GSM Um Signalling & Radio ion Training Material

GSM Um signalling & radio optimisation

GSM radio radio optimisa optimisation tion . Figure Figure 1

Course Outline GSM system overview Radio optimisation

1

2

Um interface


3

Course Outline GSM system overview Radio optimisation

1

2

Um interface


3

Section A

GSM GSM system system overview overview


Topic Outline

Bursts & frames

1

System architecture

2

Channels & channel organisation

GSM radio optimisation . Figure 4

3

GSM Frequency Bands Uplink

Absolute Radio Frequency Channel Number (ARFCN)

880 MHz 876 MHz

Carrier spacing 200 kHz

915 MHz

876 MHz

P-GSM E-GSM

Downlink

Primary-GSM : 1-124 Extended-GSM : 0-124, 975-1023

R-GSM

Railway-GSM : 0-124, 955-1023

Uplink

+45 MHz +45 MHz +45 MHz

Downlink 1785 MHz

1710MHz

DCS-1800

DCS-1800 : 512-885


+95 MHz

GSM Channel Coding: Normal TDMA Burst Structure Stealing flags for FACCH

Data

TSC

Data

57

1 26 1

57

3

Guard bits

3 8.25

156.25 bits, 577 µs 114 bits payload

0

1

2

3

4 4

5

6

7

TDMA frame, 8 timeslots = 4.615 ms

*TSC: Training Sequence GSM radio optimisation . Figure 6

GSM Channel Structure: Multi-Frame and Burst Types


GSM Channel Structure: Logical channels RACH (UL)

BCCH (DL)

PCH (DL)

CCCH

AGCH (DL)

TCH/F TCH/H FACCH

Dedicated Channels Signalling & Control Channels

SACCH SDCCH


Mapping onto physical channels 0 1 2 3 4 5 6 7

GSM channel coding: Block structure SDCCH or SACCH Channel Coding

TCH Channel Coding

SDCCH block

20 ms Speech Frame 456 coded bits

Data 184

BCS 40

Data 4

FR:260, EFR 244

Rate 1/2 Convolutional coding 114

114

114 114

114

Mapped on 4 TDMA TS 01234567

01234567

01234567

114

114

114

57 57 57 57 57 57 57 57

Mapped on 8 HALF TDMA TS

01234567


SACCH Channel SACCH DOWNLINK Block Rsvd

Ordered MS power (5 bits)

Rsvd Ordered timing advance (7 bits)

Payload (21 octets)

SACCH UPLINK Block Rsvd

Typical message sequence on SACCH

Actual MS power (5 bits)

Rsvd Actual timing advance (7 bits) Payload (21 octets)

3.270 DL RR System Info 5 3.320 UL RR Measurement Report 3.750 DL RR System Info 5 3.800 UL RR Measurement Report 4.210 DL RR System Info 6 4.260 UL RR Measurement Report 4.700 DL RR System Info 5 4.750 UL RR Measurement Report 5.170 DL RR System Info 5 5.220 UL RR Measurement Report 5.660 DL RR System Info 6 5.700 UL RR Measurement Report 6.120 DL RR System Info 5 6.190 UL RR Measurement Report


Channel Organization Most important combinations TS0 TS0

TS0 TS0

Example: cell with only 1 TRX

01234567


Logical Channels Mapping on TS 0 FCCH + SCH + BCCH + CCCH Cycle of 51 TDMA Frames TDMA Frame

012345670123456701234567

BCCH+CCCH (Downlink) 9 Paging Blocks

In 51-TDMA Frame we have 9 paging Blocks (DL) In a complete paging cycle the maximum number of 51-TDMA frames is 9 In Uplink only RACH is used GSM radio optimisation . Figure 12

Alternative Mapping on TS 0 Used in Low Signaling Traffic Cells

1st 51-TDMA-frames

2nd 51-TDMA-frames

Paging Blocks reduced to 3 in one 51-TDMAframes cycle.


