06_PacketScheduling_RU10

Packet SchedulerModule Objectives
At the end of the module you will be able to:
Describe the RRC connection states and their relationship to the packet scheduler
Identify the transport channels used for NRT traffic
Explain how packet scheduler influences the controllable load
Explain the capacity request procedure
Identify the reasons for TFCS modification
Name and describe the main RAN parameters related to packet scheduler
* © Nokia Siemens Networks RN3007EN06GLN00
PS RAB Reconfiguration
Single APN concept
Packet Transfer States
Discussed later in the course
PS interruption timer feature removed (RAS06)
Function is covered by Priority Based Scheduling feature
Optimization of network resources dynamically by aligning the QoS parameters with the QoS requirements of the service
SGSN or UE can request modification of QoS characteristics of RAB
Main RAB Parameters:
Avg. Bitrate (UL/DL)
Traffic Class, THP, ARP, Max Bitrate (UL/DL) Parameters can be changed on-the-fly
RAB – Radio Access Bearer
UE RRC state
Service: HSPA or DCH
If UE is in URA_PCH or CELL_PCH state, RABAssignemtRequest message does not trigger paging procedure for UE – RNC stores the data to be applied in next active phase
CELL_FACH state the new parameters are taken into us on net state transition to
CELL_DCH
If UE has DCH service, the handling depends on requested parameter change:
THP, ARP and Traffic Class are taken into use immediately
Maximum bitrate increase on next RRM resource allocation
Furthermore the resources are taken into use immediately if
UE has HSPA service and upgrade/downgrade of maximum bitrate or other RAB parameters is requested
The UE has a DCH service and the downgrade of the maximum bit rate and/or the modification of other RAB parameters is requested.
If RAB reconfiguration is executed in RNC, all UTRAN capacity areas are
reconfigured as well:
Packet Scheduler Functions
UL: Noise
Requires fast resource allocation
(when HSDPA preferred over NRT DCH)
Changes in non-controllable load are due to establishment of new RABs or new power requirements of existing RABs
Similar principle to GPRS territory allocation – realtime users get desired capacity and non-realtime users utilise remaining capacity (RAN 1.5)
Differences: Available capacity has to be checked in all cells of Active Set
In soft(er)-HO, the NRT from the serving BTS is RT traffic in other BTS
Scheduling of capacity occurs in regular intervals (not event driven, i.e. when a call is cleared)
In subsequent RAN releases PS will be enhanced to provide QoS also to NRT traffic.
Soc Classification level
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 uplink and downlink 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.
Packet scheduler and MAC layer together make the decision of the used channel type for downlink direction, data transmission on dedicated channel is initiated when MAC layer requests transmission capacity
For uplink 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
PS done for DCH and common control channels (RACH/FACH)
For more information on Packet Access on HSPA, see RRM of HSDPA/HSUPA NOLS documents.
Packet Scheduler
The packet scheduler takes care of scheduling radio resources for non-real time radio bearers for both the uplink and the downlink directions
Packet access is implemented for dedicated (DCH) as well as common control transport channels (RACH/FACH)
Packet access is implemented for high speed downlink shared channel (HS-DSCH) in the case of HSDPA
Packet access is implemented for enhanced dedicated channel (E-DCH) in the case of HSUPA
The packet scheduler and the medium access control (MAC) layer together make the decision regarding which type of channel to use in the downlink and uplink direction
Packet Scheduler as part of RRM
The packet scheduler (PS) co-operates with other radio resource management functions like handover control (HC), load control (LC), admission control (AC) and the resource manager (RM)
HC provides active set information
LC provides periodical load information to PS on a cell basis
PS informs AC and LC of the load caused by non-real time radio bearers
AC informs PS when new non-real time radio bearers are admitted, reconfigured or released
RM allocates the RNC internal resources, downlink spreading codes and takes care of allocating radio links using the base station application protocol (NBAP)
RM also takes care of transport resource reservation for non-real time radio bearers using transport resource manager (TRM) services. RM actions are done when requested by the PS
The radio resource control (RRC) protocol takes care of L3 signalling between the RNC and the UE
The L3 RRC signalling needed by the PS includes uplink capacity requests and channel allocation procedures in both directions (uplink and downlink)
The medium access control (MAC) protocol produces radio bearer-specific downlink capacity requests to the PS according to the radio link control (RLC) buffer levels in the RNC
MAC also sends activity and inactivity indications on an RB basis.
Packet Scheduler as part of RRM
The packet scheduler is located in the interface control and signalling unit (ICSU) of the serving radio network controller (SRNC)
In the drift RNC, non-real time bearers are handled as real-time bearers, and therefore are not taken into account in packet scheduling
TRM – Transport
resource manager
AC Admission control BTS Base transceiver station HC Handover control LC Load control MAC Medium access control NBAP Node B application protocol PS Packet scheduler RLC Radio link control RM Resource manager RRC Radio resource control TRM Transport resource manager
Packet Scheduler and protocol layers
IP packets arrive to the PDCP/RLC buffers of the RNC in the downlink and UE in uplink direction
The position of RRM and PS is close to WCDMA L2 protocols, RLC and MAC
Packet Scheduler 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 and conditions
Cell-specific part
UE Specific:
NRT DCH throughput measurements and minimum utilisation
Flexible upgrade of the NRT DCH and High throughput measurement
Dynamic link optimisation for non-real time traffic coverage
Cell Specific:
Queuing of capacity requests
Bit rate allocation process/method
Load decrease - Overload control
Enhanced priority based scheduling
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
CS = circuit switched
PS = packet switched
PS S UL:E-DCH/DL:HS-DSCH
QoS class
AMR (5.90, 4.75)
CS = circuit switched
PS = packet switched
PS I/B DCH(0,8,16,32,64,128,256,384)/DCH(0,8,16,32,64,128,256,384)
PS I/B DCH(16,64,128,384)/HS-DSCH
PS I/B E-DCH/HS-DSCH
Speech + PS Streaming
PS S DCH(8,16,32,64,128)/DCH(8,16,32,64,128,256,384)
PS S DCH(8,16,32,64,128)/HS-DSCH
PS S E-DCH/HS-DSCH
+ 0-3 PS Interactive / Background
PS S E-DCH/HS-DSCH
Multiple PS RABs always use the same transport channels!
