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authorization from Alcatel.

Introduction to QUALITY OF SERVICE and TRAFFIC LOAD

MONITORING BSS release B9

TRAINING MANUAL3FL10491ACAAWBZZA ed 2 October 2006

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Safety Warning

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Caution

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2004 Alcatel. All rights reserved.

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Product Line EVOLIUM Mobile Radio Solutions

Course Title Introduction to GSM QoS and traffic load monitoring / B9

Course Number 3FL10491ABAA

Audience

Customer personnel in charge of the radio optimization, quality of service and radio traffic-engineering.

Objectives

During this training, the participant will learn how interpret counters and indicators of the Alcatel BSS System.

By the end of the course, the participant will be able to interpret :

- Global indicators, in order to assess the general quality of the network

- Detailed indicators, in order to detect / identify / locate the main malfunctions

- Handover indicators, in order to quantify efficiency and reason of HO

- Directed retry indicators, in order to quantify efficiency of directed retry

- RMS indicators to ease radio optimisation and fault detection

- Traffic indicators, in order to detect/predict overload and compute adequate cell dimensioning as well as to understand how RTCH resources are used in the network

Prerequisites

In depth knowledge of GSM BSS system architecture

Windows literate

Training Methods

Theory and practice on PC

Language

English - French

Duration

5 days

Location

Alcatel University or Customer Premises

Number of participants

8 maximum

Course content

1 Introduction 1.1 Monitoring the Qos of the BSS

1.2 Monitoring the traffic Load of the BSS

1.3 Information sources available

1.4 Introduction to K1205 PC emulation

2 Global Indicators 2.1 Indicators definition

2.2 Methodological precautions

2.3 Typical call failures

2.4 Description of global indicators

2.5 Traps and restrictions of global indicators

2.6 Global indicators interpretation

3 Detailed Indicators 3.1 Indicator reference name

3.2 Indicators classification

4 HO Indicators 4.1 Intra-cell handover indicators per cell

4.2 Internal handover indicators per cell

4.3 External handover indicators per cell

4.4 Handover indicators per couple of cells

5 Directed Retry Indicators 5.1 Internal directed retry indicators

5.2 External directed retry indicators

6 Radio Measurement Statistics (RMS) indicators 6.1 Radio Measurement Statistics objectives

6.2 RMS implementation in the BSS

6.3 RMS data

6.4 Call quality statistics per TRX

6.5 Radio quality statistics per TRX

6.6 C/I statistics

6.7 RMS indicators usage

6.8 Additional information

7 Traffic Indicators 7.1 Call mix definition

7.2 Basis of traffic theory

7.3 TCH resource allocation indicators

7.4 Resource occupancy indicators

7.5 Traffic model indicators

7.6 Preemption indicators

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Objectives

Instructional objectives Yes (or Globally yes)

No (or globally no)

Comments

1- To be able to interpret Global indicators, in order to assess the general quality of the network

2- To be able to interpret Detailed indicators, in order to detect / identify / locate the main malfunctions

3- To be able to interpret Handover indicators, in order to quantify efficiency and reason of HO

4- To be able to interpret Directed retry indicators, in order to quantify efficiency of directed retry

5- To be able to interpret RMS indicators to ease radio optimisation and fault detection

6- To be able to interpret Traffic indicators, in order to detect/predict overload and compute adequate cell dimensioning as well as to understand how RTCH resources are used in the network

Contract number :

Course title :

Client (Company, centre) :

Language : dates from : to :

Number of trainees : Location :

Surname, First name :

Did you meet the following objectives ?

Tick the corresponding box

Please, return this sheet to the trainer at the end of the training

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Instructional objectives Yes (or Globally yes)

No (or globally no)

Comments

Objectives (continued)

Thank you for your answers to this questionnaire

Other comments

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All rights reserved 2004, Alcatel

1 INTRODUCTION

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8Introduction to Quality of the Service and Traffic Load Monitoring BSS Release B9


1 IntroductionSection presentation

> Objective: to be able to explain what is QoS and Traffic Load monitoring of the BSS and what are the information sources available for that purpose

> Program:

1.1 Monitoring the QoS of the BSS

1.2 Monitoring the Traffic Load of the BSS


1.4 Introduction to K1205 PC emulation

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1 INTRODUCTION

1.1 Monitoring the QoS of the BSS

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1.1 Monitoring the QoS of the BSSDefinition

> Monitor" "network" "quality"

monitor = measure or ensure?

network = BSS? BSS+NSS? BSS+NSS+PSTN

quality = service (end-user) and/or system (technical)

> But also detect, localize, diagnose outages

detect (decide according to thresholds)

localize (which cell, BSC, etc.)

diagnose: radio, BSS, TC problems

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1.1 Monitoring the QoS of the BSSUsage

QoS ResultsQoS Results

Managementnetwork monitoringcomparison with competitorcomparison of manufacturerscontractual requirement: licencequality responsible

Managementnetwork monitoringcomparison with competitorcomparison of manufacturerscontractual requirement: licencequality responsible

Radio optimizationcell radio quality surveyHO quality monitoringassessment of tuning efficiency

Radio optimizationcell radio quality surveyHO quality monitoringassessment of tuning efficiency

BSS maintenancecell/BSC/TC problem detectionBSS maintenancecell/BSC/TC problem detection

> 3 usages of QoS data 3 levels of QoS reports:

1. Management team: has to compare Network QoS with competitors' one and to plan Network evolutions.

needs to have a general view of the Network QoS on a monthly (and sometimes weekly) basis.

2. Radio Optimization team: has to detect bad QoS areas in the network and to implement and assess modifications for QoS improvement.

needs to have a detailed status and evolution of the QoS at BSS and cell (and sometimes TRX) levels on a weekly, daily (and sometimes hourly) basis.

3. Supervision and Maintenance team: has to detect dramatic QoS degradations and identify the responsible Network Element (and if possible component).

needs to have the most detailed status of QoS at cell and TRX levels on an hourly basis.

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1 INTRODUCTION

1.2 Monitoring the Traffic Load of the BSS

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1.2 Monitoring the Traffic Load of the BSS Definition

> Measure the "quantity" of traffic handled by:

the network

the BSCs

the cells

> Analyze traffic characteristics

call, handover, location update, etc.

> As input for dimensioning/architecture team

> Traffic characteristics used as a "call mix" to dimension or re-dimension the network will be developed in the section Monitoring the Traffic Load of the BSS.

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1 INTRODUCTION


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1.3 Information sources available Observation means

> DIFFERENT WAYS TO OBSERVE/MEASURE the GSM network

External Interface AnalysisA interface: MSC/TC-BSCAbis interface: BSC/BTSAir MS/BTS

Counter browser

OMC CountersBSC(NSS)

Tektronix K1205

Gnnettest MPAW&G NPA

> QoS data can be built-up from different and complementary kinds of information sources.

> Usually post-processing applications will build up QoS indicators from:

OMC-R counters provided by the BSS system itself.

Signaling messages provided by a protocol acquisition tool on the different interfaces handled by the BSS: Air, Abis, A (or Ater).

Abis

A

MSC/VLR

AbisBSC TC

BTS

Ater

Air

SACCH RSL N7 N7

drive test tool protocol analyzer

MS

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1.3 Information sources available A interface trace

INFORMATION SOURCE: EXTERNAL INTERFACE "A"

> Capture/decode signaling between MSC and BSC-TC (A or Ater MUX)

with "protocol analyzer" (Wandel, Tektronix, Gnnettest, etc.)

+ GSM standard, can be used for arbitrage between manufacturers

+ Complete information (message contents, time-stamp)

+ Possible detection of User/MS/BSS/TC/NSS problems

- High cost of equipment

- Time consuming, "post mortem" (installation of tool, file analysis)

- Expertise needed for analysis

- Low coverage (K1103/MA10: 8 COCs, K1205/MPA: 32 COCs maximum!)

