3-wcdma load control

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Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

WCDMA Load Control

CHAPTER 3

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Page2Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.

Contents

1. Load Control Overview

2. Basic Load Control Algorithms

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Load Definition

�� Load: the occupancy of capacityLoad: the occupancy of capacity

�� Two kinds of capacity in CDMA systemTwo kinds of capacity in CDMA system

�� Soft capacitySoft capacity

�� Interference (UL)Interference (UL)

�� Power (DL)Power (DL)

�� Hard capacityHard capacity

�� Code resourceCode resource

�� Hard ware resource: Transport resource, NodeB processing capabilHard ware resource: Transport resource, NodeB processing capability (CE)ity (CE)

�� Load Control is used to keep system stable, Maximize system capaLoad Control is used to keep system stable, Maximize system capacity city

while ensuring the coverage and QoSwhile ensuring the coverage and QoS

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Load Control Algorithms for different access phases

�� In different phases of UE access as shown in following figure , In different phases of UE access as shown in following figure ,

different load control algorithms are used different load control algorithms are used

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

�� During UE access : Call Admission Control During UE access : Call Admission Control ( CAC )( CAC )

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

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

Time

• LDRCACPUC• OLC

•

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Load Control Algorithms used at different cell load level

No Load control

PUC starts: to enable UEs in idle mode to camp on cells with light loadLDR starts: to check and release initial congestion in cells

CAC : to prevent new calls into cells with heavy loadDRD starts: to enable rejected UEs to retry neighboring cells or GSM cells

NodeB transmitpower (noise)

Cell load

OLC starts: to reduce the TFs of BE

subscribers, and release some UEs forcibly

Icons for different load levels

In a cell, the higher the cell load, the higher the NodeB transmit power.

In this diagram, different icons indicates different load levels. And for

different load levels, the different load control algorithm will function.

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Contents



2.1 PUC (Potential User Control)

2.2 CAC (Call Admission Control)

2.3 LDR (Load Reshuffling)

2.4 OLC (Overload Control)

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PUC Principles

Freq1

Freq2

System InfoSIB3,11,12



Heavy load

Light load Normal load

Idle state CCH state

Modify

1.Easy to trigger reselection1.Easy to trigger reselection

2.Easy to select light load2.Easy to select light load

InterInter--freq neighbor Cellfreq neighbor Cell

Decrease the POTENTIAL loadDecrease the POTENTIAL load

Modify

1.Hard to trigger reselection1.Hard to trigger reselection

2.Easy to camp on the cell2.Easy to camp on the cell

Increase the POTENTIAL loadIncrease the POTENTIAL load

Stay

�� The function of PUC is to balance traffic load among interThe function of PUC is to balance traffic load among inter--frequency cells. By frequency cells. By

modifying cell selection and reselection parameters and broadcasmodifying cell selection and reselection parameters and broadcasting them ting them

through system information, PUC leads UEs to cell with light loathrough system information, PUC leads UEs to cell with light load. The UE may be d. The UE may be

in idle mode, Cell_FACH state, Cell _PCH state, URA_PCH statein idle mode, Cell_FACH state, Cell _PCH state, URA_PCH state

The load of a cell can be defined as “Heavy”, “Normal” or “Light”.

PUC can be used to avoid too many UEs to stay in “Heavy Load”

cells through controlling cell reselection procedure. So users in IDLE,

CELL_FACH, CELL_PCH or URA_PCH states will be affected by PUC.

Note: PUC just happens between inter-frequency cells.

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PUC Realization

�� PUC can modify interPUC can modify inter--frequency cell reselection parameters to frequency cell reselection parameters to

control the user distribution between cellscontrol the user distribution between cells

�� QOffset1sn and QOffset2snQOffset1sn and QOffset2sn: when the load of a cell is : when the load of a cell is ““HeavyHeavy””, PUC will , PUC will

decrease these parameters; when the load of a cell is decrease these parameters; when the load of a cell is ““LightLight””, PUC will , PUC will

increase these parametersincrease these parameters

�� SintersearchSintersearch: when the load of a cell is : when the load of a cell is ““HeavyHeavy””, PUC will increase this , PUC will increase this

parameter; when the load of a cell is parameter; when the load of a cell is ““LightLight””, PUC will decrease this parameter, PUC will decrease this parameter

According to the load level of a cell, system will adjust the cell-reselection parameters in SIB3, 11 and 12:

1. QOffset1sn and QOffset2sn:

These parameters are offsets of CPICH measured values of

neighboring cells. QOffset1sn is used for the RSCP measurement

and the neighboring cell measurement value participates in cell reselection sequencing after this offset is deducted from it.

QOffset2sn is used for the Ec/No measurement and the

neighboring cell measurement value participates in cell reselection

sequencing after this offset is deducted from it.

The bigger these values are, the smaller the probability of

selecting the neighboring cell will be; the smaller these values are,

the bigger the probability of selecting the neighboring cell will be.

2. Sintersearch:

When the UE detects that the quality of the service cell (CPICH

Ec/N0 measured by the UE) is lower than the sum of the minimum

quality criterion of the service cell (Qqualmin) plus this threshold, it will start the inter-frequency cell reselection process.

If this parameters are too high, cell reselection will probably start frequently, resulting in UE battery waste; If they are too low, cell

reselection will probably start difficultly.

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Huawei Parameters for PUC Algorithm Switch

�� NBMLdcAlgoSwitchNBMLdcAlgoSwitch (Cell algorithm switch) (Cell algorithm switch)

�� Value RangeValue Range::

�� ON , OFFON , OFF

�� Default statusDefault status: : OFFOFF

�� Set CAC Algorithm Switch through Set CAC Algorithm Switch through ADD CELLALGOSWITCHADD CELLALGOSWITCH, query it through , query it through LST LST

CELLALGOSWITCHCELLALGOSWITCH, and modify it through , and modify it through MOD CELLALGOSWITCHMOD CELLALGOSWITCH

Set CAC Algorithm Switch through ADD CELLALGOSWITCH, query it through LST CELLALGOSWITCH, and modify it through MOD CELLALGOSWITCH.

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Huawei Parameters for PUC (1)

�� SPUCHEAVY (Load level division threshold 1)SPUCHEAVY (Load level division threshold 1)

�� Value RangeValue Range: 0 to 100%: 0 to 100%

�� Recommended valueRecommended value: 70,: 70, namely 70%namely 70%

�� SPUCLIGHT (Load level division threshold 2)SPUCLIGHT (Load level division threshold 2)



�� SPUCHYST (Load level division hysteresis)SPUCHYST (Load level division hysteresis)



�� Set these parameters through Set these parameters through ADD CELLPUCADD CELLPUC, query it through , query it through LST CELLPUCLST CELLPUC, and , and

modify it through modify it through MOD CELLPUCMOD CELLPUC

SPUCHEAVY (Load level division threshold 1):

One of the threshold used to judging cell load level, it is used to decide whether

the cell load level is "Heavy" or not. If the load of a cell is equal to or higher than

this threshold, the load level of this cell is heavy. If the load level of a cell is heavy, the PUC algorithm will configure selection/reselection parameters for this cell to

lead the UE camping on this cell to reselect another inter-frequency neighboring

cell with light load.

SPUCLIGHT (Load level division threshold 2):

One of the thresholds used to judging cell load level, it is used to decide whether the cell load level is "Light" or not. If the load of a cell is equal to or lower than this

threshold, the load level of this cell is light. If the load level of a cell is light, the

PUC algorithm will configure selection/reselection parameters for this cell to lead

the UE to reselect this cell rather than the previous inter-frequency neighboring

cell with heavy load.

SPUCHYST (Load level division hysteresis):

The hysteresis used while judging cell load level, it is used to avoid the

unnecessary ping-pong of a cell between two load levels due to tiny load change.

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�� OFFSINTERLIGHT (Sintersearch offset 1)OFFSINTERLIGHT (Sintersearch offset 1)

�� Value RangeValue Range: : --10 to 1010 to 10

�� Physical Value RangePhysical Value Range: : --20 to 20dB, step 2dB20 to 20dB, step 2dB

�� Recommended valueRecommended value: : --2,2, namely namely --4dB4dB

�� Content: The offset of Sintersearch when center cell load level Content: The offset of Sintersearch when center cell load level is "Light"is "Light"

�� OFFSINTERHEAVY (Sintersearch offset 2)OFFSINTERHEAVY (Sintersearch offset 2)

�� Value RangeValue Range: : --10 to 1010 to 10

�� Physical Value RangePhysical Value Range: : --20 to 20dB, step 2dB20 to 20dB, step 2dB

�� Recommended valueRecommended value: 2,: 2, namely 4dBnamely 4dB

�� Content: The offset of Sintersearch when center cell load level Content: The offset of Sintersearch when center cell load level is is ““Heavy"Heavy"



OFFSINTERLIGHT (Sintersearch offset 1):

The offset of Sintersearch when center cell load level is "Light“ (Note:

Sintersearch is used to decide whether to start the inter-frequency

cell reselection).

