amx pr - lac border opt process

• INTRODUCTION.

• CELL SELECTION PROCEDURE AND MEASUREMENT RULES.

• CELL RESELECTION CRITERIA.

• ANALYSIS:

CELL RESELECTION FROM WCDMA SERVING CELL TO WCDMA NEIGHBOUR.

CELLS WITH DIFFERENT LAC.

• REVIEW PARAMETERS.

• RECOMMENDED CHANGES.

• SUMMARY.

• EXAMPLE A GEOGRAPHICAL AREA TO OPTIMIZE.

AGENDA

INTRODUCTION

The cell selection and reselection process allows the UE to look for a suitable cell in the selected PLMN and to camp on it. When a suitable cell is found, the UE camps on it in a state defined as “camped normally”. In this state, the UE monitors paging and system information, performs periodical radio measurements, and evaluates cell reselection criteria. If the UE finds a better cell, that cell is selected by the cell reselection process. The change of cell may imply a change of the RAT. The WCDMA RAN is sensitive to intra frequency interference, which may depend on the data rate, traffic load, or modified radio link due to multipath fading. Therefore, the measurements that are used in the cell selection and reselection process are not only the signal strength but also the quality value. These measurements are performed on the Common Pilot Channel (CPICH).

To improve accessibility to the 3G network and hence the quality of service is proposed to adjust the parameters cells reselections in WCDMA to ensure that the mobile in idle state select the best cell serving. It seeks to avoid the ping-pong of “Location Update” between sectors with different LAC too. This document describes the reasons and variables needed to support this suggestion.

• INTRODUCTION.



• ANALYSIS:





• SUMMARY.


AGENDA

CELL SELECTION PROCEDURE AND MEASUREMENT RULES

CELL SELECTION PROCEDURE

For cell selection criteria the UE calculates

Squal = Qqualmeas - qQualMin (for WCDMA cells) Srxlev = Qrxlevmeas - qRxLevMin – Pcompensation (for all cells)

Where Pcompensation = max (maxTxPowerUL – P, 0) P is output power of UE according to class

Cell selection criteria (S criteria) is fulfilled when:

Qqualmeas > qQualmin ( for WCDMA cells only) and Qrxlevmeas > qRxLevmin

MEASUREMENT RULES Intra frequency measurements If Squal < sIntraSearch, the UE performs Intra-Frequency measurements. Qqualmeas – qQualmin < sIntraSearch Qqualmeas < sIntraSearch(0)+ qQualmin (-18dB) Inter frequency measurements If Squal < sInterSearch, the UE performs Inter-Frequency measurements. Qqualmeas – qQualmin < sInterSearch Qqualmeas < sInterSearch(0)+ qQualmin (-18dB) Inter-RAT measurements If Squal < sRatSearch or Srxlev < sHcsRat, the UE performs Inter-RAT measurements.

The figure 1 shows the values

tipicos in Network .

Intra o Inter frequency

measurements are always

made.

Cell Selection Criteria is fulfilled

when CPICH Ec/Io >= -18 dB and

CPICH RSCP >= -115 dBm.

Inter-Rat measurements are

start when the CPICH Ec/Io<= -

16 dB or CPICH Rscp <= -112

dBm.

In this point start “Cell

Reselection Criteria” (Slide 8). Figure 1. Cell Selection Procedure and Measurements.

CELL SELECTION PROCEDURE AND MEASUREMENT RULES

• INTRODUCTION.



• ANALYSIS:





• SUMMARY.


AGENDA

CELL RESELECTION CRITERIA CELL RESELECTION CRITERIA UE ranks available cells using R criteria

R(Serving) = Qmeas(s) + qHyst(s)

R(Neighbour) = Qmeas(n) – qOffset(s,n)

Qmeas is the quality value of the received signal - Derived from the averaged received signal level for GSM cells - Derived from CPICH Ec/Io or CPICH RSCP for WCDMA cells depending on the value of qualMeasQuantity (2, Ec/Io)

qHyst(s) = qHyst1 when ranking based on CPICH RSCP qHyst(s) = qHyst2 when ranking based on CPICH Ec/Io qOffset(s,n) = qOffset1sn when ranking based on CPICH RSCP qOffset(s,n) = qOffset2sn when ranking based on CPICH Ec/Io

* Normally, the above two values are 0 for WCDMA cells and 7 for GSM cells. For WCDMA neighbors it is possible to control whether the ranking is made using CPICH RSCP or CPICH Ec/No. This is configured using the cell parameter qualMeasQuantity. The UE reselects the new cell if it is better ranked than the serving cell during a time interval treSelection.

Figure 2. Cell Reselection from a WCDMA Serving Cell to a WCDMA Neighbor.

• INTRODUCTION.



• ANALYSIS:





• SUMMARY.


