LTE ACCESSIBILITY KPIs
Evolved Radio Access Network (E-UTRAN)E-UTRAN represents the
access network of LTEwhich is a network of eNodeBs. For normal user
traffic there is no centralized controller in E-UTRAN, i.e. the
EUTRAN architecture is considered to be flat. The Evolved eNodeB
(eNodeBs1) are normally inter-connected with each other by means of
an interface known as X2 (see Fig.2). The NodeB also interfaces
with the User Equipment (UE). The eNB hosts the PHYsical (PHY),
Medium Access Control (MAC), Radio Link Control (RLC), and Packet
Data Control Protocol (PDCP) layers that includethe functionality
of user-plane header-compression and encryption. It also offers
Radio Resource Control (RRC)functionality corresponding to the
control plane. It performs many functions including radio
resourcemanagement, admission control, scheduling, enforcement of
negotiated UL QoS, cell information broadcast,ciphering/deciphering
of user and control plane data, and compression/decompression of
DL/UL user plane packetheaders [1].
Mobility Management Entity (MME)The MME is the key control node
for the LTE access network. It is responsible for idle mode UE
tracking andpaging procedure including retransmissions. It is
involved in the bearer activation/deactivation process and it is
alsoresponsible for choosing the S-GW (Serving Gateway) for a UE at
the initial attach and at time of intra-LTEhandover involving Core
Network (CN) node relocation. It is responsible for authenticating
the user (by interactingwith the HSS (Home Subscriber Server)).
Serving Gateway (S - GW)The S-GW routes and forwards user data
packets, while also acting as the mobility anchor for the user
planeduring inter-eNB handovers and as the anchor for mobility
between LTE and other 3GPP technologies.
Packet Data Network Gateway (P- GW) The P-GW provides
connectivity to the UE to external packet data networks by being
the point of exit and entry of traffic for the UE. An UE may have
simultaneous connectivity with more than one P- GW for accessing
multiple Packet Data Networks (PDNs). The P-GW performs policy
enforcement, packet filtering for each user, charging support,
lawful interception and packet screening. Another key role of the
P-GW is to act as the anchor for mobility between 3GPP and non-3GPP
technologies such as for instance WiMAX (World Interoprability For
Microwave Access) technology.
Home Subscriber Server (HSS)The HSS contains users SAE
subscription data such as EPS subscribed QoS profile and any access
restrictionsfor roaming. It also holds information about PDNs to
which user can connect.
Message flows for the initial call set up in LTE
RRC SETUP SUCCESS RATERRC CONNECTION SUCC / RRC CONN REQUESTS
ATTEMPTS
HUAWEIRRC Setup Success Rate = {100}* ([L.RRC.ConnReq.Succ.Emc]
+ [L.RRC.ConnReq.Succ.HighPri] + [L.RRC.ConnReq.Succ.Mt] +
[L.RRC.ConnReq.Succ.MoData] + [L.RRC.ConnReq.Succ.MoSig]) /
([L.RRC.ConnReq.Att.Emc] + [L.RRC.ConnReq.Att.HighPri] +
[L.RRC.ConnReq.Att.Mt] + [L.RRC.ConnReq.Att.MoData] +
[L.RRC.ConnReq.Att.MoSig])
=L.RRC.ConnReq.Succ/L.RRC.ConnReq.AttRRC Connection Setup
Measurement (Cell) (RRC.Setup.Cell)An RRC connection is a Uu
interface connection for carrying user signaling messages. The
setup success rate of the RRC connection in a cell directly
represents the capability of the cell to provide RRC connection
