LTE RAN KPIs-Part 1
POSTED ON MAY 26, 2021 BY ADMIN
LTE RAN KPIs-Part 1.
Key Performance Indicators (KPIs) can vary widely, depending on what information is available
from the equipment and on what is important to the operator. Nonetheless, they tend to fall into a
few broad categories. For LTE performance, the most used KPIs are:
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Accessibility: The ability of a subscriber to get access to the network to establish a
default bearer. Setup failures track how often a user tried to set up a session, but
was unable to do so, while paging success indicates how often a subscriber in the
area could be reached.
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Retainability: The ability of a subscriber involved in a session to stay up and
running. The intent of the retainability metric is to track the number of abnormal ERAB releases. These abnormal releases may be eNodeB generated or MME
generated.
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Integrity: This metric tracks the network’s ability to deliver IP packets to and from
the end user. Integrity can be subdivided into two quality-based KPIs, which
include throughput and latency.
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Mobility: Mobility simply measures the success rate of the handover preparation
and execution phases. This includes intra-frequency handover, inter-frequency
LTE handover, and inter-RAT handover.
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Availability: Availability is a KPI that measures the percentage of time that a cell
can provide service to end users. Typically, both scheduled and unscheduled
outages are included in the derivation of the metric.
Step of RRC Connection Setup in LTE
When the UE is powered up, it has to be RRC connected to be able to
exchange data and signaling with the network.
After the RRC connection, the Initial network attach allows to establish all the
bearers to carry the data from the UE to the gateway.
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After the RRC connection, Signaling Radio Bearers (SRBs) are
established.
An SRB is a Radio Bearer that only carries the signaling:
SRB1 carries the RRC signaling.
SBR2 carries the NAS signaling, i.e. between the Core Network
and the UE.
During the Initial Attach:
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An MME is selected.
The UE is authenticated.
An IP address is allocated to the UE.
S-GW and P-GW are selected.
Bearers are established on the S1-U, S5/S8 and on the air
interface.
The RRC connection is reconfigured to allow user data traffic.
At the end of the Initial Attach, the UE is able to reach external
networks.
The RRC Connection is basically made up of 2 steps:
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Contention Based Random Access.
Exchange of Signaling to establish the connection.
When a UE requests a connection, it has no dedicated resources
to reach the eNodeB. It uses an uplink common channel which is
able to manage the collision between 2 UEs requesting an
access at the same time.
QOS in LTE Part 1
Sensitivity: MTN South Africa - Internal
POSTED ON MAY 30, 2021 BY ADMIN
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QOS in LTE Part- 1
The LTE service provider will have a fixed amount of network resources. The goal of supporting
QoS is to allocate these resources to different customers to meet their requirements while
maximizing the revenues for the service provider.
QoS is specified in terms of parameters like bandwidth, delay, jitter, and priority. The priority is
important because the service provider may want to provide a better service to its Platinum
customers over its regular customers. To effectively support QoS, a service provider identifies a
network in which QoS can be defined, deployed, and enforced rapidly.
Different services have different QoS requirements. For example, a VoIP service is a real-time
service that cannot tolerate delay and jitter. It needs less but guaranteed bandwidth. Web
browsing, on the other hand, needs more bandwidth but can tolerate delay and jitter.
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QOS in LTE
The key QoS parameters associated with a service data flow are shown in this figure.
1. QoS Class Identifier (QCI): Defines the general class of the service. There are
currently nine defined QCIs. A QCI is associated with a priority, specific delay,
packet loss value and whether the service has a guaranteed bit rate. These
characteristics are used by the EPS nodes (eNB, S-GW, P-GW) to guide them in
deciding how a particular service data flow is to be processed. The QCI
determines resource scheduling, rate shaping, and queue management. The QCI
also maps to a specific DiffServ Code Point (DSCP) for IP forwarding through the
GTP tunnels. At the eNB, the QCI is also used to determine RLC configuration.
2. Bearer Type: For GBR bearers, the GBR and MBR parameters are specified. For
non-GBR bearers, the AMBR parameter is specified.
3. Allocation and Retention Priority (ARP): This parameter will be used in congestion
situations when not all users and their services can be accommodated. The ARP
will be used by the admission control function in the eNB. For example, a user may
subscribe to a service such as real-time gaming. In the EPS, real-time gaming is
defined as a specific class of service with a defined QCI value and associated
parameter values for packet delay, etc. Realtime gaming is a GBR service and,
therefore, will be assigned a guaranteed and maximum bit rate when the user
subscribes. These bit rates may depend on the type of game in question.
QOS Class Parameters
The QoS attributes associated with the QoS Class Identifiers are shown in the table.