Mapping of SDCCH/8 + SACCH

01234567 01 23456 701234567

TDMA Frame

Used on TS1-7


Mapping of TCH (FACCH) + SACCH

012345670123456 70123456 7

TDMA Frame


Overview of GSM radio subsystem Um Protocol Stack

Abis Protocol Stack

A Protocol Stack

(OSI model)

(OSI model)

(SS7 model)

Upper Layers

Upper Layers

Upper Layers

Layer 3

Layer 3

Layer 3

Layer 2

Layer 2

Layer 2

Layer 1

Um interface

Layer 1 BTS

Layer 1 BSC

Abis interface


A interface

MSC

OSI Model


Section B

UM UM interface interface


Topic Outline

Um Protocol Stack

1

MS in Dedicated Mode

3

2

MS in Idle Mode


4

Exercises

Q&A

Um Protocol Stack

Upper Layers

User

MM

Layer 3

CC

RR Layer 1 & 2

Transmission


Um Protocol Stack – Layer 1 & 2

Layer 2

LAPDm Protocol

Derived from LAPD (ISDN) Optimized for AirInterface 

Transmission

 Layer 1

Radio


Limited Resources Propagation Characteristics of Radio Link

Um Protocol Stack – Layer 3 Mobility Management (MM)

Connection Management (CM) MM

Inform network about current location of mobile, privacy of MS location

CC

RR

update

identity

check authentication

Radio Resource Management (RR) Manage logical & physical radio channels on the air interface cell

selection/reselection, Handover measurement reports channel release GSM radio optimisation . Figure 22

Call Control (CC), connection between users call

setup, alerting, connection

& disconnection

Layer 3: Connection Management Short Message Services SMS

Call Control and call related Supplementary services Call Establishment CC Procedures  Active State Procedures  Call Clearing  Miscellaneous procedures 

CM SS


Non Call Related Supplementary Services

Layer 3: CM-CC Messages BTS

MS t n e m h s i l b a t s E e t a t S e v i t c A e s a e l e R

CC Setup CC Call Proceeding CC Alerting

Call Establishment Messages

CC Connect CC Connect Ack Modify, Modify Reject, Modify Complete… Hold, Hold Ack, Hold Reject Retrieve, Retrieve Ack, Retrieve Reject…

Disconnect, Release, Release Complete…

Call Information Phase Call Related Supplementary messages

Call Clearing Messages


Layer 3: Mobility Management Support CM upper sublayer 

CM Messages (CM service Accept/Reject/Abort/Request)

CM support

Support MS mobility Update (normal, periodic, IMSI attach)

MM

 Location

 Registration

messages (IMSI detach, LA Update Accept, LA Update Reject, LA Update Request)

MS

Support User User Confidentiality  Authentication  Security messages (Authentication Reject /Request/Response, Identity Request/Response)


Layer 3: RR Management MS e d o M e l d I

MM MOC

RR

Layer 2 service

Layer 1 Measurement Control Channel Management

BTS

Receives/transmits system info (BCCH) and paging (CCCH) …

e d o M Establishes, maintains and d releases a RR connection … e t a c i d e D e s a e l e R

Normal release procedure or RLTimeout…


MOC: Establishment of RR connection initiates via MM MTC: by the peer entity on the NS via the paging channel

Um Layer 3 GSM Signaling Abis

Um MS

BTS

A BSC

MSC

CM

CM

MM

MM

RR

RR

RR

RR

CM

Connection Management Sub-layer

MM

Mobility Management Sub-layer

RR

Radio Resource Management Sub-layer


Layer 3

Layer 2

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 selects a PLMN

MS scans for BCCH frequencies stop scanning the selected PLMN MS tries cells by Rx level

No Suitable cells Found?

MS must scan at least 30 frequencies in the GSM900 and 40 frequencies in the GSM1800 band. MS will perform ‘normal’ or ‘storedlist’ cell selection.

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

Yes Camp on a “suitable cell” GSM radio optimisation . Figure 29

MS Tasks in Idle Mode: Cell Reselection Cell Reselection Triggers 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_Retrans repetitions


Cell Reselection

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 Mobile in idle mode



0.390 DL RR System Information Type 2 - BCCH BA-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 - BCCH BA-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)

The mobile performs measurements in idle mode for cell (re)selection GSM radio optimisation . Figure 31

MS Tasks in Idle Mode: Path loss criterion C1 Path loss criterion C1 is used for cell selection C1 = RLA_C – RXLEV_ACCESS_MIN - MAX(B,0) Rx level in idle mode Minimum Ms Rx level for network access MS_TXPWR_MAX_CCH - P (P = maximum output power of MS)

C1>0?

No

Yes

Highest C1?

