Optimization Guidelines:
Retainability in NSN
CONTENTS
1 0BINTRODUCTION
...
3
2 1BRETAINABILITY
...
4
2.1 6BCell Update
...
4
2.2 6BCS drop versus PS drop
...
4
3 2BRETAINABILITY KPIs (Key Performance Indicators)
...
6
3.1 8BHigh Level KPIs
...
6
3.1.1 14BRetainability Rate - RR (%)
...
6
3.1.2 15BDropped Call Rate - DCR (%)
...
6
3.1.2.1 32BUSpeech DCR (%)
...
7
3.1.2.2 33BUVideo DCR (%)
...
7
3.1.2.3 34BUCS Streaming DCR (%)
...
8
3.1.2.4 34BUPS Streaming DCR (%)
...
8
3.1.2.5 35BUPS DCR (%)
...
8
3.1.2.6 39BUFurther considerations on PS/HS DCR (%)
...
9
3.1.2.7 35BUNSN Packet Call DCR (%)
...
9
3.1.2.8 36BUHS DCR (%)
...
10
3.1.2.9 37BUEUL DCR (%)
...
11
3.1.2.10 38BUCell_FACH DCR (%)
...
11
3.1.3 16BMinutes per Drop
...
12
3.1.3.1 40BUVoice Minutes per drop
...
12
3.1.3.2 Video Minutes per drop
...
12
3.1.3.3 42BUHS Minutes per drop
...
12
3.1.4 17BDrops per Erlang (or Drops per Hour)
...
13
3.1.4.1 43BUVoice drops per hour
...
13
3.1.4.2 44BUVideo drops per hour
...
13
3.1.4.3 45BUHS drops per hour
...
13
3.1.5 18BOverall Service Retainability - OSRET (%)
...
13
3.2 9BMedium Level KPIs: Voice Drop Reasons
...
14
3.2.1 19BRADIO <RAB> DCR (%)
...
14
3.2.2 20BIu <RAB> DCR (%)
...
15
3.2.3 21BIur <RAB> DCR (%)
...
15
3.2.4 21BBTS <RAB> DCR (%)
...
16
3.2.5 20BUE <RAB> DCR (%)
...
16
3.2.6 21BUnspecified Error <RAB> DCR (%)
...
16
3.2.7 20BPre-emption <RAB> DCR (%)
...
16
3.2.8 21BRNC (OTHERS) <RAB> DCR (%)
...
17
3.2.9 22BIRAT Speech DCR (%)
...
17
4 3BPERFORMANCE ANALYSIS
...
18
4.1 10BRadio Coverage Issues
...
18
4.1.1 24BUplink Problems
...
18
4.1.1.2 47BURadio Connection Supervision for UE in Cell_FACH
...
19
4.1.2 25BDownlink Problems
...
20
4.1.3 26BLayer 2 Failures triggered by Coverage
...
21
4.1.4 27BCritical radio procedure failures due to coverage
...
21
4.1.5 28BRadio Environment Evaluation
...
22
4.1.5.1 48BUPrimary Straight Indicators
...
22
4.1.5.2 49BUSecondary Indicators
...
22
4.1.5.3 50BUW-MRR
...
22
4.1.5.4 51BUGPEH for Radio Coverage Analysis
...
23
4.1.5.5 52BURRC measurement Reports
...
23
4.2 11BMobility Issues
...
23
4.2.1 29BSSoft/Softer Handover Failures
...
24
4.2.2 30BMissing Neighbour Relations
...
25
4.2.3 31BIRAT Handover Failures
...
25
4.2.4 17BIF Handover Failures
...
28
4.3 12BCapacity Issues: Congestion Monitoring
...
29
4.4 13BOther Faults
...
30
5 4BREFERENCES
...
31
6 5BANNEX I: Call Reestablishment (Cell Update procedure)
...
32
7 5BANNEX II: UL/DL Radio Synchronization
...
33
7.1 13BDL Synchronization
...
33
1
0BINTRODUCTION
This series of Optimization Guidelines cover all main topics regarding
•
Performance Monitoring & Analysis• Configuration settings
• Troubleshooting
Refer to the internal Claro document Ref. ####.## , Optimization Process, for a summary of 3G WCDMA Radio Access Network Optimization Basics.
This specific document focuses on RETAINABILITY and its specifics in NSN infrastructure (Release RU10).
Target users for this document are all personnel requiring a detailed description of this process (Retainability Optimization), as well as configuration managers who require details to control the functions and optimize parameter settings. It is assumed that users of this document have a working knowledge of 3G telecommunication and are familiar with WCDMA.
Document Revision Control
Revisio
n Date Author Changes
Draft0
2
1BRETAINABILITY
Retainability is the ability of a service to be kept – once it was accessed – under given conditions for a requested period of time. In other words, it is the probability that a service, once obtained, will continue to be provided under given conditions for a given time duration.
Target is to get a 100% Retainability, i.e., all connections maintained until their normal release. Poor Retainability is typically due to
•
Handover performance (soft/softer/Iur/IFHO/IRAT) and missing neighbor cell• UL/DL imbalance
• Incorrect parameter settings (power, admission, release)
• Congestion
•
Radio environment impact (corner effect, fast Ec/No drop, Pilot pollution, etc)•
Node Hardware/Software failure•
Iub (E1s) CongestionRetainability is to be monitored independently for the different RAB types (e.g. Speech, CS Video, PS Interactive R99, PS Interactive HSDPA, etc.) as in certain situations only one of the RAB types will be affected.
2.1
6BCell Update
In 3G a new mechanism is available to rescue some dropped calls (both CS and PS) due to RL Failure:
Call Reestablishment by Cell Update procedure. Refer to ANNEX I for further details.
If timer T314 is set higher than 0, Voice calls that suffer from a RL Failure are not considered “dropped” till timer T314 expires and the call could not be reestablished by the Cell Update Procedure.
Similarly, if timer T315 is set higher than 0, PS calls that suffer from a RL Failure are not considered “dropped” till timer T315 expires and the call could not be reestablished by the Cell Update Procedure. We could say that in both cases, CS and PS, those RL Failures that can be rescued are just
system-perceived drops, but not user-system-perceived drops, as the user does not have to perform any additional
manual operations like for example manual re-activation of the PDP context. In reality, during the Cell Update procedure (T314 or T315 seconds), Voice calls will be perceived as “silent” by the user, and PS data sessions may suffer from delays and lower throughputs, but the fact is that the call does not drop, and it is not counted by the RAB releases counters (and therefore, neither as a drop).
