GO_NA42_E1_1 GSM Neighbor Cell Optimization 21
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7/28/2019 GO_NA42_E1_1 GSM Neighbor Cell Optimization 21
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GSM Neighbor cell Optimization
7/28/2019 GO_NA42_E1_1 GSM Neighbor Cell Optimization 21
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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
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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
11. Example 2 of Neighbor cell optimization
How Much Do You Know About Neighbor cell
Optimization?
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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.
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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.
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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.
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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.
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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
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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
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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.
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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
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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
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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.
10. Example 1 of Neighbor cell optimization
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10. Example 1 of Neighbor cell optimization
01
2
3
4
5
6
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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
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11. Example 2 of Neighbor cell optimization
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
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11. Example 2 of Neighbor cell optimization
Before After
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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
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Usage of ZXPOS CNO1-G Tool
Data processing Processes the Neighbor cell measurement data
Processes the engineering parameter table
Processes the wireless parameter table
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Usage of ZXPOS CNO1-G Tool
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.
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