4. QoS Functions in Access Networks
Transcript of 4. QoS Functions in Access Networks
4. QoS Functions in Access Networks
Dr. David Soldani([email protected], tel. +358.50.3633527)S-38.3215 Special Course on Networking Technology for Ph.D. students at TKK
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OutlineQoS management function in GERA networks
Weighted Round Robin (WRR) schedulerDeficit Round Robin (DRR) scheduler Handover and cell reselection in 2G
QoS management function in (enhanced) UTRA networksFair Throughput (FT) scheduler with QoS differentiationFair Resources (FR) scheduler with QoS differentiationHSPA differentiated scheduling
Differentiated intra-frequency, inter-frequency and inter-RAT handovers, and service performance thereof3GPP-WLAN interworking
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QoS functions in GERAN and UTRANGERAN
BSC• Handover control• Packet scheduling• Admission control
BTS• Power control
MS
ME + SIM
Enhanced UTRANUE
RNC• Power control• Handover control• Admission control• Packet scheduling
Node B• Fast power control• Fast load control• Fast packet scheduling
ME + USIM• Power control
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PS-1
PS-1
PS-1
PS-3 PS-7
Not used
BCCH
Not used
SDCCH
Not used
Not used
PS-6 PS-10
PS-6 PS-9
CS-9
PS-5 PS-8
PS-5 PS-10
PS-4 PS-2
PS-11
PS-4 PS-2
PS-11PS-6 PS-9
PS-3 PS-7
PS-3 PS-7
CS-10
PS-4 PS-2
CS-7
CS-6
CS-3
CS-1
CS-11
CS-5
CS-4
CS-12
CS-2
CS-8 TRX
4
TRX 3
TRX 2
TSL 0
TSL 1
TSL 2
TSL 3
TSL 4
TSL 5
TSL 6
TSL 7
TRX 1
Timeslots available for CS traffic
Timeslots available for PS traffic
Allocated for packet switched trafficAllocated for circuit switched trafficNot allocated Timeslot
Territory setting with PS-CS separation
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Not used
Not used
Not used
Not used
BCCH
Not used
SDCCHNot used
Not used
PS-6 PS-1
PS-6
CS-9
PS-5
PS-5
PS-5
PS-4 PS-2 PS-7
PS-4 PS-2 PS-7
PS-6 PS-1
PS-3
PS-3
CS-10
PS-4 PS-2
CS-7
CS-6
CS-3
CS-1
CS-11
CS-5
CS-4
CS-12
CS-2
CS-8
TRX 4
TRX 3
TRX 2
TSL 0
TSL 1
TSL 2
TSL 3
TSL 4
TSL 5
TSL 6
TSL 7
TRX 1
Allocated for packet switched trafficAllocated for circuit switched trafficNot allocated Timeslot
Territory setting with no PS-CS separation
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R97/98: QoS differentiation in BSSOne to one mapping ARP (1-3) – SSS (Scheduling Step Size, 1-12)Weighted Round Robin (WRR): the lower the SSS the higher the priority (= 1/SSS)
6
3
1
0
TSL
x
12
6
3
1
12
7
6
3
12
7
6
5
12
7
7
6X+1 X+2 X+3 X+4
SSS = 2
SSS = 6
SSS = 12
6
3
1
0
TSL
x
12
6
3
1
12
7
6
3
12
7
6
5
12
7
7
6X+1 X+2 X+3 X+4
SSS = 2
SSS = 6
SSS = 12
SSS = 2
SSS = 6
SSS = 12
TSLN
i i
jj R
SSS
SSSR
∑=
=
1
1
1
SSS value associated with the TBF i
N is the total number of TBFs sharing the same
TSL
RTSL is the average bit rate the TSL in question can offer during the measurement period
Throughput Rj experienced by the TBF j in one time
slot (TSL)
QoS_1 (Streaming, ARP1)
QoS_2 (Web browsing, ARP2)
QoS_3 (MMS, ARP3)
TBF Transmission Turn Value (TTV)TTV + SSSRadio Block
4 TB
Fsco
mpe
ting
for o
ne T
SL
Radio block sequence number (X)
Transmitted Radio Block
Approximation due to:• Different retransmissions and M-CS• Different number of users per slot
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0
5
10
15
20
25
30
35
40
45
50
3 TSL 5 TSL 7 TSL
Off
ered
Loa
d (k
b/s/
cell)
Number of TSLs in GPRS Territory
no QoS Diff(Same SSS)
Optimal QoS Diff(SSS = 1 Streaming, 4 Web browsing, 12 MSS)
132% Gain
175% Gain
114% Gain
QoS gains provided by WRR
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Deficit Round Robin (DRR): scheduling of packets (not bit rates)
DifferentiationDifferent priority queuesDifferentiated Quantum
R99: QoS differentiation in BSSDeficit counter (DC)i+1
Processed PDUPDU waiting for processingActual served queue
700300Q1
200Q2
500 300
500
0
0Q3
DCi+1
Q1
Q2
0
0
0Q3
Quantum (Q) = 500
Step = 1700300Q1
Q2
500 300
