Thursday, 5 November 2015

LTE Network Optimization Checking Report

We usually perform network optimization checking for customer. Here is a simple example for LTE Network Optimization Checking Report.
 We perform the basic checking based on these aspects:
----Optimization Checking
----PCI Reuse Checking
----PRACH Parameters Reuse Checking
----TAC Checking
----Neighbor Cell Checking
and prepare suggestions for the inter-RAT operation which will be deployed by customer:
----Inter-RAT Suggestion
----CSFB Parameters Suggestion
----PSHO Parameters Suggestion

1) for the PCI checking
Rule: Nearby Cell should have different PCI, the PCI reuse distance should be far enough.
Checking  Result: PCI reuse distance reasonable
Suggestion: Null 
2) for the PRACH checking
Rule: the PRACH parameters(rootSequenceIndex & prachConfigIndex) reuse distance should be far enough.
Checking  Result: Some PRACH parameters reuse times are over 20; nearby sites use the same PRACH group.
Suggestion: Re-plan PRACH parameters for these cells, make sure the reuse distance is far enough.
Here are some of the cases that the PRACH parameters not reasonable:

3)TAC checking
Rule: Normally TAC should be the same with one cluster.
Checking  Result: some sites TAC need to double check
Suggestion: double check the TAC setting is correct.
Here are some of the cases that the TAC parameters may be not reasonable:

4)Neighbor cell checking
Rule: Neighbor Cell should be valid.
Checking  Result: Some sites configured invalid neighbor cells.
Suggestion: check and make sure the configured neighbor cells are valid.
Here are some of the invalid neighbor cells:
For the inter-RAT operation
1) for CSFB, we have the suggestion from Apple in some other project, we suggest to fellow the Apple's suggestions:
2) For the PSHO to UMTS
The default B2 even for PSHO to UMTS is shown as below:
LTE will PSHO to UMTS only when LTE RSRP is lower than -90 dBm (rsrpSrvTrd) and UMTS RSCP is higher than -86 dBm (rscpSysNbrTrd). It is too easy trigger PSHO from LTE to UMTS.
Suggestion:  set rsrpSrvTrd to -110 and rscpSysNbrTrd to -90. That means LTE will PSHO to UMTS only when LTE RSRP is lower than -110 dBm  and UMTS RSCP is higher than -90 dBm.
  3) For  other inter-RAT Suggestion
Make sure the LTE TAC and UMTS LAC mapping correctly configured in core network before CSFB deployment.
Sync sites configuration changes between LTE and UMTS.
eg. If LTE have changed the PCI or DL frequency but not sync to UMTS change the LTE neighbor cell.  UE will hard to return back to LTE.

Budi Prasetyo

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