NSN 3G Uplink Optimization

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1 © © NNookkiia a SSiieemmeenns s NNeettwwoorrkks s 22001111 Customer ConfidentialCustomer Confidential

NSN response to Annex 6, Chapter 5 in

NSN response to Annex 6, Chapter 5 in T-Mobile Netherlands Single RAN RfQT-Mobile Netherlands Single RAN RfQ

September 2011 September 2011

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Introduction

Target Target Target Target Th

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measures taken to reduce the radio and basebandbaseband/RNC resource allocation in /RNC resource allocation in a higha high smartphone

smartphone penetration penetration environmenenvironment with extret with extremely high sigmely high signaling loadnaling load.. Confidentiality

Confidentiality Confidentiality Confidentiality

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2 © © NNookkiia a SSiieemmeenns s NNeettwwoorrkks s 22001111 Customer ConfidentialCustomer Confidential

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Uplink vs Downlink Traffic in Live 3G Networks (1)

Europe 2 South America Europe 1 0.25 0.20 0.15

HSUPA / HSDPA daily volume ratio at selected operators

MEA

3 © Nokia Siemens Networks 2011 Customer Confidential

Source: NSN Analysis, April 2011 0.10

0.05

0

01.03.2010 01.07.2010 01.10.2010 01.01.2011 01.04.2011

• Uplink traffic volume is

15-20% of downlink

• Uplink volume is growing

faster than downlink (due to HSUPA)

(4)

Uplink vs Downlink Traffic in Example Live 3G Network

HSDPA vs HSUPA ratio 10x now and getting smaller due to higher

HSUPA penetration

HSDPA vs HSUPA + WCDMA UL ratio 6x and

stabile

(5)

Uplink vs Downlink Capacity in Theory

1.06 1.11 1.31 1.44 1.52 1.74 0.79 1.0 1.2 1.4 1.6 1.8 2.0 / H z / c e l l

Evolution of HSPA efficiency

Downlink Uplink • Downlink 1.31 bps/Hz/cell • Uplink 0.33 bps/Hz/cell (0.53 with IC) • => Theoretical ratio 4x

0.55 0.33 0.33 0.33 0.53 0.65 0.65 0.0 0.2 0.4 0.6 . H S P A R 6 H S P A R 6 + U E e q u a l i z e r H S P A R 7 6 4 Q A M H S P A R 8 D C - H S D P A H S P A R 9 D C - H S D P A + M I M O H S P A R 1 0 Q C - H S D P A + M I M O L T E R 8 b p

(6)

Smartphones Increase Signalling Load

•

Smartphones create frequent

transmission of small packets

• More multi-RABs

due to smartphones

changes (DCH allocations) and RACH signalling which increases uplink interference

(7)

Starting Point for Uplink Optimization

•

In theory, the networks should be downlink limited because the traffic is 5-6x in downlink

while the capacity is 4x.

•

The higher uplink noise rise is mainly caused by the control overhead

– RACH preambles and messages, like RRC requests, uplink capacity request and user plane data,

especially related to smartphone traffic

– DPCCH overhead. For example, with AMR5.9 kbps 64% of interference comes from DPCCH.

– DPCCH overhead from PS 0/0 kb s users

– HS-DPCCH overhead for HSUPA

•

It is possible to improve the situation because we are not hitting any fundamental theoretical

limit. The limit is ”only” system protocol design and configuration. There are already promising indications since RU20 ontop releases have stabilized the uplink in many networks.

•

NSN uses interference based uplink RRM while some RAN vendors use throughput based

solution (number of users). The interference based solution has the benefit that cell breathing can be controlled. But interference based solution requires also careful control of the uplink interference sources to provide optimal performance.

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NSN Solutions for Uplink Interference Control – Summary

HS-RACH Interference

cancellation Dynamic HSUPA

power offset RU20

RU30

RU40 Cell_PCH

Load aware outer

loop power control RU30

3GPP Release 99-6

HSUPA DPCCH

interpolation RU30

Fast dormancy _RU20

High noise

optimized RRM1 RU20

Cell level control of

uplink parameters RU30

3GPP Release 7

Continuous packet

connectivity RU20

3GPP Release 8

High noise

optimized RRM2 RU20 Dynamic initial bit

rate allocation RU20

DPCCH overhead

calculation RU20 Downgrade of DCH

in SHO congestion RU20 RRC IPhone

workaround RU20

Fast BTS load control

RACH access class

barring RU40

Dynamic parameter settings

Dynamic CQI frequency

(9)

Dynamic HSUPA Power Offset

DynPwrOffsetTable2 (High/low power offset indication table for 2ms TTI)

RSCP [dBm] EcNo [dB]

<-108 <- 14 L L L L L L

•

Two sets of DPCCH offset values defined. Lower DPCCH power is used when the condition

