06 rn31636en20gla0 packetscheduling ru20 v12

Packet SchedulerModule Objectives
At the end of the module you will be able to:
Explain the overall Packet Scheduler functions
Identify the transport channels used for NRT traffic
Explain how Packet Scheduler influences the controllable load
Explain the Capacity Request CR procedure
Identify the reasons for TFCS modification
Name and describe the main RAN parameters related to packet scheduler
* © Nokia Siemens Networks RN31636EN20GLA0
UL: Noise
Requires fast resource allocation
Why Packet Scheduling?
It is characteristic for RT traffic that it’s load cannot be controlled in efficient way. Load caused by RT traffic, interference from other cell users and noise together is called non-controllable load. The available capacity, which is not used by non-controllable load, can be used for NRT radio bearers on best effort basis. To fill the whole load budget and achieve the maximum capacity, the allocation of NRT traffic needs to be fast.
The Packet scheduler is a general feature, which takes care of scheduling radio resources for NRT radio bearers for both UL & DL directions; Packet scheduling happens periodically (with the period of tens of milliseconds) and is implemented for both dedicated (DCH) and common control transport channels (RACH/FACH).
Additionally, packet access is implemented for HS-DSCH when using HSDPA and for E-DCH in the case of HSUPA.
Packet scheduler is not applicable to the HS-DSCH MAC-d flow in DL and E-DCH in UL.
Scheduled capacity depends on the UE capabilities, Node B capabilities, current load of the cell as well as the availability of the physical radio resources.
PS and MAC layer together make the decision of the used channel type for DL direction, data transmission on dedicated channel is initiated when MAC layer requests transmission capacity
For UL direction the decision of the used channel type is based on UE measurements and parameters controlled by network. Data transmission on dedicated channels is initiated when a capacity request is received from UE.
The selection of the channel type is done fast - taking into account the data amount in the buffers and the current radio conditions
Packet Scheduler (PS) functions
PS consists of multiple different functions which can be categorised based on the scope of the function
UE-specific part: Functions working based on single radio link/bearer status, measurements & conditions
Cell-specific part: Functions working based on cell level measurements & conditions
UE Specific:
NRT DCH throughput measurements & minimum utilisation
Flexible upgrade of the NRT DCH & High throughput measurement
Dynamic link optimisation DyLO for NRT traffic coverage
Cell Specific:
Bit rate allocation process/method
Load decrease - Overload control
Sheet1 (2)
X
X
X
X
RAN'05
Packet scheduler retry with lower bit rate in congestion (ED2 CD05)
X
X
X
RAS05
Enhanced priority based scheduling and overload control for NRT traffic
New user triggered RB downgrade
X
X
X
RAN'05
X
X
X
Throughput based RB release
Light weight flexible upgrade
X
X
X
X
RAN'05
Packet scheduler retry with lower bit rate in congestion (ED2 CD05)
X
X
X
RAN04
X
X
X
RAS05
Enhanced priority based scheduling and overload control for NRT traffic
New user triggered RB downgrade
X
X
X
RAN'05
X
X
X
Throughput based RB release
Light weight flexible upgrade
Parameters WCEL: MaxBitRateULPSNRT , MaxBitRateDLPSNRT
Maximum user bit rate allowed in a cell for an NRT PS domain RAB
Parameters WCEL: MinAllowedBitRateDL , MinAllowedBitRateUL
Min. allowed bit rate in the UL that PS can downgrade to NRT DCH bit rate in congestion situations
RAS05: Initial & minimum allowed bit rate in DL
RAS05.1: Minimum allowed bit rate in DL
The parameters WCEL: InitialBitRateUL & InitialBitRateDL
The parameter defines the initial bit rate that can be allocated by the PS in schedule situation
PS does not schedule NRT DCH bit rates that are below the value of this parameter
Parameter RNC: BitRateSetPSNRT
defines whether the predefined set of PS NRT DCH bit rates is in use. The bit rates listed in the set are the max. bit rates that can be allocated to NRT RAB.