Yes

No GSM radio optimisation . Figure 32

Cell Selection

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. Penalty Time

C2 Serving Cell

<>11111 (Encourage)

C1 + CELL_RESELECT_OFFSET

=11111 (Discourage)

C1 CELL_RESELECT_OFFSET



C2 Non-Serving Cell For T < PENALTY_TIME C1 + CELL_RESELECT_OFFSET - TEMPORARY_OFFSET For T >= PENALTY_TIME C1 + CELL_RESELECT_OFFSET C1 - CELL_RESELECT_OFFSET

Timer T starts once a cell is placed on the list of 6 strongest neighbour. GSM radio optimisation . Figure 33

MS Tasks in Idle Mode: Cell Reselection Calculate C2 (every 5 s)

No New GSM LA?

C2(n) > C2(s)? or C2(n)>C2(s)+5

Yes

C2(n) > C2(s) + Cell_Reselect_Hyst? And optional C2(n)>C2(s)+5

Yes

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

Yes

Cell Reselection LA updates generate a significant amount of load on MSCs. LA borders should be put in areas with clear cell borders GSM radio optimisation . Figure 34

Cell Re-selection Responsiveness Cell Reselection Speed Factors

Response Time

Mobile capabilities to detect new carriers

Up to 10s+

C2 measurements time interval Max {5 , ((5 * N + 6) DIV 7) * BS_PA_MFRMS / 4} Number of neighbour cells Number of paging groups

Note

For 4 multi-frames paging groups

Neighbors

10 20

Interval

8s 15s

Compare

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

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


MS Tasks in Idle Mode: Downlink signaling Failure DSC initialised to 90/BS_PA_MFRMS

decode of paging sub-channel successful?

No DSC - 4

Yes Downlink signaling Counter

DSC +1

DSC<=0? Yes

Up to 90/BS_PA_MRFMS

DL signaling Failure

Cell Reselection GSM radio optimisation . Figure 36

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 Two examples of system info Type 3, note the difference: RR System Information Type 3 MCC-MNC-LAC-CI: 123-45-401-00001 BS-AG-BLKS-RES: 1 blocks rsvd for access grant CCCH-CONF: one basic physical channel, combined with SDCCHs BS-PA-MFRMS: 4 multiframes period T3212 Time-out: 10 decihours MaxRadioLinkTimeout: 16 multiframes CellReselHyst: 4 dB MsTxPowerMaxCCH: (0) 30 dBm Additional Reselect Param Ind (ACS): 0 RxLevAccessMin: (5) -105 dBm MaxRetransmissions: 4 TxInt: 12 slots

RR System Information Type 3 MCC-MNC-LAC-CI: 123-45-702-00002 BS-AG-BLKS-RES: 1 blocks rsvd for access grant CCCH-CONF: one basic physical channel, combined with SDCCHs BS-PA-MFRMS: 4 multiframes period T3212 Time-out: 30 decihours MaxRadioLinkTimeout: 20 multiframes CellReselHyst: 10 dB RXLEV MsTxPowerMaxCCH: (5) 33 dBm Additional Reselect Param Ind (ACS): 0 RxLevAccessMin: (8) -102 dBm MaxRetransmissions: 2 TxInt: 32 slots


MS in Dedicated Mode Measurements MS Measurements in dedicate mode

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

DL RR System Info Type 5 - SACCH BA-IND: 0, EXT-IND: 0 BA List: 43 44 67 68 69 71 75 77 79 81 85 UL RR Measurement Report - SACCH RxLevFull: -86 dBm, RxQualFull: 0 RxLevSub: -86 dBm, RxQualSub: 0 BA Used: 0, UL DTX: Not Used Measurements are valid N1: Freq list [ 10 ] Level -89 dBm BSIC 34 N2: Freq list [ 1 ] Level -98 dBm BSIC 11 N3: Freq list [ 5 ] Level -95 dBm BSIC 45 N4: Freq list [ 0 ] Level -97 dBm BSIC 70 N5: Freq list [ 8 ] Level -98 dBm BSIC 34 N6: Freq list [ 2 ] Level -104 dBm BSIC 42

MS reports measurements to the network every 480 ms

RxLev 6 strongest neighbour cells


SACCH info Layer 3 field Identifies the L3 Protocol

For RR and MM = 0000 (Skip Indicator) For CM = Transaction identifier for parallel connections


Measurements in Dedicated Mode 25

24 0 1

23

4 5 6 7 0 1

4 5 6 7 0 1 2 3 4 5 6 7 0 1

Tx 0 1

Tx 23

4 5 6 7 0 1

24

23

4 5 6 7

DL

Rx

Rx

Rx MS MS measures measures at at least least 25 25 Nbor Nbor SS SS measureme measureme nt nt samples samples in in 26 26 TDMA TDMA frame frame Multiframe Multiframe