- Large amount of data (>> 10 Mbytes /hour/BSC)

> The main advantage of the A interface is to allow the detection of Call Setup failures either due to the User or to the NSS (or PSTN).

> Some typical user failure causes are: Some typical NSS failure causes are:

IMSI Unknown in VLR Temporary FailureIMSI Unknown in HLR Resource UnavailableIMEI Not Accepted Switching Equipment CongestionPLMN Not Allowed Normal UnspecifiedService Option Not Supported Recovery on Timer ExpiryRequested Service Not Supported Call Reject Unassigned Number InterworkingOperator Determined Barring Protocol ErrorUser Alerting Network FailureFacility Not Subscribed CongestionNo Route to DestinationNormal Call ClearingUser BusyInvalid Number FormatCall RejectInterworkingNormal Unspecified

> CAUTION: In order to assess the QoS of a BSS or some cells of a BSS, all N7 links between this BSC and the MSC must be traced. Indeed, as the N7 signaling load is spread over all N7 links, signaling messages relating to one call can be conveyed on any of the active N7 links.

> K1103 protocol analyzer can trace up to 8 COCs at the same time but on maximum 4 PCM physical links.

> K1205 protocol analyzer can trace up to 32 COCs at the same time but on maximum 16 PCM physical links.

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1.3 Information sources available Example of trace

On a K1205 protocol analyzer

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1.3 Information sources available Abis interface trace

INFORMATION SOURCE: EXTERNAL INTERFACE "Abis"

> Capture/decode signaling between BSC and BTS with "protocol analyzer" (Wandel, Tektronix, Gnnettest, etc.)

+ Complete information (message contents, time-stamp)

+ Possible detection of User/MS/BSS/TC/NSS problems

+ Complete radio information thanks to measurement messages

+ Downlink and uplink


- Time consuming, "post mortem" (installation of tool, file analysis)

- Important expertise needed for analysis

- Very low coverage (A few RSLs, a few cell(s))

- Very large amount of data (>> 10 Mbytes/hour/BTS)

> The main advantage of the Abis trace is to allow a detailed and precise assessment of the radioquality of a cell at TRX level. Both DownLink and UpLink paths can be observed and compared.

> BUT from B7 release, the Radio Measurement Statistics (RMS) feature implemented in the BSS provides a good level of information allowing to reduce the number of Abis traces to be done for radio network optimization.

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1.3 Information sources available Air interface trace

INFORMATION SOURCE: EXTERNAL INTERFACE "Air"

> Use trace MS to capture signaling and signal characteristics

+ Give precise location (x,y) of problems

+ Give downlink radio information

+ Only way to localize a lack of coverage

+ Only way to monitor competitor


- Very time-consuming

- Difficulty to perform a lot of calls-> number of samples insufficient

-> only a few streets

- No uplink

> The main advantage of the Air trace is to associate a radio quality measurement to a given geographical area of the network.

> Even if the RMS feature will allow to assess the radio quality as perceived by the end user, no location of the radio problems is provided through the RMS.

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1.3 Information sources available Performance Measurement counters

SUB-SYSTEM COUNTERS

> Counts events seen by sub-system, value reported periodically (1 hour)

+ Low cost: collected directly at OMC

+ Compact data: possibility to store counters for a complete network

- Raw information, having to be consolidated to be understandable

- Manufacturer's dependent: questionable/difficult to compare

- Weak to analyze other sub-systems

> The main advantage of the BSS counters is to provide easily QoS data for permanent QoS monitoring.

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1.3 Information sources available Exercise

> Draw the BSS PM counters flow on the chart

> In which sub-system are the BSS QoS indicators computed and stored?

BSC

BSC

BSC

OMC-R

OMC-R OMC-R

NPA

RNO

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1.3 Information sources available BSS counters

BSS COUNTERS

> Combined into significant formulae: indicators

> Used to monitor BSS network quality

> Over a complete network, with breakdown per cell/BSC

> SPECIFIC DRAWBACK

NSS/PSTN/MS/USER problems not seen

> As BSS PM counters are defined in order to provide information to assess the QoS of the BSS and help to detect BSS misbehavior, there is no way to identify QoS problems due to NSS, PSTN or User.

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1.3 Information sources available NSS counters

NSS COUNTERS

> Combined into significant formulas: indicators

> Used to monitor NSS network quality

> Over a complete network, with breakdown per BSC (maximum)

> SPECIFIC DRAWBACKS

BSS problems usually not precisely identified

No breakdown per cell

> The NSS QoS is provided through NSS PM counters and indicators. It is out of the scope ot this training course.

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1.3 Information sources available ALCATEL BSS counters

INFORMATION SOURCES: BSS Counters (1/2)

> Performance Management implementation

Easy and cost-effective way to monitor network and carried traffic

> Principle:

For a given duration (granularity period= typically 1 hour)

To count pre-defined events occurring on the Abis or A interface, or internally.

Counters stored with breakdown per network component (I.e. cell)

> In the BSS B9, around 1000 counters are available (without GPRS).

> Alcatel has chosen to implement PM counters in the BSC and to increment them mostly on Abis interface signaling messages.

> Other suppliers may have chosen to increment them on A interface signaling messages or to implement them in the BTS.

> Therefore caution should be taken when interpreting QoS indicators value since some discrepancies may be observed due to these possible choices.

In order to provide the operators with an easy and cost-effective way to monitor their network and carried traffic, BSS manufacturers have implemented specific software features, called performance management.

The principle is to count for a given duration called granularity period (typically 1 hour) pre-defined events occurring on the Abis or A interface, or internally. These counters are stored for each duration, with breakdown per network component (i.e. cell).

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1.3 Information sources available ALCATEL BSS counters

INFORMATION SOURCES: BSS Counters (2/2)

> In Alcatel BSS (except GPRS), counters are computed by BSC,

based mainly on Abis messages.

> Every reporting period, counters values are sent to the OMC-R for storage.

> Several counters are reported to the OMC-R permanently every PM granularity period:

Type 180: per cell adjacency

Type 110 per cell

Other Types: per TRX / N7 Link / BSC /

Millions of counters are collected every day

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1.3 Information sources available BSS counter Example

> MC718: counter number

> NB_TCH_NOR_ASS_SUCC_TRX: counter name

> Cumulative: method of computation

> Type 110: BSS PM measurement type to which the counter belongs

> Measured object: minimum object level for which the counter is provided: TRX or CELL or BSC or N7 LINK or X25 LINK etc.

> All counters are described in the "PM counters and indicators".

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1.3 Information sources available BSS counter characteristics

Collection mechanism

> Cumulative

The counter is incremented at the occurrence of a specific event

Abis or A message, or internal event

At the end of a collection period, the result is the sum of the events

> Inspection

Every 20 or 10 seconds, a task quantifies an internal resource status (usually a table)

At the end of a collection period, the result is the mean value

> Observation

Set of recorded information about a telecom procedure (handover,channel release, UL & DL measurements reporting)

> Main counters are of cumulative type.

> Inspection counters are of gauge type.

> Observation counters are grouped in a Performance Measurement record associated to a particular GSM BSS telecom procedure: SDCCH channel seizure, TCH channel seizure, internal handover, etc.

