Minimum Rate Proportional Fair
Scheduler
Feature Description
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Contents
Contents
1
Overview
1
2
Dependencies
3
3
Feature Operation
5
4
Network Impact
7
5
Parameters
8
6
Performance
9
7
Activate the Feature
10
8
Deactivate the Feature
11
9
Engineering Guidelines
12
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Minimum Rate Proportional Fair Scheduler
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1
Minimum Rate Proportional Fair Scheduler
Overview
This feature enables higher throughput due to a trade off between user
fairness and system performance. In many scenarios, cell capacity can be
increased, and the feature enables consistent cell edge throughput.
Access Type:
Feature Identity:
Value Package Name:
Value Package Identity:
Node Type:
Licensing:
LTE
FAJ 121 0920
Differentiated Mobile Broadband
FAJ 801 0409
Baseband Radio Node
Licensed feature. One license for each node.
Summary
The Minimum Rate Proportional Fair Scheduler feature allows resource sharing
of RAN, RBS, and Baseband between different radio bearers. The feature
provides a trade off between user fairness and system performance. The feature
enables the network to benefit from times when the radio conditions are different
for users.
The benefits depend on the different algorithms. Compared to the Resource Fair
Scheduling algorithm, users with higher channel quality are prioritized. This
enables higher throughput and increased cell capacity in many scenarios. For
more information about Resource Fair Scheduling, see Advanced Differentiation
for Resource Fair Scheduling.
Fairness to scheduling is also provided. Average rate is considered during the
prioritization to avoid allocating few or no resources to users because of low
channel quality.
Flows with lower bit rates than the configured minimum bit rate are prioritized
before the flows that have bit rates above the configured minimum rate.
This minimum rate QoS configuration helps consistent cell edge throughput.
In addition, the throughput of CA-capable UEs over UEs without carrier
aggregation can be adjusted, if the CA-capable UEs have at least one secondary
cell activated for downlink data transmission.
Additional Information
More information about this feature and related topics can be found in the
following documentation:
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Minimum Rate Proportional Fair Scheduler
— QoS-Aware Scheduler
— Scheduler
— Advanced Differentiation for Resource Fair Scheduling
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2
Dependencies of Minimum Rate Proportional
Fair Scheduler
The feature has dependencies with QoS-Aware Scheduler and schedulingbased features.
Table 1
Feature Dependencies
Feature
Relationship
Description
QoS-Aware Scheduler (FAJ 121
0859)
Prerequisite
Changes to the parameters
QciProfileOperatorDefined.sche
dulingAlgorithm,
QciProfilePreDefined.dlMinBitR
ate, and
QciProfilePreDefined.ulMinBitR
ate take effect only if the service
state for QoS-Aware Scheduler is
operable.
Relative Priority Scheduling (FAJ 121
2037)
Related
The Minimum Rate Proportional Fair
Scheduler feature must be active for
the Relative Priority Scheduling
feature to be operational if the
QciProfilePredefined.schedulin
gAlgorithm attribute is set to one of
the following values:
— EQUAL_RATE
— PROPORTIONAL_FAIR_HIGH
— PROPORTIONAL_FAIR_MEDIUM
— PROPORTIONAL_FAIR_LOW
Scheduler (FAJ 121 1447)
Related
When there is no license available for
the Minimum Rate Proportional Fair
Scheduler feature, the system
scheduler sets to Resource Fair as
default.
When Minimum Rate Proportional
Fair Scheduler is used, it is not
recommended to use the Resource
Fair scheduling algorithm for any
QCI. The default bearers are
recommended to use Minimum Rate
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Minimum Rate Proportional Fair Scheduler
Feature
Relationship
Radio Resource Partitioning (FAJ 121 Related
4571)
Description
Proportional Fair Scheduler in this
case.
The gain from the Minimum Rate
Proportional Fair Scheduler feature
can decrease because of the
following limitations:
— The constraints enforced by the
configurations of partitions, that
is, the limited resources available
to partitions
— The distribution of UEs over
partitions in terms of the channel
conditions and the bitrate
requirements
Hardware
No specific hardware requirements.
Limitations
No known limitations.
Network Requirements
No specific network requirements.
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3
Feature Operation of Minimum Rate
Proportional Fair Scheduler
The Minimum Rate Proportional Fair Scheduler feature divides resources
among users based on a weighted measure of the monitored channel
quality and average rate.
