GSM Um Signalling & Radio ion Training Material

GSM radio optimisation . Figure 1

GSM Um signalling & radio optimisation


Course Outline

GSM system overview

Um interface

1 2

Radio optimisation

3


Section A

GSM system overviewGSM system overview


Topic Outline

Bursts & frames System architecture

Channels &channel organisation

1 2 3


GSM Frequency Bands

P-GSM

E-GSM

R-GSM

Uplink

DCS-1800

Uplink

Primary-GSM : 1-124

Extended-GSM : 0-124, 975-1023

Railway-GSM : 0-124, 955-1023

DCS-1800 : 512-885

Absolute Radio Frequency Channel Number (ARFCN)

Carrier spacing 200 kHz

+45 MHz

+45 MHz

+45 MHz

+95 MHz

Downlink

Downlink

915 MHz876 MHz

880 MHz

876 MHz

1785 MHz1710MHz


GSM Channel Coding:Normal TDMA Burst Structure

*TSC: Training Sequence

DataData TSC

3 57 1 26 1 57 3 8.25

Guard bits

156.25 bits, 577 µs114 bits payload

1 2 3 4 5 60 7

TDMA frame, 8 timeslots = 4.615 ms

Stealing flags for FACCH

4


GSM Channel Structure:Multi-Frame and Burst Types


GSM Channel Structure:Logical channels

RACH(UL)

BCCH(DL)

CCCH

TCH/FTCH/H

SACCH

AGCH(DL)

PCH(DL)

Mapping onto

physicalchannels

SDCCH

FACCHDedicated Channels

Signalling & Control Channels

1 2 3 4 5 60 71 2 3 4 5 60 7


GSM channel coding:Block structure

SDCCH or SACCH Channel Coding TCH Channel Coding

114 114 114114

57 5757 57 57 5757 57 57 5757 57 57 5757 57

Data BCSData BCS

Rate 1/2Convolutional

coding

114 114 114114

184 40 4FR:260, EFR 244

Data

1234560 71234560 7 1234560 71234560 7 1234560 71234560 7 1234560 71234560 7

Mapped on 8 HALF TDMA TSMapped on 4 TDMA TS

SDCCH block 20 ms Speech Frame 456 coded bits


SACCH Channel

Ordered timing advance (7 bits)Rsvd

Payload (21 octets)

SACCH DOWNLINK Block

Ordered MS power (5 bits)Rsvd

Actual timing advance (7 bits)Rsvd

Payload (21 octets)

SACCH UPLINK Block

Actual MS power (5 bits)Rsvd

Typical message sequence on SACCH

3.270 DL RR System Info 53.320 UL RR Measurement Report








Channel Organization

Most important combinations

TS0

TS0

TS0

TS0

1234560 7Example: cell with only 1 TRX


Logical Channels Mapping on TS 0

FCCH + SCH + BCCH + CCCH Cycle of 51 TDMA Frames

In 51-TDMA Frame we have 9 paging Blocks (DL)In a complete paging cycle the maximum number of 51-TDMA frames is 9In Uplink only RACH is used

TDMA Frame

BCCH+CCCH(Downlink)

9 Paging Blocks

1 2 3 4 5 60 7 1 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7


Alternative Mapping on TS 0

Paging Blocks reduced to 3 in one 51-TDMA-frames cycle.

Used in Low Signaling Traffic Cells

1st 51-TDMA-frames

2nd 51-TDMA-frames


Mapping of SDCCH/8 + SACCH

Used on TS1-7

TDMA Frame1234560 71234560 7 1234560 71234560 7 1234560 71234560 7


Mapping of TCH (FACCH) + SACCH

TDMA Frame1234560 71234560 7 1234560 71234560 7 1234560 71234560 7


Overview of GSM radio sub-system

BSC MSCBTS

A interfaceAbis interfaceUm interface

Um Protocol Stack(OSI model)

Abis Protocol Stack(OSI model)

A Protocol Stack(SS7 model)

