GSM Call Flow
-
Upload
aadel-adoul -
Category
Documents
-
view
213 -
download
4
Transcript of GSM Call Flow
Call Management in GSM
Overview
Land to Mobile Call Scenario
Mobile to Mobile Call Scenario
Mobile to Land Call Scenario
Detailed Intra-MSC Handover Scenario
Handover Overview
Detailed Inter-MSC Handover Scenario
Objectives
• Recognise and describe the phases of a mobile originated call.
• Recognise and describe the phases of a mobile terminated call.
• Describe the need for handover in GSM and typical handover causes.
• Explain the different types of handover in the GSM system.
• Recognise and describe the phases of different types of handovers.
Mobile-to-Land
Call Scenario
Required Facilities for a Mobile-to-Land Call
1. Radio channel between Mobile Station and BTS selected by the BSC 2. BSC – BTS voice trunk selected by the BSC3. MSC – BSC voice trunk selected by the MSC4. MSC – PSTN voice trunk selected by the MSC5. Line from PSTN end switching office to Fixed Station (permanent link)
BSC - Base Station ControllerBTS - Base Transceiver Station MSC - Mobile Switching CentrePSTN - Public Switched Telephone Network
BTS
RadioChannel
Mobile StationBSC
MSC PSTN
BSCVoiceTrunk
VoiceTrunk to PSTN Line
MSCVoiceTrunk
Fixed PublicLand Network
Public LandMobile Network
Phases of a Mobile-to-Land Call
• Request for Service
• Authentication*
• Ciphering*
• Equipment Validation*
• Call Set-up
• Handover(s)*
• Release
* Phase might not occur
Note: Detail for authentication and ciphering is not shown. It is the same as in the location registration update scenario.
Mobile-to-Land CallRequest for Service
NewVLR
BMSCBSSMS
AUm
1
2
3
4
5
Channel Request
Dedicated SignallingChannel Assignment
Service Request TMSI, LAI
Service Request TMSI, LAI
Service Request TMSI, LAI
Mobile-to-Land CallEquipment Validation
6
7
8
9
EIRMSCMS
IMEI Request
IMEI Response
Check IMEI
IMEI Check Results
(IMEI)
Mobile-to-Land Call Set-up
VLR
BMSCBSSMS
AUm
10
11
12
13
14
Call Setup RequestDialled DN
Access Subscriber Data
Subscriber Data
Call Proceeding
Assign Trunk & RadioTrunk No.
15
16
17
Assign Radio Channel TCH
Radio Assignment Complete(on TCH)
Trunk & Radio AssignmentComplete TCH
Mobile-to-Land Call Set-upContinued
18
19
20
21
PSTNMSCMS
Network Set-up(Dialled DN, Trunk No.)
Network Alerting
Alerting
Connect (answer)
22
23
Connect
Connect Acknowledgement
Note: Network Set-up, Network Alerting and Connect are generic terms. For SS7, the network set-up message would be Initial Assignment Message (IAM).
Mobile-to-Land CallMobile Initiated Release
PSTNMSCBSSMSAUm
1
2
3
4
5
Disconnect
Network Release
Release
Release Complete
Clear Command
6
7
Channel Release
Clear Complete
Land-to-Mobile
Call Scenario
Phases of a Land-to-Mobile Call
• Routing Analysis
• Paging
• Authentication*
• Ciphering*
• Equipment Validation*
• Call Set-up
• Handover(s)*
• Release
*Phase might not occur
Note:: Detail for authentication, ciphering and equipment validation is not shown. It is the same as in location registration update and mobile-to-land call scenarios.