setups for users. The RRC.Setup.Cell measurement unit measures the
number of RRC connection setup requests, number of RRC connection
setup attempts, and number of successful RRC connection setups in a
cell. The setup success rate of the RRC connection can be
calculated on the basis of the reported counters.Figure 1shows the
measurement points of RRC connection setup.Figure 1
CounterThe following table describes the counters contained in
the "RRC Connection Setup Measurement (Cell) (RRC.Setup.Cell)"
measurement unit:Counter IDCounter NameDescription
1526726657L.RRC.ConnReq.MsgNumber of RRC Connection Request
messages received from the UE in a cell, including the number of
retransmitted messages
1526726658L.RRC.ConnReq.AttNumber of RRC Connection Request
messages received from the UE in a cell, excluding the number of
retransmitted messages
1526728217L.RRC.ConnReq.Att.EmcNumber of RRC Connection Request
messages received from the UE for the emergency cause in a cell
1526728218L.RRC.ConnReq.Att.HighPriNumber of RRC Connection
Request messages received from the UE for the highPriorityAccess
cause in a cell
1526728219L.RRC.ConnReq.Att.MtNumber of RRC Connection Request
messages received from the UE for the mt-Access cause in a cell
1526728220L.RRC.ConnReq.Att.MoSigNumber of RRC Connection
Request messages received from the UE for the mo-Signalling cause
in a cell
1526728221L.RRC.ConnReq.Att.MoDataNumber of RRC Connection
Request messages received from the UE for the mo-Data cause in a
cell
1526728216L.RRC.ConnSetupNumber of RRC Connection Setup messages
sent to the UE in a cell
1526726659L.RRC.ConnReq.SuccNumber of RRC Connection Setup
Complete messages received from the UE in a cell
1526728222L.RRC.ConnReq.Succ.EmcNumber of RRC Connection Setup
Complete messages received from the UE for the emergency cause in a
cell
1526728223L.RRC.ConnReq.Succ.HighPriNumber of RRC Connection
Setup Complete messages received from the UE for the
highPriorityAccess cause in a cell
1526728224L.RRC.ConnReq.Succ.MtNumber of RRC Connection Setup
Complete messages received from the UE for the mt-Access cause in a
cell
1526728225L.RRC.ConnReq.Succ.MoSigNumber of RRC Connection Setup
Complete messages received from the UE for the mo-Signalling cause
in a cell
1526728226L.RRC.ConnReq.Succ.MoDataNumber of RRC Connection
Setup Complete messages received from the UE for the mo-Data cause
in a cell
NSNRRC Setup Success Rate = 100*sum([SIGN_CONN_ESTAB_COMP])
/sum([SIGN_CONN_ESTAB_ATT_MO_S]+[SIGN_CONN_ESTAB_ATT_MT]+
[SIGN_CONN_ESTAB_ATT_MO_D]+
[SIGN_CONN_ESTAB_ATT_OTHERS]+[SIGN_CONN_ESTAB_ATT_EMG])
ERICSSONRRC Setup Success Rate =
100*pmRrcConnEstabSucc/(pmRrcConnEstabAtt-pmRrcConnEstabAttReatt)
pmRrcConnEstabAttThe total number of RRC Connection Request
attempts.Condition: Stepped at reception of RRC message RRC
Connection Request.
pmRrcConnEstabAttReattThe total number of RRC Connection Request
attempts that are considered as re-attempts.Condition: Stepped at
reception of RRC message RRC Connection Request while an RRC
Connection Setup is already ongoing for that S-TMSI.
pmRrcConnEstabSuccThe total number of successful RRC Connection
Establishments.Condition: Stepped at reception of RRC message RRC
Connection Setup Complete.
S1 SETUP SUCCESS RATES1 SETUP SUCC / S1 SETUP ATTEMPTSS1 - This
is the interface between eNodeBs and MME and S-GW. The signalling
protocolfor S1 is called S1-AP.