RU10
Parameters WCEL: MaxBitRateULPSNRT , MaxBitRateDLPSNRT
Maximum user bit rate allowed in a cell for an NRT PS domain RAB
Parameters WCEL: MinAllowedBitRateDL , MinAllowedBitRateUL
Minimum allowed bit rate in the uplink that PS can downgrade to NRT DCH bit rate in congestion situations
RAS05: Initial and minimum allowed bit rate in downlink
RAS05.1: Minimum allowed bit rate in downlink
The parameters WCEL: InitialBitRateUL and InitialBitRateDL
The parameter defines the initial bit rate in the downlink that can be allocated by the PS in schedule situation
PS does not schedule downlink NRT DCH bit rates that are below the value of this parameter
Parameter RNC: BitRateSetPSNRT can be used to limit allowed bit rate set
Disable UL: 16, 32, 384 and DL: 16, 32
Bit rate upgrading
The dedicated channel of a non-real time (NRT) radio access bearer (RAB) can be upgraded due to
1) High amount of data in buffer – Capacity request/ 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 dedicated channel upgrade procedure is performed in CELL_DCH state and it requires the reconfiguration of radio link, transmission and RNC internal resources
Bit rate downgrading
The dedicated channel of a non-real time (NRT) radio access bearer (RAB) can be downgraded or released due to multiple causes
1) Excessive downlink power – Dynamic link optimisation for non-real time traffic coverage feature
2) Different congestion situations – Enhanced priority-based scheduling and overload control
3) Low utilisation/throughput – Throughput-based optimisation of the packet scheduler
4) Maximum bit rate limitation – Another RAB is setup for the same UE
5) Inactivity of the radio bearer
The dedicated channel downgrade procedure is performed in CELL_DCH state and it can be performed by
Reconfiguration of radio bearer (also transmission, WBTS and RNC resources)
Limitation of the maximum transport format combinations (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 radio bearer reconfiguration to lower bit rate
PS4 - “Flexible upgrade”, PS performs radio bearer reconfiguration to higher bit rate
PS5 - “RRC state transition”, PS initiates state transition to CELL_FACH due to inactivity
AC
PS1
PS2
PS3
PS4
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
Minimum bit rate
Max. bit rate
Initial bit rate
Allocated bit rate
AAL2SIG:ECF
AAL2SIG:ERQ
Uplink 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
Downlink Direct Transfer : Activate PDP Context Accept (DCH)
Call Established
Measurement Control
Measurement Control
RRC: Radio Bearer Reconfiguration Complete (DCH)
Measurement Control
GPRS Attach
related parameters
RRC Modes and Packet Scheduling
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 three 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 uplink and the forward access channel (FACH) in downlink 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.
Infrequent small data > FACH/RACH > CELL_FACH
Frequent or large data > DCH > CELL_DCH
PS Connection Establishment
In the RRC connection setup procedure the UE is always transferred directly to CELL_DCH state in Nokia RAN (see previous slide).
The RRC connection setup and “a service establishment” for NRT RAB(s) is performed as follows:
After the UE has completed a RRC Connection setup procedure with the RNC, dedicated channel resources are allocated to the UE (a DCH for the signalling link is setup).
The UE performs a NAS connection establishment to the PS CN.
After the service negotiation has been carried out between the UE and PS CN, the PS CN sends a RAB assignment to the RNC.
The RNC’s RRC signalling entity performs a radio bearer setup with a RRC:Radio Bearer Setup procedure.
The traffic volume measurement parameters (RLC buffer level, reporting criteria, etc.) are sent to the UE by using a RRC:Measurement Control procedure
Based on this information the UE is able report the need of UL capacity (request the allocation of the DCH) by sending a RRC:MEASUREMENT REPORT message to the RNC
The RNC’s RRC signalling entity starts a supervision timers UL_DLcapacityReqWait and SignallingLinkInactivityTimer
If the capacity request is received from the UE or from the RNC’s within the UL_DLcapacityReqWait, the DCH for NRT RB(s) is allocated.
If there is no activity in RB(s) within the UL_DLcapacityReqWaitand the inactivity of signalling link is detected (‘SignallingLinkInactivityTimer’ has also expired), the state transition from CELL_DCH to CELL_FACH is initiated
In RAN05 UL_DLcapacityReqWait is used instead of RB_InactivityTimer
Release of RT RB
Cell reselection (moving UE)
UL Access (UL data/signalling)
Periodic URA update (stationary UE)
Paging response (DL data / signalling)
UL Access (UL data / signalling)
Cell_
PCH
Setup of RT/NRT RB
Cell_
DCH
Random Access (MO Call)
Max. number of periodic cell updates in Cell_FACH / Cell_PCH exceeded
UL/DL data or signalling
RNC L2 resources at low level
Fast UE with L2 inactivity
I insert classification level
TFCS construction
Traffic volume measurement and 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 Buffer Occupancy (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
BO1-4
BO5-6
BO1-6
TrCH1
TrCH2
SRB1-4
RB5
RB6
Please note: Unlike presented in the picture above, NSN RAN does not support DTCH multiplexing.
Traffic volume measurement (UL, UE)
The UE performs traffic volume measurements for each uplink non-real time radio bearer when:
UE is in CELL_FACH state
UE is in CELL_DCH state but dedicated channel is not allocated for the non-real time radio bearer in question
UE is in CELL_DCH state and the allocated bit rate is lower than the maximum bit rate for the radio bearer in question
In the CELL_FACH state the UE uses RACH as an uplink transport channel
TCTV measurement measures the total sum of buffer occupancies of all radio bearers multiplexed onto the RACH
Low and High bit rates
The parameters Uplink initial bit rate (InitialBitRateUL) and Downlink initial bit rate (InitialBitRateDL) define low uplink bit rate and low downlink bit rate respectively
When the UE is in soft handover, 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 radio bearer is 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 (fixed 512 bytes for 8 & 16 kbit/s)
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
Traffic volume measurement reporting event (UL)
If the UE does not receive dedicated channel allocation nor bit rate upgrade (RRC message)
It resends the traffic volume measurement report to the network after Uplink traffic volume measurement pending time after trigger (TrafVolPendingTimeUL)
time
Traffic volume measurement (DL, RNC)
The RNC performs traffic volume measurements for each uplink non-real time radio bearer when:
UE is in CELL_FACH state
UE is in CELL_DCH state but dedicated channel is not allocated for the non-real time radio bearer in question
UE is in CELL_DCH state and the allocated bit rate is lower than the maximum bit rate for the radio bearer in question
In the CELL_FACH state the UE has FACH as an downlink transport channel
DL TCTV measurement measures the total sum of buffer occupancies of
All user plane radio bearers
Signalling radio bearers SRB3 and SRB4
, multiplexed onto the FACH
Downlink traffic volume measurement reports are RNC internal messages
The reporting criteria are sent from L3 to the MAC entities when the entity is initialised or when the parameters are modified
Traffic volume measurements are sent to higher layers as follows
In CELL_FACH
TCTV of NRT RB x > 0 bytes
In CELL_DCH with allocated bit rate is lower than maximum bit rate for NRT RB x
TCTV of NRT RB x > TrafVolThresholdDLHigh (fixed 512 bytes for 8 & 16 kbit/s)
If the UE does not receive a DCH allocation or bit rate upgrade, UE specific entity within the RNC reports the traffic volume measurement again after a time period defined by TrafVolPendingTimeDL
Capacity request types
The traffic volume measurement reports are classified into the following three types of capacity request:
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 dedicated channel allocated
Current state
CELL_DCH
CELL_DCH
Only BOSRB1 or BOSRB2 > 0 (Only RRC signalling)
UL: Capacity request rejected DL: MAC does not send any capacity request
CELL_FACH
CELL_DCH
Capacity request for DCH allocation
CELL_DCH
Higher than zero but lower than maximum bit rate DCH allocation for the RB
Capacity request for DCH bit rate upgrade
CELL_DCH
Uplink traffic volume measurement reports
Uplink traffic volume measurement reports are included in RRC: MEASUREMENT REPORT messages. Traffic volume measurement reports from the UE are handled as uplink capacity requests in the RNC. The actions that the RNC takes on the basis of these reports depend on a number of factors
Downlink traffic volume measurement reports
Downlink traffic volume measurement reports are RNC internal messages. Traffic volume measurement reports from the MAC-layer are handled as downlink capacity requests in the RNC. The actions that the RNC takes on the basis of these reports depend on a number of factors:
RNC: TrafVolThresholdULLow
This parameter is sent to the UE using an RRC: MEASUREMENT CONTROL message.