(H=High load) is fulfilled

-105…-108 -13…-14 L L L L L L -101…-104 -11…-12 L L L L L L -98..100 - 10 H H L L L L -98..-95 - 9 H H H L L L >-95 >-9 H H H L L L 0-1 2-3 4-6 7-12 13-20 >20 # of HSPA serving cell users

(10)

High Noise Optimized RRM1

•

Five features for optimizing the power based uplink RRM

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Correction of the filtering parameter MaxIncrInterferenceUL

• Filter out the short term spikes of the measured RTWP for avoiding the unnecessary admission

control blockings during the period of the spike

•

Corrections in power increase and decrease estimations of the estimated R99 power

•

orrec on o e power ncrease an ecrease es ma ons n e ce s

•

Reference power of the management parameter DeltaPrxMaxUp

(11)

Initial SIR Target Optimization

Parameters 1-RX 2-RX 4-RX nonSHO SHO beta_d / beta_c R_b SIRDPCCHInitialDCHHS256 4.5 2.5 -0.5 -1.5 1.3 2.0 SIRDPCCHInitialDCHHS128 4.5 2.5 -0.5 -1.5 1.3 2.0 1.2 16 kbps SIRDPCCHInitialDCHHS64 4.5 2.5 -0.5 -1.5 1.3 2.0 SIRDPCCHInitialDCHHS32 6.0 4.0 1.0 0.0 1.3 2.0 1.4 64 kbps SIRDPCCHInitialDCHHS16 7.5 5.5 2.5 1.5 1.0 1.6 1.7 128 kbps SIRDPCCHInitialDCHHS8 8.0 6.0 3.0 2.0 1.0 1.6 SIRDPCCHInitialDCHHS4 9.0 7.0 4.0 3.0 0.8 1.3 2.5 384 kbps SIRDPCCHInitialDCH64 4.5 2.5 -0.5 -1.5 1.2 AMR 12.2

Initial DPCCH SIR w HSDPA AmplitudeRatioACK

SIRDPCCHInitialDCHOffset _{-2 dB} SIRDPCCHInitialDCHRxDiv2 _{-3 dB} SIRDPCCHInitialDCHRxDiv4 _{-4 dB} SIRDPCCHInitialDCHMax _{6 dB}

SFDPCCH 256

Graphs are assuming activity factor as given below: 16kbps – 63%, 64kbps – 16%, 384kbps – 3%

11 © Nokia Siemens Networks 2011 Customer Confidential UL noise rise at initial SIR with DPCCH and HS-DPCCH overhead

0 1 2 3 4 5 6 7 8 9 10 1 3 5 7 9 _1 1 _1 3 _1 5 _1 7 _1 9 _2 1 _2 3 _2 5 Number of links (DPCCH + HS-DPCCH + DPDCH) U L n o i s e r i s e ( d B ) 16 kbps 64 kbps 384 kbps

UL noise rise at initial SIR with DPCCH and HS-DPCCH overhead

0 1 2 3 4 5 6 7 8 9 10 1 3 5 7 9 _1 1 _1 3 _1 5 _1 7 _1 9 _2 1 _2 3 _2 5 Number of links (DPCCH + HS-DPCCH + DPDCH) U L n o i s e r i s e ( d B ) 16 kbps 64 kbps 384 kbps

(12)

High Noise Optimized RRM2

•

12 features for optimizing the power based uplink RRM

• Emergency call failure for the power blocking

• PrxNoise autotuning only in the cell without any CELL_DCH traffic

• PrxNoise is autotuned only if all cells of the same frequency in the BTS are on the low traffic level

• Adjusting of the increased reference noise floor value in the loaded cell

• Detection of the common measurement reports filtered by BTS

• Candidate prioritization and bit rate selection in PBS

• R99 Overload Control procedure

• Downgrading the PS NRT DCH for the soft handover branch addition congestion handling

• PRFILE parameter control for triggering the channel type switching from the SIR error

• Limited value of UL DPCCH power offset for the first RL setup in the RTWP spiking cell

• Power based Admission Control for the HSUPA call setups

• Correction in updating the the MIN and MAX PRXTOTAL counters of the Received Rel99 wideband

(13)

Dynamic Initial Bit Rate Allocation

•

Allows more PS NRT users admitted at initial and minimum bit rates in and keep the existing

PS NRT users longer in the CELL_DCH state.

•

High bit rate PS DCH users are selected first for downgrade, the QoS priority is applied only

when the PS calls of the cell are not using higher than the initial DCH bit rates

•

PBS candidates will be prioritized in all congestion cases as follows:

• PS NRT DCHs users having higher bit rate than initial bit rate users, in the QoS priority order.

•

, .

• Finally the minimum bit rate users, in the QoS priority order.