500
500
0Q3
2002700300Q1
Q2
500 300
500
0
500Q33
700300Q1
Q2
500
1000
0
200Q34
Q1
Q2
500
0
0
700Q35
6
Deficit counter (DC)i+1 = DCi + Q – Tx packets size
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80
82
84
86
88
90
92
94
96
98
100
2000
3000
4000
5000
6000
7000
8000
9000
1000
0
1100
0
1200
0
1300
0
1400
0
Traffic Volume (kb/s)
Satis
fied
Use
rs (%
)
DRR - SWIS WRR - SWIS DRR - STR WRR - STRDRR - PoC WRR - PoC DRR - MMS WRR - MMSDRR - WAP WRR - WAP DRR - WWW WRR - WWW
Spectral efficiency gains of DRR vs. WRR
G = 10%
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2G (CS-Hard) Handovers: MS, BSC, MSCRadio resource handovers
1. Uplink/downlink interference (I_Level)2. Uplink/downlink quality (Rx_Qual)3. Uplink/downlink signal level (Rx_Level)4. Power budgetImperative handover
Distance between the MS and BTS exceeds a maximum thresholdO&M command to empty the cell is issuedRapid field drop is detected; andServing cell is congested and a directed retry is needed
Traffic reason handoverSteer traffic distribution between cells and/or layers
Target cell evaluation processRx level, Quality, Load
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2G Cell reselection: MS, BSC, SGSNNormal MS control
MS performs cell reselection autonomously based on NCLNew LLC link with SGSN and BSC accordingly informedGaps up to 30 s expected!
Network Controlled Cell Reselection (NCCR)BSC commands MS to send measurement reportsMS reports NCL measurements periodicallyBSC order packet cell change (BCCH frequency, BSIC)Gaps from 2-5 s expected and efficient resource allocation
Network Assisted Cell Change (NACC)BSC provides to MS part of target Packet System Information (PSI)NCCR & NACC: Gaps of few 100 ms expected
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NCCR procedure vs. MS states
a) Idle mode b) Data transfer mode, UL c) Data transfer mode, DL
MS MSBSC BSCImmediate Assignment
Packet Control Acknowledgement
MS
mon
itors
ne
ighb
ours
Channel Request
Measurement Report
Packet Measurement Order
MS
mon
itors
ne
ighb
ours
Uplink Packet Data transfer
PACCH
Packet (Enhanced) Measurement Report
MS Serving cell
PACCH Packet Cell Change OrderMeasurement and NCCR information regarding target cell
T3174 startsTarget cell
PBCCHCurrent TBF on serving cell is aborted!
PBCCH
PBCCH of target cell is received
Waits until PSI1 occurrence in B0
PBCCH PSI messages
Packet Channel Request
Packet Uplink Assignment
PRACH
PAGCH
T3174 stops
Packet Measurement Order
Immediate Assignment
Packet Cell Change Order
Measurement Report
Packet Cell Change Order
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QoS management functions in UTRAN
Marginal load area (Offset)
Overload area
PTxTotal
PTxTarget - PtxNGBcapacity
PTxTarget + Offset
GB* + NGB Traffic
Max Planned Load
NGBPΔPTxTotal = PGB + PNGB
PtxNGBcapacity
Dedicated NGB capacity
PB G
B
PB N
GB
Overload Action (LC)
AC: If PTxTotal is below this threshold ⇒ NGB services are admitted
Actual load
Step = One RRI period
GBPΔ
PTxTarget
AC: If PGB + ΔPGB is below this threshold ⇒ DHO branches are admitted
AC: If PGB + ΔPGB is below this threshold ⇒ GB services are admitted
* Includes CCH power
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DCH: Fair Throughput (FT) scheduling
Availablecapacity for
FT scheduling 384 (1*)
PTarget
256 (1)
256 (2)
Allocation if1 DCH
requested
Allocation if2 DCHsrequested
256 (2)
Allocation if3 DCHsrequested
144 (1)
144 (3)
Allocation if4 DCHsrequested
128 (2)
128 (3)128 (4)128 (1)
Allocation if5 DCHs
requested
128 (2)128 (4)128 (1)
128 (3)
128 (5)
Priority 1 Priority 2
No allocation for this bearer,CR back to queue
Non controllable load (*) Chronological order
MinimumAllowedBit Rate
(128 kb/s)
MaximumAllowedBit Rate
(384 kb/s)
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DCH: Fair Resources (FR) scheduling
Availablecapacity for
FR scheduling 384 (1*)
PTarget
384 (1)
144 (2)
Allocation if1 DCH
requested