default value: 128 bytes; range: 8 bytes, 16 bytes, 32 bytes, 64 bytes, 128 bytes, 256 bytes, 512 bytes, 1024 bytes (1 KB)
RNC: TrafVolThresholdULHigh
The parameter is sent to the UE using the RRC: MEASUREMENT CONTROL message.
default value: 1024 bytes; range: 8 bytes (0), 16 bytes (1), 32 bytes (2), 64 bytes (3), 128 bytes (4), 256 bytes (5), 512 bytes (6), 1024 bytes. 1 KB (7), 2048 bytes. 2 KB (8), 3072 bytes. 3 KB (9), 4096 bytes. 4 KB (10), 6144 bytes. 6 KB (11), 8192 bytes. 8KB (12), 12288 bytes. 12 KB (13), 16384 bytes. 16 KB (14), 24576 bytes. 24 KB (15)
WCEL: TrafVolThresholdDLLow
default value: 128 bytes; range: 0 bytes, 8 bytes, 16 bytes, 32 bytes, 64 bytes, 128 bytes, 256 bytes, 512 bytes, 1024 bytes (1 KB)
RNC: TrafVolThresholdDLHigh
default value: 1024 bytes; range: 8 bytes (0), 16 bytes (1), 32 bytes (2), 64 bytes (3), 128 bytes (4), 256 bytes (5), 512 bytes (6), 1024 bytes. 1 KB (7), 2048 bytes. 2 KB (8), 3072 bytes. 3 KB (9), 4096 bytes. 4 KB (10), 6144 bytes. 6 KB (11), 8192 bytes. 8KB (12), 12288 bytes. 12 KB (13), 16384 bytes. 16 KB (14), 24576 bytes. 24 KB (15)
RNC: TrafVolPendingTimeUL
This parameter indicates the period of time, in seconds, during which it is forbidden to send any new traffic volume measurement reports with the same measurement ID, even if the triggering condition is fulfilled again
Parameter is sent to UE using an RRC: MEASUREMENT CONTROL message.
default value: 2000 ms; range: 250 ms, 500 ms, 1000 ms, 2000 ms, 4000 ms, 8000 ms, 16000 ms
Note: The same value should be set in all cells within a Node B
RNC: TrafVolTimeToTriggerUL
Defines, in ms, the period of time between the timing of event detection and the timing of sending a traffic volume measurement report.
This parameter is sent to the UE using an RRC: MEASUREMENT CONTROL message.
default value: 0 ms; range: 0 ms, 10 ms, 20 ms, 40 ms, 60 ms, 80 ms, 100 ms, 120 ms, 160 ms, 200 ms, 240 ms, 320 ms, 640 ms, 1280 ms, 2560 ms, 5000 ms
RNC: TrafVolTimeToTriggerDL
Defines, in ms, the period of time between the timing of event detection and the timing of sending a downlink capacity request
default value: 0 ms; range: 0 ms, 10 ms, 20 ms, 40 ms, 60 ms, 80 ms, 100 ms, 120 ms, 160 ms, 200 ms, 240 ms, 320 ms, 640 ms, 1280 ms, 2560 ms, 5000 ms
RNC: TrafVolPendingTimeDL
This parameter indicates the period of time, in ms, during which it is forbidden to send any new downlink capacity requests with the same RB id, even if the triggering condition is fulfilled again
TFCS construction
TFCS construction
There are transport format sets (TFS) for each dedicated channel (DCH) allocated to the UE
The UE-specific packet scheduler produces transport format set subsets based on the scheduled bit rates provided by the cell-specific packet scheduler and selected intermediate bit rates
On the basis of these transport format subsets, the UE- specific packet scheduler produces a transport format combination set (TFCS)
The uplink and downlink transport format sets and transport format combination sets produced by the UE-specific packet scheduler are delivered to
MAC layer of the RNC
MAC layer of the UE (RRC: Radio Bearer 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
Bit rate selection
Operator can define the maximum allowed uplink 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 and 128 kbits/s in UL direction and 0, 8, 64, 128 and 384 kbits/s in DL direction
When admission control and packet scheduler 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
TFCS construction
Feature working in parallel with good old inactivity timers
For Interactive / Background services
low utilization of resources
3 different thresholds defined
Target to control the 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 the to meet the actual utilisation, that is, the used bit rate of the DCH
Lowly utilised DCH allocations downgraded or released
Utilisation is measured as average throughput
This feature decreases significantly the capacity loss caused by too high bit rate allocations in the network
BTS HW, transmission and downlink spreading code capacity mainly
Motivation
Activation of the feature using bit string:
Feature can be “on” or “off” separately for
Interactive and Background service classes taking into account
Traffic Handling Priority (THP) from QoS parameters:
RNC: PSOpThroUsage default: 0 0 0 0 (by default feature is “off” for non-GBR services)
Interactive class THP = 1
Interactive classe THP = 2
Interactive classe THP = 3
L2 MAC
DCH is released – FACH allocated
Parameters introduced to control the downgrade/release of DCH
avg. L2 throughput
TFCS construction
The flexible upgrade of the NRT DCH data rate
Algorithm for upgrading the NRT DCH bit rate from any bit rate up to the maximum bit rate of the radio bearer
The usage of the feature is controlled with the RNW configuration parameter RNC: FlexUpgrUsage
‘On’ = Flexible upgrade of the NRT data rate is applied
High bit rate upgrades allowed from any data rate to the maximum allowed bit rate of the radio bearer AND also high throughput indication is received
‘Off’ = Flexible upgrade of the NRT data rate is not used
Bit rate upgrades are only allowed from low (initial or lower) data rate
Algorithm is based on uplink and downlink
Traffic volume measurements (TVM) Trigger upgrade algorithm
High throughput measurements Allow upgrade
Flexible upgrade of the NRT DCH data rate is allowed only if
The high throughput measurement information indicates high throughput
The dedicated channel upgrade can only be done if at least the initial bit rate has been allocated to all queued capacity requests and there is spare capacity to schedule. The dedicated channel upgrade procedure is performed in CELL_DCH state and it requires the reconfiguration of radio link, transmission and RNC internal resources.