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1.3 Information sources available BSS Performance Measurement types

N Type Name Type definition

1 Traffic Measurement Set of counters related to the traffic evaluation per telecom procedure

2 Resource Availability Measurement Set of counters related to the availability of the CCCH, SDCCH, or TCH channels

3 CCCH channel resource usage measurements Set of counters related to the usage of CCCH channel (PCH, AGCH, RACH)

4 SDCCH channel resource usage measurements Set of counters related to the usage of SDCCH channel

5 TCH channel resource usage measurements Set of counters related to the usage of TCH channel

6 TCH Handover Measurements Set of counters related to the TCH handover procedure

7 LAPD Measurement Set of counters related to the LapD logical links

8 X.25 Measurement Set of counters related to the X25 links OMC-BSC

9 N7 Measurement Set of counters related to the N7 Signaling Links

10 SDCCH Observations Observation counters on SDCCH channels allocated

11 TCH measurements observations Observation counters on 08.58 MEASUREMENT REPORT for a TCH

12 Internal Handover Observations Observation counters on internal intra-cell or inter-cell SDCCH or TCH handover

13 Incoming External Handover Observations Observation counters on incoming external SDCCH or TCH handover

14 Outgoing External Handover Observations Observation counters on outgoing external SDCCH or TCH handover

15 TCH Observation Observation counters on TCH channel allocated

18 A Interface measurements different causes of 08.08 CLEAR REQUEST and 08.08 ASSIGNMENT FAILURE

19 SMS PP Measurements Set of counters related to Short Message Service Point to Point

25 SCCP Measurements Set of counters related to SCCP Layer of the N7 signaling Links

26 TCH outgoing Handover per adjency Set of counters related to outgoing TCH handover provided per adjency

27 TCH incoming Handover per adjency Set of counters related to incoming TCH handover provided per adjency

28 SDCCH Handover Set of counter related to the SDCCH handover procedure

29 Directed Retry measurements Set of counter related to the directed retry handover procedure

30 SMS CB Measurements Set of counters related to Short Message Service Cell Broadcast

31 Radio Measurement Statistics Set of counters providing radio quality measurements for TRX/Cell

32 Change of frequency band measurements Set of counters related to handovers including a change of TCH Frequency band

33 BTS Power Measurement Average emitted power at the BTS antenna output

110 Overview measurements Set of key counters allowing to access Quality of Service of a given Cell/BSC/Network

180 Traffic Flow measurements Set of counters related to incoming inter-cell SDCCH/TCH handover performed per adjency

B9

NewB9

ANNEX 6

> BSS Performance Measurement types (PM types) are split into two categories:

standard types (7, 8, 9, 18, 19, 25, 28, 29, 30, 31, 32,110, 180)

detailed types (1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 14, 15, 26, 27)

> The most important types for QoS monitoring and Radio Network Optimization are in bold.

> A standard PM type can be activated for the whole network. It means that the related counters are reported for all the Network Elements they are implemented on (TRX, CELL, N7 link, X25 link, LAPD link, Adjacency).

> A detailed PM type can be activated only on a sub-set of the network. It means that the related counters are reported only for a limited number of Network Elements:

40 cells per BSS for PM types 1, 2, 3, 4, 5, 6, 26, 29

15 cells per BSS for PM types 10, 12, 13, 14, 15

1 cell per BSS for PM types 11, 27

> Counter numbering rules:

Cyz: cumulative or inspection counters in PM types 1, 2, 3, 4, 5, 6, 18, 19, 25, 26, 27, 28, 29, 30, 32, 180

Ly.z: cumulative counters in PM type 7 (L stands for LAPD link)

Xy.z: cumulative counters in PM type 8 (X stands for X25 link)

Ny.z: cumulative counters in PM type 9 (N stands for N7 link)

Syz: observation counters in PM type 10 (S stands for SDCCH)

Ryz:: observation counters in PM type 11 (R stands for Radio measurements)

HOyz: observation counters in PM type 12, 13, 14 (HO stands for HandOver)

Tyz: observation counters in PM type 15 (T stands for TCH)

RMSyz: cumulative counters in PM type 31 (RMS stands for Radio Measurement Statistics)

MCyz or MNy.z: cumulative counters in PM type 110 (M stands for Major)

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1.3 Information sources available Observation means

Training exercise: find the best source of informationObservation to be done: Best source Why

6- history of network quality for several

weeks

8- discriminate problems between BSS/NSS.

BSS and NSS coming from different

providers

9- In a building, one is thinking that an

elevator is inducing PCM trouble, how to

confirm ?

10- Identify potential interfering cells of 1

Cells

5- localise abnormal cells in a network

7- compare networks quality

3- get average network quality

4- localise precise location of a radio pb

1- overall radio quality of 1 cell Counters Type 31: RMS

2- monitor user failures

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2 GLOBAL INDICATORS

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2 Global indicatorsSection presentation

> Objective: to be able to explain what is a Global indicator and what are the main BSS indicators regarding GSM services provided by the Alcatel BSS

> Program:

2.1 Indicators definition



2.4 Description of global indicators

2.5 Traps and restrictions of global indicators

2.6 Global indicators interpretation

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2 GLOBAL INDICATORS

2.1 Indicators definition

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2.1 Indicators definitionGlobal / detailed

BSS INDICATORS DEFINITION (Alcatel)

> Numerical data providing information about network performance regarding:

The complete network: GLOBAL indicator

An element of the network: DETAILED indicator

TS/TRX/CELL/BTS/BSC/TC

> A formulae of several counter(s)

> Counters vs. Indicators

Counters: provided by the BSS equipments

Indicators: computed by BSS Monitoring equipments

> The indicators computation can be performed from several counters or by a simple counter mapping.

> Example:

call drop rate = Call Drop nb / Call nb = f(counters)

call drop = Call drop nb = 1 counter

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2.1 Indicators definitionGlobal

GLOBAL INDICATORS

> Measure the performance of the complete network

> Analyzed according their trend and values

Usually every day (week, month)

> Compared with:

Competitor results if available

Contractual requirements

Internal quality requirements

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2.1 Indicators definitionThresholds

EXAMPLE: Thresholds on Call Drop Rate indicator

Weekly CDR "GSM"

0,00%

0,50%

1,00%

1,50%

2,00%

2,50%

3,00%

3,50%1 5 9

13

17

21

25

29

33

37

41

45

week number

CD

R

weekly call drop rate

contractual call drop rate

quality CDR

Weekly CDR "GSM"

0,00%

0,50%

1,00%

1,50%

2,00%

2,50%

3,00%

3,50%1 5 9

13

17

21

25

29

33

37

41

45

week number

CD

R

weekly call drop rate

contractual call drop rate

quality CDR

> The Call Drop rate at network level has to compared to:

Contractual threshold: can be requested by the operator management to the operational radio team, can be requested by the operator to the provider on swap or network installation

Quality threshold: fixed internally by radio team management.

> Quality thresholds are usually more tight than contractual ones.

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2.1 Indicators definitionExercise

> TRAINING EXERCISE: GLOBAL OR NOT

INDICATOR DESCRIPTION G ?

average of call setup success rate for the network Yes

rate of call lost due to radio pb on cell CI=14, LAC=234 No

call drop rate in your capital

call drop rate of the cell covering a specific buidling

% of HO with the cause better cell (among other causes) for the network

average rate of TCH dropped for all TRX of the network carrying 1 SDCCH8

rate of SDCCH dropped on TRX1 of cell 12,24

call success of 1 PLMN

% of cells being congested today

INDICATOR DESCRIPTION G ?

average of call setup success rate for the network Yes

rate of call lost due to radio pb on cell CI=14, LAC=234 No

call drop rate in your capital

call drop rate of the cell covering a specific buidling

% of HO with the cause better cell (among other causes) for the network

average rate of TCH dropped for all TRX of the network carrying 1 SDCCH8

rate of SDCCH dropped on TRX1 of cell 12,24

call success of 1 PLMN

% of cells being congested today

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2 GLOBAL INDICATORS


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2.2 Methodological precautions Objective

METHODOLOGICAL PRECAUTIONS

> Avoid typical errors regarding indicators interpretation

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2.2 Methodological precautions Global indicator value

A good value for a global indicator

All network components are OK regarding this indicator

> Example

A global call drop rate of 1%

Can hide some cells with 10 % of call drop rate

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2.2 Methodological precautions Network Element aggregation

> The average value of an indicator for a Network

Is not the average of cell results (or any sub-part of it)

BUT the average weighted by the traffic

number of calls number of call drop call drop rate

cell 1 390 8 2,10%

cell 2 546 29 5,25%

cell 3 637 20 3,10%

cell 4 1029 12 1,14%

cell 5 536 3 0,50%

cell 6 2 1 50,00%

cell 7 3 1 33,00%

cell 8 210 4 2,11%

cell 9 432 5 1,20%

cell 10 321 4 1,11%

average of cell results 9,95%

total nb of drop/total number of calls 2,10%

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2 GLOBAL INDICATORS


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2.3 Typical call failures Call Setup phasing

> 4 stages for a call establishment, 2 for a location update:

1- Radio link establishment

2- "SDCCH phase

then only for "Circuit Switch call"

3- TCH assignment

4- "Alerting/connection" phase

> Each phase has a specific utility and weaknesses

Radio Link EstablishmentSDCCH PhaseTCH assignmentAlerting/CNX Phase

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2.3 Typical call failures Radio Link Establishment - OC success

Originated Call: RLE success case

T3101: guard timer for SDCCH allocation (Default: 3 seconds)

CR/CC are used to exchange SCCP references

Any further message related to this call will have one (or 2) of these 2 references

K1205 can extract the call using these references (SLR, DLR!!)