Layer 1

Upper Layers

Layer 3

Layer 2

Layer 1

Upper Layers

Layer 3

Layer 2

Layer 1

Upper Layers

Layer 3

Layer 2

Layer 1

Upper Layers

Layer 3

Layer 2

Layer 1

Upper Layers

Layer 3

Layer 2

Layer 1

Upper Layers

Layer 3

Layer 2


OSI Model


Section B

UM interfaceUM interface


Topic Outline

Um Protocol Stack MS in Dedicated Mode

MS in Idle Mode Exercises Q&A

1 2 3 4


Um Protocol Stack

Upper Layers

Layer 3

Layer 1 & 2

User

MM CC

RR

Transmission


Um Protocol Stack – Layer 1 & 2

Derived from LAPD (ISDN)Optimized for Air-Interface

Limited ResourcesPropagation Characteristics of Radio Link

Transmission

Layer 2

Layer 1 Radio

LAPDmProtocol


Um Protocol Stack – Layer 3

Radio Resource Management(RR)

Manage logical & physical radio channels on the air interface

cell selection/reselection, Handovermeasurement reportschannel release

Mobility Management (MM)

Inform network about current location of mobile, privacy of MS

location updateidentity checkauthentication

Connection Management (CM)

Call Control (CC), connection between users

call setup, alerting, connection &

disconnection

MM CC

RR


Call Control and call related Supplementary services

Call Establishment ProceduresActive State ProceduresCall ClearingMiscellaneous procedures

Short Message Services

Non Call Related Supplementary Services

Layer 3: Connection Management

CMCC SS

SMS

CMCC SS

SMS


Layer 3: CM-CC MessagesMS BTS

CC Setup

CC Call Proceeding

CC Alerting

CC Connect

CC Connect Ack

Act

ive

Sta

teR

elea

seE

stab

lishm

ent

Call Establishment Messages

Call Related Supplementary messages

Call Clearing Messages

Modify, Modify Reject, Modify Complete…

Hold, Hold Ack, Hold RejectRetrieve, Retrieve Ack, Retrieve Reject…

Call Information Phase

Disconnect, Release, Release Complete…


Layer 3: Mobility Management

Support MS mobilityLocation Update (normal, periodic, IMSI attach)Registration messages (IMSI detach, LA Update Accept, LA Update Reject, LA Update Request)

Support CM upper sublayerCM Messages (CM service Accept/Reject/Abort/Request)

Support User Confidentiality

AuthenticationSecurity messages (Authentication Reject/Request/Response, Identity Request/Response)

MMMS User

CM support


Layer 3: RR ManagementMS BTS

Ded

icat

ed M

ode

Rel

ease

Idle

Mod

e

Establishes, maintains and releases a RR connection …

MOC: Establishment of RR connection initiates via MM

MTC: by the peer entity on the NS via the paging channel

Normal release procedure or RLTimeout…

Receives/transmits system info (BCCH) and paging

(CCCH) …MM

RR

Layer 2 service

Layer 1Measurement ControlChannel Management

MOC


Layer 3

Layer 2Connection Management Sub-layerMobility Management Sub-layerRadio Resource Management Sub-layer

Um Layer 3 GSM Signaling

MS BTS BSC MSC

CM

MMRR RR RR

CM

MMRR

CM

MMRR

Um Abis A


MS Tasks in Idle Mode

MS BTS

Perform cell selection

Perform cell re-selection

LA update

Listen to paging subgroup

Read system information


MS Tasks in Idle Mode: Cell Selection

MS must scan at least 30frequencies in the GSM900 and 40frequencies in the GSM1800 band.

MS will perform ‘normal’ or ‘stored-list’ cell selection.

Suitable cells are not barred and have C1>0 (with some other criteria).