OFFSINTERHEAVY (Sintersearch offset 2):

The offset of Sintersearch when center cell load level is

"Heavy“ (Note: Sintersearch is used to decide whether to start the

inter-frequency cell reselection).

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�� OFFQOFFSET1LIGHT (Qoffset1 offset 1)OFFQOFFSET1LIGHT (Qoffset1 offset 1)

� Value Range: -20 to 20

� Physical Value Range: -20 to 20dB, step 1dB

� Recommended value: -4, namely -4dB

� Content: The offset of Qoffset1 when neighboring cell load is lighter than that of

center cell

�� OFFQOFFSET2LIGHT (Qoffset2 offset 1)OFFQOFFSET2LIGHT (Qoffset2 offset 1)



� Recommended value: -4, namely -4dB

� Content: The offset of Qoffset2 when neighboring cell load is lighter than that of

center cell



OFFQOFFSET1LIGHT (Qoffset1 offset 1):

The offset of Qoffset1 when neighboring cell load is lighter than that

of center cell (Note: Qoffset1 is used as a priority to decide which cell

will be selected while cell selecting or reselecting).

OFFQOFFSET2LIGHT (Qoffset2 offset 1):

The offset of Qoffset2 when neighboring cell load is lighter than that

of center cell (Note: Qoffset2 is used as a priority to decide which cell

will be selected while cell selecting or reselecting).

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�� OFFQOFFSET1HEAVY (Qoffset1 offset 2)OFFQOFFSET1HEAVY (Qoffset1 offset 2)



� Recommended value: 4, namely 4dB

� Content: The offset of Qoffset1 when neighboring cell load is heavier than that of center

cell

�� OFFQOFFSET2HEAVY (Qoffset2 offset 2)OFFQOFFSET2HEAVY (Qoffset2 offset 2)



� Recommended value: 4, namely 4dB

� Content: The offset of Qoffset2 when neighboring cell load is heavier than that of center

cell

�� Set these parameters through Set these parameters through ADD CELLPUCADD CELLPUC, query it through , query it through LST CELLPUCLST CELLPUC, and modify it , and modify it

through through MOD CELLPUCMOD CELLPUC

OFFQOFFSET1HEAVY (Qoffset1 offset 2):

The offset of Qoffset1 when neighboring cell load is heavier than that

of center cell

OFFQOFFSET2HEAVY (Qoffset2 offset 2):

The offset of Qoffset2 when neighboring cell load is heavier than that

of center cell

Set PUC parameters through ADD CELLPUC, query it through LST CELLPUC, and modify it through MOD CELLPUC.

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Contents







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Why we need CAC?

�� WCDMA is an interference limited system, after a new call is admWCDMA is an interference limited system, after a new call is admitted, the itted, the

system load will be increasedsystem load will be increased

�� If a cell is high loaded, a new call will cause ongoing user droIf a cell is high loaded, a new call will cause ongoing user droppedpped

�� We must keep the coverage planed by the Radio Network PlanningWe must keep the coverage planed by the Radio Network Planning

CAC is needed under such scenarios:

1. New call

2. New RAB(s) for ongoing call

3. Handover

4. Bandwidth increasing reconfiguration (AMRC, DCCC)

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Flow chart of CAC

The admission decision is based on:

• Cell available code resource: managed in RNC

• Cell available power resource: DL/UL load measured in Node B

• NodeB resource state, that is, NodeB credits : Reported by Node

B

• Available Iub transport layer resource, that is, Iub transmission

bandwidth: managed in RNC

• HSDPA user number (only for HSDPA service)

• HSUPA user number (only for HSUPA service)

Only when all of these resources are available can a call be

admitted.

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CAC Code Resource Admission

� For handover services

� The current remaining code resource should be enough for the

service

� For other R99 services

� RNC shall ensure the remaining code does not exceed the

configurable OM thresholds after admission of the new service

� For HSDPA services

� The code resource admission is not needed

For handover services, the code resource admission is successful if the current remaining code resource is enough for the service.

For other R99 services, RNC shall ensure the remaining code doesnot exceed the configurable OM thresholds after admission of the

new service.

For HSDPA services, the reserved codes are shared by all HSDPA services; so the code resource admission is not needed. The RNC

adjusts the reserved HS-PDSCH codes according to the real-time

usage status of the codes.

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Parameters for Code Resource Admission

� DLHOCECODERESVSF (DL HandOver Credit and Code

Reserved SF)

� Value Range: 0, 1, 2, 3, 4, 5, 6, 7

� Physical value Range: SF4, SF8, SF16, SF32, SF128, SF256,

SFOFF

� Recommended value: SF32

� Configuration Rule and Restriction:

� [Dl HandOver Credit and Code Reserved SF] >= max ([Dl LDR

Credit SF reserved threshold], [Cell LDR SF reserved threshold])

Set this parameter through ADD CELLCAC, query it through LST CELLCAC, and modify it through MOD CELLCAC.

DLHOCECODERESVSF (Dl HandOver Credit and Code Reserved

SF):

This parameter is the Downlink Credit and Code Reserved by Spread

Factor for Handover service. SFOFF means that none of them are

reserved for Handover.

If the DL spare resource can not satisfy the reserved resource after

the access of a new service, the service will be rejected.

The parameter of [Dl HandOver Credit and Code Reserved SF] must be not less than the either of [Dl LDR Credit SF reserved threshold] and [Cell LDR SF reserved threshold].

The parameters of [Dl LDR Credit SF reserved threshold] and [Cell LDR SF reserved threshold] are set in ADD CELLLDR and MOD

CELLLDR, and they can be listed by LST CELLLDR.

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CAC Power Resource Admission

�� Algorithm 1: based on UL/DL load measurement and load predictioAlgorithm 1: based on UL/DL load measurement and load prediction n

(RTWP and TCP)(RTWP and TCP)

�� The algorithm is easy to implement, but it is affected by the reThe algorithm is easy to implement, but it is affected by the result of sult of

RTWP and TCP measurementRTWP and TCP measurement

�� Algorithm 2: based on Equivalent Number of User (ENU)Algorithm 2: based on Equivalent Number of User (ENU)

�� The algorithm is no need to measure RTWP and TCP, but the The algorithm is no need to measure RTWP and TCP, but the

calculation is more complexcalculation is more complex

�� Algorithm 3: loose CAC algorithm based on UL/DL load measurementAlgorithm 3: loose CAC algorithm based on UL/DL load measurementss

�� Similar to algorithm 1, but the prediction of needed power of a Similar to algorithm 1, but the prediction of needed power of a new call new call

will be set to zerowill be set to zero

�� UL and DL CAC algorithms are independentUL and DL CAC algorithms are independent

TCP: Transmit channel power

When RTWP and/or TCP measurement value are/is

invalid/unavailable, the CAC will change from algorithm 1 to 2

automatically.

When measurement are/is valid/available, the CAC will change back

to algorithm 1 automatically.

In principle, a request will be admitted only when UL and DL are both

admitted. But if UL or DL CAC switch is closed, only one direction CAC also can be realized.

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Uplink CAC Algorithm 1 - Load Prediction

Get current RTWP, and calculate the

current load factor

Admission request

Get the traffic characteristic, and

estimate the increment of load factor

Calculate the predicted load factor

admitted rejected

End of UL CAC

Y NSmaller than

the threshold?

RTWP

PNUL −=1η

η∆

ηηη ∆+= ULpredictedUL _

Pn is uplink receive background noise.

The procedure for uplink power resource decision is as follows:

1. The RNC obtains the uplink RTWP of the cell, and calculate the

current uplink load factor.

2. The RNC calculates the uplink load increment ΔηUL based on

the service request.

3. The RNC uses the formula ηUL,predicted=ηUL + ΔηUL to forecast the uplink load factor.

4. By comparing the forecasted uplink load factor ηUL,predictedwith the corresponding threshold (UL threshold of Conv AMR

service, UL threshold of Conv non_AMR service, UL threshold of

other services, UL Handover access threshold), the RNC decides

whether to accept the access request or not.