MS BTS BSC

MSC

CHANNEL REQUEST-------------(RACH)------------> CHANNEL REQUIRED

----------------------------------------------> MC8C

CHANNEL ACTIVATION (SDCCH)

IMMEDIATE ASSIGN COMMAND

IMMEDIATE ASSIGN stop T3101

CC

The SDCCH resource allocation is performed by the BSC. Once allocated the SDCCH channel is activated by the BTS on BSC request.

> T3101 is the guard timer for the SDCCH access from the MS. The Default value is 3 seconds.

> MC8C counts the number of Channels Required received from the MS in a cell.

> MC148 counts the number of SDCCH channels activated (therefore allocated) in a cell.

> MC8B counts the number of time an MS is commanded to access an SDCCH channel in a cell.

> MC02 counts the number of MSs which have successfully accessed an SDCCH in a cell as part of a Mobile Originating (MO) call.

> The SCCP Connection Request message is conveyed on an A interface PCM timeslot chosen by the BSC (called COC).

> The SCCP Connection Confirm message is conveyed on a COC chosen by the MSC which can be located on a different PCM than the one of the COC used by the BSC to send signaling messages to the MSC.

> Take care than, when the BSC is congested on the downlink, some messages are discarded. This may result for example in call establishment failures, loss of paging messages or delay in handover procedures.

> A LapD counter that indicates the time a LapD link is congested is created to analyze the cause of a degraded quality of service. This counter is implemented in type 7 and thus only be available in a detailed measurement campaign.

Counter: L1.18: TIME_LAPD_CONG

Definition: Time in seconds during which the LapD link is congested in transmission in the BSC.

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2.3 Typical call failures Radio Link Establishment - TC success

Terminated Call: RLE success caseMS BTS BSC MSC

PAGINGPAGING COMMAND In case no MS is accessing the SDCCH channel (T3101 expiry) then the BSC does not repeat the Immediate Assignment since the MS may have accessed an SDCCH in another BSS. It is up to the MSC to repeat Paging if T3113 expires (usually around 7 seconds).

> MC8A counts the number of Paging Command messages sent on a cell.

> MC01 counts the number of MSs which have successfully accessed an SDCCH in a cell as part of a Mobile Terminating (MT) call.

> Caution:

A paging Request message sent on the Air interface by the BTS may contain several MS identities. 3 Paging Request types can be used:

in Paging Request Type 1: up to 2 MSs (IMSI1,IMSI2) can be included.

in Paging Request Type 2: up to 3 MSs (IMSI1,TMSI1,TMSI2) can be included.

in Paging Request Type 3: up to 4 MSs (TMSI1,TMSI2,TMSI3,TMSI4) can be included.

On the other hand, a Paging message and a Paging Command message relate to only one MS identity.

Alcatel 45



2.3 Typical call failures Radio Link Establishment - Paging

RLE > PagingMC8A=C8A

> Normally all cells of the same Location Area must have the same MC8A counter value since all these cells must be paged for an MT call on an MS located in the Location Area they are included in.

> If not: it means that a cell is not declared in the right LA at NSS level.

Alcatel 46



2.3 Typical call failures Radio Link Establishment - RACH counter

RLE > RACHMC8C=C8C

> Caution: All Channels Required (therefore RACH) are counted in MC8C: valid and invalid causes (see later). Indeed ghost RACHsare also counted.

> The Channel Required content corresponds to the Channel Request message sent by the MS to the BTS.

> This Channel Request message is made up of one byte with 2 Informations Elements (IEs):8 7 6 5 4 3 2 1

+-----------------------------------------------+ ESTABLISHMENT RANDOM + - - - - - - - - + CAUSE REFERENCE +-----------------------------------------------+

> ESTABLISHMENT CAUSEThis information field indicates the reason for requesting the establishment of a connection. This field has a variable length (from 3 bits up to 6 bits).

> RANDOM REFERENCEThis is an unformatted field with a variable length (from 5 bits down to 2 bits).

> Due to the fact that the NECI bit is always set to 1 in Alcatel BSS, Establishment causes can be divided into 2 categories:

Valid causes: 5 (6 if GPRS)000: Location Update (Normal, Periodic, IMSI Attach)100: Terminating call101: Emergency call 110: Call Re-establishment111: Originating call (not emergency)011: if GPRS is implemented in the cell

Invalid causes: 3 (2 if GPRS)001: 010: 011: if GPRS is not implemented in the cell

Alcatel 47



2.3 Typical call failures Radio Link Establishment - OC success counters split

RLE > success MO splitMC02x=C02x

MC02 =MC02A+MC02B+MC02C+.+MC02G+MC02H+MC02i

MC02A: LU

MC02B: SMS

MC02C: SS

MC02D: LU follow-on

MC02E: CR

MC02F: unknown

MC02G: IMSI Detach

MC02H: EC or NC

MC02i: LCS

> MC02A = Number of SDCCHs successfully seized for Normal or Periodic LU request (IMSI Attach also counted).

> MC02B = Number of SDCCHs successfully seized for Short Message Service.

> MC02C = Number of SDCCHs successfully seized for Supplementary Service.

> MC02D = Number of SDCCHs successfully seized for LU with follow-on bit set to 1 (means that the SDCCH phase will be followed by a TCH assignment for speech call establishment).

> MC02E = Number of SDCCHs successfully seized for Call Re-establishment.

> MC02F = Number of SDCCHs successfully seized in case of L3 Info (within 08.58 ESTABLISH INDICATION) unknown by the BSC but transferred to the MSC.

> MC02G = Number of SDCCHs successfully seized for IMSI Detach.

> MC02H = Number of SDCCHs successfully seized for Normal or Emergency call.

> MC02i = Number of Mobile Originating SDCCH establishments for LCS purpose.

Also, Evaluation of The Mobiles location (see the next slides)

> LCS: Location Services

Alcatel 48



2.3 Typical call failures Radio Link Establishment - SDCCH congestion failure

> Main failure cases for Radio Link Establishment


SDCCH Access Failure

SDCCH Congestion

SDCCH Congestion

SDCCH Radio Failure

SDCCH Radio Failure

SDCCH BSS Problem

SDCCH BSS Problem

Alcatel 49



2.3 Typical call failures Radio Link Establishment - SDCCH congestion

RLE > SDCCH congestion

> The Immediate Assignment Reject mechanism can be disabled at OMC-R level

And is not activated for answer to paging

If disabled, no answer to the MS

> The MS will repeat automatically its request in case of congestion (next slides)

Waiting for T3122 expiry in case of Immediate Assignment Reject

Waiting for T3120 expiry otherwise

MS BTS BSC

MSC


----------------------------------------------> MC8CNo free SDCCH !!

