NSN 3G Uplink Optimization
description
Transcript of NSN 3G Uplink Optimization
Nokia Siemens Networks – 3G Uplink OptimizationNSN response to Annex 6, Chapter 5 in T-Mobile Netherlands Single RAN RfQ
1 © Nokia Siemens Networks 2011 Customer Confidential
NSN response to Annex 6, Chapter 5 in T-Mobile Netherlands Single RAN RfQSeptember 2011
Introduction
TargetTarget
This presentation is intended to provide response to Annex 6 Chapter 5 in T-Mobile Netherlands Single RAN RfQ where the Supplier is requested to provide an overview of measures taken to reduce the radio and baseband/RNC resource allocation in a high smartphone penetration environment with extremely high signaling load.
ConfidentialityConfidentiality
2 © Nokia Siemens Networks 2011 Customer Confidential
All information related to the Nokia Siemens Networks 3G Uplink Optimization features, functionality’s and roadmaps presented in this document are strictly Nokia Siemens Networks Customer confidential.
No information shall be disclosed to any third party without permission from Nokia Siemens Networks.
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
Europe 3
3 © Nokia Siemens Networks 2011 Customer Confidential
Source: NSN Analysis, April 2011
0.10
0.05
0
01.03.2010 01.07.2010 01.01.201101.10.2010 01.04.2011
• Uplink traffic volume is 15-20% of downlink
• Uplink volume is growing faster than downlink (due to HSUPA)
Europe 3
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
4 © Nokia Siemens Networks 2011 Customer Confidential
Uplink vs Downlink Capacity in Theory
1.06 1.11
1.311.44 1.52
1.74
0.65 0.650.79
0.8
1.0
1.2
1.4
1.6
1.8
2.0
bp
s/H
z/c
ell
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
5 © Nokia Siemens Networks 2011 Customer Confidential
0.55
0.33 0.33 0.33
0.530.65 0.65
0.79
0.0
0.2
0.4
0.6
0.8
HS
PA
R6
HS
PA
R6
+ U
E
eq
ualiz
er
HS
PA
R7
64
QA
M
HS
PA
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DC
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IMO
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PA
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HS
DP
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MIM
O
LT
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8
bp
s/H
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ell
Smartphones Increase Signalling Load
• Smartphones create frequent transmission of small packets which requires frequent RRC state
• More multi-RABs due to smartphones
6 © Nokia Siemens Networks 2011 Customer Confidential
which requires frequent RRC state changes (DCH allocations) and RACH signalling which increases uplink interference
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 kbps users
7 © Nokia Siemens Networks 2011 Customer Confidential
– DPCCH overhead from PS 0/0 kbps 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.
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
High noise
Cell level control of uplink parameters RU30
3GPP Release 7
Continuous packet connectivity RU20
3GPP Release 8
RACH access class
8 © Nokia Siemens Networks 2011 Customer Confidential
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
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
-105…-108 -13…-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
9 © Nokia Siemens Networks 2011 Customer Confidential
-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
High Noise Optimized RRM1
• Five features for optimizing the power based uplink RRM
• 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
• Correction of the power increase and decrease estimations in the HSUPA cells
10 © Nokia Siemens Networks 2011 Customer Confidential
• Correction of the power increase and decrease estimations in the HSUPA cells
• Reference power of the management parameter DeltaPrxMaxUp
• Reduction of the SIR target values for the PS HSPA calls
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 dBSIRDPCCHInitialDCHMax 6 dB
SF DPCCH 256
Graphs are assuming activity factor as given below: 16kbps – 63%, 64kbps – 16%, 384kbps – 3%
Original Defaults New Recommendation
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 11 13 15 17 19 21 23 25
Number of links (DPCCH + HS-DPCCH + DPDCH)
UL n
ois
e ris
e (dB)
16 kbps
64 kbps
384 kbps
UL noise rise at initial SIR with DPCCH and HS-DPCCH overhead
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Number of links (DPCCH + HS-DPCCH + DPDCH)
UL n
ois
e ris
e (dB)
16 kbps
64 kbps
384 kbps
Original Defaults New Recommendation
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
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• 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 power measurement
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.
• PS NRT DCHs users having higher bit rate than minimum bit rate users, in the QoS priority order.
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• PS NRT DCHs users having higher bit rate than minimum 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 minimum bit rate.
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
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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.
• Function is similar if the congestion occurs in the soft handover branch addition over the Iur.
RRC IPhone Workaround UE 1 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 request has
RL setup procedure, spreading code1
UE 2Cell1
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.