The predefined bit rate set contains the following UL rates: 0; 8; 64; 128 kbps
The predefined bit rate set contains the following DL rates: 0; 8; 64; 128 & 384 kbps
Values: Predefined bit rate set is not in use (0), Predefined bit rate set is in use (1)
Bit rate upgrading & downgrading
The DCH of a NRT RAB can be upgraded due to:
1) High amount of data in buffer – Capacity Request CR / Bit rate upgrade
2) High utilisation/throughput – Flexible upgrade of the NRT DCH data rate
It is possible to upgrade the NRT DCH data rate from any bit rate below the maximum allowed bit rate to the maximum allowed bit rate
The DCH upgrade procedure is performed in CELL_DCH state and it requires the reconfiguration of RL, transmission & RNC internal resources
The DCH of a NRT RAB can be downgraded or released due to multiple causes:
1) Excessive DL power – DyLO for NRT traffic coverage feature
2) Different congestion situations – Enhanced PBS and overload control
3) Low utilisation/throughput – Throughput-based optimisation of the PS
4) Maximum bit rate limitation – Another RAB is setup for the same UE
5) Inactivity of the radio bearer
The DCH downgrade procedure is performed in CELL_DCH state and it can be performed by
RB Reconfiguration (also transmission, WBTS & RNC resources)
Limitation of the maximum Transport Format Combinations TFC (temporary)
Packet Scheduler actions during call – Unloaded cell
AC - AC makes admission decision and allocates a 0 bit rate to the NRT radio bearer
PS1 - “Bit rate allocation”, after receiving a capacity request PS allocates initial bit rate
PS2 - “Flexible upgrade”, After receiving a capacity request PS allocates maximum (high) bit rate
PS3 - “Throughput-based optimisation“, PS performs RB reconfiguration to lower bit rate
PS4 - “Flexible upgrade”, PS performs RB reconfiguration to higher bit rate
PS5 - “RRC state transition”, PS initiates state transition to CELL_FACH due to inactivity
AC
PS1
PS2
PS3
PS4
Max Bit Rate DL / UL PS
[8, 16, 32, 64, 128, 256, 320, 384] kbps, 384 kbps
PS5
Packet Scheduler actions during call – Loaded cell
AC - AC makes admission decision and allocates a 0 bit rate to the NRT radio bearer
PS1 - “Priority based scheduling”, after receiving a capacity request PS allocates initial bit rate after downgrading an existing bearer (load margin)
PS2 - “Flexible upgrade”, After receiving a capacity request PS allocates higher bit rate (normal load)
PS3 - “Enhanced Overload control“, PS performs radio bearer reconfiguration to until minimum bit rate (overload)
PS4 - “Flexible upgrade”, PS performs radio bearer reconfiguration to higher bit rate (normal load)
PS5 - “RRC state transition”, PS initiates state transition to CELL_FACH due to inactivity
Max. bit rate
Initial bit rate
Allocated bit rate
FLXU: Flexible upgrade (after CR)
EOLC: Enhanced Overload control (Overload)
PS5: Inactivity RRC state transition
AAL2SIG:ECF
AAL2SIG:ERQ
UL Direct Transfer : Activate PDP context request (DCH)
Direct Transfer : Activate PDP context request
RANAP: RAB Assignment Request
RRC: Radio Bearer Setup
Radio Bearer Setup Complete
DL Direct Transfer : Activate PDP Context Accept (DCH)
Call Established
Measurement Control
Measurement Control
RRC: Radio Bearer Reconfiguration Complete (DCH)
Measurement Control
GPRS Attach
* incl. decision whether Rel. 99 or HSDPA resources are allocated
CR = Capacity Request
RRC State Maschine
The packet access procedure in WCDMA should keep the interference caused to other users as small as possible.
Since there is no connection between the base station and the UE before the access procedure, initial access is not closed loop power controlled and thus the information transmitted during this period should be kept at minimum.
There are 3 scenarios for WCDMA packet access:
infrequent transmission of small packets
frequent transmission of small packets and
transmission of large packets
Packet data transfer in WCDMA can be performed using common, shared or dedicated transport channels.
Since the establishment of a dedicated transport channel itself requires signalling and thus consumes radio resources, it is reasonable to transmit infrequent and small NRT user data packets using common transport channels without closed loop power control. Then the random access channel (RACH) in UL and the forward access channel (FACH) in DL are the transport channels used for packet access
When the packet data is transferred on common channels, the UE is in CELL_FACH state.