MC04IMMEDIATE ASSIGN COMMAND Otherwise T3120 is computed by the MS as a random number of slots between:

250 and 250+T-1 for a phase 1 MS where: T=Tx_integer parameter (1 value per cell chosen between 3 to 50 slots)

S and T+S for a phase 2 MS where: T=Tx_integer parameter (1 value per cell chosen between 3 to 50 slots)S is a parameter depending on the CCCH configuration and on the value of Tx_integer as defined in the following table:

TX_integer S(CCCH Not Comb) S(CCCH Combined)

3, 8, 14, 50 55 41

4, 9, 16 76 52

5, 10, 20 109 58

6, 11, 25 163 86

7, 12, 32 217 115

Alcatel 50



2.3 Typical call failures Radio Link Establishment - SDCCH congestion counter


MC04=C04

Alcatel 51



2.3 Typical call failures Radio Link Establishment - SDCCH cong. consequences


MAIN CONSEQUENCES

> The MS will try "max_retrans +1 " time before giving up

Immediately for phase 1 MS

After T3126 for phase 2 MS (still waiting for Immediate Assignment during this timer)

> In case of "max_retrans+1" failures, the MS will

Either try an automatic cell reselection

Or do nothing

> In case of LU, the MS will attempt a new LU request

> In case of Call establishment, the MS will not re-attempt automatically, it is up to the subscriber to try to set up the call again


Alcatel 52



2.3 Typical call failures Radio Link Establishment - SDCCH cong. causes


MAIN CAUSES

> Too much SDCCH "normal" traffic for cell SDCCH design

Radio resource capacity not sufficient (too many calls)

Inadequate LA design (too many LUs)

> "Common Transport Effect"

Difficult to avoid for small cells

> Abnormal SDCCH traffic

Phantom" channel requests (seen in SDCCH RF failure session)

Neighboring cell barred


> SDCCH congestion can be too high because of the subscribers' traffic demand in terms of calls / LU.

Solution = add a TRX or site / redesign the LA plan

> High SDCCH congestion can be observed at peculiar period of the day due to a peak of LU requests generated by a big group of subscribers entering a new LA at the same time (bus, train, plane).

Solution = redesign the LA plan or play on radio parameters (CELL_RESELECT_HYSTERESIS, WI_OP)

> High SDCCH congestion can be abnormally observed without real MS traffic in case a high level of noise or the proximity of a non-GSM radio transmitter.

Solution = change the BCCH frequency or put an RX filter

> High SDCCH congestion can also be abnormally observed in a cell in case one of its neighboring cell is barred.

Solution = Remove the barring

Alcatel 53



2.3 Typical call failures Radio Link Establishment - SDCCH cong. Resolution?


DYNAMIC SDCCH ALLOCATION

> Too many SDCCHs will lead to a lack of TCH resources... and money.

> Too few SDCCH will result in SDCCH congestion. TCH channels cannot be allocated and, once again, the operator 's revenue decreases.

> At OMC-R level, it is possible to configure:

a set of static SDCCH/x timeslots to handle normal SDCCH traffic;

a set of dynamic SDCCH/8 timeslots, which can be used for TCH traffic, or for SDCCH traffic depending on the need.

> "Dynamic SDCCH allocation" feature:

the BSS is automatically looking after varying SDCCH traffic

adapted to the situations such as: change of LA, change of SMS traffic

> Useful in very dense (hierarchical) networks:

optimize the SDCCH configuration becomes more important.


> This feature not only improves SDCCH congestion but also successful TCH assignment rates.

> With the "Dynamic SDCCH allocation" feature, the BSS is automatically looking after varying SDCCH traffic and is particularly adapted to the situations such as: change of LA, change of SMS traffic model, SDCCH traffic varying due to LCS.

> This feature is particularly useful in very dense (hierarchical) networks, where the effort to optimize the SDCCH configuration becomes more important.

Alcatel 54



2.3 Typical call failures Radio Link Establishment - SDCCH cong. Resolution?


DYNAMIC SDCCH ALLOCATION

CHANNEL REQUESTCHANNEL REQUIRED

MS BTS BSC

(RACH)

If No free SDCCH, thenrun dynamic SDCCH/8 timeslot allocation

algorithm. If allocation is successful, then

activate dynamic SDCCH sub-channeland serve request

If allocation was unsuccessful, then reject SDCCH request (possiblyusing the Immediate Assignment Reject procedure).

MC801a&b

MC802a&b


> SPECIFIC COUNTERS (Type 110 / Cell Level):

MC800 Average number of available dynamic SDCCH/8 timeslots.

MC801a Average number of busy dynamic SDCCH/8 timeslots allocated as TCH (FR or HR).

MC801b Maximum number of busy dynamic SDCCH/8 timeslots allocated as TCH (FR or HR).

MC802a Average number of busy SDCCH sub-channels allocated on the dynamic SDCCH/8 timeslots.

MC802b Maximum number of busy SDCCH sub-channels allocated on the dynamic SDCCH/8 timeslots.These four previous counters areInspection Counters ; that means than the resource is checked regulary by the BSC and at the end of the period, an average is done. Example: 3 physical chanels are defined as Dyn SDCCH and the counter give the following indication:MC801a = 1.7 that means sometimes the 3 Dyn SD are allocated as TCH, sometimes only 2 of them, sometimes 1 or 0 and the average is 1.7

> The FOLLOWING COUNTERS ARE IMPACTED BY the Dynamic SDCCH Allocation feature:

MC28, MC29 The Number of busy radio timeslots in TCH usage takes into account the busy TCH timeslots and the dynamic SDCCH/8 timeslots allocated as TCH.

C30, MC31 The Number of busy SDCCH sub-channels takes into account the SDCCH sub-channels allocated on the static and dynamic SDCCH/8 timeslots.

C370a, MC370a, C370b, MC370b The Number of times the radio timeslots are allocated for TCH usage (FR / HR) takes into account the busy TCH timeslots and the dynamic SDCCH/8 timeslots allocated as TCH.

C/MC380a/b C/MC381a/b The Cumulated time (in second) the radio timeslots are allocated for TCH usage (FR or HR)does not take care whether the TCHs are allocated on the TCH radio timeslot or on the dynamic SDCCH/8 timeslots.

C39, MC390, C40, MC400 The Number of times or the Cumulated time (in second) the SDCCH sub-channels are busydoes not take care whether the SDCCH sub-channels are allocated on the static or dynamic SDCCH/x timeslot.

C/MC34 C/MC380 The Cumulated time (in second) all TCHs / SDCCHs in the cell are busydoes not take care whether the TCHs / SDCCHs are allocated on the TCH radio timeslot /SDCCH/x timeslot or on the dynamic SDCCH/8 timeslots.

C/MC320a/b/c/d/e Free TCH radio timeslotscount the free TCH timeslots and the free dynamic SDCCH/8 timeslots.

Alcatel 55



2.3 Typical call failures Radio Link Establishment - SDCCH radio failure



SDCCH Congestion

SDCCH Congestion

SDCCH Radio Failure

SDCCH Radio Failure

SDCCH BSS Problem

SDCCH BSS Problem


Alcatel 56



2.3 Typical call failures Radio Link Establishment - SDCCH radio access failure

RLE > SDCCH RF Failure

MS BTS BSC MSC


----------------------------------------------> MC8CCHANNEL ACTIVATION (SDCCH)


IMMEDIATE ASSIGN MC149 counts the number of SDCCH access failures due to radio problems.

Alcatel 57



2.3 Typical call failures Radio Link Establishment - real radio problems


Main causes > real radio problems

> Unbalanced cell power budget

> Bad coverage (for example a moving car)

> Interference (for example downlink)

In case of radio failure, the MS will retry as for SDCCH congestion


> Unbalanced Power Budget:

> Bad coverage:

> Interference:

DL interference area

AGCH lost

RACH

building

BTS

Channel Request

Access Grant

Max Path Loss UL

Max Path Loss DL

AGCH

RACH

Alcatel 58



2.3 Typical call failures Radio Link Establishment - Ghost RACH (1/7)


Main causes > "Phantom/Ghost/Spurious/Dummy ... RACH"

> Channel request received but not sent: 3 causes

Noise decoding

Reception of channel request sent to a neighboring cell

Reception of HO_ACCESS sent to a neighboring cell

Alcatel 59



2.3 Typical call failures Radio Link Establishment - Ghost RACH (2/7)


Main causes > "Phantom/Ghost/Spurious/Dummy ... RACH"

> Example of a channel required message

> For this Channel Required, the establishment cause is valid (Call re-establishment) but the Access Delay (corresponding to the distance between the MS and the BTS) is high.