•

Initial/minimum DCH bit rate selection of the PS call triggered the PBS:

• New functionality applies to the UL interference, DL power and UL load congestion.

• If BRM detects congestion and the PBS triggers, then:

• If high bit rate (higher than initial) PBS candidates are available, then the incoming user gets the initial

bit rate

• If only low bit rate (lower or initial) PBS candidates are available, then the incoming user gets the

(14)

Downgrading NRT DCH in Soft Handover Congestion

•

Present implementation does not allow the downgrading of the DCH bit rates of the PS

bearers if a congestion occurs in the soft handover branch addition. If the target cell is better than the ones in the active set, the failed soft handover may cause significant spiking of the RTWP, unless the PS DCH is removed.

•

In the new implementation, the PS DCH is downgraded to the minimum bit rate and then

attempted the branch addition once more.

•

If the congestion occurs still, the UE is switched to CELL_FACH state without applying the

management parameter EnableRRCRelease. If the UE has also the AMR, the PS bearers are downgraded to DCH 0/0 as it is done already in the original implementation.

(15)

RRC IPhone Workaround

UE1 Cell1 RNC

RACH: RRC: RRC Connection Request UE starts decoding FACH

FACH: RRC: RRC Connection Setup, state indicator: Cell-DCH (Spreading code 1)

RACH: RRC: RRC Connection Request cause: protocol error UE decodes some rubbish from FACH

RNC thinks first RRC connection re uest has RL setup procedure, spreading code1

UE 2 Cell1

Solution: RNC ignores the repeated RRC connection request with protocol

error cause and wait for the RRC connection setup complete for the first

RRC connection setup.

failed, and releases resources, and setup resources for second RRC connection request RL deletion procedure, spreading

code 1

RL setup procedure, spreading code2

FACH: RRC: RRC Connection Setup state indicator: Cell-DCH (Spreading code 2)

RNC allocates spreading code1 to UE2 UE decodes first RRC Connection

setup message, and starts using spreading code 1 in Cell_DCH state

UE1 and UE2 decoding the same DL spreading code and TPC bits. UE1 can cause uncontrolled interference.

(16)

DPCCH Overhead Calculation

•

DPCCH overhead included in load factor estimation has too conservative value based on

initial UL SIR target. This modification multiplies the initial SIR target value with the activity factor of the signaling link DCH.

(17)

Interference Cancellation

•

Estimate the physical channel data after channel

(Turbo) decoding. The physical channel data is

generated by encoding the decoded data. Large gain from channel decoding

•

Uplink throughput gain 23-62%

•

SW upgrade to Flexi Rel.2 baseband

RX

RX RAKERAKE

IC

IC RAKERAKE DECODERDECODER

DECODER

DECODER ENCODERENCODER

no PIC PIC

PIC

(uncod.) PIC

PIC

(uncod.) no PIC PIC

PIC (uncod.) PIC PIC (uncod.) 1 user 5,84 7,61 2 user 4,78 5,92 5,92 24% 24% 5,53 7,69 7,69 39% 39% 3 user 3,96 5,87 5,39 48% 36% 4,29 6,93 6,19 62% 44%

thrput Mbps trp gain thrput Mbps trp gain

(18)

Cell Level Control of Uplink Parameters

•

Some of the existing UL interference impacting parameters that are controlled in RNC level,

change to cell level

•

HSDPAinitialBitrateUL

•

HSDPAminallowedBitrateUL

•

TrafVolPendingTimeDL

•

TrafVolPendingTimeUL

•

Prx NoiseMaxTuneAbsolute

(19)

Load Aware of Outer Loop Power Control

•

Target: prevent too high increase of SIR target during high load

•

Reason: SIR target increases if UE hits its max power

•

Freeze AMR SIR targets and decrease NRT PS SIR targets until noise rise gets lower

•

Potentially also decrease AMR SIR and/or increase BLER target with higher noise rise

(20)

RACH Access Class Barring

•

The access classes [0,…9] which are barred are actually rotated by specified intervals.

•

If during first time interval, the access classes [1,2,3] were barred, in the next time interval [4,5,6] would be barred covering access classes 0,…,9, i.e. rotation by mod 10. Rotation time needs to be long enough.

(21)

-0.1 0

Fast BTS Load Control

•

Reduce SIR target if noise rise exceeds PrxTarget + offset (2 dB)

(

)

(

)

10 _ , _ arg , , arg , arg arg , Offset P rise Noise SIR SIR Offset P rise Noise If et t rx RNC et t BTS et t et t rx − − − = + >

21 © Nokia Siemens Networks 2011 Customer Confidential 0 2 4 6 8 10 12 14 16 18 20 -1 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 Noise rise [dB] S I R t a r g e t c o r r e c t i o n [ d B ] PrxTarget 8 dB SIR target adjustment

(22)

Dynamic Parameter Setting

•

High interference cases can be solved by using suitable timer and other parameters during

mass events. Some of those parameters are not good for the non-congested cells. Therefore, the parameters should be automatically tuned according to the instantaneous load.