AGENDA

If we use the tipics values in C&W Panama be can see that cell reselection is made when:

R(Serving) = Qmeas (s) + qHyst(s) and R(Neighbour) = Qmeas(s) - qOffset(s, n)

R(Neighbour)> Qmeas(s) + qHyst(s) + qOffset(s, n) * qualMeasQuantity = (2, EcNo)

R(Neighbour)> Qmeas(EcNo, s) + 4 dB – 0 * qHyst2 (EcNo) = 4 dB

R(Neighbour) > Qmeas(EcNo, s) + 4dB * treselection = 2 seconds

That is, the UE reselects the neighbour cell (neighbour) if it EcNo is greater to 4 dB(qHyst2) than the serving cell during a 2 seconds

(treSelection).

If we use the recommended values in C&W Panama be can see that cell reselection is made when:

R(Neighbour) > Qmeas(s) + qHyst(s) + qOffset(s, n) * qualMeasQuantity = (2, EcNo)

R(Neighbour)> Qmeas(EcNo, s) + 4 dB + 0 * qHyst2 (EcNo) = 4 dB

R(Neighbour) > Qmeas(EcNo, s) + 4dB * treselection = 2 seconds

That is, the UE reselects the neighbour cell (neighbour) if it EcNo is greater to 2 dB(qHyst2) than the serving cell during a 2 seconds (treSelection).

ANALYSIS, CELL RESELECTION FROM A WCDMA SERVING CELL to A WCDMA NEIGHBOR

Figure 2. Cell Reselection from a WCDMA Serving Cell to a WCDMA Neighbor.

Tipics Value

Recommended Value

• INTRODUCTION.



• ANALYSIS:





• SUMMARY.


AGENDA

ANaLYSIS,CELLS WITH DIFFERENT LAC/RAC

Figure 3. Offset configurable entre celdas con diferente RAC.

If the Location Area Identity (LAI) or Routing Area Identity (RAI) read on system information is different to the one stored on the USIM, the UE performs a LA or RA registration update. This types of registration update is know as Normal and happens frequently between different cells with LAC / RAC and similar coverage. In this case it is advisable to set qoffset2sn <> 0 between both, this prevents Ping-Pong Location Update or unnecessary updates. This parameter is configured to level utranrelation and if the value is the same in both directions may be delayed cell change procedure without affecting traffic. This delay depend the mobility UE.

Example qOffset2sn (EcNo):

R(Neighbour) > Qmeas(s) + qHyst(s) + qOffset(s, n) * qualMeasQuantity = (2, EcNo)

R(Neighbour)> Qmeas(EcNo, s) + 2 dB + 2dB * qHyst2 (EcNo) = 2 dB (Recommended Value

R(Neighbour) > Qmeas(EcNo, s) + 4dB * qoffset2sn = 2 dB (Recommended Value)

* treselection = 2 seconds

That is, the UE reselects the neighbour cell if it EcNo greater to 4 dB(qHyst2) than the serving cell

during a 2 seconds (treSelection).

• INTRODUCTION.



• ANALYSIS:





• SUMMARY.


AGENDA

Review Parameters

The next slides show the proposed changes to the parameters highlighted in the table. * qOffset2sn only is proposed to change in utranrelations with high interaction and different LAC.

Table #1. Parameters Audited

• INTRODUCTION.



• ANALYSIS:





• SUMMARY.


AGENDA

recommended CHANGES, SUMMARY

Reduciendo la histeresis de reselección de celdas WCDMA(4dB 2dB) se garantiza el acceso del MS a través de la mejor celda servidora aumentando las posibilidades de mejorar la accesibilidad y retenibilidad para ambos servicios. Un valor de EcNo indica menor tráfico e interferencia; por lo que es mas factible establecer el servicio; asimismo, evita SHO innecesarios por la degradación de la calidad durante este proceso. La única desventaja de este cambio es el incremento de uso en la batería del móvil por mayor número de reselecciones.

Determinar un offset de 2dB entre relaciones de vecindades (3G -3G) con diferente LAC y alta interacción reduce el excesivo location updates por cambio de área. Las siguientes condiciones de estudio fueron implementadas para determinar cuales son las utranrelations que deben ser ajustadas:

%Soft Handover entre ambos sectores mayor o igual al 5%.

Estadísticas obtenidas durante 21 días a resolución diaria.

Table # 2. Resumen de Cambios Propuestos.

EXAMPLE A GEOGRAPHICAL AREA TO OPTIMIZE.

La imagen adjuntada muestra parte de la distribución de celdas por RAC, además se muestra en color negro y en un radio más pequeño las relaciones de vecinas con diferente LAC que tienen alta interacción y están siendo propuestas para ajuste de offset.

amx pr - lac border opt process

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