Allocation if2 DCHsrequested
384 (2)
Allocation if3 DCHsrequested
128 (1)
144 (3)
Allocation if4 DCHsrequested
128 (2)64 (3)
128 (4)128 (1)
Allocation if5 DCHs
requested
128 (2)128 (4)128 (1)64 (3)64 (5)
No allocation for this bearer,CR back to queue
Priority 1 Priority 2 Non controllable load (*) Chronological order
MinimumAllowedBit Rate(64 kb/s)
MaximumAllowedBit Rate
(384 kb/s)
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WCDMA soft/softer handover algorithmsCell 1
ΔTA
Cell 1 connected Event 1A ⇒Add Cell 2
Event 1C ⇒Replace Cell 1 with Cell 3
Event 1B ⇒Remove Cell 3
Reporting Range –Hysteresis Evert 1A
Reporting Range + Hysteresis event 1B
Hysteresis Evert 1C
WindowAdd
WindowDrop
Replacement
Cell 2 Cell 3
ΔTBΔTCP-CPICH Ec/N0
Time
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Best serving HS-DSCH cell measurementsP-CPICH Ec/N0
Reporting event 1D
Time
Cell 1
Cell 2
Cell 3
ΔΤD
Hysteresis Event 1D
HS-DSCH from Cell 2HS-DSCH from Cell 1
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Serving HS-DSCH/(E-DCH) cell change
Serving RNC Drifting RNC
Node B
1 2 3
Iub
Target cell (with or without HSDPA support)
Iub
Iur
Target cell
UE
The user is moving to another cell
Node B
1 2 3
UE
Source cell
Source cell
HS-DSCHRadio Link HS-DSCH
Radio Link
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Serving HS-DSCH cell changeTriggers for serving HS-DSCH cell change
Periodical CPICH Ec/N0 measuresPeriodical UL SIRerror measuresEvent 1B: serving HS-DSCH cell is removed from the activeEvent 1C: serving HS-DSCH cell is replaced by another cellFailures in serving HS-DSCH radio link: loss of synchronization or time differenceServing HS-DSCH radio link is handed over to DRNC
Target HSDPA-capable cell (handover path)May be selected based on its allocated status, measured uplink SIRerrorand/or downlink CPICH Ec/N0
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Serving RLS (cell) for E-DCH scheduling
For the serving RLS, the SRNC may select the RLS with the highest data throughput and, for the serving cell, the cell that provides the best downlink qualityWhen an E-DCH serving cell change is triggered, the network updates the serving grant in the UE, and all L2-deactivated processes become active Processes can be enabled/disabled via RRC
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WCDMA inter-frequency handover
f1f1 f1
f1 f1f1
f2f2
f3f3 f3
f3 f3f3 f3
f3
f2f2
Micro cells
f1f1
Load balancing handover
2-frequency macro cells
Urban area Rural area
Fast moving mobilesto macro frequency
Coverage handoverCoverage handover
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WCDMA inter-RAT handover
WCDMAWCDMA WCDMAWCDMA WCDMAWCDMA
GSM/EGPRSGSM/EGPRS
Urban area Rural area
Coverage handover
Network indicated (commanded) cell reselection
GSM/EGPRSGSM/EGPRS GSM/EGPRSGSM/EGPRS GSM/EGPRSGSM/EGPRS GSM/EGPRSGSM/EGPRS
Handover for capacity extension or service optimization
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Coverage and quality reason handoversTriggers: HC may start inter-freq/RAT measurements
UE Tx power (Event 6A)Uplink DCH qualityDownlink DPCH powerCPICH RSCP or Ec/N0 (Event 1F)
Target cell selectionInter-frequency handover path
Based on best CPICH RSCP and Ec/N0 and relevant RNP parameters Based on pre-assigned priority level in the case of the same radio performance
Target cell selection: inter-RAT handover pathBased on best GSM carrier RSSI values and relevant RNP parametersFor CS voice/data services the BSIC of the target cell is always verified firstFor PS (GB and NGB) services verification should be ordered only in the case of BCCH frequency collision between neighbor cells
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WCDMA: Event triggered 6E
Tx Powerthreshold
Max Txpower
(1) Mobile Tx power increases at the edge of the coverage area
(2) Mobile sends a report to RNC when it exceeds threshold
before hitting its maximum value.
