1. CALL & MOBILITY MANAGEMENT

2. Call And Mobility Management
RF channel overview & Modes of Mobile Station.
MS Initialization ( Network Attachment )
Mobility Management and MM Procedures
Authentication & Location Updating Procedure
Connection Management (CM)
Call Processing – MO & MT Calls

3. Modes Mobile Station ( MS )
MS Switched Off - can not receive incoming paging messages.
- can not make outgoing call.
- No dedicated channel is associated with it.
MS Switched On can receive incoming paging messages.
And in Idle Mode can make outgoing call.
- No dedicated channel is associated with it.
MS in Dedicated Mode -MS is in conversation and a
dedicated traffic channel TCH is
associated with it.

4. RF Channels Overview
Broadcast Control Channels BCCH
P-MP FCCH
SCH
Common Control Channels PCH
P-P RACH
AGCH
Dedicated Control Channels SDCCH
P-P FACCH
SACCH

5. FCCH Burst Normal Burst CC SMS SS CM CC SMS SS CM 3 T 8.25 GP 142
Fixed Bits 3 T CM
FCCH Burst 3 T 57
Encrypted
8.25 GP CC 57
Encrypted
SMS SS 1S 26
Training 1 S 3 T CM
Normal Burst

6. Possible Channel Combinations On RT in One Cell
Timeslots 1 2 3 4 5 6 7
RT 0
BCCH
SDCCH
CCCH
TCH
CCCH
TCH
CCCH
TCH
RT 1
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH
RT 2
SDCCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH CC
SMS SS
RT 3
TCH
TCH
TCH
TCH
TCH
TCH
TCH
TCH CM

7. Channel Combination IV :main BCCH ( GSM 05.01)1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 49 50
FCCH
FCCH
SCH
SCH
IDLE
BCCH
CCCH
BCCH
Down-link
RACH
RACH
RACH
Up-link CC
SMS SS CM
Channel Combination IV :main BCCH ( GSM 05.01)

8. Technical Terms Used w.r.t. MM (Mobility Management )
IMSI – International Mobile Subscriber Identity
IMSISDN – Mobile Subscriber ISDN number
IMEI – International Mobile Equipment Identity
TMSI – Temporary Mobile Subscriber Identity
MSRN – Mobile Subscriber Roaming Number
LAI – Location Area Identity
A3 – Authentication Algorithm
A5 – Ciphering Algorithm
A8 – Kc Generation Algorithm

9. Location Related Identities
1. MSRN – Mobile Subscriber Roaming Number
It is a temporary number used for routing the call to MS.
Format :
MSRN = CC + NDC + SN
CC = Country Code
NDC = Network Destination Code
SN = Subscriber Number
For example for Patna MSC in IMPCS network MSRN looks like

10. Location Related Identities
MSRN
MSISDN
MSISDN
PSTN 2
GMSC 1
HLR
MSRN 6
MSRN
IMSI
MSRN 7 3 5
VLR
MSC
IMSI 4
MSRN

11. Location Related Identities
2. Location Area Identity (LAI ) -
Each location area in a GSM PLMN is identified by a Location Area Identity ( LAI ).
Location area consist of one or more than one cell which may be served by one or more BSC s.
All the cells in a Location area are served by single VLR.

12. Location Area MSC 1 SS 7 HLR MSC 2 BSC LA 1 BSC VLR 1 LA 2 BSC LA 3
BTS
MSC 1
BSC
LA 1
BTS
BSC
BTS
VLR 1
LA 2
SS 7
BTS
HLR
BSC
MSC 2
BTS
LA 3
BTS
BSC
VLR 2
Location Area

13. Location Related Identities
2 digits
2 octets max
3 digits
( 16 bits )
MCC
MNC
LAC
LAI
LAI = MCC + MNC + LAC
MCC - Mobile Country Code.
MNC - Mobile Network Code.
LAC - Location Area Code .
Maximum length of LAC is 16 bits.
Thus there can be maximum of 65,536 Location Areas defined in one GSM PLMN.

14. MS Initialization / Network Attachment
1. MS Powered on.
2. Frequency Synchronization
- MS scans entire 124 carriers and monitors RF levels.
- several readings are taken to get accurate estimate
the channel power.
- MS then searches for Frequency Correction burst (FCCH) on the channel with strongest RF level.
- FCCH present in time slot T0 & has a fixed pattern of ’s.
- After tuning to FCCH MS synchronizes in time with SCH .

15. MS Initialization / Network Attachment
3. Synchronization in Time
- SCH occurs in next frame in same time slot as FCCH.
- The occurrence of SCH is eight burst period ( BP’s ) later than FCCH.
- SCH contains precise timing information and current frame number to which MS is synchronized.
- After successful synchronization the MS will read the TDMA frame number and Base Station Identity Code BSIC .
- BSIC consists of - PLMN colour code ( 3 bits )
- BS colour code ( 3 bits ).