Large or frequent user data blocks are transmitted using shared or dedicated transport channels (DCH).
When the packet data is performed on shared or dedicated channels, the UE is in CELL_DCH state.
UL/DL data or signalling
Release of RT RB
Cell reselection (moving UE)
UL Access (UL data/signalling)
Setup of RT/NRT RB
Cell_
DCH
Random Access (MO Call)
Max. # cell updates in Cell_FACH / Cell_PCH exceeded
Inactivity detection during last 20sec
RNC L2 resources at low level
Fast UE with L2 inactivity
TFCS construction
Flexible upgrade of the NRT DCH and High throughput measurement
Dynamic link optimisation (DyLO) for NRT traffic coverage
Traffic volume measurement & report
At least every TTI, the MAC layer shall receive from each RLC entity the value of its Buffer Occupancy (BO), expressed in bytes
The parameter BO indicates for each logical channel the amount of data in number of bytes that is available for transmission and retransmission in RLC layer.
Traffic volume information is measured in MAC layer and the results are reported from MAC layer to RRC layer
Traffic volume measurement reports are handled as Capacity Requests in the RNC
Every time the BO values are reported to MAC, the UE/RNC shall verify whether an Event was triggered
If reporting is required MAC shall deliver to RRC the reporting quantities required for the corresponding RBs
Events are evaluated with respect to the Transport Channel Traffic Volume (TCTV)
Equal to the sum of the Buffer Occupancy for logical channels mapped onto a transport channel (DCH or RACH or FACH)
Events on a given transport channel shall be evaluated at least at every TTI
Traffic volume measurement (UL, UE) / Low & High bit rates
The UE performs traffic volume measurements for each UL NRT RB when:
UE is in CELL_FACH state
UE is in CELL_DCH state but DCH is not allocated for the NRT RB in question
UE is in CELL_DCH state & the allocated bit rate is lower than the max. bit rate for the RB in question
In the CELL_FACH state the UE uses RACH as an UL transport channel
TCTV measurement measures the total sum of buffer occupancies of all RBs multiplexed onto the RACH
The parameters UL initial bit rate (InitialBitRateUL) & DL initial bit rate (InitialBitRateDL) define low UL bit rate and low DL bit rate respectively
When the UE is in SHO, the smallest parameter values of active set cells are used
If ‘Maximum bit rate’ in RAB attributes (QoS parameters) is lower than InitialBitRateUL or InitialBitRateDL, ‘Maximum bit rate’ is used as a new Minimum allowed bit rate in scheduling for this particular RAB
High bit rate is defined as
Low bit rate < High bit rate ≤ Max bit rate of the RB (defined by AC)
Traffic volume measurement reporting event (UL)
Reporting criteria are signalled to the UE using an RRC: MEASUREMENT CONTROL message at RB setup or when parameters are modified
Event-triggered traffic volume measurement reporting is used in Nokia RAN
Reporting event 4A
Pending time (TrafVolPendingTimeUL)
An event-triggered report is sent when TCTV exceeds a threshold as follows
In CELL_FACH
TCTV of NRT RB x > 8 bytes
In CELL_DCH with allocated bit rate is lower than maximum bit rate for NRT RB x
TCTV of NRT RB x > TrafVolThresholdULHigh
TCTV: Transport Channel Traffic Volume
TrafVolThreshold ULLow
TrafVolThreshold ULHigh
Reporting event:
4A: Transport Channel Traffic Volume becomes larger than an absolute threshold
time
UE in CELL_FACH: TrafVolThresholdULLow (128 Bytes)
UE in CELL_DCH: TrafVolThresholdULHigh (1024 Bytes)
4A
4A
Measurement
time
4A
4A