> Indeed the Access Delay being equal to the Timing Advance is coded in slot unit representing a distance of 550m. It can take values from 0 (0m) to 63 (35km).

> Thus the Channel Required above is received from an MS located at 19km from the site. It may therefore be rather a ghost RACH than a real MS which wants re-establish a call.

> In Alcatel BSS, there is possibility to filter the Channel Required received from a distance greater than a distance defined as a parameter value: RACH_TA_FILTER tunable on a per cell basis. Caution should be taken since a too low value may reduce the network coverage.

Alcatel 60



2.3 Typical call failures Radio Link Establishment - Ghost RACH causes (3/7)


Main causes > "Phantom RACH" >noise decoding

> GSM 05.05: " 0.02 % of Rach Frame can be decoded without error without real input signal" (No impact for the system)

BCCH not combined: 51 Rach/Multi Frame > (3600 * 1000) ms / 4.615 ms at 0.02 %: 156 dummy RACH/hour

BCCH combined: 27/51 RACH/Multi-Frame > 83 dummy RACH/hour

3/8 of causes (field of channel request, 5 valid causes over 8) will be unvalid

Example of induced SDCCH traffic: (5/8*156*T3101 (3 sec))/3600 = 0.08 Erlang SDCCH

> Some tips:

Dummy Rach load depends on minimum level for decoding configured in Evolium BTS

During period with low real traffic (night), high rate of dummy RACH

For dummy RACH, the channel required has a random value of TA

STRUCTURE of the MULTIFRAME in "TIME SLOT" 0STRUCTURE of the MULTIFRAME in "TIME SLOT" 0STRUCTURE of the MULTIFRAME in "TIME SLOT" 0STRUCTURE of the MULTIFRAME in "TIME SLOT" 0

-

R = RACH

DOWNLINKDOWNLINKDOWNLINKDOWNLINKf s b b b b C C C C

31 51 1211 2 3 4 5 6 7 8 9 10 20 41f s f s f s f sC C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C -

(Multiframes of 51 frames)

f = FCCH s = SCH b = BCCH

f s

C C C C = CCCH (PCH or AGCH)

UPLINKUPLINKUPLINKUPLINKR R R RR R R R R R R RR R R R R R R RR R R R R R R RR R R R R R R RR R R RR R R RR R R R R R

(Non(Non(Non(Non----combined BCCH)combined BCCH)combined BCCH)combined BCCH)

(Combined BCCH)(Combined BCCH)(Combined BCCH)(Combined BCCH)

R = RACH R = RACH R = RACH R = RACH

DOWNLINKDOWNLINKDOWNLINKDOWNLINK

F = FCCH S = SCH B = BCCH C = CCCH (PCH or AGCH)C = CCCH (PCH or AGCH)C = CCCH (PCH or AGCH)C = CCCH (PCH or AGCH)

UPLINKUPLINKUPLINKUPLINK

F S B CCCC F S F S F S -F SCCCC CCCC D0D0D0D0 D1D1D1D1 D2D2D2D2 D3D3D3D3 A0A0A0A0 A1A1A1A1

F S B CCCC F S F S F S -F SCCCC CCCC D0D0D0D0 D1D1D1D1 D2D2D2D2 D3D3D3D3 A2A2A2A2 A3A3A3A3

RRRR RRRR RRRR RRRRRRRR RRRR RRRR RRRR RRRR RRRR RRRR RRRRRRRR RRRR RRRR RRRR RRRR RRRR RRRRRRRR RRRR RRRR RRRR RRRR RRRRRRRR RRRRD3D3D3D3 A2A2A2A2 A3A3A3A3 D0D0D0D0 D1D1D1D1 D2D2D2D2

RRRR RRRR RRRR RRRRRRRR RRRR RRRR RRRR RRRR RRRR RRRR RRRRRRRR RRRR RRRR RRRR RRRR RRRR RRRRRRRR RRRR RRRR RRRR RRRR RRRRRRRR RRRRD3D3D3D3 A0A0A0A0 A1A1A1A1 D0D0D0D0 D1D1D1D1 D2D2D2D2

DnDnDnDn/An = SDCCH/SACCH/4 /An = SDCCH/SACCH/4 /An = SDCCH/SACCH/4 /An = SDCCH/SACCH/4

51 multiframe duration = 51 x 8 x 0,577 = 235ms

Alcatel 61





Main causes > "Phantom RACH" >noise decoding

> No subscriber -> no impact for subscriber

> But MC149 incremented -> SDCCH RF access failure is impacted

MS BTS BSC MSC

CHANNEL REQUIRED

----------------------------------------------> MC8C

CHANNEL ACTIVATION (SDCCH)


IMMEDIATE ASSIGN

Alcatel 62





Main causes > "Phantom RACH" > Channel Request sent to the neighboring cell

> Subscriber not impacted (real transaction performed elsewhere)

> But MC149 incremented -> SDCCH RF access failure is impacted

> Usual radio planning rules are sufficient to avoid the trouble

2 cells must not have same (BCCH, BSIC) couple

M S B T S B SC M SC

CHANNEL REQU IRED----------------------------------------------> M C 8CCHANNEL ACT IVATION (SDCCH)

IMMED IATE ASSIGN COMMAND

IMMED IATE ASSIGN BSIC = BCC (3 bit) + NCC (3 bit)

BCC: BTS Color Code

NCC: Network Color Code

Alcatel 63





Main causes > "Phantom RACH" > Channel Request due to handover

> During HO, the first message sent to the target cell is HO Access

> This message is an Access Burst like Channel Request

> If received on BCCH, can be understood as a Channel Request (RACH)

> A new case of "Phantom RACH"

Alcatel 64





Main causes > "Phantom RACH" > Channel Request due to handover

This case is the most dangerous

> The MS sends usually a sequence of HO Access message, every frame

> In some cases, this can create a phantom RACH if

The frequency of the TCH is identical or adjacent to the one of interfered BCCH

> Characteristics of such phantom RACH (Channel Required)

Subsequent frame number

Random, but stable timing advance

> Can block very easily SDCCH

Alcatel 65



2.3 Typical call failures Radio Link Establishment - BSS failure




SDCCH Congestion

SDCCH Congestion

SDCCH Radio Failure

SDCCH Radio Failure

SDCCH BSS Problem

SDCCH BSS Problem

Alcatel 66



2.3 Typical call failures Radio Link Establishment - BSS problem

RLE > BSS problem

> No specific counter

MS BTS BSC MSC


----------------------------------------------> MC8CCHANNEL ACTIVATION (SDCCH)


IMMEDIATE ASSIGN BSS Problems are difficult to specify a priori. It is better to deduce them from other counters which are easier to implement thus more reliable.

Alcatel 67



2.3 Typical call failures Radio Link Establishment - counters

RLE counters

Request MC8C

GPRS causes P62C

GSM invalid causes unknown

Preparation GSM valid causes unknown

Congestion MC04

BSS Pb unknown

Execution Attempt MC148

Radio Access Failure MC149

BSS Pb MC148 - (MC01+MC02) - MC149

Success MC01+MC02

Radio Link Establishment

REQUEST

Congestion

ATTEMPT

Radio access failure

SUCCESS

BSS problem

Preparation Failure

Execution Failure

GPRS causes GSM/GPRS invalid causes GSM valid causes

BSS problem


> Statistically a ghost RACH can correspond to any kind of establishment cause: valid and invalid.