16. MS Initialization / Network Attachment
MS location is determined by cell identification of strongest BCCH signal received by MS.
MS regularly measures the received signal strength of BCCH at least once every 6 sec ( Superframe Duration).
MS stores at least six strongest BCCH and their cell identification in SIM.
MS decodes information on BCCH and gets Location Area Identity ( LAI ).
If the information stored on SIM does not match with the information MS thinks that it has moved to new location and sends LA update request to BSS.

17. Network Attachment Process
Switch -on MS
Measure strongest BCCH channels
PLMN Selection
Limited Service Mode
. Cell should be of selected PLMN.
Cell Selection
. Cell should not be “ barred “.
. Radio path loss between BTS and the MS must be below a threshold set by the operator.
Location Update
( Register its presence to the network. )
Idle-Mode

18. GSM Signaling Protocols Overview
BTS
BSC
MSC
DTAP CM
RIL3 - CM M
RIL3 - MM
DTAP MM A I P S
RIL 3-RR
RIL3 - RR
BSSMAP
BSSMAP
TCAP U RR
BTSM
BTSM
SCCP
SCCP
SCCP P
LAPD m
MTP
LAPD m
LAPD
LAPD
MTP
Layer 1
Layer 1
Layer 1
Layer 1 Um
A bis
A link
BCDEFG
GSM Signaling Protocols Overview

19. What is Mobility Management ( MM ) ?
Subscriber Data management at MSC/VLR
Subscriber data from HLR are retrieved by MM at the time of first location up-dating of a subscriber.
Dynamic data changes by subscriber are also managed by MM at MSC/VLR.
Operator initiated data changes for a subscriber are also managed by MM.
Services Provided to Upper Layers
MM sub-layer provides basic services to upper layer CM sub-layer.
MM handover procedures provide smooth transition from one radio link to other.

20. What is Mobility Management ( MM ) ?
Subscriber Authentication and Confidentiality management
MM procedures ensure authenticity of a subscriber.
MM procedures ensure data confidentiality at radio interface.

21. MM Procedures
MM Common Procedures :
TMSI Reallocation Procedure.
Authentication Procedure.
Identification Procedure.
IMSI Detach Procedure.
Ciphering Procedure.
Abort Procedure.
MM Specific Procedures :
Location Updating Procedure.
IMSI Attach Procedure.

22. MM Procedures
A MM specific procedure can only be started if no other MM specific procedure is running.
During the lifetime of a MM specific procedure if a MM connection establishment is requested by a CM entity, the request will either be rejected or delayed until the running of MM specific procedure is terminated.
Any MM common procedure Procedure ( except IMSI detach) may be initiated during MM specific procedure.
The MS side should wait for release of RR connection used for a MM specific procedure before a new MM specific procedure or MM connection establishment is started.

23. Authentication is used to check the validity of a mobile subscriber.
At MS
At N/W Ki Ki
RAND( 128 bits ) A3 A3
SRES
SRES
( 32 bits ) =?
AUTHENTICATION

24. Ki ( 128 bits) : Identification Key
- Purpose : Ki is used to calculate SRES and Kc.
- Ki is stored in SIM and HLR.
- Ki is never transmitted over signaling network.
RAND ( 128 bits ):Random Number
- Purpose : RAND is used to calculate SRES and Kc.
Kc ( 64 bits ) : Ciphering Key
- Purpose : Kc is used to encrypt data over radio interface.
SRES ( 32 bits) :Signed Response

25. Ciphering is used to encrypt data on radio interface.
RAND Ki
Kc generation is done at the time of Authentication. A8
Frame No. (22 bits )
Kc ( 64 bits) A5
Ciphering Stream
Ciphered Bits
XOR
Information Bits ( 114 bits )
CIPHERING

26. AUTHENTICATION PROCEDURE
Authentication procedure is always initiated and controlled by the n/w.
The purpose of authentication procedure is two fold :
. To check identity provided by the MS.
. To supply n/w parameters to MS to calculate Kc.
Authentication Request
TIME
Authentication Response
Authentication Reject MS
N/W
AUTHENTICATION PROCEDURE

27. Authentication Procedure
Authentication Triplets :
- At n/w side, authentication procedure requires authentication triplets.
- Authentication triplets contains
-RAND ( 128 bits ).
- SRES ( 32 bits ).
- Kc ( 64 bits ).
- The network can have more than one triplets.
- The operator can allow reuse of triplets.
- The index of currently used triplet is called CKSN ( Ciphering Key Sequence Number ).

28. This is a general procedure which is used for following purposes -
Location Updating Procedure
This is a general procedure which is used for following purposes -
Normal Location Updating -
MS moves to new LA.
Periodic Location Updating -
To notify periodic availability of MS to the network.
IMSI Attach -
MS switched on for first time in new LA or MS switched off and on.