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Service data flows with QCIs of a GBR bearer type will be associated with a GBR
parameter and an MBR parameter. The GBR parameter will be used in the
admission control function in the eNB.
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Each QCI value has a priority that will be used by the EPS traffic nodes during
congestion. If packet queues are close to overflow, then SDFs with lower priority
(Priority 9 is the lowest) will have their packets discarded first. Note that IMS
signaling packets have the highest priority, while QCI 9 is equivalent to best effort
service. Prioritization of SDF aggregates of the same user will use this value and it
should also be used in the prioritization across users. Although the PDB will play a
greater role in the scheduling of one user’s traffic over another.
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The Packet Delay Budget (PDB) associated with a bearer will be one of the inputs
used by the scheduler in the eNB to determine when to deliver packets of a
service. The PDB values given in the table are a measure of the maximum time
allowed for packet delivery from the P-GW to the UE. The eNB can assume that,
on average, the delay from the P-GW to the eNB is 20 ms, and from this calculate
the maximum over-the-air delay budget.
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The Packet Error Loss Rate (PELR) from the P-GW to the eNB is assumed to be
zero in non-congestion situations. Therefore, the PLR in the table refers to noncongestion-related losses over the air. It is used in an eNB to help decide how to
set up the radio bearer for a particular SDF (e.g., RLC AM or UM, modulation and
coding parameters).
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QCIs 6, 8 and 9 may be used for differentiation on a service or subscriber basis.
For example, QCI 8 can map to gold users, while QCI 9 is used for others. QCI 6
could be used to differentiate specific services separate from subscription classes.
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Note that the QoS parameter AMBR may be used to distinguish between two
users or groups of users that are both assigned QCI 9 for their services.
QOS Class in LTE
5G End to End KPI – Accessibility, Integrity and
Utilization
June 8, 2019Author5G, Cloud Computing, NR, Tech Fundas
A Key Performance Indicator (KPI) is a measurable value that demonstrates how
effectively a network is serving the user. In simple terms we can say KPIs describe the
fitness level of a network, and this fitness level is measured with different matrix, e.g.
when a doctor declare a Human being is fit and well, he measure his temperature,
high blood pressure, high heart rate, blood sugar etc. similarly, network operates
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perform some measurement like network attach success rate, Average UL/DL data
rate, Mobility success very famous for 4G/3Glegacy network to declare network as fit.
5G is quit new topic and as it will be covering too many uses cases, so we may expect
new matrix to major the newtork KPIs and it is going to be a challenge for network
operator while defining them. But if we see from the top, these KPI will under following
categories.
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Accessibility
Retainability
Availability
Mobility.
Integrity
Utilization
3GPP specification TS 28.554 has provided the definition for Accessibility, Integrity
and Utilization.
Accessibility KPI
It is the probability that the user of a service after a request to a network receives the
proceed-to-select signal within specified conditions. In 5G, successful registration to a
network slice is the proceed-to-select signal to the UE. If users or subscribers cannot
register to the network slice instance, they cannot access any network services in the
network slice instance. This KPI is focusing on network view and following are the key
matrix to measure accessibility KPI.
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Registered Subscribers of Network and Network Slice Instance through AMF:
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Name: Registered Subscribers of Single Network Slice Instance
through AMF
Description: It describe the total number of subscribers that are
registered to a network slice instance
Logical Formula definition: This KPI is obtained by counting the
subscribers in AMF that are registered to a network slice instance.
Physical formula definition:
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Measurement names used for the
KPI: RegisteredAMFSubNbrMean
 KPI Object: 5GS
 KPI category: Accessibility
 Unit of the KPI: Integer
 Type of the KPI: Cumulative measurement
Registered Subscribers of Network and Network Slice Instance through UDM
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Name: Registered Subscribers of Single Network Slice Instance
through UDM
Description:This KPI describe the total number of subscribers that
are registered to a network slice instance.
Logical Formula definition:This KPI is obtained by counting the
subscribers in UDM that are registered to a network slice instance.
Physical formula definition:
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Measurement names used for the
KPI: RegisteredSubUDMNbrMean
 KPI Object: 5GS
 KPI category: Accessibility
 Unit of the KPI: Integer
 Type of the KPI: Cumulative measurement
Registration success rate of one single network slice instance
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Name: Registration success rate of one single network slice instance
Description:This KPI describes the ratio of the number of successfully
performed registration procedures to the number of attempted
registration procedures for the AMF set which related to one single
network slice instance and is used to evaluate accessibility provided by
the end-to-end network slice instance and network performance.