> As ghost RACH which corresponds to a GSM valid cause will lead to an SDCCH allocation which will not be seized by an MS, it will lead to the incrementation of MC149 counter and therefore counted as an SDCCH access failure due to radio.

Alcatel 68



2.3 Typical call failures Radio Link Establishment - indicators

TYPICAL CALL FAILURES: RLE indicators

SDNAFLBN

SDNAFLRNSDNACGNSDNAFSUNSDNAFLR


> Refer to BSS - DEFINITION OF QUALITY OF SERVICE INDICATORS:

> GLOBAL Quality of service INDICATORS > SDCCH > Assignment Phase

SDNAUR: SDCCH assignment unsuccess rate

SDNACGR: SDCCH assignment failure rate due to congestion (Global)

SDNAFLRR: SDCCH assignment failure rate due to radio

SDNAFLBR: SDCCH assignment failure rate due to BSS problem

> A SDCCH radio access failure due to ghost RACH occurrence is easily observed during low traffic hour (night time) since ghost RACHs are almost the only cause of failure.

Alcatel 69



2.3 Typical call failures SDCCH phase - OC success

Successful SDCCH phase: OC call

> transparent message: no dedicated counters

MS BTS BSC MSC

SDCCH Phase : Originating Call case

< -------------------------------------------------------------------------------------------------------------------------

AUTHENTICATION REQUEST

------------------------------------------------------------------------------------------------------------------------- >AUTHENTICATION RESPONSE

< -------------------------------------------------------------------------------------------------------------------------

CIPHERING MODE COMMAND

------------------------------------------------------------------------------------------------------------------------- >CIPHERING MODE COMPLETE

------------------------------------------------------------------------------------------------------------------------- >

SETUP

< -------------------------------------------------------------------------------------------------------------------------

CALL PROCEEDING


> Transparent messages (DTAP) are used in order the NSS performs control procedures to enable the MS to set up a speech call.

> Authentication: Checks that the Mobile Station is the required station and not an intruder.

> Ciphering: All Information (signaling, Speech and Data) is sent in cipher mode, to avoid monitoring and intruders (who could analyze signaling data).

> Setup/Call Processing: call is being processed between the calling Party and the Called Party.

Alcatel 70



2.3 Typical call failures SDCCH phase - TC success

Successful SDCCH phase: TC call


MS BTS BSC MSC

SDCCH Phase : Terminating Call case

< -------------------------------------------------------------------------------------------------------------------------


------------------------------------------------------------------------------------------------------------------------- >

AUTHENTICATION RESPONSE

< -------------------------------------------------------------------------------------------------------------------------


------------------------------------------------------------------------------------------------------------------------- >

CIPHERING MODE COMPLETE

< -------------------------------------------------------------------------------------------------------------------------

SETUP

------------------------------------------------------------------------------------------------------------------------- >

CALL CONFIRM


> Setup/Call Confirm: the call is being processed between the Calling Party and the Called Party.

Alcatel 71



2.3 Typical call failures SDCCH phase - LU success

Successful SDCCH phase: Location Update


MS BTS BSC MSC

SDCCH Phase : Location Update Case (with TMSI reallocation)

------------------------------------------------------------------------------------------------------------------------- >

LOCATION UPDATE REQUEST

< -------------------------------------------------------------------------------------------------------------------------


------------------------------------------------------------------------------------------------------------------------- >

AUTHENTICATION RESPONSE

< -------------------------------------------------------------------------------------------------------------------------


------------------------------------------------------------------------------------------------------------------------- >

CIPHERING MODE COMPLETE

< -------------------------------------------------------------------------------------------------------------------------

LOCATION UPDATE ACCEPT------------------------------------------------------------------------------------------------------------------------- >

TMSI REALLOCATION COMPLETE


> Some transparent messages are also exchanged between the MS and the network in case of a Location Update transaction.

Alcatel 72



2.3 Typical call failures SDCCH phase - drops

SDCCH phase

> Loss of connection during SDCCH phase = "SDCCH drop"

> 3 origins of SDCCH drop

Radio problems when connected on SDCCH

BSS problems

Call lost during an SDCCH HO (handover failure without reversion to old channel)


> Generally SDCCH handover are disabled in the network since the average SDCCH duration is only around 2 to 3 seconds.

Alcatel 73



2.3 Typical call failures SDCCH phase - Radio drop

SDCCH phase > drop Radio

> Connection lost due to Radio problem

MS BTS BSC MSC

SDCCH Phase established

Radio connection lost

---------------------------------------------------- > MC138

CONNECTION FAILURE INDICATION

(cause : radio link failure)

--------------------------------------- >

CLEAR REQUESTCause : radio interface failure


> MC138 counts the number of SDCCH channel drops due to radio problems.

> Radio problems can be due to coverage, interference and sometimes BSS dysfunction which is not detected as a system alarm the by O&M Fault Management application.

Alcatel 74



2.3 Typical call failures SDCCH phase - BSS drop

SDCCH phase > drop BSS

> Connection lost due BSS problem

MS BTS BSC MSC


MC137

--------------------------------------- >

CLEAR REQUESTCause : O&M intervention

Cause : radio interface failure


> MC137 counts the number of SDCCH channel drops due to BSS problems.

> A BSS problem can be a BTS/BSC hardware or software failure. It can also be due to a problem on the Abis interface (due to Micro Wave transmission for instance).

Alcatel 75



2.3 Typical call failures SDCCH phase - HO drop

SDCCH phase > drop HO

> Connection lost during Handover

MS BTS BSC MSC


HO FAILURE WITHOUT REVERSION MC07

--------------------------------------- >

CLEAR REQUEST

Radio Interface Message Failure (Alcatel)


> MC07 counts the number of SDCCH channel drops due to handover failure.

Alcatel 76



2.3 Typical call failures SDCCH phase - counters

SDCCH phase counters

SDCCH connection MC01+MC02+MC10

SDCCH Drop Drop radio MC138

Drop BSS MC137

Drop HO MC07

SDCCH Phase

TCH assignment phase SDCCH drop

SDCCH connection

Normal release

Drop radio

Drop BSS

Drop HO


Alcatel 77



2.3 Typical call failures SDCCH phase - indicators

SDCCH phase indicators

SDCDBNSDCDRNSDCDHNSDCDR


> Refer to BSS - DEFINITION OF QUALITY OF SERVICE INDICATORS:

> GLOBAL Quality of service INDICATORS > SDCCH > Established phase

SDCDR: SDCCH drop rate (Global)

SDCDRR: SDCCH drop rate due to radio problem

SDCDBR: SDCCH drop rate due to BSS Problem

SDCDHR: SDCCH drop rate due to HO failure

Alcatel 78



2.3 Typical call failures TCH assignment - success

TCH assignment success case

> T3107: guard timer for TCH assignment

MS BTS BSC MSC

TCH ASSIGNMENT PHASE (OC or TC)

< -----------------------------------

ASSIGNMENT REQUEST

< --------------------------------------------------------

PHYSICAL CONTEXT REQUEST

-------------------------------------------------------- >

PHYSICAL CONTEXT CONFIRM

< -------------------------------------------------------- MC703

CHANNEL ACTIVATION (TCH)

-------------------------------------------------------- >

CHANNEL ACTIVATION ACKNOWLEDGE

< ----------------------------------------------------------------------------------- Start T3107

(SDCCH) ASSIGNMENT COMMAND

---------------------- >

TCH SABM -------------------------------------------------------- >

< ---------------------- ESTABLISH INDICATION

UA

----------------------------------------------------------------------------------- > Stop T3107

ASSIGNMENT COMPLETE MC718

----------------------------------- >

ASSIGNMENT COMPLETE

MC140a

MC140b

MC460a


> MC703 counts the number of TCH channels activated (therefore allocated) in a cell.