23

Idle

Measures BSIC

23 25

Tx

4 5 6 7 0 1 2 3 4 5 6 7 0 1

23

4 5 6 7

Idle

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

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


UL

Radio link failure Principles Ensure that calls with unacceptable quality are either reestablished or released in a defined manner. Known as “Radio link timeout”, or in general, dropped call. Parameter RADIO_LINK_TIMEOUT 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.” 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 radio optimisation . Figure 42

Radio link failure Implementation 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). Radio Link Failure (MS Side) 18 S16 r e14 t n12 u o 10 C k 8 n i L 6 o i 4 d a 2 R 0

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

Smax=RADIO_LINK_TIMEOUT SACCH decoded = +2 SACCH missed = -1 Radio Link Time Out

SACCH Multiframes GSM radio optimisation . Figure 43

RR System Info Type 6 Downlink SACCH Cell Id: MCC-MNC-LAC-CI: 123-20-401-15243 MaxRadioLinkTimeout: 16 multi-frames

Mobile originating call (MOC) signaling messages BTS

MS H C C C

Channel Request - RACH Immediate Assignment - AGCH CM Service Request

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

(Authent.) (Ciphering) (Identity Check) H C C D S

CC Setup CC Call Proceeding RR Assignment Command

Call initiation

Assign a traffic channel (TCH)

RR Assignment Complete H C T

CC Alerting

User alerting

CC Connect CC Connect Ack

Call accepted


Mobile originating call (MOC) Message content Channel Request

establishment cause, random reference

Immediate Assignment

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

CM-Service Request

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

CC Setup (MS to NW)

bearer capability, BCD called party number

CC Call Proceeding

bearer capability, Progress indicator

RR Assignment Command

channel description, power command

RR Assignment Complete

RR cause

CC Alerting CC Connect

Connected number, Connected subaddress

CC Connect Ack

Connect acknowledge GSM radio optimisation . Figure 45

RR establishment Contention resolution MS

Channel Request (RACH)

BTS

Immediate Assignment (AGCH)

RR Channel Request (RACH) Establishment Cause: Mobile originating call Random Reference: 3 RR Immediate Assignment (AGCH) Establishment Cause: Mobile originating call Random Reference: 3 Time: T1': 29, T2: 19, T3: 46

GSM radio radio optimis optimisation ation . Figure Figure 46

RR establishment Contention resolution Contention resolution Random Access Channel 4.6 ms RACH ...

...

Use of time stamping, e.g. MS1 and MS2 Use of random reference MS3 & MS4

MS1 Establishment cause + random reference (8 bits in total)

. RxLev MS3

MS4 Similar

MS2 Establishment cause + random reference

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


Entering the Dedicated Mode Immediate Assignment procedure T3120

MS

BTS Paging Paging Requ Request est - PC PCH H

starts 0,1,…max(8, Tx) -1 TDMA frames Channel Cha nnel Requ Request est - RACH S is depended on Tx number and Channel Combination of TS0

restarted S+Tx TDMA TDMA frames frames

restarted

Channel Request (resent, IA not received)

Up to MaxR MaxRetran etransmission smissions s Times Times Immediate Immediate Assignmen Assignmentt - AGCH

Stopped


Mobile terminating call (MTC) signaling messages MS H C C C

BTS Paging Request - PCH Channel Request - RACH

RR establishment

Immediate Assignment - AGCH Paging Response

Service request

(Authent.) (Ciphering) (Identity Check) H C C D S

CC Setup CC Call Confirmed

Call initiation

RR Assignment Command RR Assignment Complete H C T

CC Alerting

Assign a traffic channel (TCH)

User alerting

CC Connect CC Connect Ack

Call accepted


Um inter-cell handover Non-sync HO success MS H C T d l O

BTS

(… Measurement Reports ...) Handover Command Handover Access ...

...Handover Access H C T w e N

BSC starts T3103 (network specific)

Physical Information

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

Physical Information



 

Handover Complete



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.