In NSN infrastructure, T314=0 is hardcoded, and T315=30 sec (changeable), i.e., this Cell Update mechanism is only available for PS data calls (not for Voice calls).
•
In terms of Voice Calls, this means that all RL Failures in DL will finally lead to a drop (user and system perceived, and RAB release counters –and drops- increased).•
In terms of PS Calls, those RL Failures that are rescued will be system but not user-perceived, and the abnormal RAB release counter (=drops) will not be increased.As some other vendors may have the Cell Update mechanism de-activated for PS, the optimization team should keep in mind these considerations when comparing PS DCR (%) in different vendors: usually worst in those ones with this functionality disabled. Nevertheless, this worst behavior in the KPI usually does not match the user perception (that is typically good) thanks to additional implicit re-establishment mechanisms (Paging/Service Request).
2.2
6BCS drop versus PS drop
One important difference between the Circuit Switched (CS) and Packet Switched (PS) domains is that in the CS domain, the end-to-end services (voice, video-telephony, CS data) can be maintained only if all lower layer links are maintained. For example, if the Radio Bearer is broken during a voice call, the
network may allow only limited time (T314) to perform a Cell Update before terminating the end-user application.
For PS data, to accommodate the bursty nature of the traffic, links from different layers can be independent. For example, the Packet Data Protocol (PDP) context is preserved, while the Radio and Radio Access Bearers are reconfigured or disconnected during low activity periods. The behavior of an FTP session is another example; when Radio Bearers are dropped or experience a high block error rate, the FTP might time out, even if the PDP context is active.
The interdependence between layers complicates data service optimization; all layers must be considered.
A single PS call (= a single PS RAB) goes dynamically through different “phases” (DCH R99, HSDPA, EUL, Cell_FACH) based on different radio configurations. It may also go to IDLE (with “pdp context preserved”) due to inactivity periods. It is the system that re-establishes the lower layer connections, with no user intervention.
When the PS call goes to Idle with “pdp context preserved” due to inactivity, the PS RAB is considered normally released, and there will be a new process of call establishment starting with an RRC connection request, and RAB establishment, etc. (but without the UPLINK DIRECT TRANSFER [SM: Activate PDP Context Request] as it was preserved).
In case there is a RL Failure, the pdp context is also preserved and either Cell Update or implicit re-establishment mechanisms (Paging/Service Request) will re-establish the lower layer connections with no user intervention. User does not notice the call drop (but typically experiences low throughput or delay). So in terms of “user perception” (or Data Application DCR %, or Data Session DCR %, or PDP context DCR %), the retainability is not impacted. These latest metrics (from an operational point of view) can only be derived from PS CORE (GGSN) counters.
In terms of Abnormal RAB Releases due to RL Failure, typically those vendors with CU enabled (NSN & Huawei, for example) will not increase the counter (in fact, they will not increase any RAB Release counter – nor normal neither abnormal-; RAB is not released); those ones with CU disabled will (Ericsson, for instance). So, as already anticipated, you can expect a worst KPI PS DCR % performance in these last ones.
3
2BRETAINABILITY KPIs (Key Performance Indicators)
Below the main metrics used for Retainability Monitoring of a 3G WCDMA/UMTS Network, and their implementation with NSN counters.
Refer to “SMART Documentation” for further details on the actual implementation of these KPIs in the tool, together with the additional considerations regarding:
• Treatment of zeros in the denominators
• Differentiation of PS: Global, R99, HS, EUL KPIs.
•
Considerations regarding SRNS Relocations and Outgoing Hard Handover3.1
8BHigh Level KPIs
3.1.1 14BRetainability Rate - RR (%)
Based in statistical counters, it is possible to count every time a RAB is normally released, e.g.:
• Call ended by UE or user control
(user generates a “disconnect” towards the CN or UE Signaling Connection Release)
• Call ended because of any problem or action on the other part
(the monitored user receives a “disconnect” from the CN)
•
Connection ends because of user inactivity (PS calls only)•
Connection ends because the call is successfully transferred to another system (IRAT handover)and abnormally released (= DROP):
•
Call ended by the network for any other reason than NORMAL.A global Retainability Rate (%) can be calculated as follows:
However, it is common practice to use the Non Retainability Rate (NRR) instead, a.k.a. Dropped Call Rate (%), that we will use throughout this document:
As already stated, target is to keep Retainability Rate, RR (%) as closed as possible to 100%, while target for NRR (%) is to keep the DCR (%) as closed as possible to 0%.
3.1.2 15BDropped Call Rate - DCR (%)
It is the most common KPI for Retainability.
The value is dependent on the call duration: the shorter is the average call duration, the lower shall be the drop call rate and vice versa. Any changes in the network that modify the call duration shall impact on the Drop Call Rate (e.g. IRAT Handover thresholds for speech or inactivity timers for PS calls).