HUAWEIS1 Setup Success Rate = L.S1Sig.ConnEst.Succ/
L.S1Sig.ConnEst.Att
The counters measure the number of UE-specific signaling
connection setups on the S1 interface, that is, number of INITIAL
UE MESSAGE messages sent from the eNodeB to the MME and number of
first S1 messages received from the MME. The eNodeB transmits the
UE-specific NAS layer data configuration to the MME through the
INITIAL UE MESSAGE. The MME sets up S1 signaling connections based
on NAS information in the message. The first S1 interface message
received from the MME may be the INITIAL CONTEXT SETUP REQUEST,
DOWNLINK NAS TRANSPORT, or UE CONTEXT RELEASE COMMAND message. If
the message is received, an S1 signaling connection is set up
successfully.L.S1Sig.ConnEst.AttNumber of attempts to set up
UE-specific signaling connections on the S1 interface
L.S1Sig.ConnEst.SuccNumber of successful UE-specific signaling
connection setups on the S1 interface
NSNS1 Setup Success Rate = 100*sum([S1_SETUP_SUCC]) /
sum([S1_SETUP_ATT])
S1 Setup Success RatioKPI nameE-UTRAN S1 Setup Success Ratio
KPI IDLTE_5014a
DescriptionThe KPI shows the setup success ratio for the
elementary procedure "S1 Setup". When this procedure is finished,
S1 interface is operational and other S1 messages can be
exchanged.
MeasurementM8000: LTE S1AP
KPI logical formulaS1 SSR=(S1 setup successes / S1 setup
attempts)*100%
KPI formula(with Counter IDs)100*sum([M8000C7]) /
sum([M8000C6])
KPI formula(with Counter names)100*sum([S1_SETUP_SUCC]) /
sum([S1_SETUP_ATT])
ERICSSONS1 Setup Success Rate =
1*(pmS1SigConnEstabSucc/pmS1SigConnEstabAtt)
pmS1SigConnEstabAttThis measurement provides the number of S1
Signalling connection establishment attempts for any establishment
cause.pmS1SigConnEstabSuccThe total number of successful S1
signalling connection establishments.
ERAB SETUP SUCCESS RATEERAB SETUP SUCC / ERAB SETUP ATTEMPTS
E-RAB : radio and S1 bearers
HUAWEIERAB_SSR (ALL)=(ERAB Setup Success/ERAB Setup
Attempt)X100% = L.E-RAB.SuccEst/ L.E-RAB.AttEst
E-RAB Setup Measurement (Cell) (E-RAB.Est.Cell)DescriptionAn
E-RAB is the access layer bearer for carrying service data of
users. The E-RAB setup success rate in a cell directly represents
the capability of the cell to provide E-RAB connection setups for
users. The E-RAB.Est.Cell measurement unit measures the number of
E-RAB setup attempts and the number of successful E-RAB setups for
each service with a different QoS Class Identifier (QCI) in a cell.
The number of E-RABs is used as the unit. The setup of one E-RAB is
measured as one time.Figure 1shows the measurement points of an
E-RAB setup procedure during a non-handover process.Figure 2shows
the measurement points of an E-RAB setup procedure during a
handover.Figure 1
Figure 2
CounterThe following table describes the counters contained in
the "E-RAB Setup Measurement (Cell) (E-RAB.Est.Cell)" measurement
unit:
Counter NameDescription
L.E-RAB.AttEst.QCI.1Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 1 in a cell
L.E-RAB.AttEst.QCI.2Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 2 in a cell
L.E-RAB.AttEst.QCI.3Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 3 in a cell
L.E-RAB.AttEst.QCI.4Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 4 in a cell
L.E-RAB.AttEst.QCI.5Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 5 in a cell
L.E-RAB.AttEst.QCI.6Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 6 in a cell
L.E-RAB.AttEst.QCI.7Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 7 in a cell
L.E-RAB.AttEst.QCI.8Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 8 in a cell
L.E-RAB.AttEst.QCI.9Number of E-RAB setup attempts initiated by
UEs for services with the QCI of 9 in a cell
L.E-RAB.SuccEst.QCI.1Number of successful E-RAB setups initiated
by UEs for services with the QCI of 1 in a cell