15 © Nokia Siemens Networks 2011 Customer Confidential
RNC thinks first RRC connection request has
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.
DCH: RRC: RRC Connection Setup Complete spreading code 1
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.
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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
ROT = 6 dB ROT = 8 dB
17 © Nokia Siemens Networks 2011 Customer Confidential
RXRX RAKERAKE
ICIC DECODERDECODERRAKERAKE
DECODERDECODER 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
ROT = 6 dB ROT = 8 dB
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
18 © Nokia Siemens Networks 2011 Customer Confidential
• TrafVolPendingTimeUL
• Prx NoiseMaxTuneAbsolute
• WaitTimeRRC
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
19 © Nokia Siemens Networks 2011 Customer Confidential
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.
20 © Nokia Siemens Networks 2011 Customer Confidential
-0.1
0
Fast BTS Load Control
• Reduce SIR target if noise rise exceeds PrxTarget + offset (2 dB)
( )
( )10
_
,_
arg,
,arg,arg
arg,
OffsetPriseNoiseSIRSIR
OffsetPriseNoiseIf
ettrx
RNCettBTSett
ettrx
−−−=
+>
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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]
SIR
targ
et
corr
ection [
dB
]
PrxTarget 8 dB
SIR target
adjustment
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
• TrafVolPendingTimeUL
22 © Nokia Siemens Networks 2011 Customer Confidential
• TrafVolPendingTimeUL
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 be 1-(1+0.08)/(1+0.41) = 23%
23 © Nokia Siemens Networks 2011 Customer Confidential
be 1-(1+0.08)/(1+0.41) = 23%
A/N CQIA/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
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
300
400
500
600
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1300
Cell T
hro
ug
hp
ut
(kb
ps)
PedA_not gated
PedA_9/15300
400
500
600
700
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1300
Cell T
hro
ug
hp
ut
(kb
ps)
PedA_not gated
PedA_9/15
PedA_not gated
PedA_9/15
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(E-)DPCCH
E-DDCH
Web page download
User reading web page
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100
200
300
0 5 10 15 20 25 30 35 40 45 50 55
Number of no-data UEs in CELL_DCH
Cell T
hro
ug
hp
ut
(kb
ps)
PedA_9/15
PedA_12/15
PedA_9/15 ideal
PedA_12/15 ideal0
100
200
300
0 5 10 15 20 25 30 35 40 45 50 55
Number of no-data UEs in CELL_DCH
Cell T
hro
ug
hp
ut
(kb
ps)
PedA_9/15
PedA_12/15
PedA_9/15 ideal
PedA_12/15 ideal
PedA_9/15
PedA_12/15
PedA_9/15 ideal
PedA_12/15 ideal
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
[kbps]
Pred
[dB]
Relative power of E-DPDCHs over DPCCH
2 ms TTI
16
18
P(E
-DP
DC
Hs
) [d
B]
25 © Nokia Siemens Networks 2011 Customer Confidential
[kbps] [dB]
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
16
0
256
512
768
1 02
41
280
1 53
61
792
2 04
82
304
2 56
02
816
3 07
23
328
3 58
43
840
4 09
6
Data rate [kbps]
P(E
-DP
DC
Hs
) [d
B]
Computed P(E-DPDCHs)
Optimal P(E-DPDCHs)
Fast Dormancy
Other vendors
2 s IDLEIDLE
DCH/HSPA inactivity timer
CELL_FACH inactivity timer30 signalingmessages
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
26 © Nokia Siemens Networks 2011 Customer Confidential
Nokia Siemens Networks
<0.3 s
3 signalingmessages
2 s
PCH PCH
DCH/HSPA inactive
CELL_FACH inactive12 signalingmessages
Idle = <5 mA
Cell_PCH = <5 mA
Cell_FACH = >100 mA
Active = >200 mA
Network avoids signaling stormBattery lasts longer
HS-RACH
• HS-RACH allows carrying medium size data packets without allocation of dedicated resources
kB per DCH or HS-DSCH Allocation315
199
160180200220240260280300320
• 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 ⇒ largepart of smartphone traffic could becarried by HS-RACH
27 © Nokia Siemens Networks 2011 Customer Confidential
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• HS-RACH reduces controloverhead considerably
• No setup signalling
• Immediate stop of controlchannel transmission compared to DCH with >1 second timer
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.
28 © Nokia Siemens Networks 2011 Customer Confidential
• NSN has been active in 3GPP to improve the system performance