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Downlink CAC Algorithm 1 - Load Prediction

Get current TCP

Admission request


estimate the increment of TCP

Calculate the predicted TCP

admitted rejected

End of DL CAC

Y NSmaller than

the threshold?

)(NP

P∆

PNP ∆+)(

The procedure for downlink power resource decision is as follows:

1. The RNC obtains the cell downlink TCP, and calculates the

downlink load factor by multiplying the maximum downlink

transmit power by this TCP.

2. The RNC calculates the downlink load increment ΔP based on

the service request and the current load.

3. The RNC forecasts the downlink load factor.

4. By comparing the downlink load factor with the corresponding

threshold (DL threshold of Conv AMR service, DL threshold of

Conv non_AMR service, DL threshold of other services, DL Handover access threshold), the RNC decides whether to accept

the access request or not.

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Uplink and Downlink CAC Algorithm 2 - ENU

Get current total ENU

Admission request


estimate the increment of ENU

Calculate the predicted ENU

admitted rejected

End of UL/DL CAC

Y NSmaller than

the threshold?

∑=

=N

i

itotal ENUNENU1

)(

newENU

newtotaltotal ENUNENUNENU +=+ )()1(

max/)1( ENUNENUENULoad total +=

The ENUmax of DL is very different from the ENUmax of UL.

The UL ENUmax is calculated by the system automatically.

The DL ENUmax can be configured through parameter:

DL total Non-HSDPA equivalent user number

The procedure for ENU resource decision is as follows:

1. The RNC obtains the total ENU of all exist users ENUtotal.

2. The RNC get the ENU of the new incoming user ENUnew.

3. The RNC forecast the ENU load.

4. By comparing the forecasted ENU load with the corresponding

threshold (the same threshold as power resource), the RNC

decides whether to accept the access request or not.

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Typical equivalent number of users

3.9114.1715.5214.273.4 + 384 kbit/s (PS)

2.839.3610.4910.183.4 + 256 kbit/s (PS)

1.915.466.616.413.4 + 144 kbit/s (PS)

1.674.925.935.783.4 + 128 kbit/s (PS)

1.22.793.253.453.4 + 64 kbit/s (PS)

0.961.72.192.153.4 + 32 kbit/s (PS)

0.851.111.251.623.4 + 16 kbit/s (PS)

0.840.781.041.353.4 + 8 kbit/s (PS)

--1.421.443.4 + 12.2 kbit/s

--1.111.1113.6 kbit/s SIG

--0.420.443.4 kbit/s SIG

HSUPAHSDPADownlink for DCHUplink for DCH

ENUService

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Huawei Parameters for CAC Algorithm Switch

� NBMULCACALGOSELSWITCH (Uplink CAC algorithm switch)

� Value Range:

� ALGORITHM_OFF, ALGORITHM_FIRST (based on load factor),

ALGORITHM_SECOND( based on the ENU), and ALGORITHM_THIRD (loose call

admission algorithm)

� NBMDLCACALGOSELSWITCH (Downlink CAC algorithm switch)

� Value Range:

� ALGORITHM_OFF, ALGORITHM_FIRST (based on load factor),

ALGORITHM_SECOND( based on the ENU), and ALGORITHM_THIRD (loose call

admission algorithm)

� Set CAC Algorithm Switch through ADD CELLALGOSWITCH, query it through

LST CELLALGOSWITCH, and modify it through MOD CELLALGOSWITCH

Set CAC Algorithm Switch through ADD CELLALGOSWITCH, query it through LST CELLALGOSWITCH, and modify it through MOD CELLALGOSWITCH.

The algorithms the above values represent are as follow:

ALGORITHM_OFF: Disable uplink (or downlink) call admission

control algorithm.

ALGORITHM_FIRST: The load factor prediction algorithm will be

used in uplink (or downlink) CAC.

ALGORITHM_SECOND: The equivalent user number algorithm will

be used in uplink (or downlink) CAC.

ALGORITHM_THIRD: The loose call admission control algorithm will

be used in uplink (or downlink) CAC.

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Huawei Parameters for Power Resource CAC

� CELLENVTYPE (Cell environment type)

� Value Range:

� TU: typical urban district RA: rural area HT: hill terrain

� Recommended value (default value): TU

� NONORTHOFACTOR (Nonorthogonality factor)

� Value Range: 0 to 1000

� Physical value range: 0 to 1, step: 0.001

� Recommended value: 400, namely 0.4

� Set the following CAC parameters through ADD CELLCAC, query it through LST CELLCAC,

and modify it through MOD CELLCAC

Set the following CAC parameters through ADD CELLCAC, query it through LST CELLCAC, and modify it through MOD CELLCAC.

CELLENVTYPE (Cell environment type):

This parameter is used for Eb/No calculation. you can get the

corresponding curves of BLER-Eb/No according the coding mode

index and cell environment type index. The curves of BLER-Eb/No

with different coding modes and cell environment types are different from each other.

NONORTHOFACTOR (Nonorthogonality factor):

This parameter is used to predict the transmit power. Zero represents

that channels are completely orthogonal and no interference exists

between users in DL load factor prediction.

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� BACKGROUNDNOISE (Background noise)


� Physical Range: -112 to -50dBm, step: 0.1

� Recommended value: 71, namely -105dBm

� ULINTERFACTOR (UL neighbor interference factor)


� Physical Range: 0 to 2, step: 0.01

� Recommended value: 60, namely 0.6

� Set the following CAC parameters through ADD CELLCAC, query it through LST CELLCAC,

and modify it through MOD CELLCAC

Set the following CAC parameters through ADD CELLCAC, query it through LST CELLCAC, and modify it through MOD CELLCAC.

BACKGROUNDNOISE (Background noise):

This parameter specifies the background noise received in the uplink.

ULINTERFACTOR (UL neighbor interference factor )

This parameter specifies the ratio of UL neighboring cells'

interference to this cell's interference.

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�� ULCONVAMRTHD (UL threshold of Conv AMR service) ULCONVAMRTHD (UL threshold of Conv AMR service)

� Value range: 0 to 100%

� Recommended value: 75, namely 75%

�� ULCONVNONAMRTHD (UL threshold of Conv non_AMR service)ULCONVNONAMRTHD (UL threshold of Conv non_AMR service)



� Set the following CAC parameters through ADD CELLCAC, query it through LST

CELLCAC, and modify it through MOD CELLCAC

The UL load factor thresholds include this parameter, [UL threshold of Conv AMR service], [UL handover access threshold], and [UL

threshold of other services]. The four parameters can be used to limit

the proportion between conversational service, handover user and

other services in a specific cell, and to guarantee the access priority

of conversational service.

ULCONVAMRTHD (UL threshold of Conv AMR service):

This parameter is shared by algorithm 1 and algorithm 2.

If this parameter is too high, the system load after admission will probably be too high, which will affect the system stability and result

in system congestion;

If it is too low, there will be a bigger probability that users will be

rejected, and some resources will be idled and wasted.

ULCONVNONAMRTHD (UL threshold of Conv non_AMR service):

This parameter is also shared by algorithm 1 and algorithm 2.

The effect of this parameter on the network performance is similar

with ULCONVAMRTHD.

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�� ULOTHERTHD (UL threshold of other services)ULOTHERTHD (UL threshold of other services)



�� ULHOTHD (UL handover access threshold)ULHOTHD (UL handover access threshold)





ULOTHERTHD (UL threshold of other services):



with ULCONVAMRTHD.

ULHOTHD (UL handover access threshold):



with ULCONVAMRTHD.

Notes:

1. This parameter only applies to inter-frequency handover.

2. This parameter is to reserve resources for handover and to ensure the handover performance; so the value of this parameter must be

bigger than uplink threshold for conversation services and smaller

than uplink OLC trigger threshold.

Usually, UL handover access threshold>UL threshold of Conversational services>[UL threshold of other services.

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�� DLCONVAMRTHD (DL threshold of Conv AMR service) DLCONVAMRTHD (DL threshold of Conv AMR service)



�� DLCONVNONAMRTHD (DL threshold of Conv non_AMR service)DLCONVNONAMRTHD (DL threshold of Conv non_AMR service)





The DL load factor thresholds include this parameter, [DL threshold of Conv non_AMR service], [DL handover access threshold], and [DL

threshold of other services]. The four parameters can be used to limit

the proportion between conversational service, handover user and

other services in a specific cell, and to guarantee the access priority

of conversational AMR service.

DLCONVAMRTHD (DL threshold of Conv AMR service):

This parameter is shared by algorithm 1 and algorithm 2.