If the UE does not receive DCH allocation nor bit rate upgrade (RRC message)
It retransmits the traffic volume measurement report to the network after UL traffic volume measurement pending time after trigger (TrafVolPendingTimeUL)
TrafVolPendingTimeUL
Traffic volume measurement (DL, RNC)
RNC performs traffic volume measurements TVM for each UL NRT RB when:
UE is in CELL_FACH state
UE is in CELL_DCH state but DCH is not allocated for the NRT RB
UE is in CELL_DCH state; allocated bit rate is lower than max. RB bit rate
In the CELL_FACH state the UE has FACH as an DL transport channel
DL TCTV measurement measures the total sum of buffer occupancies of
All user plane radio bearers
Signalling radio bearers SRB3 & SRB4, multiplexed onto the FACH
DL TVM reports are RNC internal messages
Reporting criteria sent from L3 to MAC entities when entity initialised or parameters modified
Traffic volume measurements TVM are sent to higher layers:
In CELL_FACH: DL TCTV > TrafVolThresholdDLLow
In CELL_DCH without DCH for NRT RB x:
TCTV of NRT RB x > 0 bytes
In CELL_DCH: allocated bit rate < max. bit rate for NRT RB x
TCTV of NRT RB x > TrafVolThresholdDLHigh
If UE does not receive a DCH allocation or bit rate upgrade, UE specific
entity within RNC reports TVM again after TrafVolPendingTimeDL
TCTV: Transport Channel Traffic Volume
TrafVolThreshold DLLow
TrafVolThreshold DLHigh
TrafVolPendingTimeDL
RNC; 0.25..16s; 2 s
Capacity Request (CR) types
The TVM reports are classified into the following 3 types of CR:
Initial request for low bit rate (UL/DL); when
The NRT RB in question has no previous DCH allocation
RLC buffer payload < TrafVolThresholdDLHigh or TrafVolThresholdULHigh
Low bit rate means minimum bit rate
Initial request for high bit rate (UL/DL); when
The NRT RB in question has no previous DCH allocation
RLC buffer payload => TrafVolThresholdDLHigh or TrafVolThresholdULHigh
Upgrade request for high bit rate (DL); when
The NRT RB in question has a lower than RB maximum bit rate DCH allocated
TrafVolThreshold UL/DL Low
TrafVolThreshold UL/DL High
TVM: Traffic Volume Measurement
TFCS construction
Dynamic link optimisation for non-real time traffic coverage
TFCS construction
There are Transport Format Sets TFS for each DCH allocated to the UE
The UE-specific PS produces TFS subsets based on the scheduled bit rates provided by the cell-specific PS and selected intermediate bit rates
On the basis of these TFS subsets, the UE- specific PS produces a Transport Format Combination Set TFCS
The UL & DL TFS & TFCS produced by the UE-specific PS are delivered to
MAC layer of the RNC
MAC layer of the UE (RRC: RB setup/re-configuration)
BTS (NBAP: Radio link setup/re-configuration)
MAC layer selects the appropriate Transport Format Combination TFC to be used for transportation of the current packet data unit
TFS: Transport Format Set
TFC: Transport Format Combination
TFS: Transport Format Set
TFC: Transport Format Combination
Bit rate selection
Operator can define the maximum allowed UL DCH user bit rate in a cell for the PS domain interactive and background RABs
MaxBitRateULPSNRT, MaxBitRateDLPSNRT
Limited bit rate set enables the operator to limit the available UL and DL DCH data rates for PS
This limited DCH data rate set contains only rates 0, 8, 64 & 128 kbits/s in UL direction and 0, 8, 64, 128 and 384 kbits/s in DL direction
When AC & PS are defining the maximum data rate for a DCH, they select it from the selective NRT DCH data rate set
Limited bit rate set for PS NRT DCHs is taken in use with the RNC management parameter Bit rate set for PS NRT DCHs (BitRateSetPSNRT)
