GSM radio optimisation . Figure 1
GSM Um signalling & radio optimisation
GSM radio optimisation . Figure 2
Course Outline
GSM system overview
Um interface
1 2
Radio optimisation
3
GSM radio optimisation . Figure 3
Section A
GSM system overviewGSM system overview
GSM radio optimisation . Figure 4
Topic Outline
Bursts & frames System architecture
Channels &channel organisation
1 2 3
GSM radio optimisation . Figure 5
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 radio optimisation . Figure 6
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 s114 bits payload
1 2 3 4 5 60 7
TDMA frame, 8 timeslots = 4.615 ms
Stealing flags for FACCH
4
GSM radio optimisation . Figure 7
GSM Channel Structure:Multi-Frame and Burst Types
GSM radio optimisation . Figure 8
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 radio optimisation . Figure 9
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
GSM radio optimisation . Figure 10
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
3.750 DL RR System Info 53.800 UL RR Measurement Report
4.210 DL RR System Info 64.260 UL RR Measurement Report
4.700 DL RR System Info 54.750 UL RR Measurement Report
5.170 DL RR System Info 55.220 UL RR Measurement Report
5.660 DL RR System Info 65.700 UL RR Measurement Report
6.120 DL RR System Info 56.190 UL RR Measurement Report
GSM radio optimisation . Figure 11
Channel Organization
Most important combinations
TS0
TS0
TS0
TS0
1234560 7Example: cell with only 1 TRX
GSM radio optimisation . Figure 12
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
GSM radio optimisation . Figure 13
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
GSM radio optimisation . Figure 14
Mapping of SDCCH/8 + SACCH
Used on TS1-7
TDMA Frame1234560 71234560 7 1234560 71234560 7 1234560 71234560 7
GSM radio optimisation . Figure 15
Mapping of TCH (FACCH) + SACCH
TDMA Frame1234560 71234560 7 1234560 71234560 7 1234560 71234560 7
GSM radio optimisation . Figure 16
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
GSM radio optimisation . Figure 17
OSI Model
GSM radio optimisation . Figure 18
Section B
UM interfaceUM interface
GSM radio optimisation . Figure 19
Topic Outline
Um Protocol Stack MS in Dedicated Mode
MS in Idle Mode Exercises Q&A
1 2 3 4
GSM radio optimisation . Figure 20
Um Protocol Stack
Upper Layers
Layer 3
Layer 1 & 2
User
MM CC
RR
Transmission
GSM radio optimisation . Figure 21
Um Protocol Stack Layer 1 & 2
Derived from LAPD (ISDN)Optimized for Air-Interface Limited
Resources Propagation
Characteristics of Radio Link
Transmission
Layer 2
Layer 1 Radio
LAPDmProtocol
GSM radio optimisation . Figure 22
Um Protocol Stack Layer 3
Radio Resource Management(RR)
Manage logical & physical radio channels on the air interfacecell selection/reselection, Handovermeasurement reportschannel release
Mobility Management (MM)
Inform network about current location of mobile, privacy of MSlocation updateidentity checkauthentication
Connection Management (CM)
Call Control (CC), connection between userscall setup, alerting, connection & disconnection
MM CC
RR
GSM radio optimisation . Figure 23
Call Control and call related Supplementary services
Call Establishment Procedures
Active State Procedures
Call ClearingMiscellaneous
procedures
Short Message Services
Non Call Related Supplementary Services
Layer 3: Connection Management
CMCC SS
SMS
CMCC SS
SMS
GSM radio optimisation . Figure 24
Layer 3: CM-CC MessagesMS BTS
CC Setup
CC Call Proceeding
CC Alerting
CC Connect
CC Connect Ack
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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
GSM radio optimisation . Figure 25
Layer 3: Mobility Management
Support MS mobility Location Update
(normal, periodic, IMSI attach)
Registration messages (IMSI detach, LA Update Accept, LA Update Reject, LA Update Request)
Support CM upper sublayer CM Messages (CM service
Accept/Reject/Abort/Request)
Support User Confidentiality
AuthenticationSecurity messages
(Authentication Reject/Request/Response, Identity Request/Response)
MMMS User
CM support
GSM radio optimisation . Figure 26
Layer 3: RR ManagementMS BTS
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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
GSM radio optimisation . Figure 27
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
GSM radio optimisation . Figure 28
MS Tasks in Idle Mode
MS BTS
Perform cell selection
Perform cell re-selection
LA update
Listen to paging subgroup
Read system information
GSM radio optimisation . Figure 29
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 asuitable cell
No
Yes
GSM radio optimisation . Figure 30
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
GSM radio optimisation . Figure 31
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)
GSM radio optimisation . Figure 32
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)
GSM radio optimisation . Figure 33
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
GSM radio optimisation . Figure 34
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
GSM radio optimisation . Figure 35
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
GSM radio optimisation . Figure 36
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
GSM radio optimisation . Figure 37
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.
GSM radio optimisation . Figure 38
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:
GSM radio optimisation . Figure 39
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
GSM radio optimisation . Figure 40
SACCH info Layer 3 field
For RR and MM = 0000 (Skip Indicator)
For CM = Transaction identifier for parallel connections
Identifies the L3 Protocol
GSM radio optimisation . Figure 41
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
GSM radio optimisation . Figure 42
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.ImplementationMS-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.
GSM radio optimisation . Figure 43
Radio Link Failure (MS Side)
02468
1012141618
SACCH Multiframes
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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.)