If it is too high, the downlink coverage of the cell will be reduced, the neighboring cells will be interfered seriously, and system stability will

be affected when cell coverage is very small;

l If it is too low, the system resources will be idled, and the target

capacity of the network planning cannot be satisfied.

DLCONVNONAMRTHD (DL threshold of Conv non_AMR service):



with DLCONVAMRTHD.

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�� DLOTHERTHD (DL threshold of other services)DLOTHERTHD (DL threshold of other services)



�� DLHOTHD (DL handover access threshold)DLHOTHD (DL handover access threshold)





DLOTHERTHD (DL threshold of other services):



with DLCONVAMRTHD.

DLHOTHD (DL handover access threshold):



with DLCONVAMRTHD.

Notes:

1. This parameter only applies to inter-frequency handover.

2. This parameter is to reserve resources for handover and to ensure the handover performance; so the value of this parameter must be

bigger than downlink threshold for conversation services and smaller

than downlink OLC trigger threshold.

Usually, UL handover access threshold>UL threshold of Conversational services>[UL threshold of other services.

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� ULTOTALEQUSERNUM (UL total equivalent user number)

� Value range: 1 to 200

� Recommended value: 80, namely UL ENUmax = 80

� DLTOTALEQUSERNUM (DL total equivalent user number)


� Recommended value: 80, namely DL ENUmax = 80

ULTOTALEQUSERNUM (UL total equivalent user number):

When algorithm 2 is used, this parameter defines the total equivalent

user number corresponding to the 100% uplink load.

DLTOTALEQUSERNUM (DL total equivalent user number):

When the algorithm 2 is used, this parameter defines the total

equivalent user number corresponding to the 100% downlink load.

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CAC Credit Resource Admission

� Credit resource admission is similar with code resource

admission

� For handover services

� The current remaining credit resource should be enough for the

service

� For other R99 services

� RNC shall ensure the remaining code does not exceed the

configurable thresholds after admission of the new service

For handover service, the credit resource admission is successful if the current remaining credit resource is enough for the service.

For other R99 and HSUPA service, RNC shall ensure the remaining credit of the local cell, local cell group (if any), NodeB does not

exceed the configurable O&M thresholds (Ul HandOver Credit

Reserved SF/ Dl HandOver Credit and Code Reserved SF) after

admission of the new service.

For HSDPA service, no credit resource needed.

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Parameters for Credit Resource Admission (1)

� DLHOCECODERESVSF (DL HandOver Credit and Code

Reserved SF)

� Value Range: 0, 1, 2, 3, 4, 5, 6, 7


SFOFF



� [Dl HandOver Credit and Code Reserved SF] >= max ([Dl LDR

Credit SF reserved threshold], [Cell LDR SF reserved threshold])


DLHOCECODERESVSF (Dl HandOver Credit and Code Reserved

SF):

This parameter is the Downlink Credit and Code Reserved by Spread

Factor for Handover service. SFOFF means that none of them are

reserved for Handover.

If the DL spare resource can not satisfy the reserved resource after

the access of a new service, the service will be rejected.

The parameter of [Dl HandOver Credit and Code Reserved SF] must be not less than the either of [Dl LDR Credit SF reserved threshold] and [Cell LDR SF reserved threshold].

The parameters of [Dl LDR Credit SF reserved threshold] and [Cell LDR SF reserved threshold] are set in ADD CELLLDR and MOD

CELLLDR, and they can be listed by LST CELLLDR.

34


Parameters for Credit Resource Admission (2)

� ULHOCERESVSF (Ul HandOver Credit Reserved SF)

� Value Range:0, 1, 2, 3, 4, 5, 6, 7


SFOFF



� [Ul HandOver Credit Reserved SF] >= Ul LDR Credit SF reserved

threshold


ULHOCERESVSF (Ul HandOver Credit Reserved SF):

This parameter is the Uplink Credit Reserved by Spread Factor for

Handover service. SFOFF means that none of them are reserved for

Handover.

If the UL spare resource cant safisfy the reserved resource after the

acess of a new service, the service will be rejected.

The parameter of [Ul HandOver Credit Reserved SF] must be not

less than the [Ul LDR Credit SF reserved threshold].

The parameter of [Ul LDR Credit SF reserved threshold] is set in ADD

CELLLDR and MOD CELLLDR, and they can be listed by LST

CELLLDR.

35


Why we need IAC?

� The disadvantage of CAC:

� For PS NRT (Non-Real Time) services, CAC is not flexible

� No consideration about the priority of different users

� No consideration about Directed Retry after CAC rejection

� “Intelligent” means the algorithm can increase admission

successful rate

IAC can increase admission successful rate through the followingmethods:

1. The data rate of PS service is not fixed, so maybe the cell can admit the UE after the data rate is decreased.

2. Since the service is non-real time, the users can wait a short time,

then access to the cell.

3. The user with high priority can preempt the resource of users with

low priority.

4. If the load of neighboring cell is not “Heavy”, UE may be admitted

to the neighboring cell directly.

36


Flow chart of IAC

The IAC procedure includes rate negotiation, DRD, preemption andqueuing.

37


IAC – Rate negotiation

� Iu QoS Negotiation: based

on the UE capability

� Physical layer capability

� Transport channel capability

� RLC capability

� RAB Downsizing: based on

system load

� Channelization codes

� Iub transmission resources

� Radio resources

•384kbps

•256kbps

•128kbps

•64kbps

•32kbps

Maximum allowed bit rate

Initial / Target data rate

Scenarios: RAB setup，，，，RAB modify, SRNSR request, reconfiguration

Iu QoS Negotiation (Maximum expected rate negotiation):

In PS domain, CN will negotiate with UE about the access rate. For

every service, CN will send a QoS (includes the required data rate) to UTRAN, and UE will report its capability (the maximum supported

rate) to UTRAN. After negotiation, the maximum supported rate of UE

will be the maximum negotiation rate.

RAB Downsizing (Initial/target rate negotiation):

To save system resources and improve the admission success rate,

BE services does not require access at the maximum expected rateat setup. In stead, a proper rate is adopted for initial access, the rate

is smaller than or equal to the maximum expected rate and bigger

than or equal to the lowest guarantee rate (usually 8kbps) according

to the cell load information. After access, the rate is adjusted higher

when the traffic requires and system resources allow it to do so.

The negotiation is based on cell load information, including:

•Uplink and downlink radio bearer states of the cell

•Iub resource state

•Minimum spreading factor supported

•HSDPA capability

38


IAC – Direct Retry based on service

� Data service can be retry to HSDPA cells for better QoS

Data

service

HSDPACELL AFrequency B

R99CELL2 R99 CELL 1Frequency A

39


IAC – Preemption

Low priority

High priority

Preempting resource

� The user with high priority can preempt the resource of

users with low priority

� Triggering resource for Preemption

� Power (or ENU), SF (spreading factor), Iub transmission

resource, NodeB CE

In the service setup, modification, hard handover and transition-in scenarios, if service request supports preempting capability (core

network configuration) when application for cell resources fails,

preempting will be executed, and the resource of lower-priority user

supporting preempting is released to set up the service request.

The preemption procedure is as follows:

1.The preemption algorithm determines which radio link sets can be

preempted according to the following preemption rules:

- High priority user preempt the resource of low priority users

- Preempting the resource of users with low priority first

- Preempting single service user first

- Preempting UEs as few as possible, that is, choose the UEs that

can release the most resources

- Preempting should follow this sequence: channelization codes first,

then Iub transmission resources, radio resources last

2.Release resources occupied by candidate UEs.

3.The requested service uses the released resources to access the

network directly without further admission decision.

40


IAC – Queuing

� After CAC rejection, UE can wait a moment and queue, then

try to admit again

� Queuing priority: Pqueue = Tmax – Telapsed

� Tmax is the maximum time in the queue, default value is 5s

� Telapsed is the time has queued

The queuing algorithm is triggered by poll timer.

The specific processing is as follows:

1. Reject this request if the actual wait time of each of the other

requests is longer than the maximum queuing time of this request.

2. Calculate the weights of all requests in the queue. The weight: W

= (Tmax – Telapsed) / Tmax * Priority Level of the service.

3. Choose the request with the smallest weight to attempt resource

allocation.

4. Put it back into the queue with the time stamp unchanged if this

request is rejected.

5. Choose the request with the smallest weight from the rest and

performs another attempt until admitting a request or rejecting all

requests.