A particular maximum DCH data rate can be used in a cell, if both of the features allow it
Cell-specific data rate limitations are not significant in SRNC when the resource is allocated for diversity handover
MaxBitRateULPSNRT
MaxBitRateDLPSNRT
BitRateSetPSNRT
1: Predefined bit rate set in use
TFCS construction
for Interactive & Background services
low utilization of resources
3 different thresholds defined
Motivation: control of lowly utilised NRT DCH
frequent transmission of small packets Inactivity timers do not expire
typical DCH utilisation < 20 % of allocated bit rate
DCH resource reservation adapted to meet the actual utilisation (i.e. the used bit rate of the DCH)
lowly utilised DCH allocations downgraded or released
Utilisation is measured as average throughput
feature decreases significantly the capacity loss caused by too high bit rate allocations
BTS HW, transmission & DL spreading code capacity mainly
PSOpThroUsage
RNC; 4 bit for BG / IA THP3 / IA THP2 / IA THP1
Values: OFF (0); ON (1);
by default feature is OFF for non-GBR services
L2 MAC
DCH is released – FACH allocated
Parameters introduced to control the downgrade/release of DCH
avg. L2 throughput
DCHUtilLower
TimeToTrigger*
DCHUtilUpper
TimeToTrigger*
RNC; 0..20 s; 0.2 s; 4 s
*structured parameters; can be tuned individually for each data rate [32..384 kbps]
DCHUtilRel
TimeToTrigger*
L2 MAC throughput [kbps] / DCH Bitrate [kbps]
Upper downgrade
240.64 kbps = 256 kbps * ( 1 – 0.06 )
= UpperDowngradeBitrate * ( 1 – DCHUtilBelowDowngradeThr)
TimetoTrigger
Downgrade
8 for 64 kbps NRT
16 for 128 kbps NRT
32 for 256 kbps NRT
64 for 384 kbps NRT
DCHUtilUpperDowngradeThrBitRate; RNC
32 for 64 kbps NRT
64 for 128 kbps NRT
128 for 256 kbps NRT
256 for 384 kbps NRT
DCHUtilMeasGuardTime
TFCS construction
Traffic volume measurement
Algorithm for upgrading NRT DCH bit rate from any bit rate up to max. RB bit rate
TVM reporting thresholds are modified when
FlexUpgrUsage is ‘On’
DCH bit rate lower than the radio bearer maximum bit rate has been allocated
New reporting threshold is set when 0 < DCH bit rate < RB maximum bit rate
UL: MEASUREMENT CONTROL message to modify Event 4a reporting
The bit rate dependent high traffic threshold is selected
On basis of TrafVolThresholdULHighBitRate or
TrafVolThresholdDLHighBitRate
Structured parameter: Values for 8, 16, 32, 64, 128, 256 kbit/s
TrafVolThresholdUL/DLHighBitRate:
512 bytes for 8 & 16 kbps
1024 bytes for 32 & 64 kbps
2048 bytes for 128 kbps (& UL 256 kbps )
3072 bytes for 256 kbps NRT (DL only)
TrafVolThreshold UL/DL
FlexUpgrUsage
256
TimetoTrigger
384
128
64
32
512
MAC-d
entity
Note: If value = “0”, no throughput measurements active
DCHutilHighTimeToTrigger
DCHutilHighBelowNRTDataRateThr
TFCS construction
Dynamic link optimisation DyLO for NRT traffic coverage
Improved NRT traffic coverage
distance
Radio link is modified to use lower bit rate when Tx power of the radio link is getting close to maximum
BTS
UE
384kbps
128kbps
Ptxmax
Offset
Ptxave: averaged RL power, measured & reported to RNC by BTS; averaged in RNC over:
defined by Admission Control
DyLO triggered if:
Ptxave + DLOptimisationPwrOffset > Ptxmax
DLOptimisationUsage
1: Feature is activated with SF step 1
2: Feature is activated with SF step 2
* 0 = no effect for measurement averaging in RNC; recommended: 4
HHoMaxAllowedBitrateDL
Channel type selection
No
Yes
No
Modify the content type of the original CR in a queue
Delete the new CR
Is new CR same as original?
