GO_NA42_E1_1 GSM Neighbor Cell Optimization 21

7/28/2019 GO_NA42_E1_1 GSM Neighbor Cell Optimization 21

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GSM Neighbor cell Optimization



Course Overview

Related Basic Concepts of Adjacent Cell

How Unreasonable Settings of Neighbor cell

Affect the Network

Optimization of Adjacent Cell Examples of Neighbor cell Optimization



1. What is an adjacent cell?2. What is an external cell? What is an internal

cell?

3. What is the result of a unidirectional adjacent

cell?

4. What are the two aspects that the Neighbor

cell planning imposes impact upon?5. What is the principle of Neighbor cell

planning?

6. What are the types of unreasonable adjacent

cells, and what is the result?

7. Under what conditions do you optimize the

adjacent cell?

8. What is the detailed content of Neighbor cell

optimization?

9. What are the tools for Neighbor cell

planning?

10. Example 1 of Neighbor cell optimization


How Much Do You Know About Neighbor cell

Optimization?



1. What is an adjacent cell?

Neighbor cell refers to the possible target cell when MS performs thecross-cell handoff.

Neighbor cell includes handover cell, reselection cell, handover &reselection cell.

handover cell: An MS that is establishing a call or is in busy status istransferred to the service channel of the new cell.

Reselection cell:

Because of the location change or signal change, an MS inidle status reselects the service cell.

handover & reselection cell:This type of cell can provide the function of both thehandover cell and the reselection cell.



2. What is an external cell? What is an

internal cell?

To realize the cross-cell handover between BSCs, theexternal cell, its carrier frequency and its BSIC are defined.

If the two cells before and after handover are different cellsunder the control of one BSC, they are called internal cell.



3. What is the result of a unidirectional

adjacent cell?

If the relationship between adjacent cells is unidirectional, call dropmight occur.

The unidirectional Neighbor cell usually exists when BSC defines thehandover relationship.

Except for the special situations (beside the hill, beside the sea), therelationship between adjacent cells should be bidirectional.



4. What are the two aspects that the Neighbor

cell planning imposes impact upon?

QoS

Due to handoff, the more the adjacent cells are, the

greater the system load is.

Too many adjacent cells will cause MS to measure all the

adjacent cells, so the accuracy of measurement will be

decreased.

System

Load

An appropriate number of adjacent cells can effectively

avoid the call loss caused by handover failure.

Too few adjacent cells will cause call drop and poor QoS

due to handover failure.



5. What is the principle of Neighbor cell

planning?The same frequency and same

BSIC is not allowed between theNeighbor cell and the main cell, or between the adjacent cells under the same main cell.

The main cell and the Neighbor cell cannot be on the same

frequency.It is better not to configure toomany adjacent cells. The number of default adjacent cells cannotexceed 31. According toengineering experiences, it isrecommended to configure fewer

than 24 adjacent cells.

Except for special situations, therelationship between adjacentcells should be configured asbidirectional.

Principle of

Neighbor cell

Planning



6. What are the types of unreasonable

adjacent cells, and what is the result?

Unidirectional adjacent cell

Too many adjacent cells

Too few adjacent cells

Types of unreasonable adjacent cells

Call drop

handover failure

Frequent handoff

Isolated island

Abnormal cross-cell handoff

Unbalanced traffic

Reduced handover accuracy

Possible impacts

Unreasonable

Neighbor cell

Planning



7. Under what conditions do you optimize the

adjacent cell?

If the actual network coverage is greatly different from the theoretic value,

you need to optimize the Neighbor cell according to the actual situation.



8. What is the detailed content of Neighbor

cell optimization?

Add the

missed

adjacent

cells

Delete the

redundant

adjacent

cells

Change the

unidirectional

cell into the

bidirectional cell

Check same-

frequency same-

BSIC



9. What are the tools for Neighbor cell planning?

AIRCOM

AFP

CNP

CNO-G

Planning Optimization

NETMAX

Remark

Processes the BA

dispatching file

Provides the

suggestions for

Neighbor cell

optimization

Makes the automatic

frequency planning

Based the emulation

result

Based on the cell

distance and orientation

Performs the all-

network analysis &

evaluation

Neighbor cell

optimization

Frequency

optimization

Plans the coverageand adjacent cell



Symptom

Analysis Conclusion

Solution & Verification

The Neighbor cell planning was

unreasonable, causing the call drop.

During the planning, we should better avoid unreasonable frequency and

Neighbor cell planning.

When using the network optimization

tool to view the Neighbor cell andfrequency configuration, we found that

the Neighbor cell of cell3 was

unreasonable. There were no adjacent

cells for cell3 and other two cells under

the same site – cell1 and cell2.

According to the principle of Neighbor

cell planning, we made proper adjustment upon the adjacent cells of

cell3 by adding, deleting and

modifying its Neighbor cell

relationship.

After the above adjustment, the call

drop ratio on service channel of this

cell was apparently decreased.

In the routine inspection for network

optimization and quality improvement,

the background performance indexes

showed that the call drop ratio on

service channel of cell3 (1 carrier

frequency) was relatively high, causing

the proportion of bad cell to increase.





01

2

3

4

5

6

7

8

9

1 3 - M

a r

1 4 - M

a r

1 5 - M

a r

1 6 - M

a r

1 7 - M

a r

1 8 - M

a r

1 9 - M

a r

2 0 - M

a r

2 1 - M

a r

2 2 - M

a r

2 3 - M

a r

2 4 - M

a r

2 5 - M

a r

2 6 - M

a r

2 7 - M

a r

0

0.1

0.2

0.3

0.4

0.5

0.6

Service channel call drop ratio (including handoff) (%)

Total call drops on service channel

Service channel per-line traffic

Optimized the

Neighbor cell

on Mar 24




When MS moved southward on the road fromZhijin to Anshun, its signal level was between -

90dBm－-100dBm, and QoS was at about 5. This

location was about 1km from the Dakuo BSC.

By checking the Neighbor cell relationship, we

found that Dakuo BSC has not configured theNeighbor cell relationship of Xiongjiachang

cell1 and cell2.

Add the bidirectional Neighbor cell

relationship between Dakuo and

Xiongjiachang cell1, cell2.

1 2 3

Symptom

Analysis

Measures




Before After



Usage of ZXPOS CNO1-G Tool

Tool & data preparation Install ZXPOS CN01-G

Engineering parameter table in CNO-G format

Wireless parameter table exported from NDE

Extract the summarized Neighbor cell measurementdata in the granularity of the last week

Extract the summarized cell-level performance indexes

in the granularity of the last week, including the cell-

level traffic




Data processing Processes the Neighbor cell measurement data

Processes the engineering parameter table

Processes the wireless parameter table




Checking & output results: Check whether the redundant or wrong Neighbor cell

relationship is configured

Check whether the unidirectional Neighbor cell

relationship needs to be added Check whether the missed Neighbor cell relationship

needs to be added

Check whether there is same-frequency between the

main cell and adjacent cell, or same-frequency sameBSIC between adjacent cells.

GO_NA42_E1_1 GSM Neighbor Cell Optimization 21

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