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 the basis of the RNC: TrafVolThresholdULHighBitRate or TrafVolThresholdDLHighBitRate parameter
Structured parameter: Values for 8, 16, 32, 64, 128, 256 kbit/s
NRT DCH bit rate used as a reading parameter
High throughput measurement
The high throughput measurement is performed by the MAC-d entity of the RNC
When the NRT DCH throughput exceeds the High threshold
MAC-d entity of the RNC sends the high throughput indication to the UE-specific PS
Window size and time to trigger are common parameters for both uplink and downlink directions:
Window size: RNC: DCHUtilHighAveWin
Default value is 1 sec (1000 ms)
The special value 0 means that high throughput measurement is not active
Time to trigger: RNC: DCHutilHighTimeToTrigger
Default value is 0.2 sec (200 ms)
High threshold value = Current NRT DCH bit rate *
(1 – DCHutilHighBelowNRTDataRateThr )
RNC: DCHutilHighBelowNRTDataRateThr is common for UL/DL and all bit rates
Default 6 % (range 0 - 30 %)
Flexible upgrade of the NRT DCH - Example
This example presents the process to upgrade the NRT DCH data rate in downlink from the initial bit rate to the high bit rate and finally to the maximum allowed bit rate
Data amount in the RLC buffer exceeds the threshold TrafVolThresholdULLow
UE sends the traffic volume measurement report to the UE-specific PS in L3
Based on the traffic volume measurement report, the UE-specific PS sends the capacity request to the cell specific PS of RNC.
The cell-specific PS makes the required admission control actions including power change estimation. Average value of downlink transmission power is used
The cell-specific PS allocates the initial bit rate
The UE-specific PS modifies the traffic volume measurement by replacing the parameter TrafVolThresholdDLLow with the parameter TrafVolThresholdDLHighBitRate (64 kbit/s)
Data amount in the RLC buffer exceeds the threshold TrafVolThresholdDLHighBitRate
MAC-d entity of the RNC sends the traffic volume measurement report to the UE-specific PS as an upgrade request
The UE-specific PS forwards the upgrade request to the cell-specific PS
Cell-specific PS which tries to allocate the maximum allowed bit rate (In the example, congestion is met and a lower than maximum allowed bit rate is allocated)
The traffic volume measurement is modified to TrafVolThresholdDLHighBitRate (128 kbit/s)
Finally the upgrade to the maximum allowed bit rate succeeds
UE-specific PS stops the traffic volume measurement of the upgraded NRT DCH
High throughput indication checked by UE-specific PS before upgrade request sent to cell-specific PS
256
TimetoTrigger
384
128
64
32
Default: 6%
512
Default: 1000 ms
RNC: DCHUtilHighTimeTo Trigger
Default: 200 ms
MAC-d
entity
1
2
3
4
5
HSDPA and Throughput-based optimisation/Flexible upgrade
RNC: DynUsageHSDPAReturnChannel parameter is used to switch "On" and "Off" the Flexible Upgrade of NRT Data Rate and Throughput Based Optimisation of the PS Algorithm feature used for UL NRT DCH HSDPA return channel
When the parameter is set "On", use of the above mentioned features to UL NRT DCH HSDPA return channel is allowed
When the parameter is set "Off", use of the above mentioned features to UL NRT DCH HSDPA return channel is forbidden
TFCS construction
Dynamic Link optimisation (DyLo) for NRT Traffic Coverage
Cell coverage area is typically planned for AMR and/or low data rate service
High DL RB data rates can not be sustained over the coverage area due to RL power limitation of BTS
Solution to decrease RB bit rate when near the power limitation Dynamic Link Optimisation
Maximum RL power defined by Admission Control
DL power allocation
DLORLAveragingWindowSize parameter can be used to activate/configure the sliding window averaging of the dedicated RL transmission power measurement received from BTS
In the uplink direction, the UE reconfigures the radio link independently of the network
No need for a corresponding link optimisation in the uplink direction.
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
time
PtxRL
distance
Ptxave
Ptxmax
Offset
Ptxave is averaged radio link power, measured and reported to RNC by BTS and averaged in RNC over DLORLAveragingWindowSize
Ptxmax is determined by admission control
The offset is defined by DLOptimisationPwrOffset
Dynamic link optimization is triggered if
Ptxave + DLOptimisationPwrOffset > Ptxmax
DyLO is not possible during compressed mode
DyLO is possible for NRT DCH allocations that have lasted at least DLOptimisationProhibitTime
Highest bit rate background bearer first, selected randomly if same
DLOptimisationUsage = 1 SF is doubled
DLOptimisationUsage = 2 SF is quadrupled
Additional puncturing is not allowed
DyLO cannot reduce bit rate below the MinAllowedBitRateDL

Requirements OK (min allowed bitrate, SF, puncturing)
Reduce DCH bitrate(s)
Reconfiguration not possible
Compressed Mode active
Selection of the dedicated channel to be downgraded
NRT DCHs to be downgraded are selected according to the following order
Bit rate of background class dedicated channels are decreased
In the case of several dedicated channels of the background class, the owner of the highest bit rate is reconfigured.
Bit rate of the interactive class dedicated channels are decreased
In the case of several dedicated channels of the Interactive class, the traffic handling priority of the dedicated channel determines the reconfiguration order
If downgrading to MinAllowedBitRateDL is not enough to fulfil the spreading factor (SF) requirement, a part or all of the DCHs can be downgraded to 0 kbps
RT + NRT multi-RAB
All the NRT DCH(s) can be downgraded to 0 kbps if needed to fulfill the SF requirement
NRT RAB(s) only
At least one NRT DCH is left allocated, all cannot be downgraded to 0 bit rate
Bit Rate Upgrade
Bit rate upgrade is based on downlink traffic volume measurement reports (capacity requests):
The change of the radio link power conditions does not trigger upgrade
Normal PS bit rate allocation and upgrade methods applied (e.g Flexible Upgrade)
Possible triggering of the DyLO is checked before the bit rate is upgraded, in order to avoid ping-pong effect:
New Ptx, max is calculated by AC according to the new requested bit rate
Initial Tx power Ptx, init is calculated by AC according to the new requested bit rate
DyLO is possible if:
Ptx, init < (Ptx, max – (Offset +1.5dB )
if inequality is not valid, the next lower bit rate is tried.
The second comparison is made if the used bit rate has been decreased because of Dylo in that specific cell previously.
