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Huawei Confidential

04/17/2023

2G Large Traffic Scenarios Guide

Contents

Measures Before Event

Measures During Event

Measures After Event

Contents

Measures Before Event

KPI Analysis

Parameters

Features

Measures Before EventBefore each event, there are some facts that we must consider:

It’s needed to identify most affected cells and possible neighbors in the surrounding area.

Obtain most important KPI’s in order to identify previous status and deficiencies of the cells

Previous measures in case of degradation, like channel adding (PDTCH, SDCCH…), E1 extension, TRX extension…

Apply special parameters and features activation

Final KPI check in order to ensure the right status of the cells after the changes.

Enable 15 min measures in M2000

Contents

Measures Before Event

KPI Analysis

Parameters

Features

Measures Before EventKPI Analysis

There are some KPI’s that must be check before an event. This

is going to help us to identify possible deficiencies and launch

the corrective measures before the degradation appears.

KPI Measure if degradation

CSSR CS / TCH Blocks

In this case, the degradation use to appear during busy hour, it use to indicate TCH congestion,. In that case the usage of TCH-HR must be increased (if possible), most of the static channels must be free for CS always we don’t introduce degradation in SDCCH or PS. Finally TRX extension must be evaluated.

SDCCH Cong

In this case the problem is signaling degradation. Appropriated number of SDCCH channels must be ensure even increasing number of SDCCH static channels.Check Dynamic SDCCH is enabled. Reduce the signaling modifying MS_MAX_Retrans and CRH

GPRS/EDGE Block Rate

When the number of failure increase we must check the causes:MS_No_Response most common cause is Iub congestionNo-Channel number of PDTCH channels is not enough, we can increase number of static channels, increase the maximum number of multiplexed users (if possible)

Contents

Measures Before Event

KPI Analysis

Parameters

Features

Measures Before EventParameters

Dynamic SDCCH:

SDDYN SDCCH Dynamic Allocation Allowed Meaning: Whether to allow SDCCH dynamic allocation, that is, whether to allow dynamic conversion between TCHs and SDCCHs.Recommended Value: YESService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Related Parameters:

IDLESDTHRESMeaning: When the number of idle SDCCH channels in a cell is smaller than or equal to this parameter, the system searches for available TCHs and transforms them into SDCCH channels.Recommended Value: 2

Measures Before EventParameters

Dynamic SDCCH:

Related Parameters:

CELLMAXSDMeaning: Maximum number of SDCCHs in the cell. Before converting a TCH into an SDCCH, the BSC compares the number of SDCCHs after the conversion in the cell with Cell SDCCH Channel Maximum. If the number of SDCCHs after the conversion in the cell exceeds this parameter, the BSC does not convert the TCH into an SDCCH.Recommended Value: 80

MINRESTIMETCHMeaning: Minimum time required for a TCH to transform to a SDCCH and then transform back to a TCHRecommended Value: 60s

Measures Before EventParameters

The parameters below help to turn it into realities.

Q search I = 7(always)

Qsearch C Initial = Use Qsearch_I

FDD Q Offset = 0 (always)

FDD Qmin  = -10dB

Name Description

Qsearch IThis parameter indicates the threshold of level for cell reselection in idle mode. 7 means the UE always search for 3G cells.

Qsearch C Initial This parameter indicates the mode for searching the threshold of 3G cells.

FDD Q Offset Only when the average receive level of a 3G cells is FDD Q Offset greater than that of the current service cell, the 3G cell can become a candidate cell. 0 ： - (always select a cell if

acceptable)；

FDD QminThis parameter indicates one of the threshold of level for the reselection of 3G cells. Only when the receive level of a 3G cell is greater than FDD Qmin, the 3G cell can be one of the candidate cells for reselection.

