04 RN31674EN30GLA0 RANPAR Combined LoadControl v1.2

RN31674EN30GLA0

Load Control

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1 © Nokia Siemens Networks RN31674EN30GLA0

Course Content

Radio Resource Management Overview

Parameter Configuration

Common Channels & Power Control

Load Control

Admission Control

Packet Scheduling

Handover Control

Resource Manager

HSDPA RRM & parameters

HSUPA RRM & parameters

HSPA+ features & parameters

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Load Control:Module Objectives

At the end of the module you will be able to:

• Describe the principles of Load Control and it's parameters in detail

• Describe the relationships of Load Control with AC and PS

• Identify the parameters influencing BTS load measurements

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Load Control

• Load Control Functions

• Radio Interface Load• Power based Radio Resource Management

• Throughput based Radio Resource Management

• Planning thresholds for cell loading

• BTS Measurements and Reporting• Common Measurements

• Dedicated Measurements

• Filtering of Measurements

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Load Control Functional Overview

• LC is a cell based RRM Function, utilising cell specific:

• thresholds set by RNP,

• load measurements,

• AC, PS & LC algorithms.

• LC performs the function of load controlin association with AC & PS

• LC updates load status using resource measurements & estimations provided by AC & PS

• Continuously feeds cell load information to the other RRM functions, e.g. PS & AC

LC

ACACAC

PSPSPSRMRMRM

RNC

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Load Control Functional Overview

RRM in RNC

LC

AC

PS

Load changeestimations

Load changeestimations

Schedulingperiod

PRACH loadmeasurement

WBTS NB/RSNBAP-PRIVATE:RRIndPeriod or

3GPP NBAP :COMMONMEASUREMENTREPORT

Dedicatedmeasurement reporting

parameters

parameters

measurements

estimations

whenchanged Load change info

Load status request

Load status

NRT load

measurements

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Load Control




• Planning thresholds for cell loading




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NSN RRM: Power & Throughput based

• DL uses Power Measurements and calculations for RRM decisions

• UL uses Power & Throughput estimations and calculations for RRM decisions

=

×+=N

jjUL loadi

1)1(η

NRP

P

totalrx

noiserxUL

111_

_ −=−=η

max,_

_

BTStx

totaltxDL

P

P=η

defining Loadη = 0% – 100%

( ) jjb

jj

NE

RWL

ν1

//

1

1

0

∗+=

defining Little i→ Slide 9/10

Actual prevailing load in the cell depends on multiple factors• Number of active connections

• Properties of the connections• Bit rate

• Eb/No requirement

• BLER requirement

• Propagation channel conditions (speed, multipath profile etc.)

• SHO condition

• Activity

Different methods can be applied to measure/estimate load conditions, e.g.• Throughput Based Load Estimation

• Power Based Load Estimation

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Load Estimation Methods and other cell interference

Throughputbased

threshold

WidebandPower based

threshold

Wid

eban

dp

ow

er

leve

lI to

tal

(cov

era g

e )

Own cell load factor η(capacity)

i=0.5

i=0

i=1

2 Load estimationmethods:

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UL power based load measurement

PRx_Own

PRxTotal = PRx_Own + PRx_Other + PNoise

= PRx_NRT + PRx_RT + PRx_Other + PNoise

= PRx_NRT + PRx_NC

PRx_Other

iUL = PRx_Other / PRx_Own

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DL power based load measurement

PTx_Own

PTxTotal = PTx_Own

= PTx_NRT + PTx_RT + PTx_Common

= PTx_NRT + PTx_NC

PTx_Common

Com

mon

Cha

nnel

s

PRx_Own_DL

PRx_Other_DL

iDL = PRx_Other_DL / PRx_Own_DL

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Radio Interface Load

• The BTS measures the total received power (PrxTotal) and the total transmitted power (PtxTotal) on cell basis

• The BTS reports PrxTotal & PtxTotal of each cell to the RNC

• LC updates• Cell load status for each cell based on RADIO RESOURCE INDICATION• Non-controllable UL (PrxNC) & DL (PtxNC) load in cell• Semi-controllable UL (Prx_SC) & DL (Ptx_SC) load in the cell (related to PS Streaming)