Counters available in NSN for the Normal and Abnormal RAB Releases are:
No of Normal RAB Releases No of Abnormal RAB Releases
+Noof Abnormal RABReleases) Releases RAB Normal of (No Releases RAB Normal of No * 100
+Noof Abnormal RABReleases) Releases RAB Normal of (No Releases RAB Abnormal of No * 100
RAB_ACT_COMP_CS_VOICE +
RAB_ACT_REL_CS_VOICE_SRNC RAB_ACT_REL_CS_VOICE_P_EMP + RAB_ACT_REL_CS_V_UNSPE_ER_CN + RAB_ACT_FAIL_CS_VOICE_IU + RAB_ACT_FAIL_CS_VOICE_RADIO + RAB_ACT_FAIL_CS_VOICE_BTS + RAB_ACT_FAIL_CS_VOICE_IUR + RAB_ACT_FAIL_CS_VOICE_RNC + RAB_ACT_FAIL_CS_VOICE_UE RAB_ACT_COMP_CS_CONV +
RAB_ACT_REL_CS_CONV_SRNC RAB_ACT_REL_CS_CONV_P_EMP + RAB_ACT_REL_CS_C_UNSPE_ER_CN + RAB_ACT_FAIL_CS_CONV_IU + RAB_ACT_FAIL_CS_CONV_RADIO + RAB_ACT_FAIL_CS_CONV_BTS + RAB_ACT_FAIL_CS_CONV_IUR + RAB_ACT_FAIL_CS_CONV_RNC + RAB_ACT_FAIL_CS_CONV_UE RAB_ACT_COMP_CS_STREA +
RAB_ACT_REL_CS_STREA_SRNC RAB_ACT_REL_CS_STREA_P_EMP + RAB_ACT_REL_CS_S_UNSPE_ER_CN + RAB_ACT_FAIL_CS_STREA_IU + RAB_ACT_FAIL_CS_STREA_RADIO + RAB_ACT_FAIL_CS_STREA_BTS + RAB_ACT_FAIL_CS_STREA_IUR + RAB_ACT_FAIL_CS_STREA_RNC + RAB_ACT_FAIL_CS_STREA_UE RAB_ACT_COMP_PS_CONV +
RAB_ACT_REL_PS_CONV_SRNC RAB_ACT_REL_PS_CONV_P_EMP + RAB_ACT_REL_PS_C_UNSPE_ER_CN + RAB_ACT_FAIL_PS_CONV_IU + RAB_ACT_FAIL_PS_CONV_RADIO + RAB_ACT_FAIL_PS_CONV_BTS + RAB_ACT_FAIL_PS_CONV_IUR + RAB_ACT_FAIL_PS_CONV_RNC + RAB_ACT_FAIL_PS_CONV_UE RAB_ACT_COMP_PS_STREA +
RAB_ACT_REL_PS_STREA_SRNC RAB_ACT_REL_PS_STREA_P_EMP + RAB_ACT_REL_PS_S_UNSPE_ER_CN + RAB_ACT_FAIL_PS_STREA_IU + RAB_ACT_FAIL_PS_STREA_RADIO + RAB_ACT_FAIL_PS_STREA_BTS + RAB_ACT_FAIL_PS_STREA_IUR + RAB_ACT_FAIL_PS_STREA_RNC + RAB_ACT_FAIL_PS_STREA_UE RAB_ACT_COMP_PS_INTER +
RAB_ACT_REL_PS_INTER_SRNC RAB_ACT_REL_PS_I_UNSPE_ER_CN + RAB_ACT_FAIL_PS_INTER_IU + RAB_ACT_FAIL_PS_INTER_RADIO + RAB_ACT_FAIL_PS_INTER_BTS + RAB_ACT_FAIL_PS_INTER_IUR + RAB_ACT_FAIL_PS_INTER_RNC + RAB_ACT_FAIL_PS_INTER_UE
RAB_ACT_COMP_PS_BACKG +
RAB_ACT_REL_PS_BACKG_SRNC RAB_ACT_REL_PS_B_UNSPE_ER_CN + RAB_ACT_FAIL_PS_BACKG_IU + RAB_ACT_FAIL_PS_BACKG_RADIO + RAB_ACT_FAIL_PS_BACKG_BTS + RAB_ACT_FAIL_PS_BACKG_IUR + RAB_ACT_FAIL_PS_BACKG_RNC + RAB_ACT_FAIL_PS_BACKG_UE
NSN considers 3 possibilities for a RAB in the “ACTIVE” phase:
•
RAB_ACT_COMP_<RAB type>: Normal Release (counter updated when the RNC sends an RANAP:RAB ASSIGNMENT RESPONSE or RANAP: IU RELEASE COMPLETE to the CN after normal RAB release for a certain type of RAB)
•
RAB_ACT_FAIL_<RAB type>_<Reason>: Abnormal Release due to some abnormal reason related toIu-interface, Radio, BTS, Iur-Iu-interface, RNC or UE.
•
RAB active releases, the cause of which has been either inter-system handover, intra-system hardhandover, SRNS relocation, pre-emption or "unspecified failure”. Pre-emption for conversational and streaming and all releases with "unspecified failure" cause received from CN have been considered “Abnormal Releases”.
All above counters are in Measurement “Service Level”, so all DCR (%) KPIs we can derive from them are available at cell level. Also, as expected for a High Level KPI, they can be aggregated at nation, market/vendor, region, city, RNC, cluster,… levels.
3.1.2.1 32BUSpeech DCR (%)
High value (e.g. >2%) indicates retainability issues for Speech connections.
3.1.2.2 33BUVideo DCR (%)
E _ U E
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R N C
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U R
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ B T S
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R A D I O
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U
I L _ C S _ V O I C
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ V _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ V O I C E
R A B _ A C T _ R E
_ S R N C
L _ C S _ V O I C E
R A B _ A C T _ R E
+ E
M P _ C S _ V O I C
R A B _ A C T _ C O
E _ U E
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R N C
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U R
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ B T S
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R A D I O
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U
I L _ C S _ V O I C
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ V _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ V O I C E
R A B _ A C T _ R E
*
1 0 0
+
+
+
_ U E
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R N C
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U R
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ B T S
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R A D I O
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U
I L _ C S _ C O N V
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ C _ U N S
R A B _ A C T _ R E
+
P _ E M P
L _ C S _ C O N V _
R A B _ A C T _ R E
S R N C
L _ C S _ C O N V _
R A B _ A C T _ R E
+
M P _ C S _ C O N V
R A B _ A C T _ C O
_ U E
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R N C
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U R
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ B T S
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R A D I O
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U
I L _ C S _ C O N V
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ C _ U N S
R A B _ A C T _ R E
+
P _ E M P
L _ C S _ C O N V _
R A B _ A C T _ R E
*
1 0 0
+
+
+
High value (e.g. >2%) indicates retainability issues for Video CS64 connections.
3.1.2.3 34BUCS Streaming DCR (%)
High value (e.g. >2%) indicates retainability issues for CS Streaming connections.
3.1.2.4 34BUPS Streaming DCR (%)
High value (e.g. >2%) indicates retainability issues for PS Streaming connections.
