configureScheduler
Download Required: To use configureScheduler
,
first download the Communications Toolbox Wireless Network Simulation Library add-on.
Description
configureScheduler(
configures a scheduler at a 5G new radio (NR) base station (gNB) node. The function sets the
scheduling parameters using one or more optional name-value arguments. For example,
gnb
,Name=Value
)ResourceAllocationType=0
sets the resource allocation type to
0
. You can configure a scheduler at multiple gNB nodes in a single
configureScheduler
function call. In this case, all the nodes use the
same scheduling parameter values specified in the name-value arguments.
Note
System-level simulation dynamically selects the uplink and downlink rank based on the measured channel quality
Examples
Simulate 5G Network by Configuring Scheduler at gNB
Initialize the wireless network simulator.
networkSimulator = wirelessNetworkSimulator.init;
Create a default gNB node.
gnb = nrGNB;
Create two UE nodes, specifying their positions.
ue = nrUE(Position=[100 100 0; 5000 100 0]); % In Cartesian x, y, and z coordinates.
Configure a scheduler at the gNB with the maximum number of users per transmission time interval (TTI) as 3.
configureScheduler(gnb,MaxNumUsersPerTTI=3)
Connect the UE nodes to the gNB node.
connectUE(gnb,ue)
Create voice over Internet protocol (VoIP) application traffic pattern objects to generate VoIP application traffic patterns between the gNB and UE nodes.
traffic1 = networkTrafficVoIP(ExponentialMean=5,GeneratePacket=true); traffic2 = networkTrafficVoIP(ExponentialMean=125,GeneratePacket=true);
Add a data traffic source from the gNB node to the UE nodes.
addTrafficSource(gnb,traffic1,DestinationNode=ue(1)) addTrafficSource(gnb,traffic2,DestinationNode=ue(2))
Add the nodes to the network simulator.
addNodes(networkSimulator,gnb) addNodes(networkSimulator,ue)
Set the simulation time, in seconds.
simulationTime = 0.3;
Run the simulation for the specified simulation time.
run(networkSimulator,simulationTime)
Obtain statistics for the gNB and UE nodes.
gnbStats = statistics(gnb); ue1Stats = statistics(ue(1)); ue2Stats = statistics(ue(2));
Input Arguments
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Example: configureScheduler(gnb,ResourceAllocationType=0)
sets the
resource allocation type to 0
Scheduler
— Scheduler strategy
"RoundRobin"
(default) | "BestCQI"
| "ProportionalFair"
| object of subclass of
nrscheduler
(since R2024b)
Scheduler strategy, specified as one of these options.
"RoundRobin"
— Enable the round-robin (RR) scheduler. This scheduler provides equal scheduling opportunities to all the UE nodes."BestCQI"
— Enable the best channel quality indicator (CQI) scheduler. This scheduler gives priority to the UE node with the best CQI."ProportionalFair"
— Enable the proportional-fair (PF) scheduler. This scheduler is a compromise between the round-robin and best CQI schedulers.An object of subclass of
nrScheduler
. (since R2024b)
The scheduling strategies RR, best CQI, and PF attempt to schedule
MaxNumUsersPerTTI
UE nodes in each slot. For a custom
scheduler, the scheduling logic determines the number of UE nodes to be scheduled, but
it cannot exceed MaxNumUsersPerTTI
.
Note
When you specify the Scheduler
name-value argument as an object of subclass of nrscheduler
, the
applicable name-value arguments are RVSequence
,
ResourceAllocationType
, ,
CSIMeasurementSignalDL
MaxNumUsersPerTTI
, and MUMIMOConfigDL
.
RVSequence
— Redundancy version sequence
[0 3 2 1]
(default) | vector
Redundancy version sequence, specified as a vector limited to a maximum of 4
elements, each uniquely taking on values from 0 to 3. To disable retransmissions, set
RVSequence
to a scalar value.
Data Types: double
PFSWindowSize
— Time constant of exponential moving average
20
(default) | positive integer
Time constant of an exponential moving average, specified as a positive integer, in number of slots. The proportional-fair scheduler uses this time constant to calculate the average data rate.
Dependencies
To enable this name-value argument, specify the Scheduler
argument as "ProportionalFair"
.
Data Types: double
ResourceAllocationType
— Resource allocation type
1
(default) | 0
Resource allocation type, specified as 1
(resource allocation
type 1) or 0
(resource allocation type 0).