The high level flow is active except that the scheduler is enabled to make
prioritization based on the estimated channel quality and average rate. For more
information about the high level flow for scheduling, see Scheduler.
Operational Process
The Minimum Rate Proportional Fair Scheduler feature is based on the scheduler
having an overview picture of the channel quality of the users in the cell and the
average rates of the user flows. Therefore, the scheduler monitors channel quality
from UE-reported CSI and measurements performed in the RBS. The average
rate of the flows is calculated based on the previous transmissions. When
resources are divided among users, the prioritization is based on a weighted
measure of the channel quality and the average rate.
Note:
The cell rate is only an estimated value.
Furthermore, the scheduler maintains a configured minimum bit rate of the flows.
If the average rate of a flow is lower than the configured value, the scheduler
prioritizes to assign radio resources to that flow. These flows are prioritized
according to their configured QCI priority. The flows that are above the
configured minimum rate are prioritized lower. For more information, see QoSAware Scheduler.
If the minimum bit rate is configured high or for too many users, or both, can
affect bearers without a minimum bit rate negatively.
It is not recommended to configure different bearers in the same cell with
proportional fair and resource fair scheduling algorithms. If the QCIs
corresponding to the different bearers are also configured to use absolute priority
and have different levels of priority, the two algorithms can be used in the same
cell. For absolute priority configuration, see QoS-Aware Scheduler.
For non-GBR QCIs, priorities are recommended to be set to the same levels of
priority in case non-zero minimum rates are used. This configuration enables
fairness between non-GBR bearers, because the absolute priority of one nonGBR bearer does not negatively affect another non-GBR bearer.
The way resources are allocated to selected users differs between the uplink and
downlink scheduler.
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Minimum Rate Proportional Fair Scheduler
Table 2
Flow Direction
Transmission Power
Scheduler
Downlink
eNodeB
Tries to schedule as few
users as possible to
reduce the load on the
control channels.
No restrictions on how
much power can be
allocated to one UE.
Uplink
UE
Tries to increase the total
transmission power by
multiplexing more users
in frequency.
If frequency-selective scheduling is used in the downlink, the behavior becomes
more like the uplink behavior. The downlink scheduler tries to exploit the
frequency diversity between users so that the total spectral efficiency can be
increased.
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4
Network Impact of Minimum Rate
Proportional Fair Scheduler
The algorithms available in the Minimum Rate Proportional Fair Scheduler
feature affect cell edge throughput and capacity differently.
Capacity and Performance
The Proportional Fair Medium algorithm gives optimal trade off at high load,
when the bandwith is shared between users. The high fairness settings offer
more emphasis on cell edge throughput. The low fairness variants offer more
emphasis on cell capacity.
Interfaces
No impact.
Other Network Elements
No impact.
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Minimum Rate Proportional Fair Scheduler
5
Parameters of Minimum Rate Proportional
Fair Scheduler
The feature introduces MOM attributes for scheduling rates.
Table 3
Parameters
Parameter
Type
Description
QciProfilePredefined
.ulMinBitRate
Introduced
Uplink minimum bit rate
The scheduler attempts to achieve minimum
bit rate for all bearers before giving any user
a higher rate. This parameter is only used if
one of the five Proportional Fair scheduling
algorithms is selected.
QciProfilePredefined
.dlMinBitRate
Introduced
Downlink minimum bit rate
The scheduler attempts to achieve minimum
bit rate for all bearers before giving any user
a higher rate. This parameter is only used if
one of the five Proportional Fair scheduling
algorithms is selected.
QciProfilePredefined
.schedulingAlgorithm
Introduced
The parameter specifies which scheduling
algorithm is to be used for a certain QCI.
CarrierAggregationFu
nction.caRateAdjustC
oeff
Introduced
The parameter adjusts the factor of CC rate
for CA-capable UEs, which is used in the
proportional fairness algorithm. A smaller
value gives a CA-capable UE a greater
advantage over non-CA UE. The parameter
acts based on the configured value,
according to the following:
—
Value 0 sets the rate as 0 and this is
for testing purpose only.
—
Values 1 – 4 set the rate as a
fraction of the cell rate in increased
order.
—
Values 6 – 9 set the rate as cell rate
plus rate influence from other CCs in
increased order.
—
Value 10 sets the rate as
aggregated rate of all CCs.