Land-to-Mobile CallRouting Analysis
VLR
HLRMSC
PSTNC
1
2
3
4
5
Incoming Call MSISDN
Get Route MSISDN
Routing Information MSRN
Incoming Call MSRN
Perform Page
TMSI, LAI
B
Land-to-Mobile CallPaging
VLR
BMSCBSSMS
AUm
6
7
8
9
10
Perform Page TMSI
Page TMSI (on PCH)
Channel Request (on RACH)
Dedicated Signalling ChannelAssignment (on AGCH)
Page Response TMSI,LAI (on SDCH)
11
12
Page Response TMSI, LAI
Page Response TMSI, LAI
Land-to-Mobile Call Set-up
13
14
15
16
MSCBSSMS
Call Set-up
Call Set-up Confirm
Assign Trunk & RadioChannel TRUNK
Assign RadioChannel TCH
17
18
Radio Assignment Complete
Trunk & RadioAssignment Complete
U m A
Land-to-Mobile Call Set-upContinued
19
20
21
22
PSTNMSCMS
Mobile Alerting
Network Alerting
Connect (off-hook)
Connect
23Connect Acknowledge
Land-to-Mobile CallNetwork Initiated Call Release
PSTNMSCBSSMSAUm
1
2
3
4
5
Disconnect
Release
Release Complete
Clear Command
6
7
Channel Release
Clear Complete
Network Release
Mobile-to-Mobile
Call Scenario
Phases of a Mobile-to-Mobile Call
•Request for Service
• Authentication*
• Ciphering*
• Equipment Validation*
• Call Setup
• Routing Analysis
• Paging
• Authentication*
• Ciphering*
• Equipment Validation*
• Call Setup
• Handover(s)*
• Release
*Phase might not occur
•
Originating Mobile
Terminating Mobile
Mobile-to-Mobile Call Set-up & Release
BSSA’
MSCVLR
BSSMS-AA
Channel Request
MS-B
Um’Um
Service Request
Channel Request
Authentication
Ciphering
Equipment Validation
Paging and Response
Authentication
Ciphering
Equipment Validation
Call Set-up
Handover
Release
Call Set-up
Handover
Release
Routing AnalysisWith HLR
Handover Overview
Handover
• Maintains Call Continuity.
• Controlled by BSS.
• Based on RF subsystem criteria or traffic loading considerations.
• Both MS and BTS provide RF link measurements to the handover process.
• Handover causes are prioritised:RXQUALRXLEVDISTANCEPOWER BUDGET
Handover Types
Four Levels
• within same Base Transceiver Station (Intra-BTS)
• between different BTSs served by same BSC (intra-BSS/inter-BTS)
• between different BSSs within same MSC (intra-MSC/inter-BSS)
• between different MSCs (inter-MSC)
Intra-BTS Handover
Global Cell Identification
BSC3BSC2BSC1
MSC B MSC A PSTN
234 01 100 53
234 01 100 54
234 01 100 55
234 01 100 51
234 01 100 52
234 01 089 20
234 01 089 21
234 01 089 22
234 01 100 50
CountryCode
NetworkCode
Location AreaCode
CellIdentity
Intra-BSS/Inter-BTS Handover
Location AreaCode
Global Cell Identification
BSC3BSC2BSC1
MSC B MSC A PSTN
234 01 100 53
234 01 100 54
234 01 100 55
234 01 100 51
234 01 100 52
234 01 089 20
234 01 089 21
234 01 089 22
234 01 100 50
CountryCode
NetworkCode
CellIdentity
Intra-MSC, Inter-BSS Handover
Global Cell Identification
BSC3BSC2BSC1
MSC B MSC A PSTN
234 01 100 53
234 01 100 54
234 01 100 55
234 01 100 51
234 01 100 52
234 01 089 20
234 01 089 21
234 01 089 22
234 01 100 50
CountryCode
NetworkCode
Location AreaCode
CellIdentity
Intra-BSC, Inter-BTS Handover
Global Cell Identification
BSC3BSC2BSC1
MSC B MSC A PSTN
234 01 100 53
234 01 100 54
234 01 100 55
234 01 100 51
234 01 100 52
234 01 089 20
234 01 089 21
234 01 089 22
234 01 100 50
CountryCode
NetworkCode
Location AreaCode
CellIdentity
Detailed Intra-MSC/Inter-BSS Handover
Scenario
Intra-MSC/Inter-BSS Handover Step 1
BSS 1
MSCPSTN
Present Voice Path
BSS 2
Step 1: Handover Request from BSS
Intra-MSC/Inter-BSS Handover Step 2
BSS 1
MSCPSTN
Future Voice Path
BSS 2
Step 2: Allocation of New Resources
Intra-MSC/Inter-BSS Handover Step 3
BSS 1
MSCPSTN
Old Voice Path
BSS 2
Step 3: Handover Execution