MS selects a PLMN

MS scans for BCCH frequencies

MS tries cells by Rx level

Suitable cellsFound?

stop scanning the selected PLMN

Camp on a“suitable cell”

No

Yes


MS Tasks in Idle Mode: Cell Reselection

path loss criterion C1 becomes negative

A downlink signaling failure occurs

The camped-on cell by the MS is barred

A cell w/ better C1 in the same LA

A cell w/ much better C1 in a different LA

Random access (RR Channel Request) is still unsuccessful after Max_Retransrepetitions

Cell Reselection

Cell Reselection Triggers


MS Measurements in Idle Mode

MS reads the BCCH Allocation (BA) in the neighbour cells from the Sys Info 2 messages on the BCCH channel

The mobile performs measurements in idle mode for cell (re)selection

Mobile in idle mode

0.390 DL RR System Information Type 2 - BCCHBA-IND: 1, EXT-IND: 0

BA List: 41 43 66 68 71 73 77 79 85 (Bit Map 0)

0.540 DL RR System Information Type 2ter - BCCHBA-IND: 1, EXT-IND: 0

BA List: 547 (Variable Bit Map)

BA-IND: allows to differentiate between different BCCH Allocations, i.e. BA(BCCH, idle mode) and BA(SACCH, dedicated mode)EXT-IND (only valid in 2 & 2bis): indicates whether this is the complete message or extension (e.g. for E-GSM band)


MS Tasks in Idle Mode: Path loss criterion C1

Path loss criterion C1 is used for cell selection

C1>0?

No

YesHighest C1?

No

YesCell Selection

C1 = RLA_C – RXLEV_ACCESS_MIN - MAX(B,0)

Minimum Ms Rx level for network access

Rx level in idle mode

MS_TXPWR_MAX_CCH - P(P = maximum output power of MS)


MS Tasks in Idle Mode Re-selection criterion C2

Cell re-selection criterion C2 and Rxlev_Access_Min are typically used in multi-layer and multi-band networks to control cell re-selection.The MS will reselect the cell with the highest C2 value.

Timer T starts once a cell is placed on the list of 6 strongest neighbour.

C1 - CELL_RESELECT_OFFSETC1 -CELL_RESELECT_OFFSET

=11111(Discourage)

For T >= PENALTY_TIMEC1 + CELL_RESELECT_OFFSET

For T < PENALTY_TIMEC1 + CELL_RESELECT_OFFSET

- TEMPORARY_OFFSETC1 + CELL_RESELECT_OFFSET

<>11111(Encourage)

C2 Non-Serving CellC2 Serving CellPenalty Time


MS Tasks in Idle Mode: Cell Re-selection

For reselections within 15s, a minimum offset of 5 dB is required

LA updates generate a significant amount of load on MSCs. LA borders should be put in areas with clear cell borders

Calculate C2(every 5 s) New GSM LA?

No

Yes

C2(n) > C2(s)? or

C2(n)>C2(s)+5

C2(n) > C2(s) + Cell_Reselect_Hyst?

And optionalC2(n)>C2(s)+5

Cell Reselection

Yes

Yes


① Mobile capabilities to detect new carriers

Max {5 , ((5 * N + 6) DIV 7) * BS_PA_MFRMS / 4}C2 measurements time interval

�Number of neighbour cells

�Number of paging groups

Up to 10s+

For 4 multi-frames paging groups

15s8sInterval2010Neighbors

Handover measurements typically in a sliding window of 3-5s

Cell Reselection Speed Factors Response Time

CompareMS may select “wrong” cell:Fast moving users, long neighbor lists, high BS_PA_MFRMS

Note

Cell Re-selection Responsiveness


MS Tasks in Idle Mode: Downlink signaling Failure

Up to 90/BS_PA_MRFMS

Downlink signaling Counter

DSC initialised to 90/BS_PA_MFRMS

decode of paging sub-channel

successful?

No

Yes

DSC<=0?

Yes

DSC +1

DSC - 4

DL signalingFailure

Cell Reselection


MS Tasks in Idle Mode: Listen to Paging Group

The mobile will only listen to a limited number of paging blocks according to its IMSI.

BS_PA_MFRMS indicates the number of 51-multiframes between transmission of paging messages to mobiles of the same paging group.

Range: 2 to 9.Higher value means increased call setup time for MTC (it takes longer before the paging can be sent).

DRX: discontinuous reception mode of operation: MS powering itself down when it is not expecting paging messages from the network.