(A)
(B)
CrQueuingTimeUL ;RNC; 1…30s,1s,4s
CrQueuingTimeDL; RNC; 1…30s,1s,4s
Queue ordered based on
SPI of the request
time limit how long CR can stay in queue
CrQueuingTimeUL & CrQueuingTimeDL
Definition of Scheduling Priority Indicator SPI
For each combination of RAB QoS parameters operator can define service priority
Traffic class
Also used for HSPA scheduling
QoSPriorityMapping
PriForStreamARP1/2/3 (RNC) (0..15) ( = 1) (13/13/13)
Priority for Interactive TC with THP 1 & ARP 1/2/3
PriForIntTHP1ARP1/2/3 (RNC) (0..11) ( = 1) (11/11/11)
Priority for Background TC with ARP 1/2/3
PriForBackARP1/2/3 (RNC) (0..11) ( = 1) (0/0/0)
QoS parameter
RAB profile
RNC internal traffic volume measurement (CR)
UE traffic volume measurement (CR)
E-DCH only with
Channel Type Selection – FACH & DCH
A) Maximum allowed user data amount on FACH exceeded (traffic volume)
B) FACH in overload (throughput)
C) FACH usage forbidden by PS
(Power in CCH, RACH throughput)
Threshold & hysteresis parameters exist.
* relative to PtxTarget
(A)
(B)
(C)
RachLoadThresholdCCH
RachLoadMarginCCH
Enhanced priority based scheduling
LoadControlPeriodPS
Overload Control
Prx_nrt / Ptx_nrt: NRT / controllable power; ruled by PS
Prx_sc / Ptx_sc: semi-controllable power; PS Streaming service
PrxRtInactive: estimated received power of admitted RT bearers, which are not active yet because establishment phase is still ongoing
PrxNRTInactive: estimation of the received power that inactive bearers would cause when they are active
For details about their determination, please refer to NOLS Packet Scheduler ‘power Budget for Packet Scheduling’.
Prx/tx_total_change:
Calculation of min & max available UL load in the UL DCH scheduling
Lallowed_minDCH = LminDCH – LDCH,CELL
where LminDCH defines the minimum guaranteed UL DCH load threshold:
RDCHWPSMin is the value of the Interference margin for the minimum UL DCH load PrxLoadMarginDCH parameter transformed into the linear notation.
PrxLoadMarginDCH
LminDCH 37%
Lallowed_maxDCH = LMaxDCH – LDCH,CELL
where LmaxDCH defines the planned target for the maximum UL DCH load of the cell:
RDCHWPSMax is the value of the Interference margin for the maximum UL DCH load PrxLoadMarginMaxDCH parameter transformed into the linear notation
PrxLoadMarginMaxDCH
Decrease loading
Increase loading
Priority scheduling
Decrease loading
PtxOffset:
Remember ?!
Bit Rate Allocation in UL- Overview
PrxAllowed is the UL power budget.
the minimum & maximum available UL load in the UL DCH scheduling.
PrxLoadMarginDCH
LminDCH 37%
PrxTarget
PrxOffset
Remember ?!
Initial bit rate allocation
The basic idea of the packet scheduling method is:
(PS 1) When DCH is not allocated for NRT RB and PS receives an UL CR where low data amount is reported, it allocates initial bit rate in both directions.
(PS 1) When DCH is not allocated for NRT RB and PS receives a DL CR where low data amount is reported, it allocates initial bit rate in both directions.
AC
PS1
PS2
PS3
PS4
PS5
8..384 kbps; 64 kbps
Maximum bit rate allocation
(PS 1) When DCH is not allocated for NRT RB and PS receives an UL CR where high data amount is reported, it allocates maximum bit rate in UL and initial bit rate in DL.
(PS 1) When DCH is not allocated for NRT RB and PS receives a DL CR where high data amount is reported, it allocates maximum bit rate in DL and initial bit rate in UL.
(PS 3) When bit rate lower than the maximum is allocated for NRT RB on a certain direction and the PS receives a CR for that direction where high amount is reported, it allocates maximum bit rate for that direction it upgrades the bit rate.
PS1
PS2
PS3
PS4
Max Bit Rate DL / UL PS
[8, 16, 32, 64, 128, 256, 320, 384] kbps, 384 kbps
Bit rate Upgrade Process
DeltaPtxMaxUp
DeltaPrxMaxUp / DeltaPtxMaxUp:
max. received UL / transmitted DL power increase in a cell, used when bit rates are allocated or increased by the PS, relative to PrxTotal / PtxTotal
Lallowed_min_DCH (LnewDCH,CELL) ≥ 0 OR
(PrxAllowed (PrxTotalNew) > 0 AND
Lallowed_min_DCH = LminDCH – LnewDCH,CELL
Lallowed_max_DCH = LmaxDCH – LnewDCH,CELL
Step 1
Step 2
Step 3
Step 4
128 (1)
Step 5
Target exceeded, allocation according to Step 4, check against DyLO is made
LoadControlPeriodPS: Overload Control Period;
defines how often PS can perform load control actions for each bearer.