New Voice Path
Intra-MSC/Inter-BSS Handover Step 4
BSS 1
MSCPSTN
BSS 2
Step 4: Release of Old Resources
Intra-MSC Handover Signalling
VLR
BMSCBSSMS
AUm
1
Signal Strength MeasurementSIG, MEAS
2
Rank-ordered list of target BSSsHAND, REQ
3
Kc, Identity of trunk, LAIHAND, REQ
4
New Radio Channel IDHAND, REQ, ACK
5
New Radio Channel IDHAND, REQ, ACK
6
New Radio Channel IDHAND, REQ, ACK
7HAND, ACC
8
On New Radio ChannelPHYS, INFO
9HAND, DET
10HAND, COMP
11HAND, COMP
12REL, RCH
13REL, RCH, COMP
Intra-MSC HandoverSignalling (Continued)
VLR
BMSCBSSMS
AUm
1
Signal Strength MeasurementSIG, MEAS
2
Rank-ordered list of target BSSsHAND, REQ
3
Kc, Identity of trunk, LAIHAND, REQ
4
New Radio Channel IDHAND, REQ, ACK
5
New Radio Channel IDHAND, REQ, ACK
6
New Radio Channel IDHAND, REQ, ACK
7HAND, ACC
8
On New Radio ChannelPHYS, INFO
9HAND, DET
10HAND, COMP
11HAND, COMP
12REL, RCH
13REL, RCH, COMP
Detailed Inter-MSC Handover Scenario
Basic Inter-MSC Handover Steps
BSS A
MSC APSTN
Future Talk Path
BSS B
Step 2: Allocation of New Resources
MSC B
BSS A
MSC APSTN
Present Talk Path
BSS B
Step 1: Handover Request from BSS
MSC B
Present Talk Path
Basic Inter-MSC Handover StepsContinued
BSS A
MSC APSTN
BSS B
Step 4: Release of Old Resources
MSC B
BSS A
MSC APSTN
Old Talk Path
BSS B
Step 3: Handover Execution
MSC B
New Talk Path
Inter-MSC Handover Voice Facilities
MSC A
MSC B
MSC C
MSC D
PSTN
Inter-MSC Trunks (dedicated)
PSTN Trunks
MSC A
MSC B
MSC C
MSC D
PSTN
MSC Directory Number Spectrum
LocalExchange
Directory Number Spectrum
MSC
MSC
PSTN
MSISDN
MSRN
MSHN Used to referenceInter-MSC handovers
TrunksTrunks
Inter-MSC SignallingTwo Signalling Paths
MSC B
E
Mobile Application Part (MAP)(Defined in GSM Specification 09.02)
MSC A
PSTN
Dedicated Trunk Group
or
Inter-office Signalling such as ISDN-UP or TUP(Outside scope of GSM specification)
SS7
ISDN-UP – ISDN User PartTUP – Telephone User Part
Basic Inter-MSC HandoverInitial Condition
MSC A
BSS A
PSTN
Talk Path
Dialled Number720-1234
Serving CellGlobal Cell ID234-01-235-43
720-1234
MSC B
BSS B
Candidate CellGlobal Cell ID234-02-120-65
VLR B
Basic Inter-MSC HandoverHandover Number Allocation
MSC A
BSS A
PSTN
Perform Handover(234-02-120-65, Kc)
720-1234
Serving CellGlobal Cell ID234-01-235-43720-1234
MSC B
BSS B
Candidate CellGlobal Cell ID234-02-120-65
VLR B
Perform Handover(234-02-120-65, Kc)
E Interface
PSTN/ISDN Interface
SS7
PSTN
Basic Inter-MSC HandoverInter-MSC Trunk Set-up
MSC A
BSS A
PSTN720-1234
Serving CellGlobal Cell ID234-01-235-43720-1234
MSC B
BSS B
Candidate CellGlobal Cell ID234-02-120-65
VLR B
Network Set-up(219-9221)
Set-up Complete
E InterfaceSS7
Basic Inter-MSC HandoverEvents After Handover Command
MSC A
BSS A
PSTN720-1234
720-1234
MSC B
BSS B
VLR B
Send End Signal
E Interface
Answer
PSTN/ISDN Interface
New Talk Path
Inter-MSC Handover Signalling
ServingBSS
MS
1
Signal Strength MeasurementSIG, MEAS
TargetMSC
ServingMSC
TargetVLR
TargetBSS
6 HAND, REQ
2Rank-ordered list of
Target BSSs
3 HAND, PER
4 HAND, NUM
5 HAND, NUM, COMP
7New Radio Channel ID
HAND, REQ, ACK
8 HAND, PER, ACK
Inter-MSC Handover Signalling(Continued)
ServingBSS
MS
9 NET_SETUP
TargetMSC
ServingMSC
TargetVLR
TargetBSS
14 PHYS_INFO
10 SETUP_COMP
11
New Radio Channel ID
HAND_COMP
12
13
15 HAND_DET
16 HAND_COMP
New Radio Channel ID
HAND_COMP
On New Radio Channel
HAND_ACC
Inter-MSC Handover Signalling(Continued)
ServingBSS
MS
17 HAND_COMP
TargetMSC
ServingMSC
TargetVLR
TargetBSS
22 END_SIGNAL
18 SEND_ENDSIG
19 ANSWER
20
21
23 NET_REL
24 REL_HAND_NUM
REL_RCH_COMP
REL_RCH