Data Types: double
MaxNumUsersPerTTI
— Maximum number of users per TTI
8
(default) | positive integer
Maximum number of users per transmission time interval (TTI), specified as a positive integer.
Data Types: double
FixedMCSIndexDL
— MCS index for DL
[]
(default) | integer in range [0, 27]
Modulation and coding scheme (MCS) index for downlink (DL), specified as an
integer in the range [0, 27]. The MCS index corresponds to a row in TS 38.214, table
5.1.3.1-2 [1]. The gNB node stores
the MCS table as the static property MCSTable
. The
default value of []
indicates for the gNB to select the MCS based
on the CSI-RS measurement report.
Dependencies
This name-value argument is not applicable when you specify the Scheduler
name-value argument as an object of subclass of
nrscheduler
.
Data Types: double
FixedMCSIndexUL
— MCS index for UL
[]
(default) | integer in range [0, 27]
Modulation and coding scheme (MCS) index for uplink ( UL), specified as an integer
in the range [0, 27]. The MCS index corresponds to a row in TS 38.214, table
5.1.3.1-2. The gNB node stores the MCS table as static property MCSTable
. The
default value of []
indicates for the gNB to select the MCS based
on the sounding reference signal (SRS) measurements.
Dependencies
This name-value argument is not applicable when you specify the Scheduler
name-value argument as an object of subclass of
nrscheduler
.
Data Types: double
CSIMeasurementSignalDL
— DL CSI measurement signal
"CSI-RS"
(default) | "SRS"
Since R2024b
DL channel state information (CSI) measurement signal, specified as
"SRS"
or "CSI-RS"
.
Note
While integrating a custom scheduler or using a built-in scheduler, setting
CSIMeasurementSignalDL
to "SRS"
populates the SRS
field of the
CSIMeasurementDL
structure of the UEContext
property of the nrScheduler
base class. By default, the built-in schedulers uses the CSI-RS based measurements
for the DL scheduling. However, the responsibility for using these SRS based
measurements for custom scheduling falls to the developer of the custom
scheduler.
MUMIMOConfigDL
— Configuration of DL MU-MIMO
structure
Configuration of DL multi-user multiple-input and multiple-output (MU-MIMO), specified as a structure. The structure must contain these fields.
MaxNumUsersPaired
— The maximum number of users that the scheduler can pair for a MU-MIMO transmission, specified as integer in the range[2, 4]
. The default value is2
.MinNumRBs
— The minimum number of resource blocks (RBs) the scheduler must allocate to a UE for considering the UE as an MU-MIMO candidate, specified as a positive integer. The default value is6
. The scheduler calculates the number of RBs based on the buffer occupancy and channel state information (CSI) reported by the UE node.MinCQI
— The minimum channel quality indicator (CQI) required for considering a UE as an MU-MIMO candidate, specified as an integer in the range[1, 15]
. The default value is7
. For more information about the CQI table, see TS 38.214 Table 5.2.2.1-2 [1].SemiOrthogonalityFactor
— Inter-user interference (IUI) orthogonality factor, specified as a numeric scalar in the range[0, 1]
. The scheduler uses this value to decide whether to pair up the UE nodes for MU-MIMO.SemiOrthogonalityFactor
values of0
and1
indicate nonorthogonality and orthogonality between the UE nodes, respectively. The default value ofSemiOrthogonalityFactor
is0.75
.
Note
When integrating a custom scheduler, providing
MUMIMOConfigDL
(empty or as a structure with defined fields)
only activates type-II CSI reporting. This approach ensures users can access type-II
reports, but the responsibility for MU-MIMO scheduling still falls to the developer
of the custom scheduler. In contrast, for built-in schedulers,
MUMIMOConfigDL
both enables type-II reporting and implements
the MU-MIMO algorithm based on the type-II report.
LinkAdaptationConfigDL
— LA configuration structure for DL transmissions
structure
Link adaptation (LA) configuration structure for DL transmissions, specified as a
structure. To enable LA for DL transmissions, create an LA configuration structure and
specify it to this argument. If not set, LA remains disabled. The
LinkAdaptationConfigDL
value of []
enables LA
with default configuration parameters. If you configure LA, do not specify the
FixedMCSIndexDL
argument. An LA structure must contain these fields.