Improves battery life in idle mode. Higher value for BS_PA_MFRMS will increase the mobile battery life in idle mode.


MS Tasks in Idle Mode: System Information

RR System Information Type 3

MCC-MNC-LAC-CI: 123-45-401-00001BS-AG-BLKS-RES: 1 blocks rsvd for access grantCCCH-CONF: one basic physical channel, combined with SDCCHsBS-PA-MFRMS: 4 multiframes periodT3212 Time-out: 10 decihoursMaxRadioLinkTimeout: 16 multiframesCellReselHyst: 4 dBMsTxPowerMaxCCH: (0) 30 dBmAdditional Reselect Param Ind (ACS): 0RxLevAccessMin: (5) -105 dBmMaxRetransmissions: 4 TxInt: 12 slots

RR System Information Type 3

MCC-MNC-LAC-CI: 123-45-702-00002BS-AG-BLKS-RES: 1 blocks rsvd for access grantCCCH-CONF: one basic physical channel, combined with SDCCHsBS-PA-MFRMS: 4 multiframes periodT3212 Time-out: 30 decihoursMaxRadioLinkTimeout: 20 multiframesCellReselHyst: 10 dB RXLEVMsTxPowerMaxCCH: (5) 33 dBmAdditional Reselect Param Ind (ACS): 0RxLevAccessMin: (8) -102 dBmMaxRetransmissions: 2TxInt: 32 slots

Two examples of system info Type 3, note the difference:


MS in Dedicated Mode Measurements

MS Measurements in dedicate mode

DL RR System Info Type 5 - SACCHBA-IND: 0, EXT-IND: 0BA List: 43 44 67 68 69 71 75 77 79 81 85

UL RR Measurement Report - SACCHRxLevFull: -86 dBm, RxQualFull: 0RxLevSub: -86 dBm, RxQualSub: 0BA Used: 0, UL DTX: Not UsedMeasurements are validN1: Freq list [ 10 ] Level -89 dBm BSIC 34N2: Freq list [ 1 ] Level -98 dBm BSIC 11N3: Freq list [ 5 ] Level -95 dBm BSIC 45N4: Freq list [ 0 ] Level -97 dBm BSIC 70N5: Freq list [ 8 ] Level -98 dBm BSIC 34N6: Freq list [ 2 ] Level -104 dBm BSIC 42

BA-IND: Differentiate between different BA listsEXT-IND (for 5 & 5bis only): Indicates complete message or extension

RxLev 6 strongest neighbour cells

MS reports measurements to the network every 480 ms


SACCH info Layer 3 field

For RR and MM = 0000 (Skip Indicator)

For CM = Transaction identifier for parallel connections

Identifies the L3 Protocol


Measurements in Dedicated Mode

Full Measurement report needs 4 SACCH bursts: 4x25=100 Nbor SS samples

MS measures at least 25 Nbor SS measurement samplesin 26 TDMA frame Multiframe

MS measures at least 25 Nbor SS measurement samplesin 26 TDMA frame Multiframe

Nbor BSIC is measured during the Idle frame using the sliding window technique

Nbor BSIC is measured during the Idle frame using the sliding window technique

DL

UL24 25 Idle

24 25 Idle

RxTx Measures BSIC

RxTx

1 2 3 4 5 60 7 1 2 3 4 5 60 7 1 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7

1 2 3 4 5 60 7 1 2 3 4 5 60 7 1 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7 1 2 3 4 5 60 71 2 3 4 5 60 7

RxTx


Radio link failure PrinciplesEnsure that calls with unacceptable quality are either re-established or released in a defined manner.Known as “Radio link timeout”, or in general, dropped call.Parameter RADIO_LINK_TIMEOUT

Sent on SACCH to MS in System Information type 6 messages.Implementation

MS-implementation is specified in GSM 05.08. Based on the successful decoding of messages on the downlink SACCH.

BTS-implementation is manufacturer-specific. Based on successful SACCH decoding and/or RxLev/RxQual measurements.