Measures Before EventParameters

Dynamic PDCH:

MAXPDCHRATE

Maximum Rate Threshold of PDCHs in a Cell Meaning: Maximum value of the PDCH ratio in a cell. The number of available TCHs and PDCHs in a cell is set to a fixed value. The PDCH ratio is: Number of available PDCHs/(Number of available TCHFs + Number of available static PDCHs). This parameter is used to restrict the PDCH ratio.Recommended Value: 40Service Interrupted After Modification : YesImpact on Network Performance: If this parameter is set to an excessive value, there are excessive PDCHs and insufficient TCHs. This affects CS services. If this parameter is set to a modest value, there are insufficient PDCHs and excessive TCHs. This affects PS services.

Measures Before EventParameters

Dynamic PDCH:

DYNCHFREETM

Timer of Releasing Idle Dynamic Channel Meaning: Time to wait for releasing the dynamic channel after the TBF on the dynamic channel is released. When all the TBFs on the channel are released, the dynamic channel is not released at once. Instead, the timer is started when the channels are idle. Before the timer expires, if new service request is received, the dynamic channel is still occupied and timer is stopped; otherwise, the dynamic channel is released after the timer expired.Recommended Value: 20sService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: If this parameter is set to an excessive value, the dynamic channel resources may be wasted when there are no services for a long time. If this parameter is set to a modest value, it is possible that a dynamic channel is requested immediately after being released. Therefore, the dynamic channel request is sent frequently.

Measures Before EventParameters

Dynamic PDCH:

ABISTSFREETM

Timer of Releasing Abis Timeslot Meaning: Interval between detection of the Abis timeslot being in idle state and releasing of the Abis timeslot. When channels are idle, the timer is started. When the timer is expires, the Abis timeslot is released. When all the TBFs on the channel are released, the Abis timeslot is not released at once. Instead, the timer is started when the channels are idle. Before the timer expires, if new service request is received and the Abis timeslot is occupied, then the timer is stopped; otherwise, the timeslot is released after the timer expires.Recommended Value: 15Parameter Relationship: NoneService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: If this parameter is set to a higher value, the period of reserving the Abis timeslots is prolonged and thus the delay is shortened. However, there may be insufficient idle Abis timeslots and thus the service rate is decreased. If this parameter is set to a lower value, Abis timeslots may be requested frequently.

Measures Before EventParameters

PDCH Paging:

BSAGBLKSRES

CCCH Blocks Reserved for AGCH Meaning: BS-AG-BLKS-RES, indicating the number of the CCCH message blocks reserved for the AGCH. After the CCCHs are configured, the value of this parameter indicates the actual seizure rates of the AGCHs and the PCHs over the CCCHs.Recommended Value: 1Parameter Relationship: NoneService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: The setting of this parameter may affect the MS paging response and performance of the system. A greater value may decrease the number of paging blocks, paging capacity, and paging success rate.

Measures Before EventParameters

PDCH Paging:

PAGTIMES

Paging Times Meaning: For the BTS, this parameter is used to determine paging retransmissions. This parameter and the number of paging times configured in the MSC determine the number of paging retransmissions. Recommended Value: 1Parameter Relationship: NoneService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: Properly setting this parameter can increase the paging success rate. If this parameter is set to a greater value, paging overload may occur and the paging success rate may decrease.

Measures Before EventParameters

PDCH Paging:

CCCHLOADTHRES

CCCH Load Threshold Meaning: This parameter is used by the BTS to inform the BSC of the load on a CCCH timeslot, that is, the load of the access requests on the RACH and the load of all the messages (such as paging messages and packet immediate assignment messages) on the PCH. For details, see GSM Rec. 08.58. If the load on a CCCH timeslot exceeds the value of this parameter, the BTS periodically sends the CCCH overload message to the BSC. The interval for sending the CCCH overload message is CCCH Load Indication Period.Recommended Value: 80Parameter Relationship: NoneService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: If this parameter is set to smaller value, the signaling flow over the Abis interface increases, thus burdening the [MBSC]. If this parameter is set to a greater value, the [MBSC] cannot handle the exceptions on the BTS in time, thus causing network congestion.