GSM radio optimisation . Figure 44
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
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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
GSM radio optimisation . Figure 45
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
GSM radio optimisation . Figure 46
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
GSM radio optimisation . Figure 47
RR establishmentContention resolution
Contention resolutionUse of time stamping, e.g. MS1 and MS2Use of random referenceMS3 & 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
GSM radio optimisation . Figure 48
Entering the Dedicated ModeImmediate Assignment procedure
MS BTSPaging Request - PCH
Immediate Assignment - AGCH
Channel Request - RACH
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
GSM radio optimisation . Figure 49
Mobile terminating call (MTC)signaling messages
MS BTSPaging Request - PCH
Immediate Assignment - AGCH
Paging Response
(Authent.) (Ciphering) (Identity Check)
CC Setup
CC Call Confirmed
RR Assignment Command
RR Assignment Complete
CC Alerting
CC Connect
CC Connect Ack
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H RR establishment
Assign a traffic channel (TCH)
Call accepted
User alerting
Service request
Call initiation
Channel Request - RACH
GSM radio optimisation . Figure 50
Um inter-cell handoverNon-sync HO success
MS BTS
Handover Command
Handover Access ...
...Handover Access
Physical Information
Physical Information
Handover Complete
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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 ...)
GSM radio optimisation . Figure 51
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
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GSM radio optimisation . Figure 52
Um inter-cell handoverMessage content
Handover Command contains BCCH/BSIC to identify
neighbour cell Details of new channel:
ARFCN, timeslot, training sequence
Handover referenceHandover 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 doesnt impact the handover message flow.
Note
GSM radio optimisation . Figure 53
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 doesnt 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
GSM radio optimisation . Figure 54
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
GSM radio optimisation . Figure 55
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 message
Cause in CC Disconnect, CC Release, CC Release Complete message.
DL RR Channel ReleaseCause: Abnormal release, unspecified
DL_RxQual
DL_Lev
GSM radio optimisation . Figure 56
Section C
GSM radio optimisationGSM radio optimisation
GSM radio optimisation . Figure 57
Topic Outline
1
CS call analysisCS call benchmarking
analysis
2
GSM radio optimisation . Figure 58
CS Call Analysis
Identify Problems Negative Events
Dropped Call Setup Failure Handover Failure
Poor Level 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
GSM radio optimisation . Figure 59
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 60
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. Lets look into this in more detail
GSM radio optimisation . Figure 61
RX Lev Analysis-Using Filter
Create the following filter
GSM radio optimisation . Figure 62
Rx Lev Analysis
GSM radio optimisation . Figure 63
Serving Cell Analysis
Press the layers button on the map and change the labelling of the GSM Cell Beam-widthlayer to be BCCH
GSM radio optimisation . Figure 64
Serving Cell Analysis
Press the layers icon againAlso for the GSM_Cell_Beamwidth layer, click lines & change the
GSM radio optimisation . Figure 65
Serving Cell Analysis
Before clicking OK click on the neighbour tab click disable then click OK
GSM radio optimisation . Figure 66
Serving Cell Analysis
Now click the area control icon and draw a box around the area circled earlier.
GSM radio optimisation . Figure 67
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
GSM radio optimisation . Figure 68
Serving Cell Analysis-TA
Display Timing Advance from Dedicated Radio Link Attributes
GSM radio optimisation . Figure 69
Turn off Filter
GSM radio optimisation . Figure 70
RX Qual Analysis
Right click the DL Serving Rxqual & put on the map
GSM radio optimisation . Figure 71
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 optimisation . Figure 72
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)
GSM radio optimisation . Figure 73
Rx Qual Analysis- Binned Queries
Right click the query & display this on the map
GSM radio optimisation . Figure 74
Negative Events Analysis
Dropped Calls From the events menu drag the dropped calls on to the map
GSM radio optimisation . Figure 75
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
GSM radio optimisation . Figure 76
Dropped Call Analysis-Event Query
Choose event dropped call as the trigger & a 5 second window before event & then click next
GSM radio optimisation . Figure 77
Dropped Call Analysis-Event Query
Select the statistics that we want to analyse
GSM radio optimisation . Figure 78
Dropped Call Analysis-Event QueryAverage Level Average quality last BCCH
Last CI Interference Timing Advance
GSM radio optimisation . Figure 79
Dropped Call Analysis-Event Query
Once all statistics are entered OK and then view the query results in the statistic explorer
GSM radio optimisation . Figure 80
Dropped Call Analysis-Event Query
Save/export your Query for Future use
GSM radio optimisation . Figure 81
Handover Analysis
Import the HO OK Event query & display on the statistics explorer
GSM radio optimisation . Figure 82
Handover Analysis
Using a map we can look into handovers in more detail
GSM radio optimisation . Figure 83
Handover Analysis
The following Analysis pack gives some useful over view figures regarding handovers & call set up.
GSM radio optimisation . Figure 84
Handover Analysis
GSM radio optimisation . Figure 85
Call Setup Analysis
Call Setup Flow Diagram
GSM radio optimisation . Figure 86
Call Setup Analysis
We can use the protocol stack browser to check the flow of messages around call set up
GSM radio optimisation . Figure 87
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 88
CS Call Benchmarking
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 KPIs per Cell this can then be used to start to identify problem cells
GSM radio optimisation . Figure 89
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.
GSM radio optimisation . Figure 90
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
GSM radio optimisation . Figure 91
CS Call Benchmarking
Measurement Charts report Shows distribution of Level, Quality and
Timing Advance
GSM radio optimisation . Figure 92
CS Call Benchmarking
Neighbor level This report looks into the dominance of
your server