The parameter specifies which scheduling
algorithm is to be used for a certain QCI.
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Performance of Minimum Rate Proportional
Fair Scheduler
The Minimum Rate Proportional Fair Scheduler has KPIs and counters for
downlink and uplink throughput calculations.
KPIs
Table 4
KPIs
KPI
Description
Downlink Throughput
Data volume for each time unit in the downlink
The impact of the feature depends on the algorithm chosen.
Uplink Throughput
Data volume for each time unit in the uplink
The impact of the feature depends on the algorithm chosen.
More information can be found in Key Performance Indicators.
Counters
— EUtranCellFDD.pmRadioThpVolDl
— EUtranCellTDD.pmRadioThpVolDl
— EUtranCellFDD.pmRadioThpVolUl
— EUtranCellTDD.pmRadioThpVolUl
— EUtranCellFDD.pmRadioThpResDl
— EUtranCellTDD.pmRadioThpResDl
— EUtranCellFDD.pmRadioThpResUl
— EUtranCellTDD.pmRadioThpResUl
Events
This feature has no associated events.
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Minimum Rate Proportional Fair Scheduler
7
Activate Minimum Rate Proportional Fair
Scheduler
To use the feature, it must be activated following the usual feature
activation procedure.
Prerequisites
— The license key is installed in the node.
— Continuous Cell Trace Recording (CCTR) is activated since at least one week.
This ensures there is troubleshooting data available if something goes
wrong.
— The QoS-Aware Scheduler feature is activated.
Steps
1. Set the FeatureState.featureState attribute to ACTIVATED in the
FeatureState=CXC4011033 MO instance.
After This Task
Let the CCTR be active for one week, for continued collection of troubleshooting
data.
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Deactivate Minimum Rate Proportional Fair
Scheduler
If the feature is no longer needed, it can be deactivated following the usual
feature deactivation procedure. It must also be deactivated before the
activation of any conflicting feature.
Prerequisites
Continuous Cell Trace Recording (CCTR) is activated since at least one week. This
ensures there is troubleshooting data available if something goes wrong.
Steps
1. Set the FeatureState.featureState attribute to DEACTIVATED in the
FeatureState=CXC4011033 MO instance.
After This Task
Let the CCTR be active for one week, for continued collection of troubleshooting
data.
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Minimum Rate Proportional Fair Scheduler
9
Engineering Guidelines of Minimum Rate
Proportional Fair Scheduler
The operator needs to select an algorithm based on the level of fairness
preferred.
The feature allows selecting a preferred scheduling algorithm per QCI. There are
five Proportional Fair scheduling algorithms for the operator to select from:
— Equal Rate
— Proportional Fair High
— Proportional Fair Medium
— Proportional Fair Low
— Maximum C/I
If the Equal Rate scheduling algorithm is in use, the scheduler aims on providing
an equal average bit rate for the flows in the cell.
The scheduler provides a balance between the cell capacity and cell edge
throughput if the following three algorithms are used:
— Proportional Fair High
— Proportional Fair Medium
— Proportional Fair Low
The names indicate that these three algorithms are fair on different levels, high,
medium or low.
If the Maximum C/I scheduling algorithm is used, the scheduler focuses on
allocating resources to users with good channel conditions to maximize cell
capacity.
The feature also includes setting a minimum bit rate for QCIs that are configured
for one of the Proportional Fair scheduling algorithms. The minimum rate for
uplink and downlink can be set independently and the operator configures them
for each QCI.
By setting parameter CarrierAggregationFunction.caRateAdjustCoeff, the
rate portion used in downlink Proportional Fair algorithms can be used for
adjusting CA-capable UEs. Making adjustments can improve aggregated rates to
a fraction of the cell-based rate. The lower the value of
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CarrierAggregationFunction.caRateAdjustCoeff is set, the higher the
throughput for CA-capable UEs is, compared to UEs without CA-capability.
Table 5
Approximate Rates in Adjusting CA-Capable UEs
Value
Approximate rate
10
Aggregated rate (default)
9
Cell rate + 80% of rate from other cell components
8
Cell rate + 60% of rate from other cell components
7
Cell rate + 40% of rate from other cell components
6
Cell rate + 20% of rate from other cell components
5
Cell rate
4
80% of the cell rate
3
60% of the cell rate
2
40% of the cell rate
1
20% of the cell rate
0
Rate = 0 (not recommended)
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