Compressed mode
DyLO is not allowed during the compressed mode measurements
Dylo can be started only if the current bit rate is higher than WCEL: HHoMaxAllowedBitRate (enable compressed mode due to DL power)
Parameter minimum value is 32 kbps
Defines absolute minimum bitrate where DyLo can downgrade, even if the parameter WCEL: MinAllowedBitRateDL has lower (8 or 16 kbps) value
RNC: DLOptimisationUsage
0 (Feature is not activated), 1 (Feature is activated with SF step 1), 2 (Feature is activated with SF step 2)
Default value: 1 (hidden set at 1 pre RAS05.1)
WBTS: DLORLAveragingWindowSize (New in RAS05.1)
Range and step: 1..10, step 1
Default value: 0
Range and step: 0..6 dB, step 0.1 dB
Default value: 2 dB (hidden set at 2 dB pre RAS05.1)
RNC: DLOptimisationProhibitTime
Range and step: 0..120 s, step 1 s
Default value: 2 s (Guard time fixed 2 s pre RAS05.1)
WCEL: MinAllowedBitRateDL
WCEL: HHoMaxAllowedBitRate
WCEL: PtxDLAbsMax
WBTS: PtxDPCHmax
Immediate Scheduling
If the cell has no other Capacity Request in the PS scheduling queue, the actual
request is scheduled immediately – PS does not wait for periodic trigger.
Periodic Scheduling
The received PS NRT DCH resource requests are scheduled in regular intervals. The resource requests are queued for the next scheduling moment.
The regular interval can be controlled with parameter [WBTS] SchedulingPeriod.
Range and Step: [50..2000 ms], step 50 ms default = 100ms
Cell-based load information
Load control in the RNC provides periodical load information on cell basis to the cell-specific packet scheduler.
These information include BTS measurements and estimations made by load control.
Also includes part of Streaming services.
The cell based load information are described in the table aside.
Averaging can be configured
Cell-load measurements with HSUPA
BTS is able to measure and report the interference power share of the E-DCH users LEDCH,CELL together with the received total wideband interference power PrxTotal of the cell where HSUPA has been configured.
LEDCH,CELL is included in the HSUPA Measurement Information IE of the Radio Resource Measurement Report which the BTS sends to the CRNC.
Measurement period of the LEDCH,CELL measurement is equal to what one BTS uses for the PrxTotal measurement.
The CRNC uses LEDCH,CELL to produce the value of the total received non-EDCH intereference power, PrxNonEDCH.
PrxNonEDCH = (1 – LEDCH,CELL) * PrxTotal
Cell-load measurements with HSUPA
RRM of the CRNC uses PrxNonEDCH instead of the PrxTotal for the power-based resource management of the uplink DCHs in the cell where HSUPA has been configured.
LC keeps updated also the uplink DCH own cell load factor, LDCH,CELL., which represents the received power share of all DPCH users in the cell.
LC keeps updated also the uplink NRT DCH own cell load factor LnrtDCH,CELL of all NRT DCH users of the cell. Both active and inactive NRT DCHs are included.
LC keeps updated also the active uplink NRT DCH own cell load factor LactiveDCH,NRT, which is produced in a similar way as LnrtDCH,CELL is done but only the active NRT DCHs are included in it.
Averaged PrxTotal and PtxTotal estimations are used by PS.
PSAveragingWindowSize is a BTS specific RNC configuration parameter that defines the averaging window size for the estimated received wideband power and estimated transmit power samples for the scheduling of DCH resources. Similar conc
PrxTotal used in PS estimations is averaged using the following formula:
where:
Prx_total j are the samples of the estimated received wideband power at the previous
scheduling moments.
Prx_Total is the sample of estimated received wideband power at the moment t when the resource request is scheduled (immediate or periodic)
N= PSAveragingWindowSize
WBTS: PSAveragingWindowSize
This parameter determines the uplink and downlink load measurement averaging window sizes in number of the scheduling periods for packet scheduling. This window is used in averaging the estimated received wide power sample values and estimated transmitted carrier power values for packet scheduling of the NRT DCH resources. The sliding type window is used: the oldest sample value of the estimated power is removed when a new one is drawn.
default value: 4; range: 1 ... 20 , step 1
PrxnonHSUPA averaging window size for LC
PSAveragingWindowSize defines the size of the averaging window also for PrxNonEDCH in the HSUPA cell, when measurements need to be averaged for UL NRT DCH scheduling.
Different averaging criteria can be used instead when the PrxNonEDCH measurements are averaged for UL NRT DCH overload control algorithm
WinLCHSDPA defines then the averaging window size
PtxnonHSDPA averaging window size for LC
This parameter defines the averaging window size for the estimated transmitted non HSPA carrier power. The window size is used for averaging the estimated Transmitted carrier power of all codes not used for HS-PDSCH, HS-SCCH, E-AGCH, E-RGCH or E-HICH transmission (PtxNonHSPA) in the downlink DCH overload control. The window size is defined in the number of the scheduling periods. Arithmetic mean value of the samples is calculated. The sliding type window is used: the oldest sample value of the estimated power is removed when a new one is drawn.
WBTS: WinLCHSDPA
Default value: 5
Tx power of radio link averaging window size for PS
The cell-specific packet scheduler can use the averaged DPDCH code power of radio link (Ptx_average) in estimation of the power change in case of NRT DCH bit rate upgrade and in case of NRT DCH bit rate downgrade due to overload
To avoid a ping-pong effect when downlink radio link power varies
WBTS: PSRLAveragingWindowSize defines how many radio link specific measurement results of the average transmission power of the DPDCH bits (Ptx_average,) are included in the sliding window used in the averaging of the cell-specific PS for calculation of power change for up- or downgrade
Range and step: 1..10, step 1
Default value: 0
Default value notes: The recommended value is 4 when the radio link/dedicated measurement period is 500 ms
Note: Reporting is not periodic due to Report filtering
Processing of Capacity Request
There are separate queues for uplink and downlink capacity request messages.
If the packet scheduler is not able to allocate capacity requests for every radio bearer, these un-full-filled requests remain in the queue.
There is a time limit how long the request can stay in the queue
This limit is set by using RNC configuration parameters CrQueuingTimeUL and CrQueuingTimeDL, separately for uplink and downlink.
When the limit is exceeded for the certain capacity request, it is permanently removed from the queue.
New capacity request is then required when allocation is needed for that bearer
CrQueuingTimeUL and CrQueuingTimeDL parameters are related to the parameters TrafVolPendingTimeUL and TrafVolPendingTimeDL, which define the time between consecutive capacity requests
These parameters should be set accordingly
No
Yes
No
Modify the content type of the original capacity request in a queue
Delete the new capacity request
Yes
to the queue
Capacity request for same NRT RB already in a queue?
Is new capacity request same as original?
(A)
(B)
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
Priority for Streaming traffic class with ARP1/2/3
PriForStreamARP1/2/3 (RNC) (0..15) ( = 1) (13/13/13)
Priority for Interactive TC with THP 1 and 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: CrQueuingTimeUL
Defines how long an uplink capacity request can stay in the queue before it is permanently removed
default value: 4 sec; range: 1 ... 30 sec; step 1 sec
RNC: TrafVolPendingTimeUL
This parameter indicates the period of time, in seconds, during which it is forbidden to send any new traffic volume measurement reports with the same measurement ID, even if the triggering condition is fulfilled again. Parameter is sent to UE using an RRC: SYSTEM INFORMATION or an RRC: MEASUREMENT CONTROL message
default value 2000 ms; range: 250 ms, 500 ms, 1000 ms, 2000 ms, 4000 ms, 8000 ms, 16000 ms
RNC: CrQueuingTimeDL
Defines how long an downlink capacity request can stay in the queue before it is permanently removed.
default value:4 sec; range: 1 ... 30 sec; step 1 sec
RNC: TrafVolPendingTimeDL
This parameter indicates the period of time, in milliseconds, during which it is forbidden to send any new downlink capacity requests with the same RB id, even if the triggering condition is fulfilled again.