> MC718 counts the number of MSs which have successfully accessed a TCH in a cell as part of a call establishment (Normal Assignment).

> Both counters are implemented at TRX level.

> MC140a counts the number of normal assignment requests for TCH establishment.

> MC140b counts the number of normal assignment commands for TCH establishment.

> Both counters in order to discriminate BSS problems in Preparation and Execution phases.

> MC460a is a counter for type 110: NB_TCH_EMERGENCY_HO_PRESERVATION: Definition: Number of high priority TCH requests served when:

the number of free TCH timeslots is less than or equal to NUM_TCH_EGNCY_HO.

the queue for this cell is not empty.

> MC140a, MC140b and MC460 are given at Cell level

Alcatel 79



2.3 Typical call failures TCH assignment - TCH congestion

TCH assignment > congestion

> 5 causes of congestion 5 counters: C612A, B, C, D, E whenever

Queuing is not allowed

Queue is Full

T11 expires

RTCH request is removed from the queue due to a higher priority request to be queued

No Abis-TCH resource is available

MS BTS BSC MSC


< -----------------------------------------------

ASSIGNMENT REQUEST

No RTCH available on requested cell MC812

------------------------------------------------ >

ASSIGNMENT FAILURE

Cause No Radio Resource Available


> C612E: Number of 08.08 ASSIGNMENT REQUEST for TCH normal assignment rejected due to congestion on the Abis interface. (from B8)

> Therefore B6 counter MC612 is replaced by MC812 from B7. MC812 = C612A+C612B+C612C+C612D+C612E of PM Type 1.

> But as C612E was in restriction in B8 (always = 0) then MC812(B7) = MC612(B6)

> MC612A, MC612B, MC612C, MC612D also exist in PM Type 110.

> A TCH request is attached a Priority Level from 1 (highest priority) to 14 (lowest priority).

Alcatel 80



2.3 Typical call failures TCH assignment - radio failure

TCH assignment > radio failure

> Radio problemMS BTS BSC MSC


< -----------------------------------

ASSIGNMENT REQUEST

< --------------------------------------------------------


-------------------------------------------------------- >


< -------------------------------------------------------- MC703


-------------------------------------------------------- >


< ----------------------------------------------------------------------------------- Start T3107


SABM

----(TCH)------X

T3107 Expiry

MC746B

----------------------------------- >

ASSIGNMENT FAILURE

Radio interface failure

MC140a

MC140b


> MC746B counts the number of TCH access failures due to radio problems.

> MC746B counter is implemented at TRX level from B7.

> In case of TCH access failure, the MS will try to revert back to the SDCCH channel. Whether it succeeds in reverting to the SDCCH or not the call establishment fails. On the other hand some MSCs may resend the ASSIGNMENT REQUEST again.

Alcatel 81



2.3 Typical call failures TCH assignment - BSS problem

TCH assignment > BSS problem

> BSS problem (Abis, BTS/BSC HW or SW)MS BTS BSC MSC


< -----------------------------------

ASSIGNMENT REQUEST

< --------------------------------------------------------


-------------------------------------------------------- >


< -------------------------------------------------------- MC703


-------------------------------------------------------- >


< ----------------------------------------------------------------------------------- Start T3107


SABM

----(TCH)---- >

MC14B

MC140a

MC140b

No specific counter


> The number of TCH Assignment failures due to BSS Pb can be correctly deduced and distinguished for preparation and execution phases from B8 with the 2 counters MC140a and MC140b.(see the next slide)

> B7 counters MC14b has been removed.

Alcatel 82



2.3 Typical call failures TCH assignment - counters

TCH assignment counters

Congestion

ATTEMPT

Radio access failure

SUCCESS

BSS problem

Preparation Failure

Execution Failure

REQUEST

BSS problemTCH Assignment

Preparation Request MC140a

Congestion MC812

BSS Pb MC140a-MC140b-MC812

Execution Attempt MC140b

Radio Access Failure MC746b

BSS Pb MC140b-MC718-MC746b

Success MC718


Alcatel 83



2.3 Typical call failures TCH assignment - indicators

TCH Assignment indicators

TCNAFLBN

TCNAFLRNTCNACGNTCAHCANTCNAUR


> Refer to BSS - DEFINITION OF QUALITY OF SERVICE INDICATORS

> GLOBAL Quality of service INDICATORS > RTCH > Assignment Phase

TCNAUR: TCH assignment unsuccess rate (Global)

TCNACGR: TCH assignment failure rate due to congestion

TCNAFLRR: TCH assignment failure rate due to radio problems

TCNAFLBR: TCH assignment failure rate due to BSS Problems.

> From B7.2 some indicators can be provided on a per TRX basis due to the availability of counters provided per TRX in Type 110:

TCNAEFR = RTCH_assign_efficiency_rate (RNO name) = MC718 / MC703

Rate of successful RTCH seizures in relation to all RTCHs allocated, during the TCH assignment procedure.

TCNAAFLRR = RTCH_assign_allocated_fail_radio_rate (RNO name) = MC746B / MC703

Rate of RTCH seizures failed during the normal assignment procedure because of radio problems in relation to all RTCHs allocated for TCH assignment procedure.

> This will help a lot to detect bad QOS due to TRX hardware related problem.

Alcatel 84



2.3 Typical call failures TCH phase - success

TCH phase:

> OC

> TC

Transparent messages for BSS, no specific counters

TCH DROP: any problems occurring after TCH assignment (during or after connection) cannot be discriminated

MS BTS BSC MSC

Alerting Connection Phase (OC case) : ringing phase

< ---------------------------------------------------------------------------------------------------------------------------

ALERTING

< ---------------------------------------------------------------------------------------------------------------------------

CONNECT

--------------------------------------------------------------------------------------------------------------------------- >

CONNECT ACK

MS BTS BSC MSC

Alerting Connection Phase : TC case

--------------------------------------------------------------------------------------------------------------------------- >

ALERTING

--------------------------------------------------------------------------------------------------------------------------- >

CONNECT

< ---------------------------------------------------------------------------------------------------------------------------

CONNECT ACK


MS BTS BSC MSC


< -----------------------------------

ASSIGNMENT REQUEST

< --------------------------------------------------------


-------------------------------------------------------- >


< --------------------------------------------------------


-------------------------------------------------------- >


< ----------------------------------------------------------------------------------- Start T3107


---------------------- >

TCH SABM -------------------------------------------------------- >

< ---------------------- ESTABLISH INDICATION

UA

----------------------------------------------------------------------------------- > Stop T3107

ASSIGNMENT COMPLETE

----------------------------------- >

ASSIGNMENT COMPLETE

< ---------------------------------------------------------------------------------------------------------------------------

ALERTING

< ---------------------------------------------------------------------------------------------------------------------------

CONNECT

---------------------------------------------------------------------------------------------------------------------------->CONNECT ACK

Call Setup

Call phase

Call Setup

Call phase

> The Call setup phase and the Stable call phase are not corresponding between the BSS and the NSS.

> For the BSS, a call is established when the MS has successfully accessed a TCH channel on the Air interface.

> For the NSS, a call is established when the speech data exchanged is started between end users.

> Thus the Call setup phase is shorter and the Call phase is longer in the BSS.

> Therefore Call Setup Success rate is worse in the NSS and the Call Drop rate is worse in the BSS.

Alcatel 85



2.3 Typical call failures TCH phase - radio drop

TCH phase > drop radio

> Radio problem

MS BTS BSC MSC

Alerting Connection Phase or Communication : at any time

Radio problem

-------------------------------------------------------- > MC736

CONNECTION FAILURE INDICATION --------------------------------------- >

Cause radio link failure CLEAR REQUEST

Cause radio interface failure

(alcatel)


> MC736 counts the number of TCH channel drops due to radio problems.

> MC736 counter is implemented at TRX level.

> Radio problems can be due to coverage, interference and sometimes BSS dysfunction which is not detected as a system alarm by the O&M Fault Management application.

Alcatel 86


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