3.1.2.5 35BUPS DCR (%)
A _ U E
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ R N C
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ I U R
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ B T S
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ R A D I O
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ I U
I L _ C S _ S T R E
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ S _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ S T R E A
R A B _ A C T _ R E
_ S R N C
L _ C S _ S T R E A
R A B _ A C T _ R E
+A
M P _ C S _ S T R E
R A B _ A C T _ C O
A _ U E
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ R N C
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ I U R
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ B T S
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ R A D I O
I L _ C S _ S T R E
R A B _ A C T _ F A
+
A _ I U
I L _ C S _ S T R E
R A B _ A C T _ F A
+
P E _ E R _ C N
L _ C S _ S _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ S T R E A
R A B _ A C T _ R E
*
1 0 0
+
+
A _ U E
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ R N C
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ I U R
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ B T S
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ R A D I O
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ I U
I L _ P S _ S T R E
R A B _ A C T _ F A
P E _ E R _ C N
L _ P S _ S _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ P S _ S T R E A
R A B _ A C T _ R E
_ S R N C
L _ P S _ S T R E A
R A B _ A C T _ R E
+A
M P _ P S _ S T R E
R A B _ A C T _ C O
A _ U E
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ R N C
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ I U R
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ B T S
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ R A D I O
I L _ P S _ S T R E
R A B _ A C T _ F A
+
A _ I U
I L _ P S _ S T R E
R A B _ A C T _ F A
+
P E _ E R _ C N
L _ P S _ S _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ P S _ S T R E A
R A B _ A C T _ R E
*
1 0 0
+
+
G _ U E
I L _ P S _ B A C K
R A B _ A C T _ F A
R _ U E
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ R N C
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R N C
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ I U R
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ I U R
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ B T S
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ B T S
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ R A D I O
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R A D I O
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ I U
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ I U
I L _ P S _ I N T E
R A B _ A C T _ F A
P E _ E R _ C N
L _ P S _ B _ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ P S _ I _ U N S
R A B _ A C T _ R E
_ S R N C
L _ P S _ B A C K G
R A B _ A C T _ R E
_ S R N C
L _ P S _ I N T E R
R A B _ A C T _ R E
+
G
M P _ P S _ B A C K
R A B _ A C T _ C O
R
M P _ P S _ I N T E
R A B _ A C T _ C O
G _ U E
I L _ P S _ B A C K
R A B _ A C T _ F A
R _ U E
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ R N C
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R N C
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ I U R
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ I U R
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ B T S
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ B T S
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ R A D I O
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R A D I O
I L _ P S _ I N T E
R A B _ A C T _ F A
+
G _ I U
I L _ P S _ B A C K
R A B _ A C T _ F A
+
R _ I U
I L _ P S _ I N T E
R A B _ A C T _ F A
P E _ E R _ C N
L _ P S _ B _ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ P S _ I _ U N S
R A B _ A C T _ R E
*
1 0 0
+
+
+
+
+
+
+
+
+
High value (e.g. >2%) indicates retainability issues for Packet Switch connections.
This is an overall PS RAB DCR (%) based in counters from Measurement type “Service Level”. Typically, CU mechanism is enabled for PS and rescues many potential RAB abnormal releases due to RL Failure (RADIO), so values for this metric are commonly very low (i.e., very good).
According to NSN documentation (See References), formula above gives the “Network perspective” of the KPI.
By just substracting next 2 counters from the numerator, we obtain the “User perspective”: RAB_ACT_FAIL_PS_INT_PCH: When a call with the PS data interactive RAB in cell-PCH state is dropped. RAB_ACT_FAIL_PS_BACKG_PCH: When a call with the PS data background RAB in cell-PCH state is dropped.
3.1.2.6 39BUFurther considerations on PS/HS DCR (%)
The Drop Call Rate for PS connections (Packet Interactive/Background) requires a special consideration. Counters in the formula above refer to RAB Releases (Normal or Abnormal) of the PS connection at any active phase, no matter if in dedicate or common channels.
In order to calculate the Drop Call Rate for each single PS phase (HSDPA or EUL or FACH or PS R99) you need to count all the transitions at the end of that specific phase. For instance, to calculate the HS DCR % you should consider all the possibilities:
If counters for all those transitions are not available, then the KPI could be not that meaningful.
3.1.2.7 35BUNSN Packet Call DCR (%)
Another metric is available in NSN, based in counters from Measurement “Packet Call”, where the impact of RL Failures can be observed. This is a Packet Active Sessions DCR (%), i.e., a retainability KPI to account for issues during active data transfer periods.
For your reference, Packet Calls (sessions) are shown in blue in the following diagram, their Normal Releases in green and an Abnormal Release due to RL Failure in red. Note that the data transfer was interrupted by the RL Failure, but the RAB was kept until its Normal Release.
) _other_RAB _HS_to_any ching_from annel_Swit Success_Ch Release HS_Normal_ al_Release (HS_Abnorm l_Release HS_Abnorma * 100 + +
•
Normal Releases (of NSN Packet Call) counters are updated, for example, due to inactivity or RABrelease. The counters are also updated in case of outgoing SRNC relocations, outgoing Inter-RNC hard handovers, Inter-System hard handovers, and state transitions to DCH (0/0)/FACH/PCH.
•
Abnormal (=Failure) Releases (of NSN Packet Call) counters are updated in case of Radio Linkfailures, pre-emption and RT over NRT. In case of RL failure, all radio links go out of sync state during a packet call, and as a consequence, the dedicated user plane allocation is released and the call is dropped into the Cell_FACH or Cell_PCH state. The counter for other failures is updated when a packet call is released due to some other failure cause than a radio link failure, pre-emption, or RT over NRT. The counter is updated, for example, if the reservation of the DMPG resource does not succeed when switching the HSPA to a DCH, or when a DSP runtime error occurs.
This NSN metric is closer to the PS RAB DCR (%) in vendors with no CU enabled, where PS RAB drops due to RL failures are count. It is certainly “Closer” as account for RL Failures but nor “completely comparable” as this formula above refers to the NSN concept of Packet Call (data transfers in FACH not included) and the PS RAB DCR (%) refers to PS RABs (FACH included).
Note also that transitions between the different PS states have not been considered (HS <> R99 DCH, etc).
To be agreed if Pre-empted NRT calls are to be considered Abnormal or Normal Releases.
3.1.2.8 36BUHS DCR (%)
This metric has been built based also on counters in Measurement PACKET CALL and following the considerations included in section 3.1.2.6 (i.e., channel switching transitions from HS to other PS RAB states have been considered):
High value (e.g. >2%) indicates retainability issues for HSDPA connections.