Uplink Channel Type Selection (with HSUPA)
The HSUPA channel type selection feature determines the optimal uplink transport channel for the user (RACH, DCH or E-DCH).
The main input for the channel type selection is the traffic volume measurement, which the MAC layer of the the UE performs for each NRT RB.
The result of the traffic volume measurement is handled in the PS as a capacity allocation request (for example, as a request for DCH or E-DCH).
It is possible to allocate uplink E-DCH only in conjunction with downlink HS-DSCH.
If the allocation of HS-DSCH in downlink is not possible, the packet scheduler tries to allocate the DCH in both uplink and downlink.
The HSDPA channel type selection feature determines the optimal downlink transport channel for the user (FACH, DCH or HS-DSCH).
The UE-specific packet scheduler (PS) performs the channel selection.
The main input for channel selection is the traffic volume measurement, which the MAC layer of the RNC performs for each NRT RB.
The result of the traffic volume measurement is handled in the PS as a capacity allocation request (for example, as a request for a DCH or HS-DSCH).
Downlink Channel Type Selection (with HSDPA)
Channel Type Selection – FACH and 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 and hystersis parameters exist.
Request DCH/HS-DSCH from PS
Initial transmission on FACH
DL Traffic Type Selection
Dedicated channel is selected and a downlink capacity request is sent to the packet scheduler if:
A) The sum load of RLC buffers of each radio bearer, SRB3 and SRB4 is greater than the value set by Downlink traffic volume measurement low threshold (TrafVolThresholdDLLow). SRB1 and SRB 2 data do not trigger capacity request.
B) Buffer status in FACH scheduling buffer is greater than the value set by Maximum allowed total data amount on FACH (FachDataAllowedTotal)
C) FACH is in overload when FACH load exceeds FachLoadThresholdCCH. FACH usage is possible again when the FACH load is decreased under threshold by margin FachLoadMarginCCH.
D) FACH usage is forbidden by PS when RACH load exceeds RachLoadThresholdCCH or when PtxTotal exceeds PtxThresholdCCH. When one or both of the conditions are fulfilled, PS indicates that FACH usage is forbidden. FACH usage is possible again when the RACH load and PtxTotal are decreased below thresholds set by margins RachLoadMarginCCH and PtxMarginCCH.
The reason why the total transmission power is checked is that, from the interference point of view, it is less efficient to use the FACH (no closed loop power control) than a dedicated channel.
WCEL: FachLoadThresholdCCH
The threshold for the total load of SCCPCH (FACH/PCH) channel for downlink channel type selection. If the threshold is exceeded, DCH is allocated
default value: 75%; range: 0 ... 100%; step 1%
WCEL: FachLoadMarginCCH
The margin for the total load of SCCPCH (FACH/PCH) for downlink channel type selection. When the measured load is below the threshold by at least this margin, FACH usage is possible
WCEL: RachLoadThresholdCCH
The threshold for the total load of RACH channel for uplink channel type selection. If the threshold is exceeded, DCH is allocated
WCEL: RachLoadMarginCCH
The margin for the RACH load for downlink channel type selection
When the measured load is below the set threshold by this margin, FACH usage is possible
WCEL: PtxThresholdCCH
This is the threshold for the total downlink transmission power for downlink channel type selection
If the threshold is exceeded, a DCH is allocated. Assumption here is that a DCH is more efficient than a FACH, due to fast power control.
Relative to PtxTarget
default value: -1 dB; range: -5 ... 0 dB; step 0.1 dB
WCEL: PtxMarginCCH
The margin for the total downlink transmission power for downlink channel type selection
When the measured load is below the threshold by this margin, FACH usage is possible
default value: 0.5dB; range: 0 ... 2 dB; step 0.1 dB
Channel type selection (UPDATE)
Power Budget for Packet Scheduling
In uplink direction the current total received interference power of a cell (PrxTotal) can be expressed as the sum of the non-controllable power (PrxNc), semi-controllable power Prx(SC) and the controllable power (PrxNrt).
PrxNc consists of the powers of real-time users, other-cell users and noise.
PrxNrt consists of the powers influenced by PS
PrxSC PS Streaming services
In downlink direction the current total transmitted power of a cell (PtxTotal) can be expressed as the sum of the non-controllable power (PtxNc), semi-controllable power (PtxScRT) and the controllable power, which is caused by NRT traffic (PtxNrt).
The controllable power is used for NRT users on best effort basis by the packet scheduler.
The power available for best effort NRT traffic is the load target subtracted by the non-controllable power.
The semi-controllable power is part from streaming services
The bit rate allocation algorithm includes load increase and load decrease algorithms, which are the same in both uplink and downlink directions
PrxAllowed and PtxAllowed must be calculated by using:
where
PrxTotal is the averaged value for estimated received wideband power
PrxRtInactive is the estimated received power of admitted RT bearers, which are not active yet because establishment phase is still ongoing.
PrxNRTInactive is the 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’.
Target threshold for power budget scheduling
Target threshold (PrxTarget and PtxTarget , separately for the uplink and downlink) define the optimal operating point of the cell load, up to which the packet scheduler and admission control can operate normally.
In case of HSPA allocations
other parameters become
Power Budget for UL packet scheduling with HSUPA
In the case of dynamic sharing of the received intereference between the HSPA and the DCH users, if there is at least one E-DCH MAC-d flow established in the cell, the PrxNonEDCH measurement and the dynamically adjusted target threshold PrxTargetPS are applied in the NRT uplink power budget calculation instead of PrxTotal and PrxTarget.
Power Budget for DL packet scheduling with HSDPA
In the case of HSDPA Dynamic Resource Allocation, if there is at least one HS-DSCH MAC-d flow allocated in the cell, the PtxNonHSDPA measurement and the dynamically adjusted target threshold PtxTargetPS are used in the downlink NRT power budget calculation instead of PtxTotal and PtxTarget.
When using the HSDPA Static Resource Allocation, PtxTargetHSDPA and PtxOffsetHSDPA are used instead of PtxTarget and PtxOffset.
Non-HSDPA transmitted power (Transmitted carrier power of all codes not used for HS-PDSCH or HS-SCCH transmission) is used instead of total transmitted power in:
Downlink channel type selection between FACH and DCH
DL packet scheduling
DL overload control
Power allocation – Initial bit rate allocation & Bit rate upgrade
For each capacity request, PrxNrtNew and PtxNrtNew are calculated based on the new or bitrate increase (to be scheduled) radio bearer Eb/No requirement (bitrate requirement):
where: Prx/tx_total_change is the power change estimation.