• AC and PS algorithms work on the current cell load status provided by LC

• Denying call admission (AC) & throttling back NRT traffic (PS) are the overload actions

• After scheduling PS provides LC with PrxNRT, PtxNRT & LNRT estimates

• After admitting RT RAB, AC provides LC with NC load increase estimate

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System Noise & PrxNoise Autotuning Algorithm

• System noise PrxNoise is the sum of all stationary noises:• thermal noise• interference caused by spurious emissions of other systems,• noise caused by additional equipment such as repeaters

• PrxNoise can vary place to place & even time to time

• PrxNoise setting affects the capacity of cell:• PrxNoise too low: overestimation of cell load and can lead to unnecessary call blocking

• PrxNoise too high: underestimation of cell load and can lead to overload situation

• RNC provides Autotuning-Tool to measure unloaded system noise: PrxUnloaded; it adjusts PrxNoise parameter based on these measurements

• PrxTotal = PrxUnloaded when own cell considered unloaded / very low load;LRT ≤ UnloadedRT & LNRT ≤ UnloadedNRT & no EDCH users in the cell

UnloadedRT & UnloadedNRT are RNC parameters (values for NRT: 1 %, RT: 2 %)

LRT & LNRT: UL load factor for own cell RT (AC estimates) & PS users (PS estimates)

• PrxNoise updated by the autotuning algorithm based on PrxUnloaded

• PrxNoise autotuning step size limited by PrxNoiseMaxTuneAbsolute

PrxNoiseWCEL: -130..-50; 0.1; -105 dBm

PrxNoiseAutotuningWCEL: 0 (Off) / 1 (On)

PrxNoiseMaxTuneAbsoluteWCEL: 0..60; 0.5; 255 dB

255 dB: Autotuning is not limited

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UL Preventive & Overload Thresholds

Prx Target [dB]

PrxTarget [dB] + PrxOffset [dB]

load factor ηRange [0..1]

No

ise

Ris

e[d

B]

Overloaded Area

Marginal Load Area

Feasible Load Area

PrxTarget: WCEL; 0 .. 30; 0.1; 4dB

PrxOffset: WCEL; 0 .. 6; 0.1; 1dB

( ) [ ]dBLog η−⋅− 110 10PrxTarget =

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DL Preventive & Overload Thresholds

Ptx Target [dBm]

Ptx Target [dBm] + PtxOffset [dB]

load factorη

tota

l tra

nsm

itte

dp

ow

erP

txT

ota

l [dB

m]

Overloaded Area

Marginal Load Area

Feasible Load Area

Cell Maximum

PtxTarget: WCEL; -10 .. 50; 0.1; 40 dBm

PtxOffset: WCEL; 0 .. 6; 0.1; 1dB

PtxCellMax WCEL: 0…50; 0.1; 43dBm

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Load Control







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Common measurements taken & reported by WBTS

• PtxTotal – Transmitted Carrier Power

• Nokia Private NBAP

• PtxNonHSPATransmitted Code Power of all codes not used for HSDPA


• PrxTotal – Received Total Wideband Power


• REPS – Received E-DCH Power Share


• Acknowledged PRACH preambles


• Provided HSDPA Bitrate

• Provided HSUPA Bitrate

• Required Power

RRM in RNC needs this information for Streaming mapped on HSPA(NST – Non Scheduled Transmission)

Nokia Private part is protocol extension specified in 3GPP

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WBTS Common Measurements sent to CRNC

WBTS sends measurements periodically according setting of RRM parameter:

(Nokia Private part)

RADIO RESOURCE MEASUREMENT REPORT

RRIndPeriodRadio Resource Indication Period

WBTS; 200 .. 2000; 100; 400 ms

RACHloadIndicationPeriod

WBTS; 0 (Off); 1 .. 20; 1; 1 RRI report

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Measurement filtering & reporting criteria in BTS

• BTS measurements are averaged/filtered in BTS before reporting

• L1 filtering

• L3 filtering

• Higher Layer filtering

• BTS reports measurements to RNC when needed

• Reporting criteria

Step 1:L1 Filtering:1 Frame = 10 ms

Step 2L1 measurement period(= L1 Filtering) = 100 ms = 10 frames(→ Slide 30)

Step 3:L3 Filtering: RRI period = 400 ms(→ Slide 27)

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L1 Filtering: Prx and Ptx Total Measurements

Pr x

Tot

al/ P

txT

otal

Frame average measurements

Frame Prx and Ptx Total measurements

=14

0// 15

1TotalPTotalP txrxtxrx

0 141 2 ...