41


IAC – Directed Retry based on Load Balance

� Service will be set up to the cell with lightest load

� The advantages

� Keeping the load of the network balanced

� Supporting higher data rate for the user

Cell 1

Cell 2

RRC

Connection

Cell 1

Cell 2

RAB

If the load of neighboring cell is lighter than current cell, UE may be admitted to the neighboring cell directly.

The RAB DRD procedure is as follows:

1. The RNC determines the admission of the inter-frequency target

cell for blind handover.

2. If the admission is accepted, DRD procedure is performed for the

inter-frequency target cell for blind handover.

3. The RNC starts the RL setup procedure to complete the inter-

frequency hard handover.

4. The RNC starts the RB setup procedure to complete the inter-

frequency hard handover on the Uu interface and the service

setup.

42


Parameters for IAC Algorithm Switch (1)

� IU_QOS_NEG_SWITCH (Switch for IU QoS Negotiation)

� Value range: 0 (close), 1 (open)

� Default value: 0

� RAB_DOWNSIZING_SWITCH (RAB Downsizing Switch)

� Value range: 0 (close), 1 (open)


Set IU_QOS_NEG_SWITCH and RAB_DOWNSIZING_SWITCH through SET CORRMALGOSWITCH, and query them through LST CORRMALGOSWITCH

43


Parameters for IAC Algorithm Switch (2)

� PREEMPTALGOSWITCH (Preempt algorithm switch)

� Value range: On, Off

� Default value: Off

� QUEUEALGOSWITCH (Queue algorithm switch)

� Value range: On, Off

� Default value: Off

Set QUEUEALGOSWITCH and PREEMPTALGOSWITC through SET QUEUEPREEMPT, and query them through LST QUEUEPREEMPT.

44


Parameters for RAB Downsizing

� ULBETRAFFINITBITRATE (Uplink BE traffic initial access

rates) & DLBETRAFFINITBITRATE (Downlink BE traffic

initial access rates)

� Value range: D8, D16, D32, D64, D128, D144, D256, D384,

D768, D1024, D1536, D2048

� Physical Value range: 8, 16, 32, 64, 128, 144, 256, 384, 768,

1024, 1536, 2048, Unit: kbps

� Default value: D64, namely 64kbps

Set the parameter through SET FRC, and query it through LST FRC.

The selection of the initial access rate for BE services takes the UL BE traffic Initial bit rate and DL BE traffic Initial bit rateparameters into consideration only when the DCCC algorithm is

enabled

45


Parameters for Queuing (1)

� QUEUELEN (Queue length)


� Recommended value: 10

� POLLTIMERLEN (Poll timer length)


� Physical value range: 10 to 60000 ms step: 10ms

� Recommended value: 50, namely 500 ms

Set the parameters through SET QUEUEPREEMPT, and query them through LST QUEUEPREEMPT.

46


Parameters for Queuing (2)

� MAXQUEUETIMELENx (Max queuing time length 1~12)

� Value range: 1 to 60s

� Recommended value: 5, namely 5 seconds

Set the parameters through SET QUEUEPREEMPT, and query them through LST QUEUEPREEMPT.

47


Contents







48


LDR (Load Reshuffling)

Overload state: OLC will be used to

release overload state quickly, keep

system stability and the service of

high priority users:

1.Fast TF control

2. Release of some uses

Lo

ad

%

THLDR

THOLC

100%section A

section B

section C

1 2

Normal state: access admitted

Times

Basic congestion state: LDR will be

used to optimize resource distribution,

the main rules is not to affect the

feeling of users as possible as we can

LCC (Load Congestion Control) consist of LDR (Load Reshuffling) and OLC (OverLoad Control).

In congestion state, system is still stable but the resource is very

limited. The LDR can be used, which includes:

•Inter-frequency load handover

•BE service rate reduction

•AMR rate reduction

•Inter-system load handover in the CS domain

•Inter-system load handover in the PS domain

•Iu QoS negotiation

In overload state, system is not stable now. The OLC can be used,

which includes:

•Restricting the TF (Transmission Format) of the BE service

•Choosing and releasing some UEs

49


LDR (Load Reshuffling)

�� ReasonReason

�� When the cell enters congestion state, new coming calls could beWhen the cell enters congestion state, new coming calls could be rejected by rejected by

system directlysystem directly

�� CharacteristicCharacteristic

�� No influence to the system stability, but admission rejection ofNo influence to the system stability, but admission rejection often happenedten happened

�� PurposePurpose

�� Optimizing cell resource distributionOptimizing cell resource distribution

�� Decreasing load level, increasing admission successful rateDecreasing load level, increasing admission successful rate

When the usage of cell resource exceeds the basic congestion trigger threshold, the cell enters the basic congestion state. In this case,

LDR is needed to reduce the cell load and increase the access

success rate.

Basic congestion is triggered when the load of radio resources

reaches the basic congestion trigger threshold. When the load of

radio resources is lower than the basic congestion trigger threshold,

the system comes back to normal.

50


Huawei Parameters for LDR Algorithm Switch


�� Value RangeValue Range::

�� ULLDR, DLLDRULLDR, DLLDR

�� Default statusDefault status: : OFFOFF

�� Most of the LDR actions (except interMost of the LDR actions (except inter--frequency load handover) affect QoSfrequency load handover) affect QoS

�� Set LDR Algorithm Switch throughSet LDR Algorithm Switch through ADD CELLALGOSWITCHADD CELLALGOSWITCH, , query it throughquery it through LST LST

CELLALGOSWITCHCELLALGOSWITCH, , and modify it throughand modify it through MOD CELLALGOSWITCHMOD CELLALGOSWITCH

Set LDR Algorithm Switch through ADD CELLALGOSWITCH, query it through LST CELLALGOSWITCH, and modify it through MOD CELLALGOSWITCH.

The preliminary congestion is a transition status. For the uplink, it

means the uplink interference is close to the admission threshold; for the downlink, it means the cell’s downlink transmit power is close to

the admission threshold and the call rejection rate will increase

significantly. The preliminary congestion algorithm’s control objective

is to slowly lower the cell load within the admission threshold, to

obtain higher call success rate at the cost of sacrificing the QoS of the low–priority users, and to balance the inter-cell load (through

inter-frequency load handover).

Since most of the LDR actions (except inter-frequency load handover)

affect QoS, it is desirable to set the algorithm switch to default OFF at

the preliminary stage of the network construction when user feelings

are important.

51


Huawei Parameters for Triggering of Basic Congestion

�� ULLDRTRIGTHD (UL LDR trigger threshold)ULLDRTRIGTHD (UL LDR trigger threshold)



� Content: If the UL load of the cell is not lower than this threshold, the UL load

reshuffling function of the cell is triggered

�� ULLDRRELTHD (UL LDR release threshold)ULLDRRELTHD (UL LDR release threshold)



� Content: If the UL load of the cell is lower than this threshold, the UL load

reshuffling function of the cell will be stopped

� Set these parameters through ADD CELLLDM, query it through LST CELLLDM, and

modify it through MOD CELLLDM

Set these parameters through ADD CELLLDM, query it through LST CELLLDM, and modify it through MOD CELLLDM.

When uplink basic congestion status is triggered, the uplink LDR

action will be started. LDR control objective is to preserve space for

admission to increase the success rate. Therefore under the current policy, the LDR trigger threshold shall be so set that the congestion is

less than or close to the concerned admission threshold index.

The smaller the LDR trigger threshold and release threshold, the

easier the system is in preliminary congestion status, the harder it is

released from this status, the easier the LDR action happens, and the

more likely the users are affected. However, since the resources are

preserved, the admission success rate becomes higher. The carrier shall make tradeoff between these factors.

The uplink LDR trigger thresholds must be greater than uplink LDR release thresholds, and the recommended difference between the

two thresholds is larger than 10%, otherwise maybe the basic

congestion state is “Ping-Pong”.

52


Huawei Parameters for Triggering of Basic Congestion

�� DLLDRTRIGTHD (DL LDR trigger threshold)DLLDRTRIGTHD (DL LDR trigger threshold)



� Content: If the DL load of the cell is not lower than this threshold, the DL load

reshuffling function of the cell will be triggered

�� DLLDRRELTHD (DL LDR release threshold)DLLDRRELTHD (DL LDR release threshold)



� Content: If the DL load of the cell is lower than this threshold, the DL load

reshuffling function of the cell will be stopped

�� Set these parameters through ADD CELLLDM, query it through LST CELLLDM, and

modify it through MOD CELLLDM

When downlink basic congestion status is triggered, the downlinkLDR action will be started. LDR control objective is to preserve space

for admission to increase the success rate. Therefore under the

current policy, the LDR trigger threshold shall be so set that the

congestion is less than or close to the concerned admission threshold

index.