L.E-RAB.SuccEst.QCI.2Number of successful E-RAB setups initiated
by UEs for services with the QCI of 2 in a cell
L.E-RAB.SuccEst.QCI.3Number of successful E-RAB setups initiated
by UEs for services with the QCI of 3 in a cell
L.E-RAB.SuccEst.QCI.4Number of successful E-RAB setups initiated
by UEs for services with the QCI of 4 in a cell
L.E-RAB.SuccEst.QCI.5Number of successful E-RAB setups initiated
by UEs for services with the QCI of 5 in a cell
L.E-RAB.SuccEst.QCI.6Number of successful E-RAB setups initiated
by UEs for services with the QCI of 6 in a cell
L.E-RAB.SuccEst.QCI.7Number of successful E-RAB setups initiated
by UEs for services with the QCI of 7 in a cell
L.E-RAB.SuccEst.QCI.8Number of successful E-RAB setups initiated
by UEs for services with the QCI of 8 in a cell
L.E-RAB.SuccEst.QCI.9Number of successful E-RAB setups initiated
by UEs for services with the QCI of 9 in a cell
L.E-RAB.InitAttEstTotal number of initial E-RAB setup attempts
initiated by UEs in a cell
L.E-RAB.InitAttEst.QCI.1Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 1 in a cell
L.E-RAB.InitAttEst.QCI.2Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 2 in a cell
L.E-RAB.InitAttEst.QCI.3Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 3 in a cell
L.E-RAB.InitAttEst.QCI.4Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 4 in a cell
L.E-RAB.InitAttEst.QCI.5Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 5 in a cell
L.E-RAB.InitAttEst.QCI.6Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 6 in a cell
L.E-RAB.InitAttEst.QCI.7Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 7 in a cell
L.E-RAB.InitAttEst.QCI.8Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 8 in a cell
L.E-RAB.InitAttEst.QCI.9Number of initial E-RAB setup attempts
initiated by UEs for services with the QCI of 9 in a cell
L.E-RAB.InitSuccEstTotal number of successful initial E-RAB
setups initiated by UEs in a cell
L.E-RAB.InitSuccEst.QCI.1Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 1 in a
cell
L.E-RAB.InitSuccEst.QCI.2Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 2 in a
cell
L.E-RAB.InitSuccEst.QCI.3Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 3 in a
cell
L.E-RAB.InitSuccEst.QCI.4Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 4 in a
cell
L.E-RAB.InitSuccEst.QCI.5Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 5 in a
cell
L.E-RAB.InitSuccEst.QCI.6Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 6 in a
cell
L.E-RAB.InitSuccEst.QCI.7Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 7 in a
cell
L.E-RAB.InitSuccEst.QCI.8Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 8 in a
cell
L.E-RAB.InitSuccEst.QCI.9Number of successful initial E-RAB
setups initiated by UEs for services with the QCI of 9 in a
cell
L.E-RAB.SuccEstTotal number of successful E-RAB setups initiated
by UEs
L.E-RAB.AttEstTotal number of attempts by UEs to initiate E-RAB
setup procedures
L.E-RAB.AttEst.HOInTotal number of E-RAB setup attempts for
incoming handovers
L.E-RAB.SuccEst.HOInTotal number of successful E-RAB setups for
incoming handovers
L.S1Sig.ConnEst.AttNumber of attempts to set up UE-specific
signaling connections on the S1 interface
L.S1Sig.ConnEst.SuccNumber of successful UE-specific signaling
connection setups on the S1 interface
NSNERAB_SSR =100*sum([EPS_BEARER_SETUP_COMPLETIONS]) /
sum([EPS_BEARER_SETUP_ATTEMPTS])
M8006C0 / EPS Bearer setup attemptsCounter ID: M8006C0Network
element name: EPS Bearer setup attempts
Version: 4.1NetAct name: EPS_BEARER_SETUP_ATTEMPTS
Description: The number of EPS bearer setup attempts. Each
bearer of the "SAE Bearer to Be Setup List" IE is counted.
Updated: The receipt of an S1AP:Initial Context Setup Request or
an S1AP:E-RAB SETUP REQUEST message sent by the MME to eNB.