There is a second option based on counters in Measurement TRAFFIC, i.e., considering dedicated transport channel allocations and their releases. In other words, all the DCH-related resources (RNC, BTS, transport, UE) are released, i.e., HS-DSCH MAC-d flow and its return channel allocations are released:
In this case, NSN proposal considers Pre-emptions as Normal Releases.
High value (e.g. >2%) indicates retainability issues for HSDPA connections.
D S C H _ B G R
L _ F A I L _ H S _
R E L _ A L L O _ R
+
D S C H _ I N T
L _ F A I L _ H S _
R E L _ A L L O _ R
+
D S C H _ B G R
T H _ F A I L _ H S
R E L _ A L L O _ O
+
D S C H _ I N T
T H _ F A I L _ H S
R E L _ A L L O _ O
+
H _ B G R
O R M _ H S _ D S C
R E L _ A L L O _ N
+
H _ I N T
O R M _ H S _ D S C
R E L _ A L L O _ N
D S C H _ B G R
L _ F A I L _ H S _
R E L _ A L L O _ R
+
D S C H _ I N T
L _ F A I L _ H S _
R E L _ A L L O _ R
+
D S C H _ B G R
T H _ F A I L _ H S
R E L _ A L L O _ O
+
D S C H _ I N T
T H _ F A I L _ H S
R E L _ A L L O _ O
* 10 0
]
G R
D _ T O _ D _ D _ B
P S _ S W I _ H S _
N T
D _ T O _ D _ D _ I
P S _ S W I _ H S _
G R
E _ T O _ D _ D _ B
P S _ S W I _ H S _
N T
E _ T O _ D _ D _ I
P S _ S W I _ H S _
_ B G R
_ F A I L _ H S _ D
P S _ R E L _ O T H
+
_ I N T
_ F A I L _ H S _ D
P S _ R E L _ O T H
+
_ B G R
_ F A I L _ H S _ E
P S _ R E L _ O T H
+
_ I N T
_ F A I L _ H S _ E
P S _ R E L _ O T H
B G R
F A I L _ H S _ D _
P S _ R E L _ R L _
+
I N T
F A I L _ H S _ D _
P S _ R E L _ R L _
+
B G R
F A I L _ H S _ E _
P S _ R E L _ R L _
+
I N T
F A I L _ H S _ E _
P S _ R E L _ R L _
B G R
_ E M P _ H S _ D _
P S _ R E L _ P R E
+
I N T
_ E M P _ H S _ D _
P S _ R E L _ P R E
+
B G R
_ E M P _ H S _ E _
P S _ R E L _ P R E
+
I N T
_ E M P _ H S _ E _
P S _ R E L _ P R E
M _ H S _ D _ B G R
P S _ R E L _ N O R
+
M _ H S _ D _ I N T
P S _ R E L _ N O R
+
M _ H S _ E _ B G R
P S _ R E L _ N O R
+
M _ H S _ E _ I N T
P S _ R E L _ N O R
)
M _ H S _ D _ B G R
P S _ R E L _ N O R
+
M _ H S _ D _ I N T
P S _ R E L _ N O R
M _ H S _ E _ B G R
P S _ R E L _ N O R
+ T
R M _ H S _ E _ I N
( P S _ R E L _ N O
-[1
*
1 0 0
+
+
+
+
+
+
+
+
]
B G R
_ F A I L _ D _ D _
P S _ R E L _ O T H
I N T
_ F A I L _ D _ D _
P S _ R E L _ O T H
_ B G R
_ F A I L _ H S _ D
P S _ R E L _ O T H
+
_ I N T
_ F A I L _ H S _ D
P S _ R E L _ O T H
+
_ B G R
_ F A I L _ H S _ E
P S _ R E L _ O T H
+
_ I N T
_ F A I L _ H S _ E
P S _ R E L _ O T H
G R
F A I L _ D _ D _ B
P S _ R E L _ R L _
N T
F A I L _ D _ D _ I
P S _ R E L _ R L _
B G R
F A I L _ H S _ D _
P S _ R E L _ R L _
+
I N T
F A I L _ H S _ D _
P S _ R E L _ R L _
+
B G R
F A I L _ H S _ E _
P S _ R E L _ R L _
+
I N T
F A I L _ H S _ E _
P S _ R E L _ R L _
G R
_ E M P _ D _ D _ B
P S _ R E L _ P R E
N T
_ E M P _ D _ D _ I
P S _ R E L _ P R E
B G R
_ E M P _ H S _ D _
P S _ R E L _ P R E
+
I N T
_ E M P _ H S _ D _
P S _ R E L _ P R E
+
B G R
_ E M P _ H S _ E _
P S _ R E L _ P R E
+
I N T
_ E M P _ H S _ E _
P S _ R E L _ P R E
M _ D _ D _ B G R
P S _ R E L _ N O R
M _ D _ D _ I N T
P S _ R E L _ N O R
M _ H S _ D _ B G R
P S _ R E L _ N O R
+
M _ H S _ D _ I N T
P S _ R E L _ N O R
+
M _ H S _ E _ B G R
P S _ R E L _ N O R
+
M _ H S _ E _ I N T
P S _ R E L _ N O R
M _ D _ D _ B G R
P S _ R E L _ N O R
M _ D _ D _ I N T
P S _ R E L _ N O R
M _ H S _ D _ B G R
P S _ R E L _ N O R
+
M _ H S _ D _ I N T
P S _ R E L _ N O R
M _ H S _ E _ B G R
P S _ R E L _ N O R
+
M _ H S _ E _ I N T
P S _ R E L _ N O R
-[ 1
*
1 0 0
+
+
+
+
+
+
+
+
+
+
+
+
+
+
3.1.2.9 37BUEUL DCR (%)
This metric has been built based also on counters in Measurement PACKET CALL and following the considerations included in section 3.1.2.6 (i.e., channel switching transitions from EUL to other PS RAB states have been considered):
High value (e.g. >2%) indicates retainability issues for HSUPA connections. There is a second option based on counters in Measurement TRAFFIC:
High value (e.g. >2%) indicates retainability issues for HSDPA connections.
3.1.2.10 38BUCell_FACH DCR (%)
High value (e.g. >2%) indicates retainability issues for data connections when in state Cell_FACH.