Time hysteresis
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Load based handovers (1/2)
Used for balancing the traffic (load) between different WCDMA frequency layers or between WCDMA and GSM/GPRS cellular networksTriggers, which may be checked periodically
Too high uplink or downlink interferenceThe CRRR for NGB traffic is higher than a thresholdThe cell is running out of downlink spreading codesThe cell is hardware- or logical resources limited
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Load based handovers (2/2)
Threshold
Time hysteresis Delay
t
PerformanceMetric
Load based HO state trigger: OFF
Load based HO state trigger: ON
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Service based handovers (1/2)
Service-based handovers are used for directing UEsto preferred RAT or hierarchical WCDMA layersService-based handover actions may be taken periodically, and the checking period is usually a parameter for the operator to set
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Service based handovers (2/2)Service type Target RAT or layer
(RNP parameter) CS Conversational Speech E.g. “GSM” Transparent data E.g. “GSM” PS Conversational Speech E.g. “WCDMA” Real time data E.g. “WCDMA” CS Streaming Non transparent data E.g. “WCDMA macro” PS Streaming Real time data E.g. “WCDMA macro” Interactive THP1 – NGB data E.g. “WCDMA micro” or “HSDPA” THP2 – NGB data E.g. “WCDMA micro” or “HSDPA” THP3 – NGB data E.g. “WCDMA micro” or “HSDPA” Background NGB data E.g. “WCDMA micro” or “HSDPA”
Handover Service Priority IE (From CN)
Cell based service priority information (From above table)
Combined service priority list (RNP parameter)
“RAB should be handed over to GSM” Target RAT or Layer Target RAT or Layer “RAB should not be handed over to GSM” Target RAT or Layer Target RAT or Layer “RAB shall not be handed over to GSM” Target RAT or Layer Target RAT or Layer
Service Priority IE not available Target RAT or Layer Target RAT or Layer
+
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Service and load-based handovers
Not performed for multi-service connections where the combined service priority lists are not compatibleHandovers or network-controlled cell reselections(in the case of GPRS) are performed only for those connections that are in Cell_DCH stateMeasurements as well as the criteria adopted for the selection of the target layer are (may be) the ones described for coverage and quality reasons
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WCDMA: QoS differentiation gains
40
50
60
70
80
90
100
0.0590 0.0690 0.0790 0.0890 0.0990 0.1090 0.1190 0.1290 0.1390
Satis
fied
Use
rs (%
)
Cell Capacity (b/s/Hz)
NPM1 - PoCPDM1 - PoCNPM1 - StreamingPDM1 - StreamingNPM1 - WAPPDM1 - WAPNPM1 - MMSPDM1 - MMSNPM1 - DialupPDM1 - DialupNPM1 - SWISPDM1 - SWIS
G
G = 50%
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HSDPA: QoS parameters (1/2)
Scheduling Priority Indicator (SPI)
Guaranteed bit rate requirement (GBR)
Discard Timer (DT)
HS-DSCH provided bit rate per SPI
Non HSDPA power measurement
HS-DSCH required power (the power to fulfill GBR)
Allocation Retention Priority (ARP): Known at MAC-hs
Traffic Handling Priority (THP): NOT know at MAC-hs
Node B
MAC-hs scheduling based on these parameters
RNC
New HSDPA “QoS”can be set per PDP context
“Traditional QoS parameters”
Feedback measurements that RNC can use to monitor MAC-hs performance
Traffic Class (TC): NOT know at MAC-hs
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HSDPA: QoS parameters (2/2)Traffic Class SPI MAC-hs GBR
(RNP parameter) Discard Timer (DT) (RNP parameter)
Streaming 4 (high) BRtarget_4 = GBR (RAB attribute) Defined as a function of the RAB attribute Transfer Delay
THP1 3 BRtarget _3 DT_3
THP2 2 BRtarget _2 DT_2
Interactive
THP3 1 BRtarget _1 DT_1
Background 0 (low) BRtarget _0 DT_0
Traffic Class Allowed to use HS-DSCH (RNP parameter)
Conversational No Streaming Yes
THP1 Yes THP2 Yes
Interactive
THP3 Yes Background Yes
For MAC-hs GBR may alsobe defined for other traffic classes
than Conversational and Streaming
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HSDPA power allocation (power budget)
GB HSDPA