GSM 05.08: “The parameters that control radio link failure should be set such that the forced release will not occur until the call has degraded to a quality below that at which the majority of subscribers would have manually released. This ensures that a call on the edge of a radio coverage area, although of bad quality, can usually be completed if the subscriber wishes.”


Radio Link Failure (MS Side)

02468

1012141618

SACCH Multiframes

Rad

io L

ink

Cou

nter

S

Smax=RADIO_LINK_TIMEOUT

SACCH decoded = +2

SACCH missed = -1

Radio Link Time Out

Radio link failure Implementation

RR System Info Type 6 Downlink SACCH

Cell Id: MCC-MNC-LAC-CI: 123-20-401-15243MaxRadioLinkTimeout: 16 multi-frames

Higher Radio-Link-Timeout values will “trick” the number of dropped calls: User will terminate the call (due to unacceptable quality), but the release will be classified as normal release.Typical values for Radio-Link-Timeout: 16 to 40 (or roughly 8 to 20 s).

S is initialised on every channel change (SDCCH-TCH, intra-cell HO, HO failure with return, etc.)


Mobile originating call (MOC)signaling messages

MS BTS

Immediate Assignment - AGCH

CM Service Request

(Authent.) (Ciphering) (Identity Check)

CC Setup

CC Call Proceeding

RR Assignment Command

RR Assignment Complete

CC Alerting

CC Connect

CC Connect Ack

SD

CC

HTC

HC

CC

H

Radio resource (RR) establishment. Request and assign a radio resource for signaling (SDCCH)

Assign a traffic channel (TCH)

Call accepted

User alerting

Service request

Call initiation

Channel Request - RACH


Mobile originating call (MOC) Message content

Connect acknowledgeCC Connect Ack

Connected number, Connected subaddressCC Connect

CC Alerting

RR causeRR Assignment Complete

channel description, power commandRR Assignment Command

bearer capability, Progress indicatorCC Call Proceeding

bearer capability, BCD called party numberCC Setup (MS to NW)

service type, ciphering key, mobile classmark (MS capabilities), mobile identity (TMSI, IMSI, IMEI)

CM-Service Request

establish cause & random reference; assigns dedicated resource (ARFCN or hopping parameters, timeslot, sub-timeslot) or GPRS resource (TBF).

Immediate Assignment

establishment cause, random referenceChannel Request


RR establishmentContention resolution

MS BTSChannel Request (RACH)

Immediate Assignment (AGCH)

RR Channel Request (RACH)Establishment Cause: Mobile originating call Random Reference: 3

RR Immediate Assignment (AGCH)Establishment Cause: Mobile originating callRandom Reference: 3Time: T1': 29, T2: 19, T3: 46


RR establishmentContention resolution

Contention resolution①Use of time stamping, e.g. MS1 and MS2②Use of random reference

③MS3 & MS4.

......

Random Access Channel RACH

MS1Establishment cause+ random reference

(8 bits in total)MS2

Establishment cause+ random reference

4.6 ms

MS3 MS4

different random reference:Strongest MS will get channel (with correct random reference in Imm. Assign)

MS3>>MS4 same random reference:both MS seize the channel. The weakest MS will fail to establish a layer-2 link with the network due to interference from strongest MS

invalid RACH due to interference. both mobiles must re-attempt

Similar

ResolutionRxLev


Entering the Dedicated ModeImmediate Assignment procedure

MS BTSPaging Request - PCH



Channel Request (resent, IA not received)

S is depended on Txnumber and Channel Combination of TS0

T3120

starts0,1,…max(8, Tx) -1TDMA frames

restartedS+Tx TDMA frames

restartedUp to MaxRetransmissions Times

Stopped


Mobile terminating call (MTC)signaling messages

MS BTSPaging Request - PCH


Paging Response

(Authent.) (Ciphering) (Identity Check)

CC Setup

CC Call Confirmed

RR Assignment Command

RR Assignment Complete

CC Alerting

CC Connect

CC Connect Ack

SD

CC

HTC

HC

CC

H RR establishment

Assign a traffic channel (TCH)

Call accepted

User alerting

Service request

Call initiation



Um inter-cell handoverNon-sync HO success

MS BTS

Handover Command

Handover Access ...