Note: Value must not be smaller than scheduling period.
Load too high PS starts modification or reconfiguration in DCH(s) of the Interactive or Background class radio bearers.
PS supports different overload control methods:
UL:
DL:
the system automatically
LoadControl
PeriodPS
Node B, Iub & RNC
If every lower priority bearer has been already downgraded or released.
Candidate selection
MinAllowedBitRate UL/DL
LoadControlPeriodPS
UL Load decrease algorithm
WCEL; 0..5; 0.2; 0.8 dB
defines max. received UL power decrease in a cell, used when bit rates are decreased by PS, relative to PrxTotal
If every lower priority bearer has been already downgraded or released.
SPI: Scheduling Priority Indicators Sl. 90
Candidate selection
MinAllowedBitRate UL/DL
PrxTotalChange <
DeltaPtxMaxDown
defines the max. transmitted DL power decrease in a cell, used when bit rates are decreased by PS, relative to PtxTotal
Yes
No
384
128
128
128
Step 2: 256 -> 128(TFCC)
Allocation according to step 4
Overload Control – Example
all Bearer of same priority
MinAllowedBitRateUL/DL = 128 kbps
Selection of the radio bearer to be downgraded
Selection of the RBs to be downgraded, is done based on:
QoS priority value (lowest priority)
Connection allocation time (longest allocation time)
Bit rate (highest bit rate)
Bit Rate
Scheduling and
RRind Period
reconfiguration is not allowed
factor increased, RL
NRT DCH allocation time > parameter
DCH rate decreased or released
0..60; 1; 60 s = Enhanced Overload Control not activated; if activated Rec. 10s
Enhanced overload control:
modifies DCH bit rate & spreading factor
reconfigures L2 by sending the new TFC set to the UE specific MAC-d entity of RNC
RRC initiates RB Reconfiguration procedure
Original bit rate of DCH(s) not automatically returned back once overload situation is over
new CR required Normal scheduling
Step 1: 256 -> CCH
Step 2: 256 -> 128
PtxTarget
128
Enhanced Priority Based Scheduling PBS
The feature Enhanced PBS allows the operator to select alternative methods for the PS.
PBS is based on the radio bearer reconfiguration procedures
Existing NRT allocations can be downgraded or released if there are higher/higher or equal/any priority users requesting capacity in the congested situation, activated and steered by PBSpolicy parameter
Congestion of the following resources can trigger the enhanced PBS function
DL power
UL interference
Enhanced PBS
PBS operation performed only for 1 CR per scheduling period, i.e. for the first in queue
PBS has no effect on bit rate upgrades
RAB requesting capacity is not allowed to have existing NRT DCH allocation for the same RB
The enhanced PBS function is not performed during CM
Minimum allocation time can be configured via parameters
PBS - Priority
Priority 2
Interactive bearer
Priority 3
Interactive bearer
Priority 4 (lowest)
2: Higher THP
RAB of the incoming CR must have higher THP than the RAB of the DCH to be downgraded or released
3: Higher or equal THP
RAB of the incoming CR must have higher or equal THP than the RAB of the DCH to be downgraded or released
4: Higher or equal THP (not THP 1)
same as 3, but DCHs of the RABs that have THP 1 are excluded.
5: Any THP
6: Any THP (not THP 1)
Florian Reymond
Florian Reymond
RAS06_v1.0
RANPAR; Minor corrections Minor change in Dylo Different UL scheduling process in RAS06 Packet Scheduler Interruption Timer is deleted from RAS06 onwards
Florian Reymond
RANPAR 1; RU20 version; Several corrections; concentration of contents (Andreas Annen)
Benedikt Aschermann
Tunable inactivity timerXXX
Radio interface overload
(ED2 CD05)
Data Rate
Affected resourcesRAN/RAS

06 rn31636en20gla0 packetscheduling ru20 v12

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