Please see Admission Control session for more information on Power Increase (PIE) and
Power Decrease (PDE) calculations
Channel type selection (UPDATE)
Scheduling targets - Uplink
Packet Scheduler applies scheduling targets (similar to RT Admission Control) to ensure that existing services do not experience quality degradations
ΔL is the portion of new scheduled load
v - Activity Factors can be set with RRM Parameters
Calculations of load change follow same formulas used in Admission Control (PIE, PDE)
Decrease loading
Increase loading
Priority scheduling
Bit Rate Allocation in UL- Overview
PrxAllowed is the UL power budget.
the minimum and maximum available UL load in the UL DCH scheduling.
Decrease loading
Increase loading
Priority scheduling
Minimum available uplink load Lallowed_minDCH in the uplink DCH
scheduling
Calculation of minimum available UL load in the UL DCH scheduling
Where LMinDCH defines the minimum guaranteed uplink DCH load threshold:
RDCHWPSMin is the value of the Interference margin for the minimum UL DCH load (PrxLoadMarginDCH) management parameter transformed into the linear notation.
PrxLoadMarginDCH:
LminDCH 0.37
Rationale for minimum UL load for scheduling
Operator is provided with PrxLoadMarginDCH management parameter to define for the uplink DCH resource allocation the minimum total uplink throughput of the cell to guarantee the minimum nominal data rate for the uplink DCH users though there was interference spiking in the cell.
If the uplink DCH traffic level of the cell is low then the source of the interference is considered to be outside of the cell and the uplink DCH resources are allocated without any interference estimates. When the own cell throughput exceeds a particular level, the interference estimations are initiated and the planned interference target is applied in the uplink DCH resource allocations.
Quantity Lallowed_minDCH defines the uplink throughput, which is available in the uplink DCH scheduling regardless of the value of UL power budget Prx_allowed.
Calculation of maximum available UL load in the UL DCH scheduling
Where LMaxDCH defines the planned target for the maximum uplink DCH load of the cell:
RDCHWPSMax is the value of the Interference margin for the maximum UL DCH load (PrxLoadMarginMaxDCH) management parameter transformed into the linear notation
PrxLoadMarginMaxDCH:
Rationale for maximum UL load for scheduling
Overestimation of the noise power level of a cell may lead to the situation when too much uplink DCH traffic is admitted in the cell. Interference thresholds, which are used in the uplink DCH resource allocation, are defined in the relation to the noise power level and therefore may trigger too late.
Excess interference is experienced in the own cell and the adjacent cells. Uplink coverage and network stability may suffer.
A cell level throughput-based upper limit is introduced, PrxLoadMarginMaxDCH management parameter,for the uplink DCH traffic against the overestimation in the noise power level.
Limit value is possible to be set with a management parameter.
Quantity Lallowed_maxDCH defines defines the maximum uplink total DCH throughput, which is allowed in the uplink DCH scheduling.
The basic idea of the packet scheduling method is:
(PS 1) When DCH is not allocated for NRT RB and packet scheduler receives an UL capacity request 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 packet scheduler receives a DL capacity request where low data amount is reported, it allocates initial bit rate in both directions.
AC
PS1
PS2
PS3
PS4
PS5
Maximum bit rate allocation
(PS 1) When DCH is not allocated for NRT RB and packet scheduler receives an UL capacity request 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 packet scheduler receives a DL capacity request 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 packet scheduler receives a capacity request 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
PtxAllowed (PtxTotalNew) > 0
Expression:
Lallowed_min_DCH (LnewDCH,CELL) ≥ 0
Where:
Lallowed_min_DCH = LminDCH – LnewDCH,CELL
Lallowed_max_DCH = LmaxDCH – LnewDCH,CELL
WCEL: DeltaPrxMaxUp
Defines the maximum received uplink power increase in a cell, used when bit rates are allocated or increased by the packet scheduler, relative to PrxTotal
default value: 1.2dB; range: 0 ... 5 dB, step 0.2 dB
WCEL: DeltaPtxMaxUp
Defines the maximum transmitted downlink power increase in a cell, used when bit rates are allocated or increased by the packet scheduler, relative to PtxTotal
Step 1
Step 2
Step 3
Step 4
128 (1)
Step 5
Target exceeded, allocation according to Step 4, check against DyLO is made
For new or modified allocated radio link:
The maximum Ptx,max and initial Ptx_initial transmit power of the upgraded bit rate are calculated.
Then, it is checked that:
Ptx_initial < Ptx,max – 2 dB (Dylo offset)
For reconfigured radio link
The maximum Ptx,max power and power increase of the upgraded bit rate Ptx is calculated
It is checked that
where Ptx_average is the dedicated RL measurement from BTS
This 2 dB is subtracted from Ptx,max because of dynamic link optimisation feature.
Overload Control
If the load is 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:
In the uplink direction the transport format combination control (TFCC) RRC procedure is used
DL:
Overload Control Methods, UL
When the packet scheduler has detected an overload situation in the uplink, it:
Reduces power by reducing the scheduled throughput schedules a subset of the original transport format combination set (TFCS)
Requests the RRC signalling entity of RNC to initiate the transport format combination control (TFCC) procedure.
The RRC signalling entity sends an RRC: TRANSPORT FORMAT COMBINATION CONTROL message to the UE on a dedicated channel.
Overload Control Methods, DL
When the packet scheduler has detected an overload situation in downlink it:
Selects Enhanced overload control if it is activated
OR
Schedules a subset of the original transport format combination set
Reconfigures the L2 by sending the transport format combination subset to the UE-specific MAC-d entity of the RNC
After transport format combination control procedure or TFC Subset method once the overload situation is over, the system automatically reverts to the original transport format combination set using the same procedure.
The selection of the radio bearer to be downgraded
The selection of the radio bearers, whose bit rates have to be decreased, is done based on
QoS priority value (lowest priority)
Connection allocation time (longest allocation time)
Bit rate (highest bit rate)
UL Load decrease algorithm
If every lower priority bearer has been already downgraded or released.
Candidate selection
DL Load decrease algorithm
If every lower priority bearer has been already downgraded or released.
Candidate selection
384
PrxTarget
PrxTarget
128
128
128
Step 2: 256 -> 128(TFCC)
Allocation according to step 4
new and old : the planned Eb/N0 values for the modified RB ; new Eb/N0 (new) value and old Eb/N0 (old) value
Rnew and Rold : bit rates, new being the current bitrate in the load increase/decrease algorithm
Ptx_average,RL : radio link average transmission power, which reported to RNC by BTS
WBTS: LoadControlPeriodPS
Defines how often PS can perform load control actions for each bearer.
default value: 2000ms; range: 100 ... 2000 ms, step 100 ms
Note: The value must not be smaller than scheduling period.
WCEL: DeltaPtxMaxDown
Defines the maximum transmitted downlink power decrease in a cell, used when bit rates are decreased by the packet scheduler, relative to PtxTotal.
WCEL: DeltaPrxMaxDown
Defines the maximum received uplink power decrease in a cell, used when bit rates are decreased by the packet scheduler, relative to PrxTotal.