...Handover Access

Physical Information

Physical Information

Handover Complete

New

TC

HO

ld T

CH

BSC starts T3103 (network specific)

BSC starts T3105 (network specific). On expiry, repeat Phys. Info maximum of Ny1 times (network specific). On receipt Phys. Info, MS stops T3124 and switches to new channel.

RR establishment on new cell complete.Data transfer is resumed on new cell.BSC stops T3103 and releases old channel.

MS starts T3124 (320 ms for TCH, 675 ms for SDCCH) and repeats Handover Access until Phys. Info is received

(… Measurement Reports ...)


Um inter-cell handoverNon-sync HO failure

MS BTS

Handover Command BSC starts T3103

Handover Failure

Handover Access ….MS starts T3124

HO failure, return to old channelHO failure, return to old channel

MS timer T3124 expires,

or lower layer failure

MS BTS

Handover Command BSC starts T3103

Handover Access ….MS starts T3124

HO failure, MS lost during HOHO failure, MS lost during HO

MS timer T3124 expires,

or lower layer failure

BSC timer T3103 expires, or lower layer

failureMS and BSC release

all radio resources

New

TC

HO

ld T

CH

Old

TC

H

New

TC

HO

ld T

CH

Old

TC

H


Um inter-cell handoverMessage content

Handover Command containsBCCH/BSIC to identify neighbour cellDetails of new channel: ARFCN, timeslot, training sequenceHandover reference

Handover Access burst contains the Handover reference

DL RR System Info Type 5BA-IND: 0, EXT-IND: 0

BA List: 777 780 782 784 787 790

UL RR Measurement ReportRxLevFull: -86 dBm, RxQualFull: 0RxLevSub: -86 dBm, RxQualSub: 0

BA Used: 0, UL DTX: Not UsedMeasurements are valid

N1: Freq list [ 3 ] Level -79 dBm BSIC 20N2: Freq list [ 1 ] Level -98 dBm BSIC 11

Downlink RR Handover CommandBCCH: 784 BSIC: 20

TimeSlot: 7 TrainingSeq: 0Hopping: No, ARFCN: 838

HandoverRef: 127 OrderedPowerLevel: 0Synchronized: No

Handover algorithms are proprietary to network equipment manufacturers (although often based on the same principles). The handover algorithm at the origin of a handover preparation and execution doesn’t impact the handover message flow.

Note


Um intra-cell handover

Intra-cell TCH-TCH handovers are initiated by the RR Assignment Command

In general, the Assignment Command is used to instruct the mobile to change dedicated channel within a cell, whereas the Handover Command is used to change channel across cells.

Note

none of these messages are sent. The MS doesn’t manage to seize the new channel, and fails to return to the old channel. The MS will return to idle mode

MS lost during channel change

Assignment Failure is sent on old channelFailure, return to old channel

Assignment Complete message is sent on new channel

Success


Um call clearingInitiated by MS

Call clearing

MS BTSCC Disconnect

CC Release

CC Release Complete

RR Channel Release Release of RR

MS BTSCC Disconnect

CC Release

CC Release Complete

RR Channel Release

Initiated by network

Causes (Note abnormal releases in CAUSE analysis)Messages

normal release, abnormal release - unspecified, abnormal release - timer expired, etc.

RR Channel Release

CC Release & CC Release Complete: optional information element ‘cause’

Normal call clearing, User busy, No user responding, User alerting - no answer, Call rejected, Pre-emption, Invalid number format (incomplete number), Normal - unspecified, No circuit/channel available, Network out of order, Temporary failure, switching equipment, congestion, etc.

CC Disconnect


Um dropped call

Normally the cause for dropped calls cannot be inferred from drive test data.

Typical dropped calls:Radio link timeout at MS

MS goes to idle mode and starts analysing Sys Info (type 3)

Cause in RR channel release messageCause in CC Disconnect, CC Release, CC Release Complete message.

