecting a cell
3. Click Next. A dialog box is displayed, as shown in Figure 3.
  Figure 3 Configuring neighboring cells
4. Click Set Adjacent Cells. A dialog box is displayed, as shown in Figure 4.
  Figure 4 Changing reciprocal relations between cells
5. Select 3012-2 from the Bidirectional Adjacent Cells list box and delete it from the Bidirectional Adjacent Cells list box, as shown in Figure 5.
  Figure 5 Deleting the original bidirectional neighboring cell
6. Click OK to return to the dialog box, as shown in Figure 3.
7. Use the same method to delete the unidirectional neighboring cells 3012-5, 11-0, and 22-0 of cell 3012 from the Single Directional Adjacent Cells list box.
8. Click Finish.
If there are missing cells, add them to the neighboring cell list.
1. On the BSC6000 Local Maintenance Terminal, right-click the target cell. Choose Configure Adjacent Cell. A dialog box is displayed, as shown in Figure 6.
  Figure 6 Configuring Cells Attributes dialog box
2. Add the cell from the Cell view list box to the Selected cells list box, as shown in Figure 7.
  Figure 7 Selecting a cell
3. Click Next. A dialog box is displayed, as shown in Figure 8.
  Figure 8 Configuring neighboring cells
4. Click Set Adjacent Cells. A dialog box is displayed, as shown in Figure 9.
  Figure 9 Changing reciprocal relations between cells
5. Select 3012-3 from the System Cells list box and add it to the Bidirectional Adjacent Cells list box, as shown in Figure 10.
  Figure 10 Adding a bidirectional neighboring cell
6. In the Bidirectional Adjacent Cells list box, select 3012-3 and set Inter-cell HO Hysteresis, Min Access Level Offset, PBGT HO Threshold, BQ HO Margin, Chain Neighbor Cell, Adjacent Cell Inter-layer HO Hysteresis, Direct Retry Handover Level Range, IBCA Neighbor Cell Flag, and IBCA Dynamic Measure Neighbor Cell Flag.
7. Use the same method to add the unidirectional neighboring cells 3012-6, 11-1, and 22-1 of cell 3012 to the Single Directional Adjacent Cells list box.
  NOTE:
  - To setting the parameters of a 3G external cell, you need to set only RCSP Offset and Ec/No Offset. you can click Batch Modify to set these parameters at a time.
  - Under normal conditions, use the default settings of Inter-cell HO Hysteresis, Min Access Level Offset, PBGT HO Threshold, BQ HO Margin, Chain Neighbor Cell, Adjacent Cell Inter-layer HO Hysteresis, Direct Retry Handover Level Range, IBCA Neighbor Cell Flag, and IBCA Dynamic Measure Neighbor Cell Flag. You can also set them according to actual requirements. In the dialog box shown in Figure 10, you can click Batch Modify to set these parameters at a time.
8. Click OK to return to the dialog box, as shown in Figure 8.
9. Click Finish.
If call drops occur frequently when the MSs in a cell are handed over to a neighboring cell, you need to set the related parameters of reciprocal relations between cells.
1. On the BSC6000 Local Maintenance Terminal, right-click the target cell. Choose Configure Adjacent Cell. A dialog box is displayed, as shown in Figure 11.
  Figure 11 Configuring Cells Attributes dialog box
2. Add the cell from the Cell view list box to the Selected cells list box, as shown in Figure 12.
  Figure 12 Selecting a cell
3. Click Next. A dialog box is displayed, as shown in Figure 13.
  Figure 13 Configuring neighboring cells
4. Click Set Adjacent Cells. A dialog box is displayed, as shown in Figure 14.
  Figure 14 Changing reciprocal relations between cells
5. In the Bidirectional Adjacent Cells list box, select cell 3012-1, as shown in Figure 15.
  Figure 15 Setting reciprocal relation parameters
6. Set Inter-cell HO Hysteresis, Min Access Level Offset, PBGT HO Threshold, BQ HO Margin, Chain Neighbor Cell, Adjacent Cell Inter-layer HO Hysteresis, Direct Retry Handover Level Range, IBCA Neighbor Cell Flag, and IBCA Dynamic Measure Neighbor Cell Flag according to the network planning.
7. Click OK to return to the dialog box, as shown in Figure 13.
8. Click Finish.
  NOTE:
  If call drops are not reduced during handovers after these parameters are set, you need to change the handover data of the related cells according to the network planning.
  
  The neighboring cells configured for the cell whose automatic neighboring cell optimization function is enabled takes effect only after the neighboring cell optimization task is complete. Before configuring reciprocal relations between cells or setting the parameters in 2G BA2 table, you are advised to check whether the automatic neighboring cell optimization function of the cell is enabled.