The smaller the LDR trigger threshold and release threshold, the

easier the system is in preliminary congestion status, the harder it is released from this status, the easier the LDR action happens, and the

more likely the users are affected. However, since the resources are

preserved, the admission success rate becomes higher. The carrier

shall make tradeoff between these factors.

The downlink LDR trigger thresholds must be greater than downlink

LDR release thresholds, and the recommended difference between

the two thresholds is larger than 10%, otherwise maybe the basiccongestion state is “Ping-Pong”.

53

LDR procedure

Mark "current LDR state = uncongested"

Wait for congestion indication

Congestion

state indication

Turn on LDR algorithm switch

Current LDR state = congested?

Start LDM congestion indication report

Mark "current action = first LDR action"

Clear "selected" mark of all UE LDR actions

Sequence of

actions can be

configured

(current action

is taken firstly)

Inter-system

handover

in CS domain

AMR rate

reduction

Inter-freq

load handover

QoS renegotiation

on Iu interface

BE rate

reduction

Succeed?

Mark

"current action

= successful

action"

Wait time

for LDR

action duration

Y

Y

Y

Y

Y

N

N

N

N

N

N

Mark "current action = first LDR action"No related action can be found

N

Inter-system

handover

in PS domain

Succeed?

Succeed?

Succeed?

Succeed?

Succeed?

Code

reshufflingSucceed?

Y

N

MBMS power

reduction

N

Succeed?

Y

Y

54


√√DL

–

Code

√√√√√DL

√√√√√UL

Iub

√*√√*√√√√DL

√√√√√√UL

Power

MBMS

Power

Reductio

n

Code

Reshuffli

ng

Iu QoS

Negotiati

on

AMR

Rate

Reductio

n

Inter-

System

Handove

r in PS

Domain

Inter-

system

Handove

r in CS

Domain

BE Rate

Reductio

n

Inter-

Frequenc

yLoad

Handove

r

LDR ActionsUL/DL

Resource

LDR actions intended for different resources

* If the downlink power admission uses the equivalent user number algorithm, basic congestion may also be triggered by the equivalent number of users. In this situation, LDR actions do not involve AMR rate reduction or MBMS power reduction.

55


Huawei Parameters for LDR

�� UL (DL) LDRFIRSTACTION (UL/DL LDR First action) ~ UL (DL) LDRFIRSTACTION (UL/DL LDR First action) ~

UL (DL) LDREIGHTHACTION (UL/DL LDR Eighth action)UL (DL) LDREIGHTHACTION (UL/DL LDR Eighth action)

�� Value rangeValue range: NOACT, INTERFREQLDHO, BERATERED, QOSRENEGO, : NOACT, INTERFREQLDHO, BERATERED, QOSRENEGO,

CSINTERRATLDHO, PSINTERRATLDHO, AMRRATEREDCSINTERRATLDHO, PSINTERRATLDHO, AMRRATERED

�� Default Default valuevalue: : UlLdrFirstAction or DlLdrFirstAction is INTERFREQLDHO, UlLdrFirstAction or DlLdrFirstAction is INTERFREQLDHO,

UlLdrSecondAction or DlLdrSecondAction is BERATEREDUlLdrSecondAction or DlLdrSecondAction is BERATERED，，the other is NOACTthe other is NOACT

�� Set the following parameters through Set the following parameters through ADD CELLLDRADD CELLLDR, query it through , query it through LST CELLLDRLST CELLLDR, ,

and modify it through and modify it through MOD CELLLDRMOD CELLLDR

Set the following parameters through ADD CELLLDR, query it through LST CELLLDR, and modify it through MOD CELLLDR.

This set of parameters determines the action sequence for the uplink/downlink LDR.

•NOACT: NO ACTION

•INTERFREQLDHO: INTER-FREQ LOAD HANDOVER

•BERATERED: BE TRAFF RATE REDUCTION

•QOSRENEGO: UNCONTROLLED REAL-TIME TRAFF QOS RE-NEGOTIATION

•CSINTERRATLDHO: CS DOMAIN INTER-RAT LOAD HANDOVER

•PSINTERRATLDHO: PS DOMAIN INTER-RAT LOAD HANDOVER

•AMRRATERED: AMR TRAFF RATE REDUCTION

Inter-frequency handover is no effect to the QoS of users, and through it the load of the cells can be balanced, so UlLdrFirstAction or DlLdrFirstAction is INTERFREQLDHO;

UlLdrSecondAction or DlLdrSecondAction is BERATERED, BE Rate Reduction is controlled by DCCC algorithm.

56


LDR Actions - Inter-frequency Load Handover

�� Target cellsTarget cells

�� Load difference between current load and the Load difference between current load and the basic congestion trigger basic congestion trigger

thresholdthreshold of target cell is larger than of target cell is larger than UL/DL InterUL/DL Inter--freq cell load handover freq cell load handover

load space thresholdload space threshold

�� Target usersTarget users

�� Based on user priority and the current service rateBased on user priority and the current service rate

�� ResultResult

�� The load of two cells is lower than the The load of two cells is lower than the basic congestion trigger thresholdbasic congestion trigger threshold

�� The user with low priority hand over to the The user with low priority hand over to the ““Light loadLight load”” cellscells

The LDR algorithm is implemented as follows:

1. The LDR check whether the existing cell has a target cell of inter-

frequency blind handover. If there is no such a target cell, the

action fails, and the LDR performs the next action.

2. The LDR checks whether the load difference between the current

load and the basic congestion trigger threshold of each target cell for blink handover is larger than UL/DL Inter-freq cell load

handover load space threshold (Both uplink and downlink

condition must be all fulfilled). If the basic congestion trigger

threshold is not set, the admission threshold of the cell is used. If

the difference is not larger than the threshold, the action fails. The LDR performs the next action.

3. If the LDR finds out a target cell that meets the specified blind handover conditions, the LDR selects one UE to make an inter-

frequency blind handover, depending on the UE’s integrate priority

and occupied bandwidth. The selected UE has lower integrate

priority and its bandwidth is less than and has the least difference

between the UL/DL Inter-freq cell load handover maximum bandwidth parameter. If the LDR cannot find such a UE, the

action fails. The LDR performs the next action.

57


Huawei Parameters for LDR

�� ULINTERFREQHOCELLLOADSPACETHD (UL InterULINTERFREQHOCELLLOADSPACETHD (UL Inter--freq cell load handover freq cell load handover

load space threshold)load space threshold)



� Content: The neighbor inter-frequency cell could be selected as the destination of

load handover, only when its UL load remaining space is larger than this threshold.

Cell UL load space = cell UL LDR trigger threshold - cell UL load

�� DLINTERFREQHOCELLLOADSPACETHD (DL InterDLINTERFREQHOCELLLOADSPACETHD (DL Inter--freq cell load handover freq cell load handover

load space threshold)load space threshold)



� Content: The neighbor inter-frequency cell could be selected as the destination of

load handover, only when its DL load remaining space is larger than this threshold.

Cell DL load space = cell DL LDR trigger threshold - cell DL load



58


LDR Actions - BE Rate Reduction

�� Candidate Candidate usersusers

�� The data rate of BE service is larger than GBRThe data rate of BE service is larger than GBR

�� Target usersTarget users

�� Rank the cRank the candidate andidate users by the priority, the low priority user reduce BE rate users by the priority, the low priority user reduce BE rate

firstfirst

�� ResultResult

�� Cell load is decreased under Cell load is decreased under basic congestion trigger thresholdbasic congestion trigger threshold

�� The BE service rate of low priority user is limited in GBRThe BE service rate of low priority user is limited in GBR

BE rate reduction is implemented by reconfiguring the bandwidth.Bandwidth reconfiguration requires signaling interaction on the Uu

interface. This procedure is relatively long.


1. Based on the integrate priority, the LDR sorts the RABs in

descending order. The top RABs related to the BE services whose rates are higher than a threshold (target rate of UL/DL LDR-BE

rate reduction) are selected. The target rate is

ULPSBEGUARRATE/DLPSBEGUARRATE which is configured

DCCC algorithm (ADD CELLDCCC).

2. The bandwidth of the selected services is reduced to the specified

rate.

3. If services can be selected, the action is successful. If services

cannot be selected, the action fails. The LDR performs the next

action.

4. The BE rate reduction algorithm is controlled by the DCCC

algorithm switch. BE rate reduction can be performed only when the DCCC algorithm switch is turned on.