NGB HSDPATarget power HS
Maximum power
HS- DSCH required power
Non-HSDPA power
Total allocated HSDPA power
GB DCH
Common channels
NGB DCH
Cell Txpower
HSDPA
DCH
Common channels
HS-SCCHHSDPASCCHHS
kxknew PPPPP ≤+++ −
≥∑ 0
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HSDPA: example of MAC-hs scheduler
HS-DSCH link Adaptation
User(s) scheduled on HS-DSCH
CQI measurements
Data from RNC
SPI, BRtarget
User specific QoS parameters (from RNC)
MAC-hs Scheduling Algorithm
(scheduling decision based on priority class, distance from the target bit rate and radio
conditions)
MAC-hs User Data buffer
BRmax
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HSUPA power allocation (power budget)
GB DCH users
Other cell interferencePrx_Noise
Prx_Total
Prx_Target
Node B controlled resources
RNC controlled resources
NGB DCH users
GB E-DCH users
NGB E-DCH users
Prx_available_EDCH
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Node B RNC
DCH user
E-DCH userNon-scheduled
E-DCH userScheduled
Data Packets
ACK/NACK
Data PacketsACK/NACK
Data Packets
ACK/NACK
Data PacketsACK/NACK
Scheduling information
Scheduling grant
Measure available resources
Handle possible congestion
Process scheduling requests, allocate resources
Send scheduling grants to UEs
Different uplink transmission mechanisms
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1 2 3 4 5 6 7 80
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Noise Rise [dB]
Prob
abili
ty
20 users/cell − 5% NR outage = 6 dB
RNC schedulingNode B scheduling
10 12 14 16 18 201000
1100
1200
1300
1400
1500
Average number of users per cell
Aver
age
cell
thro
ughput
[kbps]
RNC scheduling - simulation results
Node B scheduling - simulation results
RNC scheduling - analytical results
Node B scheduling - analytical results
6% - 9%
RNC vs. Node B packet scheduling
Reduction of PC headroom ⇒UL capacity increase at a given QoE
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PS: From UTRAN to GERAN
0 2 4 6 8 10 12 14Seconds
R6 Packet ISHO
Long TBF timer(or R6 enhanced TBF)
No security procedure
IS-NACC
Packet SI(PCCCH)
Gs-interface (SGSN-MSC/VLR for RA/LA comb.)
Network Cell Change
Read 2G SIUL TBF establishmentRA/LA updateDL TBF establishmentTCP delaysFirst user data packet
Service Break from 3G → 2G Access ChangeService Break from 3G → 2G Access Change
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PS: From GERAN to UTRAN
During cell reselection from GERAN to UTRAN, quite similar procedures have to be performed
Gaps about 5 s with some variation depending on whether combined or separated RAU/LAU is performed and which bit rate is used for the SRB signaling bearer in WCDMA (3.4 kb/s or 13.6 kb/s)
In 3GPP R6, PS handover will be the ultimate feature to get interruption times down to the subsecond area
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CS: inter-system HO performance
Service interruption unnoticeableWCDMA to GSM direction
Gap of about 200 msGSM to WCDMA direction
Gap of about 350 ms (due to SFN decoding)
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WCDMA WCDMA
Non-Dual Transfer Mode (DTM) terminalsNon-DTM dual-
mode mobile
GPRS GPRS GPRSCS voice
PS data
PS suspended due to incoming CS call Handover to WCDMA as soon
as coverage available
PS service resumed in WCDMA ⇒ multi-RAB call
EGPRS capable mobile
E-GPRSGPRS
E-GPRSGPRS
E-GPRSGPRS
WCDMA
Coverage endsX
X NCCR directly to E-GPRS
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3GPP-WLAN system based AAA
Authentication (A)Authorization (A)Accounting (A)
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Access to 3GPP IMS PS-based services
Packet Data Gateway
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Unlicensed Mobile Access (UMA)
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References
D. Soldani, M. Li and R. Cuny (eds.), QoS and QoE Management in UMTS Cellular Systems, John Wiley and Sons, June, 2006, 460 pp.
http://eu.wiley.com/WileyCDA/WileyTitle/productCd-0470016396.htmlhttp://www.connecting.nokia.com/NOKIA/nns.nsf/a/78786C61AB5A7C5AC225718F0026BAA3(contact Mr. Geoff Farrell @ Wiley [email protected] )
See also: http://lib.tkk.fi/Diss/2005/isbn9512278340/