Logical Formula Definition: This KPI is obtained by successful
registration procedures divided by attempted registration procedures.
Physical Formula Definition:
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Measurement names used for the KPI: AMF.5GSRegisAtt.Type,
AMF.5GSRegisAttachSucc.Type
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KPI Object: 5GS
KPI category: Accessibility
Unit of the KPI: Interger
Type of the KPI: Cumulative measurement
Accessibilty KPI Use Case: The no.of registered subscribers of single network slice
instance can be used to describe the amount of subscribers that are successfully
registered, it can reflect the usage of network slice instance. It is also useful to evaluate
accessibility performance provided by one single network slice instance which may
trigger the life cycle management (scale up, scale down etc.) of the network slice. This
kind of KPI is valuable especially when network functions (e.g. AMF) are shared
between different network slice instances. This KPI is focusing on both network and
user view.
Sensitivity: MTN South Africa - Internal
Integrity KPI
Integrity is the property that data have not been altered in an unauthorized manner
and Service integrity is the degree to which a service is provided without excessive
impairments, once obtained.
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Downlink latency in gNB-DU
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Name: Downlink latency for IP packets through gNB in split scenario
Description:This KPI describes the gNB-DU part of the packet
transmission latency experienced by an end-user. It is used to evaluate
the gNB latency contribution to the total packet latency.
Logical Formula Definition: This KPI is the average (arithmetic mean)
of the time from reception of IP packet to gNB-DU until transmission of
first part of that packet over the air interface, for a packet arriving when
there is no previous data in queue for transmission to the UE
Physical Formula Definition:
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Measurement names used for the KPI: DRB.RlcSduLatencyDl,
DRB.RlcSduLatencyDl.QoS,
 KPI Object: NG-RAN
 KPI category: Integrity
 Unit of the KPI:Time interval (millisecond)
 Type of the KPI:MEAN
gNB-DU Latency KPI User Case: The end-to-end latency is an important
performance parameter for operating 5G network. In some scenarios (e.g.
uRLLC), if end-to-end latency is insufficient, the 5G network customer cannot
obtain guaranteed network performance provided by the network operator. So
it is necessary to define end-to-end latency of network related measurement to
evaluate whether the end-to-end latency that network customer requested has
been satisfied. A procedure is invoked by network management system and is
used:
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To update the CSMF/NSMF with the end-to-end latency parameter for
monitoring;
To inform the network customer/network operator the end-to-end
latency;
To make CSMF/NSMF aware if the end-to-end latency can meet
network customer’s service requirement.
If high end-to-end latency are measured, it is also of benefit to pinpoint
where in the chain from application to UE that the latency occurs.
Upstream Throughput for Network and Network Slice Instance
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Name: Upstream throughput for network and network slice instance
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Description:This KPI describes the upstream throughput of one single
network slice instance by computing the packet size for each
successfully transmitted UL IP packet through the network slice
instance during each observing granularity period and is used to
evaluate integrity performance of the end-to-end network slice instance.
Logical Formula Definition: This KPI is obtained by upstream
throughput provided by N3 interface from NG-RAN to UPF which is
related to the single network slice instance.
Physical Formula Definition:
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Measurement names used for the KPI:GTP.InDataOctN3UPF
KPI Object: 5GS
KPI category: Integrity
Unit of the KPI:Kbit/s
Type of the KPI: Cumulative measurement
Downstream Throughput for Single Network Slice Instance
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Name: Downstream throughput for network and network slice
instance.
Description:This KPI describes the downstream throughput of one
single network slice instance by computing the packet size for each
successfully transmitted DL IP packet through the network slice
instance during each observing granularity period and is used to
evaluate integrity performance of the end-to-end network slice
instance.
Logical Formula Definition: This KPI is obtained by downstream
throughput provided by N3 interface from NG-RAN to UPF which is
related to the single network slice instance.
Physical Formula Definition:
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Measurement names used for the KPI:GTP.OutDataOctN3UPF
KPI Object: 5GS
KPI category: Integrity
Unit of the KPI: Kbit/s
Type of the KPI: Cumulative measurement
Upstream Throughput at N3 interface
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Name: Upstream GTP data throughput at N3 interface
Description: This KPI describes the total number of octets of all
incoming GTP data packets on the N3 interface (measured at UPF)
which have been generated by the GTP-U protocol entity on the N3
interface, during a granularity period. This KPI is used to evaluate
upstream GTP throughput integrity performance at the N3 interface.
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Logical Formula Definition: This KPI is obtained by measuring the
GTP data upstream throughput provided by N3 interface from NGRAN to UPF, during the granularity period.