]
G R
E _ T O _ D _ D _ B
P S _ S W I _ H S _
N T
E _ T O _ D _ D _ I
P S _ S W I _ H S _
B G R
E _ T O _ H S _ D _
P S _ S W I _ H S _
I N T
E _ T O _ H S _ D _
P S _ S W I _ H S _
_ B G R
_ F A I L _ H S _ E
P S _ R E L _ O T H
+
_ I N T
_ F A I L _ H S _ E
P S _ R E L _ O T H
+
B G R
F A I L _ H S _ E _
P S _ R E L _ R L _
+
I N T
F A I L _ H S _ E _
P S _ R E L _ R L _
+
B G R
_ E M P _ H S _ E _
P S _ R E L _ P R E
+
I N T
_ E M P _ H S _ E _
P S _ R E L _ P R E
+
M _ H S _ E _ B G R
P S _ R E L _ N O R
+
M _ H S _ E _ I N T
P S _ R E L _ N O R
)
M _ H S _ E _ B G R
P S _ R E L _ N O R
+ T
R M _ H S _ E _ I N
( P S _ R E L _ N O
-[1
*
1 0 0
+
+
+
+
To be completed with NSN Formula
B G R
T H E R _ F A I L _
R E L _ E D C H _ O
+
I N T
T H E R _ F A I L _
R E L _ E D C H _ O
+
L _ F A I L _ B G R
R E L _ E D C H _ R
+
L _ F A I L _ I N T
R E L _ E D C H _ R
+
O R M _ B G R
R E L _ E D C H _ N
+
O R M _ I N T
R E L _ E D C H _ N
B G R
T H E R _ F A I L _
R E L _ E D C H _ O
+
I N T
T H E R _ F A I L _
R E L _ E D C H _ O
+
L _ F A I L _ B G R
R E L _ E D C H _ R
+
L _ F A I L _ I N T
R E L _ E D C H _ R
*
1 0 0
3.1.3 16BMinutes per Drop
This KPI gives the average time length (in minutes) between 2 consecutive drops. In other words: It is the average number of minutes of a continuous service before a RAB is abnormally dropped.
i.e., Erlangs translated into minutes divided by the number of drops.
As all High Level KPIs, it can be produced at nation, market/vendor, region, city, RNC, cluster,… levels , but also on cell basis (as both elemnets involved in the formula, erlangs and drops, can be extracted from the UtranCell MO counters).
Please also note that:
• It is not dependent on the call duration.
• It can be used to evaluate the retainability of each single phase of a call (HSDPA, DCH, and FACH).
•
Target values are difficult to define. It is better used to analyze performance trends.• The values are instable in case of good performances (the indicator points to infinite for a perfect
network).
• A certain level of traffic is needed to have a stable indicator.
Formulas to calculate the Minutes per drop for different call types are shown next. In all the cases: ROP (Report Output Period) = Measurement time in minutes (examples: 15’, 30’, hour = 60’, day = 1440’)
3.1.3.1 40BUVoice Minutes per drop
3.1.3.2 Video Minutes per drop
3.1.3.3 42BUHS Minutes per drop
+
E _ U E
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R N C
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U R
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ B T S
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R A D I O
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U
I L _ C S _ V O I C
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ V _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ V O I C E
R A B _ A C T _ R E
*
6 0 0 0
IC E
D _ T M _ C S _ V O
A V G _ R A B _ H L
Releases RAB Abnormal of Number 60 * RAB a of Erlangs Traffic = = *60 Number of Abnormal VoiceReleases
3600 * 100 ICE D_TM_CS_VO AVG_RAB_HL Releases Voice Abnormal of Number 60 * Erlangs Traffic Voice
+
_ U E
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R N C
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U R
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ B T S
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R A D I O
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U
I L _ C S _ C O N V
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ C _ U N S
R A B _ A C T _ R E
+
P _ E M P
L _ C S _ C O N V _
R A B _ A C T _ R E
*
6 0 0 0
N V
D _ T M _ C S _ C O
A V G _ R A B _ H L
To be completed with NSN Formula3.1.4 17BDrops per Erlang (or Drops per Hour)
It is the average number of dropped calls per 1 hour of connection.
i.e., just the inverse of the previous KPI (Minutes per drop).
• It is not often used because it is not easily mapped on the user perception.
• It is not dependent on the call duration.
• It is more stable than Minutes per Drop in case of good values.
3.1.4.1 43BUVoice drops per hour
3.1.4.2 44BUVideo drops per hour
3.1.4.3 45BUHS drops per hour
3.1.5 18BOverall Service Retainability - OSRET (%)
Since there are many different services defined in UMTS and each one can have a different retainability at any time, an overall service reatainability can be defined to obtain an overall measure of network retainability averaged over all services. This metric can be used in case one single measurement is to be applied to sort out the worst overall cells in terms of drops.
The OSRET criterion will be based on a weighted averaging of the retainability for the CS and PS services supported by the cell. The weighting factors will be chosen to be the demand for the service given by the number of RAB Establish attempts for that service.
OSRET = 100 * [(CS DCR * Total CS Releases) + (PS DCR * Total PS Releases)] / Total CS & PS
Releases where:
CS/PS DCR = Dropped Call Rate, as described in the previous section.