M8006C1 / EPS Bearer setup completionsCounter ID: M8006C1Network
element name: EPS Bearer setup completions
Version: 4.1NetAct name: EPS_BEARER_SETUP_COMPLETIONS
Description: The number of EPS bearer setup completions. Each
bearer of the "SAE Bearer Setup List" IE is counted.
Updated: The transmission of an S1AP:Initial Context Setup
Response or an S1AP:S1AP:E-RAB SETUP RESPONSE message sent by the
eNB to MME.
ERICSSONERAB_SSR =
100*(pmErabEstabSuccInit)+(pmErabEstabSuccAdded)/(pmErabEstabAttInit)+[pmErabEstabAttAdded)
pmErabEstabAttAddedThe total number of added E-RAB Establishment
attempts. Added E-RABs are all E-RABs present in S1 message E-RAB
Setup Request.
pmErabEstabSuccAddedThe total number of successfully added
E-RABs. Added E-RABs are all E-RABs present in S1 message E-RAB
Setup Request.pmErabEstabAttInitThe total number of initial E-RAB
Establishment attempts. Initial E-RABs are all E-RABs present in
the S1 message Initial Context Setup Request.
pmErabEstabSuccInitThe total number of successful initial E-RAB
Establishments. Initial E-RABs are all E-RABs present in the S1
message Initial Context Setup Request.
The three KPIs multiplied would result in the Call Setup Success
Rate formula.Call Setup Success Rate (%)CSSR_ALL = RRC Setup
Success Rate x S1 Setup Success rate xERAB Setup Success Rate
BEARERS IN LTEEPS uses the concept of EPS bearers to route IP
traffic from a gateway in the PDN to the UE. A bearer is an IP
packet flow with a defined Quality of Service (QoS). The E-UTRAN
and EPC together set up and release bearers as required by
applications.
Two types of Bearer exist Dedicated bearer and Default bearer.
Default bearer is established when a UE is initially attached to
LTE network while dedicated bearer is always established when there
is need to provide QoS to specic service (like VoIP, video
etc).
Default Bearer in LTEWhen LTE UE attaches to the network for the
first time, it will be assigned default bearer which remains as
long as UE is attached. Default bearer is best effort service. Each
default bearer comes with an IP address.UEcan have additional
default bearers as well. Each default bearer will have a separate
IP address. QCI 5 to 9 (Non- GBR) can be assigned to default
bearer.
Dedicated BearerTo put it simple, dedicated bearers provides
dedicated tunnel to one or more specific traffic (i.e. VoIP, video
etc). Dedicated bearer acts as an additional bearer on top of
default bearer. It does not require separate IP address due to the
fact that only additional default bearer needs an IP address and
therefore dedicated bearer is always linked to one of the default
bearer established previously. Dedicated bearer can be GBR or
non-GBR (whereas default bearer can only be non-GBR). For services
like VoLTE we need to providebetter user experience and this is
where dedicated bearer would come handy. Dedicated bearer uses
Traffic flow templates (TFT) to give special treatment to specific
services
ExampleUsually LTE networks with VoLTE implementations has two
default and one dedicated bearer
Default bearer 1: Used for signaling messages (sip signaling)
related to IMS network. It uses qci 5Dedicated bearer: Used for
VoLTE VoIP traffic. It uses qci 1 and is linked to default bearer
1Default bearer 2: Used for all other smartphone traffic (video,
chat, email, browser etc)Quality of Service and EPS BearersIn a
typical case, multiple applications may be running in a UE at the
same time, each one having different QoS requirements. For example,
a UE can be engaged in a VoIP call while at the same time browsing
a web page or downloading an FTP file. VoIP has more stringent
requirements for QoS in terms of delay and delay jitter than web
browsing and FTP, while thelatter requires a much lower packet loss
rate. In order to support multiple QoS requirements, different
bearers are set up within EPS, each being associated with a QoS.