29. Location Update Scenario
Each time MS moves to new LA corresponding VLR is informed.
Case - I Old LA and new LA in same VLR area
MS given new TMSI .
Location updated in VLR memory.
Case - II Old LA and new LA in different VLR area
HLR updates.
old VLR erases data.
new VLR records relevant parameters.
MS is given new TMSI.

30. Location Update Scenario
Phases of Location Update Scenario
Request for service.
Authentication
Ciphering
HLR/ VLR updation
TMSI reallocation.

31. LOCATION UPDATE SCENARIO - I
Request For Service
Old MSC/ VLR
New MSC/ VLR
HLR /AUC MS
BSS
Channel Request 1
RACH
SDCCH Assignment 2
AGCH
Location Update Request ( TMSI , LAI 0 ) 3
SDCCH
Request IMSI
( TMSI ) 4
Send IMSI

32. LOCATION UPDATE SCENARIO - II Authentication and Ciphering
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS 5
Get Authentication Parameters
( IMSI )
Authentication Parameters
Authenticate MS ( RAND )
( RAND,Kc,SRES )
SDCCH 6
Authentication Response ( SRES )
SDCCH
Cipher Radio Channel 7
( Kc )
Cipher Up Link Channel
SDCCH

33. LOCATION UPDATE SCENARIO - III Authentication and Ciphering
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS
Up Link Ciphered 8
SDCCH
BSS Ciphers Down link Channel . 9
Ciphering Complete

34. LOCATION UPDATE SCENARIO - IV Update HLR/VLR & TMSI Reallocation
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS
Update Location 10
De Register Mobile 11
Mobile De-registered 12
Location Updated
Location Updated Accept TMSI 13
SDCCH

35. LOCATION UPDATE SCENARIO - V Update HLR/VLR & TMSI Reallocation
New MSC/ VLR
Old MSC/ VLR
HLR/ AUC MS
BSS
Location Updated Complete 14
SDCCH
Clear Signaling Connection 15
Clear Complete 16
Release Radio Signaling Channel
SDCCH

36. ND Mobile moves to CA and Powers on MS
LOCATION UPDATION
Listens
BCCH/FCCH
ND Mobile moves to CA and Powers on MS
Update Location
HLR
GMSC MSC
Location Update
TAX CA ND CA
( TMSI, LAI )
LU Accept MS
LU Accept
VLR
Update Location
( New TMSI)
New VLR records subscriber data. CA
VPLMN
LU Accept
HLR
HPLMN ND
LU Accept
( Update Location/ Authentication )
GMSC MSC/VLR
TAX ND ND
LU Accept
(Subs data)
Update Location
ACK from old MSC/VLR
VLR
De register Mobile to Old VLR

37. SETUP PHASE RINGING PHASE CONVERSATION PHASE RELEASE PHASE
Mobile To Land Call Set-up Scenario
Phases of Mobile To Land Call
( Mobile Originated Call- MO Call )
SETUP PHASE
RINGING PHASE
CONVERSATION PHASE
RELEASE PHASE

38. SETUP PHASE Mobile To Land Call Set-up Scenario
- REQUEST FOR SERVICE ( CHANNEL ) BY MS
- CM SERVICE REQUEST
- AUTHENTICATION
- CIPHERING
- EQUIPMENT VALIDATION ( EIR CHECK )
- SETUP MESSAGE
- VALIDATION AT VLR
- ASSIGNMENT

39. MOBILE TO LAND CALL - I Request For Service
MSC/VLR
BSS MS
Channel Request 1
RACH
SDCCH Assignment 2
AGCH
CM Service Request 3
SDCCH
CM Service Accept 4

40. Mobile To Land Call Set-up Scenario
CM SERVICE REQUEST
- The Call Control (CC) entity of MS initiates the establishment of CC connection by requesting MM sub-layer of the mobile to establish MM sub-layer connection.
- Upon establishment of MM connection CM SERVICE ACCEPT message is received from n/w.
SETUP MESSAGE
- CC entity sends a setup message to its peer entity.

41. MOBILE TO LAND CALL - II Call Setup
MSC/VLR
BSS MS
Call Setup Request 5
SDCCH
Call Proceeding 6
SDCCH
Assign Trunk and radio
Assign TCH 7
SDCCH
Radio Assignment Complete
SDCCH
Trunk and Radio Assignment Complete

42. Mobile To Land Call Set-up Scenario
Call Setup message
MSC/VLR
Release Complete
message to MS
Is the requested basic service
provisioned for the subscriber ? No
Yes
Release Complete
message to MS
Preliminary Digit Analysis
Yes
Is the number of digits less than the
minimum expected?
1. Check of ODB( BAOC/BOIC/ BOIC Ex HC ) No
2. Subscriber call barring checks ( BAOC/BOIC etc. )
ASSIGNM ENT

43. Mobile To Land Call Set-up Scenario
ASSIGNMENT
- A BSSMAP message ‘Assignment Command ’ is sent by MSC to BSS.
- The message contains a free CIC on A-Interface for terrestrial channel allocated by MSC.
- A free TCH is allocated by the BSS and MS is informed to attach to this TCH.
- On receiving a response from BSS MSC switches the speech path towards the calling MS.
Note : Mobile has not connected user connection as yet.