60 * RAB a of Erlangs Traffic Releases RAB Abnormal of Number To be completed with NSN Formula
IC E
D _ T M _ C S _ V O
A V G _ R A B _ H L
E _ U E
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R N C
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U R
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ B T S
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ R A D I O
I L _ C S _ V O I C
R A B _ A C T _ F A
+
E _ I U
I L _ C S _ V O I C
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ V _ U N S
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ V O I C E
R A B _ A C T _ R E
*
6 0 0 0
+
N V
D _ T M _ C S _ C O
A V G _ R A B _ H L
_ U E
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R N C
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U R
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ B T S
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ R A D I O
I L _ C S _ C O N V
R A B _ A C T _ F A
+
_ I U
I L _ C S _ C O N V
R A B _ A C T _ F A
P E _ E R _ C N
L _ C S _ C _ U N S
R A B _ A C T _ R E
+
P _ E M P
L _ C S _ C O N V _
R A B _ A C T _ R E
*
6 0 0 0
+
Or simplifying:
100 * {[(CS Abnormal Releases / CS Normal & Abnormal Releases) * CS Normal & Abnormal Releases ] +
[(PS Abnormal Releases / PS Normal & Abnormal Releases) * PS Normal & Abnormal Releases ]} / (CS Normal & Abnormal Releases + PS Normal & Abnormal Releases) =
100 * (CS Abnormal Releases + PS Abnormal Releases) /
(CS Normal & Abnormal Releases + PS Normal & Abnormal Releases) The KPI can be built for NSN in the following way:
3.2
9BMedium Level KPIs: Voice Drop Reasons
In order to dig deeper into the different reasons for the drops detected by the High Level KPIs described so far, we can build the following Medium Level KPIs, for each type of Calls. This way, for instance: Speech DCR (%) =
•
RADIO Speech DCR +•
Iu Speech DCR + • Iur Speech DCR + • BTS Speech DCR + • UE Speech DCR +• Unspecified Error Speech DCR +
•
Pre-emption Speech DCR +•
RNC (OTHERS) Speech DCRTo be CONFIRMED with NSN if IRAT drops are already counted in this split of reasons above. We guess they are.Maybe included in RNC (Others) reason.
This set of reasons are analyzed further in Section 4 (Performance Analysis – Low Level KPIs)
3.2.1 19BRADIO <RAB> DCR (%)
(Percentage of <RAB> calls dropped due to radio interface synchronization failure, i.e., the radio connection is lost)
G _ U E
IL _ P S _ B A C K
R A B _ A C T _ F A
R _ U E
IL _ P S _ IN T E
R A B _ A C T _ F A
_ U E
IL _ C S _ C O N V
R A B _ A C T _ F A
E _ U E
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ R N C
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R N C
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ R N C
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ R N C
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ IU R
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ IU R
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ IU R
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ IU R
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ B T S
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ B T S
IL _ P S _ IN T E
R A B _ A C T _ F A
_ B T S
IL _ C S _ C O N V
R A B _ A C T _ F A
E _ B T S
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ R A D IO
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R A D IO
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ R A D IO
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ R A D IO
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ IU
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ IU
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ IU
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ IU
IL _ C S _ V O IC
R A B _ A C T _ F A
+
P _ E M P
L _ C S _ C O N V _
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ V O IC E
R A B _ A C T _ R E
P E _ E R _ C N
L _ P S _ B _ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ P S _ I_ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ C S _ C _ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ C S _ V _ U N S
R A B _ A C T _ R E
_ S R N C
L _ P S _ B A C K G
R A B _ A C T _ R E
_ S R N C
L _ P S _ IN T E R
R A B _ A C T _ R E
S R N C
L _ C S _ C O N V _
R A B _ A C T _ R E
_ S R N C
L _ C S _ V O IC E
R A B _ A C T _ R E
+
G
M P _ P S _ B A C K
R A B _ A C T _ C O
R
M P _ P S _ IN T E
R A B _ A C T _ C O
+
E
M P _ C S _ V O IC
R A B _ A C T _ C O
G _ U E
IL _ P S _ B A C K
R A B _ A C T _ F A
R _ U E
IL _ P S _ IN T E
R A B _ A C T _ F A
_ U E
IL _ C S _ C O N V
R A B _ A C T _ F A
E _ U E
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ R N C
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R N C
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ R N C
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ R N C
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ IU R
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ IU R
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ IU R
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ IU R
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ B T S
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ B T S
IL _ P S _ IN T E
R A B _ A C T _ F A
_ B T S
IL _ C S _ C O N V
R A B _ A C T _ F A
E _ B T S
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ R A D IO
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ R A D IO
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ R A D IO
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ R A D IO
IL _ C S _ V O IC
R A B _ A C T _ F A
+
G _ IU
IL _ P S _ B A C K
R A B _ A C T _ F A
+
R _ IU
IL _ P S _ IN T E
R A B _ A C T _ F A
+
_ IU
IL _ C S _ C O N V
R A B _ A C T _ F A
+
E _ IU
IL _ C S _ V O IC
R A B _ A C T _ F A
P E _ E R _ C N
L _ P S _ B _ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ P S _ I_ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ C S _ C _ U N S
R A B _ A C T _ R E
P E _ E R _ C N
L _ C S _ V _ U N S
R A B _ A C T _ R E
+
P _ E M P
L _ C S _ C O N V _
R A B _ A C T _ R E
+
_ P _ E M P
L _ C S _ V O IC E
R A B _ A C T _ R E
*
1 0 0
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
E
I L _ ( R A B ) _ U
R A B _ A C T _ F A
+
N C
I L _ ( R A B ) _ R
R A B _ A C T _ F A
+
U R
I L _ ( R A B ) _ I
R A B _ A C T _ F A
+
T S
I L _ ( R A B ) _ B
R A B _ A C T _ F A
+
A D I O
I L _ ( R A B ) _ R
R A B _ A C T _ F A
+ U
I L _ ( R A B ) _ I
R A B _ A C T _ F A
S P E _ E R _ C N
L _ ( R A B ) _ U N
R A B _ A C T _ R E
+
E M P
L _ ( R A B ) _ P _
R A B _ A C T _ R E
N C
L _ ( R A B ) _ S R
R A B _ A C T _ R E
+
M P _ ( R A B )
R A B _ A C T _ C O
A D I O
I L _ ( R A B ) _ R
R A B _ A C T _ F A
*
1 0 0
+
+
Where the string “(RAB)” must be replaced by one of the following RAB types:
•
CS_VOICE (CS_V),•
CS_CONV (CS_V),•
CS_STREA (CS_S),•
PS_CONV (PS_C),•
PS_STREA (PS_S),•
PS_INTER (PS_I),•
PS_BACKG (PS_B).Note: In brackets, the string to be used for counters “…_UNSPE_ER_CN”.
For <Reason> PS DCR, counters for both PS_INTER and PS_BACKG are to be added in the formula. Note that these 2 RAB types (PS_INTER and PS_BACKG) do not have counters for drops due to pre-emption (P_EMP): Pre-pre-emption is not done for NRT RABs (interactive and background). NRT DCHs can be released to make room for RT RABs but this is not called “pre-emption” but “RT over NRT”.
It is possible to put together in a similar formula all types of RABs to estimate the total contribution of a certain <Drop Reason> to the Overall DCR.