Overload Control Methods – TFCC procedure in UL
When PS has detected the overload situation in downlink and scheduled a subset from the original TFCS, it reconfigures the L2 by sending the TFC subset to the UE specific MAC-d entity of RNC. After the procedure data transmission can begin using TFC subset.
The original TFCS is taken into use using the same procedure, when the overload situation is over.
BTS
RNC-L2
RNC-NBAP
RNC-RRM
packet scheduling

UE in CELL_DCH state
Candidate selection
Allowed when OCdlNrtDCHgrantedMinAllocT is other than 60 sec (max value)
Range: 0…60 sec, step: 1 sec, default 60 sec (=off), recommended 10 sec, if activated
In Enhanced overload control method when the packet scheduler has detected the overload situation in downlink it
Modifies DCH bit rate and spreading factor
Reconfigures the L2 by sending the new transport format combination set to the UE specific MAC-d entity of RNC
RRC initiates Radio Bearer Reconfiguration procedure
The original bit rate of the DCH(s) is not automatically returned back to the DCH(s) once the overload situation is over
A new capacity request required Normal scheduling
Candidate selection
Bit Rate
Scheduling and
RRind Period
reconfiguration is not allowed
factor increased, RL
due to LoadControlPeriod timer
PtxTarget
128
256
256
128
128
128
128
128
128
128
128
128
128
128
128
256
new and old : the planned Eb/N0 values for the modified RB ; new Eb/N0 (new) value and old Eb/N0 (old) value
Rnew and Rold : bit rates, new being the current bitrate in the load increase/decrease algorithm
Ptx_average,RL : radio link average transmission power, which reported to RNC by BTS
OCdlNrtDCHgrantedMinAllocT defines whether it is possible to apply Enhanced overload control
If the DCH has been allocated longer than OCdlNrtDCHgrantedMinAllocT For that radio bearer the Enhanced overload control method is available
If the modified DCH allocation time is lower than OCdlNrtDCHgrantedMinAllocT TFC subset method is used
When overload is detected and dedicated channel is modified using TFC subset or Enhanced overload control method, it takes some time before the decrease in load (PrxTotal and PtxTotal) as can be seen in RNC from the RADIO RESOURCE INDICATION messages.
This delay may be longer than scheduling period and therefore it is necessary to wait that load control actions have effected, in order to prevent new unnecessary load control actions in the next scheduling period
The parameter LoadControlPeriodPS determines the period how often PS can perform load control actions
The feature Enhanced priority based scheduling (PBS) allows the operator to select alternative methods for the packet scheduling
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 priority based scheduling function
Downlink power
Uplink interference
Priority based scheduling operation is performed only for one capacity request in each scheduling period, i.e. for the first in queue
The priority based scheduling has no effect on the bit rate upgrades
RAB requesting capacity is not allowed to have existing NRT DCH allocation for the same radio bearer
The enhanced priority based scheduling function is not performed during the compressed mode
Minimum allocation time can be configured via parameters
Priority 1 (highest)
Priority 2
Interactive bearer
Priority 3
Interactive bearer
Priority 4 (lowest)
Defining priority based scheduling policy
The alternative methods for priority based scheduling are defined by RNW configuration parameter PBSpolicy
1: Priority based scheduling is not active
2: Higher traffic handling priority
RAB of the incoming capacity request must have higher traffic handling priority than the RAB of the DCH to be downgraded or released
3: Higher or equal traffic handling priority
RAB of the incoming capacity request must have higher or equal traffic handling priority than the RAB of the DCH to be downgraded or released
4: Higher or equal traffic handling priority (not traffic handling priority 1)
Same as 3, but DCHs of the RABs that have traffic handling priority 1 are excluded.
5: Any traffic handling priority
Any capacity request can cause downgrade or release of existing
6: Any traffic handling priority (not traffic handling priority 1)
Default: 1
Selection of the radio bearer(s) to be released or downgraded
The selection is based on comparison of the priority of the incoming capacity request (first capacity request in queue) to the priorities of the existing NRT radio bearers and the selected PBS policy
If there are more radio bearers with same priority and suitable to be selected to be downgraded than needed, an additional comparison will be made in the following order:
Cell uplink interference and downlink transmission power congestion:
RAB whose radio link power in downlink is closest to the maximum radio link power
RAB whose DCH maximum bit rate is highest
RAB whose DCH allocation time is longest
Downlink spreading code, BTS HW or Iub AAL2 transmission congestion:
RAB whose DCH maximum bit rate is highest
RAB whose DCH allocation time is longest
Enhanced priority based scheduling – Timers
Set of timers are applied to priority based scheduling operations in order to
Guarantee minimum total allocation time before downgrade or release due to PBS
Limit time between consecutive PBS operation to prevent frequent reconfigurations
The minimum total allocation time and time between PBS operations depend on comparison of the
Priority of the radio bearer to be released or downgraded
Priority of the incoming radio bearer
The minimum total allocation time is controlled by
PBSgrantedMinDCHallocThigherP
Priority of the radio bearer to be released or downgraded is higher than incoming
PBSgrantedMinDCHallocTequalP
Priority of the radio bearer to be released or downgraded is equal to incoming
PBSgrantedMinDCHallocTlowerP
Priority of the radio bearer to be released or downgraded is lower than incoming
The minimum time between PBS operations is defined respectively as
FactorMinPBSInterval * PBSgrantedMinDCHallocTxxxxP
PBSgrantedMinDCHallocThigherP
Default value: 30s
Default value: 20s
Default value: 15s
Default value: 0.2
AAL2 resource change req
AAL2 resource change resp
RRC: Radio Bearer Reconfiguration
Start Minimum Allocation Timer
PBS decision in RNC (PS)
New PS call
AAL2 resource change req
AAL2 resource change resp
RRC: Radio Bearer Reconfiguration
InitialAndMinAllowedBitrate allocated
taking away capacity..
providing gained capacity
to new user
Chapter 5
-Packet Scheduling-
Which channel types the PS selects based on traffic load and parameters?
Name the scenarios for the WCDMA packet access.
What are the advantages of the URA_PCH state?
What task does the cell specific part of the PS perform?
If RT RAB’s require temporarily the target transmission power of the node B, what will happen to the NRT RAB’s on the same node B at that time?
How the traffic volume measurements are sent to the UE?
What parameter will affect to the DyLo Operation ?
Florian Reymond
RAS06_v1.0
Minor corrections Minor change in Dylo Different UL scheduling process in RAS06 Packet Scheduler Interruption Timer is deleted from RAS06 onwards
Florian Reymond
UE in CELL_DCH state
RRM detects overload
situation in uplink
Tunable inactivity timer XXX
(ED2 CD05)
RAS05 Throughput based RB release XXX
RAS05.1 Throughput based RB
RAS05.1 Flexible upgrade XXX
Flexible upgrade of NRT DCH
Data Rate
Affected resourcesRAN/RAS

06_PacketScheduling_RU10

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