Broadly, bearers can be classified into two categories based on the
nature of the QoS they provide:
Minimum Guaranteed Bit Rate (GBR) bearers which can be used for
applicationssuch as VoIP. These have an associated GBR value for
which dedicated transmissionresources are permanently allocated
(e.g. by an admission control function in theeNodeB) at bearer
establishment/modification. Bit rates higher than the GBR may
beallowed for a GBR bearer if resources are available. In such
cases, a Maximum BitRate (MBR) parameter, which can also be
associated with a GBR bearer, sets an upperlimit on the bit rate
which can be expected from a GBR bearer. Non-GBR bearers which do
not guarantee any particular bit rate. These can be usedfor
applications such as web browsing or FTP transfer. For these
bearers, no bandwidthresources are allocated permanently to the
bearer.In the access network, it is the eNodeBs responsibility to
ensure that the necessary QoS for a bearer over the radio interface
is met. Each bearer has an associated Class Identifier (QCI), and
an Allocation and Retention Priority (ARP). Each QCI is
characterized by priority, packet delay budget and acceptable
packet loss rate. The QCI label for a bearer determines the way it
is handled in the eNodeB. Only a dozen such QCIs have been
standardized so that vendors can all have the same understandingof
the underlying service characteristics and thus provide the
corresponding treatment, including queue management, conditioning
and policing strategy. This ensures that an LTE operator can expect
uniform traffic handling behaviour throughout the network
regardless of the manufacturers of the eNodeB equipment. The set of
standardized QCIs and their characteristics (from which the PCRF in
an EPS can select) is provided in Table 2.
An EPS bearer has to cross multiple interfaces as shown in
Figure 2.7 the S5/S8 interface from the P-GW to the S-GW, the S1
interface from the S-GW to the eNodeB, and the radio interface
(also known as the LTE-Uu interface) from the eNodeB to the UE.
Across each interface, the EPS bearer is mapped onto a lower layer
bearer, each with its own bearer identity. Each node must keep
track of the binding between the bearer IDs across its different
interfaces.An S5/S8 bearer transports the packets of an EPS bearer
between a P-GW and an S-GW. The S-GW stores a one-to-one mapping
between an S1 bearer and an S5/S8 bearer. The bearer is identified
by the GTP tunnel ID across both interfaces.An S1 bearer transports
the packets of an EPS bearer between an S-GW and an eNodeB. A radio
bearer [6] transports the packets of an EPS bearer between a UE and
an eNodeB. An E-UTRAN Radio Access Bearer (E-RAB ) refers to the
concatenation of an S1 bearer and the corresponding radio bearer.
An eNodeB stores a one-to-one mapping between a radio bearerID and
an S1 bearer to create the mapping between the two. The overall EPS
bearer service architecture is shown in Figure 2.8. As part of the
procedure by which a UE attaches to the network, the UE is assigned
an IP address by the P-GW and at least one bearer is established,
called the default bearer, and it remains established throughout
the lifetime of the PDN connection in order to provide the UE with
always-on IP connectivity to that PDN. The initial bearer-level QoS
parameter valuesof the default bearer are assigned by the MME,
based on subscription data retrieved from the HSS. The PCEF may
change these values in interaction with the PCRF or according to
local configuration. Additional bearers called dedicated bearers
can also be established at any time during or after completion of
the attach procedure. A dedicated bearer can be either GBR or
non-GBR (the default bearer always has to be a non-GBR bearer since
it is permanently established). The distinction between default and
dedicated bearers should be transparent to the access network (e.g.
E-UTRAN). Each bearer has an associated QoS, and ifmore than one
bearer is established for a given UE, then each bearer must also be
associated with appropriate TFTs. These dedicated bearers could be
established by the network, based for example on a trigger from the
IMS domain, or they could be requested by the UE. The dedicated
bearers for a UE may be provided by one or more P-GWs. The
bearer-level QoS parameter values for dedicated bearers are
received by the P-GW from the PCRF and forwarded to the S-GW. The
MME only transparently forwards those values received from the S-GW
over the S11 reference point to the E-UTRAN.