44. MOBILE TO LAND CALL - III
Call Setup
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Network Setup ( Dialed Digits ) 8
Network Alerting
Alerting 9
FACCH
Connect
Start Billing 10
Connect
FACCH
Connect Acknowledge 11
FACCH

45. MOBILE TO LAND CALL - IV Call Release
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Disconnect 12
Network Release
Release 13
FACCH
Release Complete 14
FACCH
Clear Command 15
Channel Release
FACCH
Release Complete

46. Land To Mobile Call Set-up Scenario
Phases of Land To Mobile Call
( Mobile Terminating - MT Call )
Routing Analysis
Paging
Authentication
Ciphering
Call-Setup
Call Release

47. Architecture For Mobile Terminated Call
VISITING PLMN
A- Interface
MSC-B
IAM ( ISUP )
BSS-B
GMSC- B
Air Interface
VLR-B
ACK ( MSRN )
SRI ( MSISDN )
PRN
ACK ( MSRN ) MS
HLR-B

48. Routing Analysis LAND TO MOBILE CALL - I HLR MSC/VLR GMSC PSTN
Incoming Call 1
( MSISDN )
Get Route 2
Get Route
( MSISDN ) 3
( IMSI )
Routing Information 4
( MSRN )
Routing Information
( MSRN )
Incoming Call 5
( MSRN )

49. Paging LAND TO MOBILE CALL - II BSS MS MSC (TMSI) PCH ( RACH )
Perform Page
Page
(TMSI) 6
PCH
Channel Request 7
( RACH ) 8
Access Granted
( AGCH )
Paging Response
( TMSI, LAI ) 9
SDCCH
Page Response

50. LAND TO MOBILE CALL - III
Call Set-up
BSS
MSC MS
Call Set Up 10
SDCCH
Call Set Up Confirm 11
SDCCH
Assign Trunk & Radio Channel
Assign Radio Channel 12
SDCCH
Radio Channel Assigned
SDCCH
Trunk and Radio Channel Assignment Complete

51. LAND TO MOBILE CALL - IV Call Setup
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Mobile Alerting 13
FACCH
Network Alerting
Connect ( off-hook ) 14
FACCH
Start Billing
Connect
Connect Acknowledge 15

52. LAND TO MOBILE CALL - V Call Release
MSC/VLR
GMSC
BSS
HLR
PSTN MS
Network Release
Disconnect 16
Stop Billing
FACCH
Release 17
Release Complete
FACCH
Release Complete 18
FACCH
Clear Command 19
Clear Channel
Clear Complete
FACCH

53. 1. ND PSTN Subscriber Dials ND Mobile Subscriber in ND.
Page(TMSI) ND
HLR MS
GMSC MSC/VLR
SRI ND
TAX ND
MSRN ND
MSISDN
PRN to MSC/VLR ND
MSISDN
ACK from MSC/VLR
ND (MSRN)
MSISDN
TANDEM LE

54. 2. ND PSTN Subscriber Dials CA Mobile Subscriber in CA.
TANDEM
HLR
MSISDN
MSISDN
GMSC MSC/VLR
TAX ND LE ND ND
MSISDN CA
HLR
MSISDN
SRI
GMSC MSC/VLR
TAX CA
MSRN CA CA
PRN to MSC/VLR CA
ACK from MSC/VLR CA (MSRN)
Page(TMSI) MS

55. 3. ND PSTN Subscriber Dials ND Mobile Subscriber in CA.
HLR
GMSC MSC/VLR ND
TAX CA MS
MSRN CA CA
Page(TMSI)
MSRN
HLR
MSRN
SRI
GMSC MSC/VLR ND
TAX ND
MSRN ND
MSISDN
PRN to MSC/VLR CA
ACK from MSC/VLR CA (MSRN)
MSISDN
MSISDN
TANDEM LE

56. 4. CA PSTN Subscriber Dials ND Mobile Subscriber in CA.
TANDEM
HLR
MSISDN
MSISDN
GMSC MSC/VLR
TAX CA LE CA
MSRN ND
Page(TMSI) CA
MSISDN MS
MSRN ND
HLR
MSRN
SRI
GMSC MSC/VLR
TAX ND
MSRN ND
MSISDN
PRN to MSC/VLR CA
ACK from MSC/VLR CA (MSRN)

57. THANKS !