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L3 filtering: Higher layer filtering

• The Measurement Filter Coefficient (k) IE indicates how filtering of the measurement values shall be performed before measurement event evaluation and reporting.

• The averaging shall be performed according to the following formula.• L1 measurement period is 100 ms (20 ms for Acknowledged PRACH preambles)

Filter response

32

33

34

35

36

37

38

39

40

41

42

t 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33

Measurements

Val

ue,

dB Measured

Filtered, k = 3

Filtered, k = 7

Filter response

-105.5

-105

-104.5

-104

-103.5

-103

-102.5

-102

-101.5

t 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33

Measurements

Val

ue,

dB Measured

Filtered, k = 3

Filtered, k = 7

The higher the coefficient value, the more emphasis on old filtered measurements

Examples:k=2, a=0,5 both an old filtered measurement and a new measurement have the weight of 50%K = 0 a = 1 no L3 filtering

MeasFiltCoeffMeasurement filter

coefficient kWCEL; 0 (Off); 1 ..

14; 1; 5

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Measurement filtering

• The RNC can order BTSs to report cell-based & connection-based measurements only if internal thresholds are exceeded.

• However, a report is sent at least once per 10 reporting periods (RNP parameters).

• The filtering functionality decreases the amount of measurement messages between the BTS and the RNC and thus decreases the load of RNC computer units.

• Internally RNC repeats the cell based measurements every WBTS: RRIndPeriod to provide RRM functions a continuous flow of measurements

BTS Measurements

Reporting period

10 * Reporting period

RRIndPeriodWBTS; 200 .. 2000;

100; 400 ms

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WBTS Measurements sent to CRNC

WBTS can filter a measurement report (not sent to RNC) –

• only inform RNC about important load changes

• reduce common NBAP signaling on IuB interface

RNC provides load threshold and value change threshold to WBTS

Parameter settings for

PtxTotal Measurement

0,5 dB

20 % of Ptx max

non-configurable:

PtxTotalLoadThreshold: 20%

PtxTotalChangeThreshold: 0.5dB

PrxTotalLoadThreshold: 20%

PrxTotalChangeThreshold: 0.2dB

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Dedicated Measurements in BTS

• Transmitted Code Power

• WBTS send periodic measurement reports with code power measurement results from all Radio Links (UEs in Cell_DCH)

• Depending on allocated service type WBTS applies different reporting frequency:

• CS Services & SRB:

• CS Data Services:

• PS Data Services:

DedicatedMeasRepPeriodWBTS; 0.5..5; 0.5; 2.5 s

DediMeasRepPeriodCSdataWBTS; 0.5..5; 0.5; 1.5 s

DediMeasRepPeriodPSdataWBTS; 0.5..5; 0.5; 0.5 s

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Version control

Version Date Status Owner

RAS051_v1.0 1.10.2006 RAS051 level Florian Reymond

RAS051_v1.1 21.4.2007 Minor corrections Florian Reymond

RAS051_v1.2 10.5.2007 Corrected formula slide 27/ J.Itkonen Florian Reymond

RAS06_v1.0 29.10.2007 HSUPA measurements included and some minor additions (e.g. parameters related to SIRerror filtering and reporting)/ S. Cardamone, review & deletion of alpha trimmed filter (JI)

Florian Reymond

RU10 06.01.2008 Draft Thorsten Hagedorn

RU10_v1.0 14.08.2009 RU10 level, RANPAR Combined version (Andreas Annen) Benedikt Aschermann

RU20_v1.0 31.12.2009 RU20 level, RANPAR Combined (Andreas Annen) Benedikt Aschermann

RU30_v1.2 08.04.2011 RU30 level, RANPAR Combined (Andreas Annen) Benedikt Aschermann

04 RN31674EN30GLA0 RANPAR Combined LoadControl v1.2

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