InitialOffset
— Initial MCS offset applied to all UEs, specified as an integer in the range[-27, 27]
. This offset considers the errors in channel measurements at the UE node. Upon receiving the CSI report, the gNB node resets the MCS offset to theInitialOffset
value. The scheduler then determines the MCS for the physical downlink shared channel (PDSCH) transmission by subtracting the MCS offset from the MCS obtained from the channel measurements. The default value is0
.StepUp
— Incremental value for the MCS offset when a packet reception fails, specified as a numeric scalar in the range[0, 27]
. LA considers only the failure of new transmissions while ignoring any retransmission feedback. The default value is0.27
.StepDown
— Decremental value for the MCS offset when a packet reception is successful, specified as numeric scalar in the range[0, 27]
. LA considers only the success of new transmissions while ignoring any retransmission feedback. The default value is0.03
.
Dependencies
This name-value argument is not applicable when you specify the Scheduler
name-value argument as an object of subclass of
nrscheduler
.
LinkAdaptationConfigUL
— LA configuration structure for UL transmissions
structure
LA configuration structure for UL transmissions, specified as a structure. To
enable LA for UL transmissions, create an LA configuration structure and specify it to
this argument. The LinkAdaptationConfigUL
value of
[]
enables LA with default configuration parameters. If you
configure LA, do not specify the FixedMCSIndexUL
argument. The
LinkAdaptationConfigUL
structure contains fields with identical
definitions and ranges as those in the LinkAdaptationConfigDL
structure.
Dependencies
This name-value argument is not applicable when you specify the Scheduler
name-value argument as an object of subclass of
nrscheduler
.
More About
Link Adaptation Algorithm
The function implements the link adaptation algorithm outlined in Proceedings of
European Wireless 2015 [2], with a notable
modification. Whereas the original approach applies an offset to the signal-to-noise ratio
(SNR), the method used by the function applies the offset directly to the MCS index. The
link adaptation algorithm for the configureScheduler
function consists
of these steps.
Define the LA configuration parameters
StepUp
andStepDown
. The algorithm defines the target Block error rate asStepDown
/(StepDown
+StepUp
).Upon receiving channel measurements feedback (CQI) from the UE node, the gNB node maps the reported CQI to an appropriate MCS value. The MCS table used for the DL LA complies with TS 38.214, Table 5.1.3.1-2 [3].
Reset the MCS offset to the initial offset on each CSI reporting periodicity, considering any channel measurement errors.
Determine the MCS for physical downlink shared channel (PDSCH) transmission as the downlink MCS mapped by the gNB node minus the MCS offset.
If the UE node reports a successful PDSCH reception, decrease the MCS offset by
StepDown
.If the UE node reports a failed PDSCH reception, increase the MCS offset by
StepUp
.
Similarly, for UL link adaptation, the gNB node calculates the UL MCS based on the sounding reference signal (SRS) channel measurements. The function determines the MCS for the physical uplink shared channel (PUSCH) transmission as the MCS calculated by the gNB node minus the MCS offset.
References
[1] 3GPP TS 38.321. “NR; Medium Access Control (MAC) protocol specification.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.
[2] Sarret, Marta Gatnau, Davide Catania, Frank Frederiksen, Andrea F. Cattoni, Gilberto Berardinelli, and Preben Mogensen. “Dynamic Outer Loop Link Adaptation for the 5G Centimeter-Wave Concept.” In Proceedings of European Wireless 2015; 21st European Wireless Conference, 1–6, 2015. https://ieeexplore.ieee.org/document/7147668
[3] 3GPP TS 38.214. “NR; Physical layer procedures for data.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.
Version History
Introduced in R2023aR2024b: Includes support for custom scheduler and DL CSI measurement signal
The configureScheduler object function now supports these functionalities.
You can now plug a custom scheduler into the system-level simulation by using the
Scheduler
name-value argument.You can now choose the DL CSI measurement signal by using the
CSIMeasurementSignalDL
name-value argument of the configureScheduler object function.
R2024a: Includes support for link adaptation
The configureScheduler object function now supports link adaptation for both the downlink and uplink directions.
R2023b: Includes support for selecting a scheduling strategy and setting time constant of an exponential moving average
The configureScheduler object function now supports these functionalities.
Select a scheduling strategy through the
Scheduler
name-value argument.Set time constant of an exponential moving average through the
PFSWindowSize
name-value argument.
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