59


LDR Actions - AMR Rate Reduction

�� Target user (downlink e.g.)Target user (downlink e.g.)

�� Candidate users: users accessing the AMR services (conversationaCandidate users: users accessing the AMR services (conversational) and with l) and with

the bit rate higher than the GBRthe bit rate higher than the GBR

�� Rank the candidate users by the priority, the AMR service user wRank the candidate users by the priority, the AMR service user with lowest ith lowest

priority will be selectedpriority will be selected

�� ResultResult


�� The AMR user with low priority is reduced to low voice rate modeThe AMR user with low priority is reduced to low voice rate mode

In the WCDMA system, voice services work in eight AMR modes. Each mode has its own rate. Therefore, mode control is

functionally equal to rate control.


1. Based on the integrate priority, the LDR sorts the RABs in the

descending order. The top UEs accessing the AMR services (conversational) and with the bit rate higher than the GBR are

selected.

2. In downlink, the RNC sends the “Rate Control request” message

through the Iu-UP to the CN to adjust the AMR rate to the GBR.

3. In uplink, The RNC sends the TFC CONTROL command to the

UE to adjust the AMR rate to the assured rate.

4. If the RNC cannot find a proper service for AMR rate reduction,

the action fails. The LDR performs the next action.

60


LDR Actions - interRAT Handover in the CS/PS Domain

�� Target userTarget user

�� Based on the priority, sorting the UEs in descending order. TheBased on the priority, sorting the UEs in descending order. The top CS/PS top CS/PS

services are selectedservices are selected

�� ResultResult


WCDMA cell

GSM cell

The 2G and 3G systems have different cell sizes and coverage modes. Therefore, blind handover across systems is not taken

into account.

The LDR is implemented in the downlink (e.g.) as follows:

1. Based on the integrate priority, the LDR sorts the UEs in

descending order. The top CS/PS services are selected.

2. For the selected UEs, the LDR sends the load handover

command to the inter-system handover module to ask the UEs to hand over to the 2G system.

3. The handover module decides to trigger inter-system handover, depending on the capability of the UE and the capability of the

algorithm switch to support the compression mode.

4. This action is successful if any load handover UE is found.

Otherwise, this action fails.

61


LDR Actions - Uncontrolled Real-time QoS Renegotiation


�� Rank the candidate users by the priority, the service with lowesRank the candidate users by the priority, the service with lowest priority and t priority and

current rate higher than GBR will be selectedcurrent rate higher than GBR will be selected

�� ResultResult


�� The data rate of low priority user is reduced to GBRThe data rate of low priority user is reduced to GBR

The load is reduced by adjusting the rate of the realtime services through uncontrolled realtime OoS renegotiation.

Upon receipt of the message, the CN sends the RAB ASSIGNMENT

REQUEST message to the RNC for RAB parameter reconfiguration. Based on this function, the RNC can adjust the

rate of realtime services to reduce the load.


1. Based on the integrate priority, the LDR sorts the realtime services in the PS domain in descending order. The top services

are selected for QoS renegotiation.

2. The LDR performs QoS renegotiation for the selected services.

The GBR during service setup is the maximum rate of the service

after QoS renegotiation.

3. The RNC initiates the RAB Modification Request message to the

CN for QoS renegotiation.

4. If the RNC cannot find a proper service for QoS renegotiation, the

action fails. The LDR performs the next action.

62


LDR Actions - Code Reshuffling

� Purpose

� Cell load is decreased under basic congestion trigger threshold

� Sufficient code resources can be reserved for subsequent

service

When code resources are in basic congestion state, sufficient code resources can be reserved for subsequent service access

through code reshuffling.


1. Select a subtree. Ensure that the number of users in the subtree

is not higher than Max user number of code adjust.

2. Treat each user in the subtree as a new user and allocate code

resources to each user.

3. Initiate the reconfiguration procedure for each user in the subtree

and reconfigure the channel codes of the users to the newly-allocated code resources.

4. The reconfiguration procedure on the air interface is implemented through the PHYSICAL CHANNEL RECONFIGURATION

message and that on the Iub interface through the RL

RECONFIGURATION message.

63


LDR Actions - MBMS Power Reduction

� Purpose

� The downlink power load can be reduced by lowering power on

MBMS traffic channels


1. Select all RABs with low priorities.

2. The RNC initiates the reconfiguration procedure and resets the

transmit power of MTCH (FACH) to the minimum value. The

transmit power corresponds to the MBMS service.

3. The reconfiguration procedure on the Iub interface is implemented

through the COMMON TRANSPORT CHANNEL

RECONFIGURATION REQUEST message.

64


Huawei Parameters for LDR (2)

�� UL (DL) LDRBERATEREDUCTIONRABNUM,UL (DL) LDRBERATEREDUCTIONRABNUM,

UL (DL) LDRPSRTQOSRENEGRABNUM,UL (DL) LDRPSRTQOSRENEGRABNUM,

UL (DL) LDRCSINTERRATHOUSERNUM,UL (DL) LDRCSINTERRATHOUSERNUM,

UL (DL) LDRPSINTERRATHOUSERNUM,UL (DL) LDRPSINTERRATHOUSERNUM,

ULLDRAMRRATEREDUCTIONRABNUMULLDRAMRRATEREDUCTIONRABNUM


� Default value

� UL (DL) LDRBERATEREDUCTIONRABNUM: 1

� UL (DL) LDRPSRTQOSRENEGRABNUM: 1

� UL (DL) LDRCSINTERRATHOUSERNUM: 3

� UL (DL) LDRPSINTERRATHOUSERNUM: 1

� UL (DL) LDRAMRRATEREDUCTIONRABNUM: 3



This set of parameters determines the action sequence for the uplink/downlink LDR.

UL (DL) LDRBERATEREDUCTIONRABNUM: UL/DL LDR-BE rate

reduction RAB number

UL (DL) LDRPSRTQOSRENEGRABNUM: UL/DL LDR un-ctrl RT

Qos re-nego RAB number

UL (DL) LDRCSINTERRATHOUSERNUM: UL/DL LDR CS inter-rat

ho user number

UL (DL) LDRPSINTERRATHOUSERNUM: UL/DL LDR PS inter-rat

ho user number

UL (DL) LDRAMRRATEREDUCTIONRABNUM: UL/DL LDR-AMR

rate reduction RAB number

The larger these parameters are, the more obviously the current cell’s

load is reduced. Its cost is that user feelings are affected and that it

gives rise to congestion of the target cell. The smaller these parameters are, the smaller the amplitude of the load adjusted by

LDR. Its benefit is that the QoS is guaranteed and the target cell load

is stable.

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Contents







66


OLC (Over Load Control)

� Reason

� In overload state, system is not stable

� Purpose

� Ensuring the system stability and making the system back to the normal state

as soon as possible

� Triggering of OLC

� Power resources only

After the UE access is granted, the power consumed by a single link is adjusted by the single link power control algorithm. The power

varies with the mobility of the UE and the changes in the environment

and the source rate. In some situations, the total power load of the

cell may be higher than the target load. To ensure system stability,

overload congestion must be handled. The OLC includes:

•Restricting the TF (Transmission Format) of the BE service

•Choosing and releasing some UEs

Only power resources could result in overload congestion. Hard

resources such as equivalent user number, Iub bandwidth, and credit

resources do not cause overload congestion.

67

OLC Procedure

68


OLC Actions - TF Control


�� Rank the candidate users by the integrate priority, the low prioRank the candidate users by the integrate priority, the low priority user will be rity user will be

selectedselected

�� ExecutionExecution

�� Send the control message to UE to Send the control message to UE to restricts the TFC selectionrestricts the TFC selection

�� After the congestion is released, the BE service rate will be rAfter the congestion is released, the BE service rate will be recoveryecovery

The OLC algorithm for TF control is implemented as follows:

1. Based on the integrate priority, the OLC sorts the RABs in the

descending order. The RABs with the BE services and its bit rate

is higher than DCCC rate reduction threshold and with the lowestintegrate priority are selected. The selected RAB number is UL/DL

OLC fast TF restrict RAB number.

2. The RNC sends the control message to the MAC, during the

continuous time (till congestion is released and traffic volume

upsizing), MAC will restricts the TFC selection of these BE

services to reduce data rate step by step.

3. Each time, RNC will select a certain number of RABs (which is

determined by “UL/DL OLC fast TF restrict RAB number” ) to

perform TF control, the times to perform TF control is determined by the UL/DLOLCFTFRSTRCTTimes parameter.