•

Example parameters

• WaitTimeRRC

•

(23)

Dynamic CQI Frequency

•

Channel Quality Information (CQI) frequency is 4 ms currently

•

CQI frequency could be lowered during high uplink load to minimize the interference in the

same way as DPCCH offset values are optimized

•

Current CQI interference contribution with 4 ms period = 0.41 x DPCCH. If we would lower

CQI frequency to 10 ms or 20 ms, the interference would reduce to 0.08..0.16 x DPCCH.

•

The total uplink interference from HSDPA users without any uplink activity would be reduced

- =

. . A/N CQI A/N CQI DPCCH HS-DPCCH DPCCH

A/N CQI CQI power offset –2 dB in

single link and +4 dB in SHO compared to DPCCH

(24)

Continuous Packet Connectivity

•

Uplink DPCCH and E-DPCCH gating

reduces interference especially for low data rate users

•

Gating is part of Continuous packet

connectivity (CPC). It is part of 3GPP Release 7 400 500 600 700 800 900 1000 1100 1200 1300 l l T h r o u g h p u t ( k b p s ) PedA_not gated PedA_9/15 400 500 600 700 800 900 1000 1100 1200 1300 l l T h r o u g h p u t ( k b p s ) PedA_not gated PedA_9/15 PedA_not gated PedA_9/15

(E-)DPCCH E-DDCH Web page

download User readingweb page

0 100 200

0 5 10 15 20 25 30 35 40 45 50 55 Number of no-data UEs in CELL_DCH

C _ PedA_12/15 PedA_9/15 ideal PedA_12/15 ideal 0 100 200 0 5 10 15 20 25 30 35 40 45 50 55 Number of no-data UEs in CELL_DCH

C _ PedA_12/15 PedA_9/15 ideal PedA_12/15 ideal _ PedA_12/15 PedA_9/15 ideal PedA_12/15 ideal

(25)

HSUPA DPCCH Interpolation

•

Release 7 solution allows to minimize DPCCH overhead for low data rate HSUPA users

•

Fixed DPCCH power in Release 6 leads typically to too high DPCCH overhead at low kbps

Optimised gain factors

E-TFC Pred

Relative power of E-DPDCHs over DPCCH 2 ms TTI

16 18

25 © Nokia Siemens Networks 2011 Customer Confidential 32 6 64 7.1 128 8.1 256 8.9 384 9.9 512 8.1 768 8.1 1024 6 1450 6 1920 6 2900 7.1 3800 8 4 6 8 10 12 14 0 2 5 6 5 1 2 7 6 8 1 0 2 4 1 2 8 0 1 5 3 6 1 7 9 2 2 0 4 8 2 3 0 4 2 5 6 0 2 8 1 6 3 0 7 2 3 3 2 8 3 5 8 4 3 8 4 0 4 0 9 6 Data rate [kbps] P ( E - D P D C H s ) [ d B ] Computed P(E-DPDCHs) Optimal P(E-DPDCHs)

(26)

Fast Dormancy

Other vendors

2 s IDLE

IDLE

DCH/HSPA inactivity timer

CELL_FACH inactivity timer

30 signaling messages

Heavy signaling load Low battery life time

Idle = <5 mA Cell_PCH = <5 mA Cell_FACH = >100 mA Active = >200 mA IDLE Fast Dormancy to save battery

Nokia Siemens Networks <0.3 s 3 signaling messages PCH PCH DCH/HSPA inactive CELL_FACH inactive 12 signaling messages Idle = <5 mA Cell_PCH = <5 mA Cell_FACH = >100 mA Active = >200 mA

Network avoids signaling storm Battery lasts longer

(27)

HS-RACH

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HS-RACH allows carrying medium size data packets without allocation of dedicated resources

kB per DCH or HS-DSCH Allocation 315 199 180 200 220 240 260 280 300 320

•

The avarage data volume per

allocation is typically 10-60 kB for the smartphones. The median value is even smaller: 60% of

allocations are below 1 kB ⇒ large

part of smartphone traffic could be

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•

HS-RACH reduces control

overhead considerably

•

No setup signalling

•

Immediate stop of control

channel transmission

compared to DCH with >1 second timer

(28)

Summary

•

3G networks have turned to be uplink limited due to interference limited nature of CDMA

uplink. The main problems come from the control channel and signalling overhead which is driven by increased smartphone traffic and HSUPA high data rates

•

NSN has introduced a large number of features in RU20 and RU30 to improve the uplink

performance. The features have already shown to be highly useful in the practical networks.