DL RR Channel ReleaseCause: Abnormal release, unspecified

DL_RxQual

DL_Lev


Section C

GSM radio optimisationGSM radio optimisation


Topic Outline

1

CS call analysisCS call benchmarking

analysis

2


CS Call Analysis

Identify ProblemsNegative Events

Dropped Call Setup FailureHandover Failure

Poor LevelRx Lev AnalysisMissing HandoverMissing Neighbour

Poor QualityPoor Rx Qual in poor LevelInterference Poor RX Qual in good levelExcessive or ping-pong handover


Add Cell Refs

Please ensure your cell refs

Is pointed to the following file Please load the logfile: Nemo Drive test 1. dt1


RX Lev Analysis

We analyse the DL Rx level to indicate the coverage Right click the level from GSM-Downlink measurements & place on the Map

We can see from the map that generally the level is good but in the area circled the level is bad. Let’s look into this in more detail


RX Lev Analysis-Using Filter

Create the following filter


Rx Lev Analysis


Serving Cell Analysis

Press the layers button on the map and change the labelling of the “GSM Cell Beam-width”layer to be BCCH



Press the layers icon againAlso for the “GSM_Cell_Beamwidth” layer, click lines & change the



Before clicking OK click on the neighbour tab click disable then click OK



Now click the “area control” icon and draw a box around the area circled earlier.



We can see that some areas are being served by a distant server.This may be due to

Variable TerrainCells off airNeighbour definitions and parameters


Serving Cell Analysis-TA

Display Timing Advance from Dedicated Radio Link Attributes


Turn off Filter


RX Qual Analysis

Right click the DL Serving Rxqual & put on the map


Rx Qual Analysis

Correlation between areas of poor level and poor quality

This is expected, and is more pronounced as traffic volumes increase

We can see other areas of poor quality where coverage was good

Interference?Excessive or ping-pong handover?

We are interested in further analysis of these areas


Rx Qual Analysis-Binned Queries

From the tools menu choose Analysis Manager, choose a binned query & click newEnter the expression: if(((ServRxLevSub > -85) AND (ServRxQualSub>= 4)) , ServCI, null)


Rx Qual Analysis- Binned Queries

Right click the query & display this on the map


Negative Events Analysis

Dropped CallsFrom the events menu drag the dropped calls on to the map


Dropped Call Analysis-Event Query

We are interested in the general conditions prior to a call dropWe use the Event Query to build a picture of the conditions prior to the dropFrom the tools menu open the Analysis manager & choose a new Event query



Choose “event dropped call” as the trigger & a 5 second window before event & then click next



Select the statistics that we want to analyse


Dropped Call Analysis-Event QueryAverage Level Average quality last BCCH

Last CI Interference Timing Advance



Once all statistics are entered OK and then view the query results in the statistic explorer



Save/export your Query for Future use


Handover Analysis

Import the HO OK Event query & display on the statistics explorer


Handover Analysis

Using a map we can look into handovers in more detail


Handover Analysis

The following Analysis pack gives some useful over view figures regarding handovers & call set up.


Handover Analysis


Call Setup Analysis

Call Setup Flow Diagram


Call Setup Analysis

We can use the protocol stack browser to check the flow of messages around call set up


CS Call Benchmarking

Why Benchmark?

Overview of Performance on certain routes

KPI performance can give picture of “user perception”

High Level Analysis can help distinguish between area-specific and network-level problems

It is useful to run benchmark reports prior to detailed analysis to get a feel for the problems on the route



Actix design validation & quick analysis application pack provides a series of reports & statistics that can be used to bench mark your networkRight click the “stream” & open the design validation & quick analysis application packThe statistics window displays a count of various KPI’s per Cell this can then be used to start to identify problem cells



Call details ReportThis gives details of the of the main call events such as call set up & call drops negative events are highlighted in red.



The Design Validation report

This report looks at the level quality & interference with your network & compares to a series of Matrix to decide if the area driven is of good or bad design



Measurement Charts report

Shows distribution of Level, Quality and Timing Advance



Neighbor levelThis report looks into the dominance of your server

Documents

GSM Um Signalling & Radio ion Training Material