High value (e.g. >2%) indicates retainability problems related to the RF environment.
3.2.2 20BIu <RAB> DCR (%)
(Percentage of <RAB> calls dropped due to some abnormal reason related to Iu-interface)
Where the string “(RAB)” must be replaced by one of the following RAB types: CS_VOICE (CS_V), CS_CONV (CS_V), CS_STREA (CS_S), PS_CONV (PS_C), PS_STREA (PS_S), PS_INTER (PS_I), PS_BACKG (PS_B). Note: In brackets, the string to be used for counters “…_UNSPE_ER_CN”.
For <Reason> PS DCR, counters for both PS_INTER and PS_BACKG are to be added in the formula.
Note that these 2 RAB types (PS_INTER and PS_BACKG) do not have counters for drops due to pre-emption (P_EMP).
High value (e.g. >2%) indicates retainability problems related to Iu-interface.
3.2.3 21BIur <RAB> DCR (%)
(Percentage of Voice calls dropped caused by drift RNC procedures; for example, radio link reconfiguration failure in DRNC)
Where the string “(RAB)” must be replaced by one of the following RAB types: CS_VOICE (CS_V), CS_CONV (CS_V), CS_STREA (CS_S), PS_CONV (PS_C), PS_STREA (PS_S), PS_INTER (PS_I), PS_BACKG (PS_B). Note: In brackets, the string to be used for counters “…_UNSPE_ER_CN”.
For <Reason> PS DCR, counters for both PS_INTER and PS_BACKG are to be added in the formula.
Note that these 2 RAB types (PS_INTER and PS_BACKG) do not have counters for drops due to pre-emption (P_EMP).
E
I L _ ( R A B ) _ U
R A B _ A C T _ F A
+
N C
I L _ ( R A B ) _ R
R A B _ A C T _ F A
+
U R
I L _ ( R A B ) _ I
R A B _ A C T _ F A
+
T S
I L _ ( R A B ) _ B
R A B _ A C T _ F A
+
A D I O
I L _ ( R A B ) _ R
R A B _ A C T _ F A
+ U
I L _ ( R A B ) _ I
R A B _ A C T _ F A
S P E _ E R _ C N
L _ ( R A B ) _ U N
R A B _ A C T _ R E
+
E M P
L _ ( R A B ) _ P _
R A B _ A C T _ R E
N C
L _ ( R A B ) _ S R
R A B _ A C T _ R E
+
M P _ ( R A B )
R A B _ A C T _ C O
U
I L _ ( R A B ) _ I
R A B _ A C T _ F A
*
1 0 0
+
+
E
I L _ ( R A B ) _ U
R A B _ A C T _ F A
+
N C
I L _ ( R A B ) _ R
R A B _ A C T _ F A
+
U R
I L _ ( R A B ) _ I
R A B _ A C T _ F A
+
T S
I L _ ( R A B ) _ B
R A B _ A C T _ F A
+
A D I O
I L _ ( R A B ) _ R
R A B _ A C T _ F A
+ U
I L _ ( R A B ) _ I
R A B _ A C T _ F A
S P E _ E R _ C N
L _ ( R A B ) _ U N
R A B _ A C T _ R E
+
E M P
L _ ( R A B ) _ P _
R A B _ A C T _ R E
N C
L _ ( R A B ) _ S R
R A B _ A C T _ R E
+
M P _ ( R A B )
R A B _ A C T _ C O
U R
I L _ ( R A B ) _ I
R A B _ A C T _ F A
*
1 0 0
+
+
High value (e.g. >2%) indicates retainability problems related to Iur-interface.
3.2.4 21BBTS <RAB> DCR (%)
(Percentage of Voice calls dropped caused by BTS (for example, radio link setup or reconfiguration problem)
Where the string “(RAB)” must be replaced by one of the following RAB types: CS_VOICE (CS_V), CS_CONV (CS_V), CS_STREA (CS_S), PS_CONV (PS_C), PS_STREA (PS_S), PS_INTER (PS_I), PS_BACKG (PS_B). Note: In brackets, the string to be used for counters “…_UNSPE_ER_CN”.
For <Reason> PS DCR, counters for both PS_INTER and PS_BACKG are to be added in the formula.
Note that these 2 RAB types (PS_INTER and PS_BACKG) do not have counters for drops due to pre-emption (P_EMP).
High value (e.g. >2%) indicates retainability problems related to Iur-interface.
3.2.5 20BUE <RAB> DCR (%)
(Percentage of <RAB> calls dropped caused by the UE.
The RNC sends IU/RAB RELEASE REQUEST message to the CN because the UE is not responding to an RRC message or the UE is responding with such failure message that the connection must be released).
Where the string “(RAB)” must be replaced by one of the following RAB types: CS_VOICE (CS_V), CS_CONV (CS_V), CS_STREA (CS_S), PS_CONV (PS_C), PS_STREA (PS_S), PS_INTER (PS_I), PS_BACKG (PS_B). Note: In brackets, the string to be used for counters “…_UNSPE_ER_CN”.
For <Reason> PS DCR, counters for both PS_INTER and PS_BACKG are to be added in the formula.
Note that these 2 RAB types (PS_INTER and PS_BACKG) do not have counters for drops due to pre-emption (P_EMP).
High value (e.g. >2%) indicates retainability problems related to the UE.
3.2.6 21BUnspecified Error <RAB> DCR (%)
(Percentage of <RAB> active releases with "unspecified failure" cause received from CN).
Where the string “(RAB)” must be replaced by one of the following RAB types: CS_VOICE (CS_V), CS_CONV (CS_V), CS_STREA (CS_S), PS_CONV (PS_C), PS_STREA (PS_S), PS_INTER (PS_I), PS_BACKG (PS_B). Note: In brackets, the string to be used for counters “…_UNSPE_ER_CN”.
For <Reason> PS DCR, counters for both PS_INTER and PS_BACKG are to be added in the formula.
Note that these 2 RAB types (PS_INTER and PS_BACKG) do not have counters for drops due to pre-emption (P_EMP).
High value (e.g. >2%) indicates retainability problems to be investigated further, likely CORE, TX, Protocol,… issues.
3.2.7 20BPre-emption <RAB> DCR (%)
(Percentage of RT <RAB> released due to pre-emption).