Um inter-cell handover Non-sync HO failure HO HO failure, failure, return return to to old old channel channel BTS

MS H C T d l O H C T w e N

H C T d l O

HO failure, MS lost during HO

Handover Command BSC starts T3103

Handover Access …. MS starts T3124 MS timer T3124 expires, or lower layer failure

Handover Failure

MS H C T d l O H C T w e N

H C T d l O


BTS

Handover Command BSC starts T3103

Handover Access …. MS starts T3124 MS timer T3124 expires, or lower layer failure BSC timer T3103 expires, or lower layer failure MS and BSC release all radio resources

Um inter-cell handover Message content Handover Command contains  



BCCH/BSIC to identify neighbour cell Details of new channel: ARFCN, timeslot, training sequence Handover reference

Handover Access burst contains the Handover reference Note 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.

DL RR System Info Type 5 BA-IND: 0, EXT-IND: 0 BA List: 777 780 782 784 787 790 UL RR Measurement Report RxLevFull: -86 dBm, RxQualFull: 0 RxLevSub: -86 dBm, RxQualSub: 0 BA Used: 0, UL DTX: Not Used Measurements are valid N1: Freq list [ 3 ] Level -79 dBm BSIC 20 N2: Freq list [ 1 ] Level -98 dBm BSIC 11 Downlink RR Handover Command BCCH: 784 BSIC: 20 TimeSlot: 7 TrainingSeq: 0 Hopping: No, ARFCN: 838 HandoverRef: 127 OrderedPowerLevel: 0 Synchronized: No


Um intra-cell handover Intra-cell TCH-TCH handovers are initiated by the RR Assignment Command Success

Note 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.

Assignment Complete message is sent on new channel

Failure, return Assignment Failure is sent on old channel to old channel MS lost during none of these messages are sent. The MS channel doesn’t manage to seize the new channel, change and fails to return to the old channel. The MS will return to idle mode GSM radio optimisation . Figure 53

Um call clearing Initiated by MS MS

Initiated by network BTS

MS

CC Disconnect

CC Disconnect

CC Release

Call clearing

CC Release Complete RR Channel Release Messages CC Disconnect

BTS CC Release

CC Release Complete Release of RR

RR Channel Release

Causes (Note abnormal releases in CAUSE analysis) 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 Release & CC Release Complete: optional information element ‘cause’ RR Channel Release

normal release, abnormal release - unspecified, abnormal release - timer expired, etc. GSM radio optimisation . Figure 54

Um dropped call

DL_RxQual

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

Radio link timeout at MS 

DL_Lev  

DL RR Channel Release Cause: Abnormal release, unspecified

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

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


Section C

GSM GSM radio radio optimisation optimisation


Topic Outline CS call benchmarking analysis

CS call analysis

1


2

CS Call Analysis Identify Problems 

Negative Events   



Poor Level   



Dropped Call Setup Failure Handover Failure

Rx Lev Analysis Missing Handover Missing Neighbour

Poor Quality   

Poor Rx Qual in poor Level Interference Poor RX Qual in good level Excessive 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 GSM radio optimisation . Figure 59

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 layer to be BCCH

on the map and change the labelling of the “GSM Cell Beam-width”


Serving Cell Analysis Press the layers icon again Also for the “GSM_Cell_Beamwidth” layer, click lines & change the


Serving Cell Analysis Before clicking OK click on the neighbour tab click disable then click OK


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


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

Variable Terrain Cells off air



Neighbour 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 GSM radio radio optimis optimisation ation . Figure Figure 71

Rx Qual Analysis-Binned Queries From the tools menu choose Analysis Manager, choose a binned query & click new if(((ServRxLevSub vSub > -85) AND AND (ServRxQual (ServRxQualSub Sub Enter the expression: if(((ServRxLe >= 4)) , ServCI, null)


Rx Qual Qual Analy Analysis sis-- Binned Binned Querie Queries s Right click the query & display this on the map


Negative Events Analysis Dropped Calls 

From 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 drop We use the Event Query to build a picture of the conditions prior to the drop From the tools menu open the Analysis manager & choose a new Event query


Dropped Call Analysis-Event Query Choose “event dropped call” as the trigger & a 5 second window before event & then click next


Dropped Call Analysis-Event Query Select the statistics that we want to analyse


Dropped Call Analysis-Event Query Average Level

Last CI

Average quality last BCCH

Interference

Timing Advance


Dropped Call Analysis-Event Query Once all statistics are entered OK and then view the query results in the statistic explorer


Dropped Call Analysis-Event Query 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 GSM radio optimisation . Figure 87

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


CS Call Benchmarking Call details Report 

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


CS Call Benchmarking 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


CS Call Benchmarking Measurement Charts report 

Shows distribution of Level, Quality and Timing Advance


GSM Um Signalling & Radio ion Training Material

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