Physical Formula Definition:
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Measurement names used for the KPI:GTP.InDataOctN3UPF
KPI Object: 5GS
KPI category: Integrity
Unit of the KPI: Kbit/s
Type of the KPI: MEAN
Downstream Throughput at N3 interface
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Name: Downstream GTP data throughput at N3 interface.
Description:This KPI describes the total number of octets of all
downstream GTP data packets on the N3 interface (transmitted
downstream from UPF) which have been generated by the GTP-U
protocol entity on the N3 interface, during a granularity period. This
KPI is used to evaluate integrity performance at N3 interface.
Logical Formula Definition: This KPI is obtained by measuring the
GTP data downstream throughput provided by N3 interface from UPF
to NG-RAN, during the granularity period.
Physical Formula Definition:
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Measurement names used for the KPI:GTP.OutDataOctN3UPF
KPI Object: 5GS
KPI category: Integrity
Unit of the KPI: Kbit/s
Type of the KPI: MEAN
Throughput KPI Use Case: Measuring throughput is useful to evaluate
system load of end to end network slice. If the throughput of the specific
network slice instance cannot meet the performance requirement, some
actions need to be performed to the network slice instance e.g. reconfiguration,
capacity relocation. So it is necessary to define the IP throughput for one single
network slice instance. This KPI is focusing on network and user view.
RAN UE Throughput
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Name: RAN UE Throughput.
Description: A KPI that shows how NG-RAN impacts the service
quality provided to an end-user
Logical Formula Definition:Payload data volume on RLC level per
elapsed time unit on the air interface, for transfers restricted by the air
interface.
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Physical Formula
Definition:
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Measurement names used for the KPI:DRB.UEThpDl,
DRB.UEThpUl, DRB.UEThpDl.QoS, DRB.UEThpUl.QoS
 KPI Object: NG-RAN
 KPI category: Integrity
 Unit of the KPI: Kbit/s
 Type of the KPI: MEAN
UE Throughput KPI Use Case:The UE perceived throughput in NG-RAN is
an important performance parameter for operating 5G network. If the UE
throughput of the NR cell cannot meet the performance requirement, some
actions need to be performed to the network, e.g. reconfiguration or capacity
increase. So it is necessary to define UE throughput KPI to evaluate whether
the endusers are satisfied. The KPI covers volume large enough to make the
throughput measurement relevant, i.e. excluding data volume of the last or only
slot.
The UE throughput KPI covers also “NR option 3” scenarios. Then the gNB is
“connected” towards the EPC, and not towards 5GC. It is proposed to allow the
KPI separated based on mapped 5QI (or for QCI in case of NR option 3). When
network slicing is supported by the NG-RAN, multiple Network Slice Instances
may be supported. The UL and DL UE throughput for each NSI (NSI) is then of
importance to the operator to pinpoint a specific performance problem.
Utilization KPI
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Mean number of PDU sessions of network and network Slice Instance
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Name: Mean number of PDU sessions of Single Network Slice
Instance.
Description: This KPI describes the mean number of PDU sessions
that are successfully established in a network slice instance.
Logical Formula Definition: This KPI is obtained by successful PDU
session establishment procedures of SMFs which is related to the
network slice instance.
Physical Formula Definition:
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Measurement names used for the KPI: PDUSessionNum
KPI Object: 5GS
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KPI category: Utilization
Unit of the KPI: Erlang
Type of the KPI: MEAN
o KPI Use Case: It is necessary to evaluate the mean PDU session number in
the network slice instance to indicate system load level. For example, if the
mean value of the PDU sessions is high, maybe the system capacity should be
increased. This KPI is focusing on network view.
Virtualised Resource Utilization of Network Slice Instance
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Name: Virtualised resource utilization of single network slice instance
Description: This KPI describes utilization of virtualization resource
(e.g. processor, memory, disk) that are allocated to a
network slice instance.
Logical Formula Definition: This KPI is obtained by the usage of
virtualization resource (e.g. processor, memory, disk) divided by the
system
capacity that allocated to the network slice instance.
Physical Formula Definition:
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Measurement names used for the
KPI: MeanProcessorUsage, MeanMemoryUsage, MeanDiskUsage,
System capacity indicates amount of virtualised resource which
allocated to the network slice instance.
 KPI Object: 5GS
 KPI category: Utilization
 Unit of the KPI:Percentage
 Type of the KPI:Ratio
Utilization KPI Use Case: It is necessary to evaluate the current utilization of
virtualised resources (e.g. memory and storage utilization) that a network slice
instance is occupied. If the utilization is larger or smaller than the threshold,
maybe some scale in/out operations will be made by the management system.
This KPI is focusing on network and user view.