Measures Before EventParameters

Directed Retry:

DIRECTRYEN

Directed Retry Meaning: Whether to enable a directed retry. The directed retry is to hand over an MS to a neighboring cell in the same procedure as the handover. The directed retry is an emergency measure applicable to abnormal traffic peaks in some areas of a radio network. You should not use the directed retry as a major means of solving traffic congestion. If the directed retry always occurs in some areas of a network, consider adjusting the sector and TRX configuration and the network layout.Recommended Value: YESParameter Relationship: NoneService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventParameters

Directed Retry:

DTLOADTHRED

Directed Retry Load Access Threshold Meaning: Threshold of the load in the target cell for the directed retry. Only a cell whose load is lower than or equal to this threshold can be selected as a candidate target cell.Recommended Value: 85%Parameter Relationship: The value of DTLOADTHRED must be set when REASSEN in the SET GCELLBASICPARA command is set to DIRECTRYEN.Service Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventParameters

Mobility:

LAYER

Layer of the cell Meaning: A network basically consists of four layers, namely, Umbrella, Macro, Micro, and Pico. Cell priorities influence the sorting of neighboring cells during handovers as well as handover algorithms including PBGT and inter-layer handovers. For example, PBGT handovers can only occur among cells on a same layer and of a same priority level. If you assign different layers and priorities to a 1800-M cell and a 900-M cell, PBGT handovers from the 1800-M cell to the 900-M cell will not occur. This causes slow handovers even when the receive quality is good.Recommended Value: 2-3Parameter Relationship: There are four network layers, that is, layer 1 to layer 4. A lower layer No. indicates a higher priority. The cell priority is determined by both the network layer and the PRIOR parameter.Service Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventParameters

Mobility:

PRIOR

Cell Priority Meaning: This parameter controls the handovers among cells on a same layer. A smaller priority value indicates a higher priority. Cells with higher priorities are preferentially selected as the handover target cells.Recommended Value: Prior-1Parameter Relationship: This parameter, together with LAYER, determines the priority of the cell.Service Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventParameters

Mobility:

CRH

Cell Reselect Hysteresis Parameters Meaning: Cell reselection hysteresis. This is one of the parameters used for deciding whether to reselect cells in different location areas. This parameter can avoid the increase of network signaling traffic due to frequent location update and reduce the risk of losing paging messages.Recommended Value: 6dBParameter Relationship: NoneService Interrupted After Modification : No (Impact on the UE in idle mode)Impact on Network Performance: The MS cannot respond to the paging during the location update, thus decreasing the call completion rate in the system. If this parameter is set to a smaller value, pingpong location update may occur, thus increasing the signaling load on the SDCCH. If this parameter is set to a greater value, the MS may not camp on an optimum cell for a long time after entering a new location area.

Measures Before EventParameters

Mobility:

CRO

Cell Reselect Offset Meaning: Cell Reselect Offset (CRO), indicating a correction of the C2.Proper setting of this parameter can reduce the number of handover times, helpful for assigning an MS to a better cell. In a special case that the PT is 31, the larger the CRO value is, the lower the possibility of handing over an MS to the cell.Generally, do not set the CRO to a value larger than 25 dB. The CRO with a too large value will cause uncertain states in a network. The CRO values of the cells with different priorities in a network are almost the same. Refer to GSM Rec. 05.08 and GSM Rec. 04.08. The setting of this parameter affects only the MSs supporting the protocol of GSM Phase 2 or a later version.Recommended Value: 8-10Parameter Relationship: NoneService Interrupted After Modification : No (Impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventParameters

Handover:

HOTHRES

Inter-layer HO Threshold Meaning: Handover threshold during the handovers between cells on different layers or of different priorities. This value is used to suppress inter-layer ping-pong handovers. Inter-layer handover threshold of the serving cell = Inter-layer HO threshold - Inter-layer HO Hysteresis; Inter-layer handover threshold of a neighboring cell = Inter-layer HO Threshold + Adjacent Cell Inter-layer HO Hysteresis - 64.Recommended Value: 20-DCS 30-GSM (dB)Parameter Relationship: NoneService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventParameters

Handover:

INTERCELLHYST

Inter-cell HO Hysteresis Meaning: Hysteresis value during the handovers between cells, This value is used to suppress ping-pong handovers between cells.Default Value: 68 dBRecommended Value: In densely populated urban areas, the recommended value is 68; in the suburbs, the recommended value is 72.Parameter Relationship: When Current HO Control Algorithm in SET GCELLHOBASIC is set to HOALGORITHM1(Handover algorithm I), Inter-cell HO Hysteresis should be set within the range of 64-127.Service Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Contents

Measures Before Event

KPI Analysis

Parameters

Features

Measures Before EventFeatures

Load Handover:

LoadHoEn

Load Handover Support Meaning: This parameter specifies whether a traffic load-sharing handover is enabled. The load handover helps to reduce cell congestion, improve success rate of channel assignment, and balance the traffic load among cells, thus improving the network performance. The load handover is used as an emergency measure instead of a primary measure to adjust abnormal traffic burst in partial areas. If load handovers occur frequently in a partial area, the cell and TRX configuration of BTSs and the network layout should be adjusted.Recommended Value: YESParameter Relationship: NoneService Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventFeatures

Load Handover:

TRIGTHRES

Load HO Threshold Meaning: The load handover is triggered when the traffic load in a cell is greater than the value of this parameter.Recommended Value: 90Parameter Relationship: This parameter is valid only when LOADHOEN in SET GCELLHOBASIC is set to YES.Service Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: None

Measures Before EventFeatures

Load Handover:

LoadAccThres

Load handover Load Accept Threshold Meaning: If the load of a cell is lower than the value of this parameter, the cell can admit the users handed over from other cells with higher load. Otherwise, the cell rejects such users.Recommended Value: 80Service Interrupted After Modification : No (No impact on the UE in idle mode)Impact on Network Performance: If this parameter is set to a too small value, the corresponding cell may reject some handover requests; thus the traffic congestion on the neighboring cells with heavy traffic cannot be relieved. If this parameter is set to a too great value, the corresponding cell may be overloaded.

Contents

Measures During Event

KPI Monitoring

Emergency Measures

Measures During EventDuring the event there are two principle task that must be done to ensure the quality:

Most important KPI’s must be checked during the event in order to ensure the quality and identify possible degradations.

In case of degradation, some emergency measures must be taken.

Contents

Measures After Event

KPI Monitoring

Emergency Measures

Measures Before EventKPI Monitoring

These are most important KPI that must be check during the event.

KPI Measure if degradation

CSSR CS / TCH Blocks

In case of degradation it’s needed to increase the number of resources (something difficult during the event) or reduce the number of users by CRO, RXLEV…

SDCCH Cong In case of degradation it’s needed to increase the resources by adding new channels (needs to release the TRX) or reduce the signaling CR increase, MS_MAX_RETRANS reduction..

GPRS/EDGE Block Rate

In case of degradation it’s needed to increase number of resources adding new channels or reduce PS traffic FDDQmin reduction

PagingIn this case the problem is signaling degradation. It’s needed signalling reduction or CCCH channel increase

Contents

Measures During Event

KPI Monitoring

Emergency Measures

Measures During EventEmergency measures in case of degradation:

Modify RXMin, CRO of the cell and the adjacent cells in order to distribute the traffic in case of TCH block rate degradation

Increase CRH and decrease MS_Max_Retrans in case of SDDH congestion

FDDQmin increase in case of 2G congestion and 3G resources available

Adding PDTCH, SDCCH or CCCH channels if needed, however we must know that the channel adding needs TRX release.

Thank You

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