4. If the RNC cannot find a proper service for TF control, the action fails. The OLC performs the next action.

5. If the congestion is released, the RNC sends the congestion release indication to the MAC.

6. If the congestion is released and 4A report is received, and if rate recover timer (which length is RateRecoverTimerLen) is started

and when this timer is expired, MAC will increase data rate step

by step.

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OLC Actions – Forcibly Release UEs

� Target user (downlink e.g.)

� Rank the candidate users by the integrate priority, the low

priority user will be selected

� Execution

� The selected RABs are released directly.

OLC Algorithm for the Release of Some RABs in the Uplink

1. The OLC algorithm for the release of some RABs in the uplink is

implemented as follows:

2. Based on the integrate priority, the OLC sorts all RABs including

HSUPA and DCH services in descending order.

3. The top RABs selected. If the integrate priorities of some RABs

are identical, the RAB with higher rate (current rate for DCH RAB

and GBR for HSUPA RAB) in the uplink is selected. The number of selected RABs is equal to UL OLC traff release RAB number.

4. The selected RABs are released directly.

OLC Algorithm for the Release of Some RABs in the Downlink

The OLC algorithm for the release of some RABs in the downlink is

implemented as follows:

If the Sequence of user release parameter is set to USER_REL:

• Based on the integrate priority, the OLC sorts all non-MBMS

RABs in descending order.

• The top priority RABs are selected. If the integrate priorities of

some RABs are identical, the RAB with higher rate (current rate

for DCH RAB and GBR for HSUPA RAB) in the downlink is

selected. The number of selected RABs is equal to DL OLC traffrelease RAB number.

• The selected RABs are directly released.

• If all non-MBMS RABs are released but congestion persists in the

downlink, MBMS RABs are selected.

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Huawei Parameters for OLC Algorithm Switch


� Value Range:

� ULOLC, DLOLC

� Default status: OFF

� OLC actions affect QoS heavily

� Set OLC Algorithm Switch through ADD CELLALGOSWITCHADD CELLALGOSWITCH, query it through LST LST

CELLALGOSWITCHCELLALGOSWITCH, and modify it through MOD CELLALGOSWITCHMOD CELLALGOSWITCH

Set OLC Algorithm Switch through ADD CELLALGOSWITCH, query it through LST CELLALGOSWITCH, and modify it through MOD CELLALGOSWITCH.

Cell overload is an emergent status, OLC algorithm can quickly

relieve uplink/downlink load by TF restriction or user release but may also cause oscillation of the cell load and affect the call drop rate.

For the uplink, overload means the cell’s uplink interference is close to or reaches the limit and may give rise to difficulty in BTS uplink

reception and decoding, resulting in call drop;

For the downlink, overload means the downlink transmit power is

close to or reaches the limit and the user’s downlink inner loop power

control cannot be increased as needed because of the BTS power

restriction, resulting in call drop.

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Huawei Parameters for Triggering of Overload (1)

�� ULOLCTRIGTHD (UL OLC trigger threshold)ULOLCTRIGTHD (UL OLC trigger threshold)


�� RecommendedRecommended valuevalue: 95: 95, namely 95%, namely 95%

�� Content: If the UL load of the cell is not lower than this thresContent: If the UL load of the cell is not lower than this threshold, the UL overload hold, the UL overload

congestion control function of the cell will be triggered congestion control function of the cell will be triggered

�� ULOLCRELTHD (UL OLC release threshold)ULOLCRELTHD (UL OLC release threshold)



�� Content: If the UL load of the cell is lower than this thresholdContent: If the UL load of the cell is lower than this threshold, the UL overload , the UL overload

congestion control function of the cell will be stopped congestion control function of the cell will be stopped

� Set these parameters through ADD CELLLDMADD CELLLDM, query it through LST CELLLDMLST CELLLDM, and

modify it through MOD CELLLDMMOD CELLLDM


The uplink OLC trigger threshold judges whether the system uplink is

in overload status. If the cell load is consecutively higher than the

threshold for pre-determined times, it means the system is in overload status for a long time. Under this circumstance, if the cell’s OLC

switch is open, the system will perform OLC algorithm, including fast

TF restriction or even user release.

The smaller the OLC trigger threshold is, the easier the system will be

in overload status. Since OLC will ultimately use extreme method like

user release to lower the load, too low value will be very detrimental

to the system performance.

The smaller the OLC release threshold is, the harder for the system

to release the overload. Since the consequence of overload is not as severe as expected, it is desirable to set the two parameters a bit

higher given that the difference between OLC trigger threshold and

OLC release threshold is fixed.

The uplink OLC trigger thresholds must be greater than up OLC

release thresholds, and the recommended difference between the



72


Huawei Parameters for Triggering of Overload (2)

�� DLOLCTRIGTHD (DL OLC trigger threshold)DLOLCTRIGTHD (DL OLC trigger threshold)



� Content: If the DL load of the cell is not lower than this threshold, the DL overload

congestion control function of the cell will be triggered

�� DLOLCRELTHD (DL OLC release threshold)DLOLCRELTHD (DL OLC release threshold)



�� Content: If the DL load of the cell is lower than this thresholdContent: If the DL load of the cell is lower than this threshold, the DL overload , the DL overload

congestion control function of the cell will be stoppedcongestion control function of the cell will be stopped

� Set these parameters through ADD CELLLDMADD CELLLDM, query it through LST CELLLDMLST CELLLDM, and modify it

through MOD CELLLDMMOD CELLLDM


The downlink OLC trigger threshold judges whether the system

downlink is in overload status. If the cell load is consecutively higher

than the threshold for pre-determined times, it means the system is in overload status for a long time. Under this circumstance, if the cell’s

OLC switch is open, the system will perform OLC algorithm, including

fast TF restriction or even user release.

The smaller the OLC trigger threshold is, the easier the system will be

in overload status. Since OLC will ultimately use extreme method like

user release to lower the load, too low value will be very detrimental

to the system performance.

The smaller the OLC release threshold is, the harder for the system

to release the overload. Since the consequence of overload is not as severe as expected, it is desirable to set the two parameters a bit

higher given that the difference between OLC trigger threshold and

OLC release threshold is fixed.

The downlink OLC trigger thresholds must be greater than down OLC

release thresholds, and the recommended difference between the



73


Huawei Parameters for OLC (1)

�� ULOLCFTFRSTRCTTIMES (UL OLC fast TF restrict times)ULOLCFTFRSTRCTTIMES (UL OLC fast TF restrict times)



�� DLOLCFTFRSTRCTTIMES (DL OLC fast TF restrict times)DLOLCFTFRSTRCTTIMES (DL OLC fast TF restrict times)



� Set the following parameters through ADD CELLOLCADD CELLOLC, query it through LST CELLOLCLST CELLOLC,

and modify it through MOD CELLOLCMOD CELLOLC

Set the following parameters through ADD CELLOLC, query it through LST CELLOLC, and modify it through MOD CELLOLC.

When uplink/downlink overload is triggered, the RNC will immediately

execute OLC action by first executing uplink/downlink fast TF

restriction. The internal counter is incremented by 1 with each execution. If the number of overloads does not exceed the OLC

action threshold, the system lowers the BE service rate by lowering

TF to try to relieve the overload. Exceeding OLC action threshold

means that the previous operation has no obvious effect on

alleviating the overload and the system has to release users to solve the overload problem.

The lower the parameter value, the more likely the users are released, resulting in negative effect on the system performance. If the

parameter value is set too high, the overload status is released

slowly.

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�� ULOLCFTFRSTRCTRABNUM (UL OLC fast TF restrict RAB number)ULOLCFTFRSTRCTRABNUM (UL OLC fast TF restrict RAB number)



�� DLOLCFTFRSTRCTRABNUM (DL OLC fast TF restrict RAB number)DLOLCFTFRSTRCTRABNUM (DL OLC fast TF restrict RAB number)





The higher the parameter value, the more users involved in fast TF restriction under identical conditions, the quicker the cell load

decreases, and the more users’ QoS affected.

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�� RATERSTRCTCOEF (OLC fast TF restrict coefficient)RATERSTRCTCOEF (OLC fast TF restrict coefficient)





The higher the parameter value, the more users involved in fast TF restriction under identical conditions, the quicker the cell load

decreases, and the more users’ QoS affected.

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� ULOLCTRAFFRELRABNUM (UL OLC release RAB number)



�� DLOLCTRAFFRELRABNUM (DL OLC release RAB number)DLOLCTRAFFRELRABNUM (DL OLC release RAB number)





The higher the parameter value, the more obvious the cell load decreases at the cost of negatively affecting user feelings.

77

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