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UMTS Admission Control Feature (PUC)

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Overview

PUC

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Load Control exists in all phasesLoad Control is used to keep system stable, maximize system capacity while ensuring the coverage and QoS.

Different load control algorithms according to different phases provided:

a) Before UE access: Potential User Control (PUC)

b) During UE access: Call Admission Check (CAC) and Intelligent Access Control (IAC)

c) After UE access: Load Reshuffling (LDR), and Overload Control (OLC)

3. After UE access2. During UE access1. Before UE access

Time

• LDRCACPUC• OLC

•• IAC

PUC: Potential User Control CAC: Call Admission Control IAC: Intelligent Admission Control LDR: Load Reshuffling OLC: Overload Control

PUC (Potential User Control ) Features:a) The function of PUC is to balance traffic load among inter-frequency cells.

b) By modifying cell selection and reselection parameters and broadcasting them through system information, PUC leads UEs to cells with light load.

c) The UEs may be in idle mode, CELL_FACH state, CELL_PCH state, or URA_PCH state.

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Load Control for different cell load level

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Thresholds and actions of the load control algorithms

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Overview

PUC

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Potential User Control Procedure

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Potentioal User Control Threshold

Notes: PUC can take effect only in downlink.

Cell load comes with three levels: heavy, normal, and light.

a) When cell load is higher than the load level division upper threshold plus the load level division hysteresis, it is decided to be heavy.

b) When cell load is lower than the load level lower threshold plus the load level division hysteresis, it is decided to be light.

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Action of Potential User ControlBased on the cell load, PUC works as follows:

a) If the cell load becomes heavy, PUC modifies cell selection and reselection parameters and broadcasts them through system information(SIB3 and SIB11). In this way, PUC leads UEs to neighboring cells with light load.

b) If the cell load becomes normal, PUC uses the cell selection and reselection parameters configured on the LMT.

c) If the cell load becomes light, PUC modifies cell selection and reselection parameters and broadcasts them through system information. In this way, PUC leads UEs to this cell.

The NodeB periodically reports the total TCP of the cell and the PUC periodically triggers the following activities:

a) Assessing the cell load level based on the total TCP;

b) Configuring Sintersearch, Qoffset1(s,n), and Qoffset2(s,n) based on the cell load level;

c) Updating the parameters of system messages SIB3 and SIB11.

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PUC Adjustment Principle

Rs = Qmeas,s + Qhysts + Qoffmbms Rn = Qmeas,n - Qoffsets,n + Qoffmbms - TOn * (1 – Ln)

4. Cell Reselection Criteria: a) Qoffmbms is only applied to those cells (serving or neighbouring) belonging to the MBMS;

b) TO is only applicable if the usage of HCS is indicated in system information.

1. Based on the characteristics of inter-frequency cell selection and reselection.Sintersearch:

a) When this value is increased by the serving cell, the UE starts inter-frequency cell reselection ahead of schedule.

b) When this value is decreased by the serving cell, the UE delays inter-frequency cell reselection.

The UE will start inter-frequency cell reselection when Squal is less than Sintersearch.

Squal=Qqualmeas-Qqualmin<= Sintersearch.

2. Qoffset1(s,n): applies to R (reselection) rule with CPICH RSCPa) When this value is increased by the serving cell, the UE has a lower probability of selecting

a neighboring cell.

The offset is subtracted from the neighboring cell measurement value before cell reselection.

b) When this value is decreased by the serving cell, the UE has a higher probability of selecting a neighboring cell.

3. Qoffset2(s,n): applies to R (reselection) rule with CPICH Ec/I0

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Change of Sintersearch Parameter according to the Load state

The configuration of Sintersearch affects the current cell.

Its value is related to the load of the current cell.

Notes: The PUC command is ADD CELLPUC.

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Change of Qoffset1 and Qoffset2 according to the Load state

1) The configuration

of Qoffset1 and

Qoffset2 affects the

neighbour cell. 2) Its value are

related to the load

of the current cell

and the neighboring

cells.

Notes: The prerequisite for the changes of the parameters is that these parameters take their default values.

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PUC Parameters

1. Run the ADD CELLALGOSWTICH command to set the cell-oriented PUC algorithm switch under Cell LDC algorithm switch to 1.

2. Run the SET LDCPERIOD command to specify the period of potential user control (PUC period timer length).

3. Run the ADD CELLPUC command to set the cell-oriented PUC algorithm parameters. These parameters are as follows: Load level division threshold 1 Load level division threshold 2 Load level division hysteresis Sintersearch offset 1 Sintersearch offset 2 Qoffset1 offset 1 Qoffset1 offset 2 Qoffset2 offset 1 Qoffset2 offset 2

Examplea) ADD CELLALGOSWITCH: NBMLdcAlgoSwitch=PUC-1; b) SET LDCPERIOD: PucPeriodTimerLen=180; c) ADD CELLPUC: CellId=1, SpucLight=46, SpucHeavy=71, SpucHyst=6, OffSinterLight=-

1, OffSinterHeavy=3, OffQoffset1Light=-3, OffQoffset2Light=-3, OffQoffset1Heavy=5, OffQoffset2Heavy=5;

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