GSM Network and Services - Personliga hemsidor på KTHjohanmon/attic/2g1723/lectures/map.pdf · GSM...
Transcript of GSM Network and Services - Personliga hemsidor på KTHjohanmon/attic/2g1723/lectures/map.pdf · GSM...
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1GSM Network and Services 2G1723 Johan Montelius
GSM Network and Services
Call Control, SMS and MAP signaling - BSC/MSC/VLR/HRL/AUC/SMSC and more
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2GSM Network and Services 2G1723 Johan Montelius
Signaling protocols MS - BSS
LAPDm LAPDm LAPD
L1 L1 E1
LAPD
E1
RR BTSM BTSM
RRRR
MM
CM
Um Abis A
Layer 2
Layer 3
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3GSM Network and Services 2G1723 Johan Montelius
Connection Management
• Call Control
– establish and terminate calls
– call related supplementary services
• Supplementary Services
– call forwarding / barring
– Number identification
– Charging
• SMS
– Sending and receiving of short messages
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4GSM Network and Services 2G1723 Johan Montelius
CC procedures – mobile originated call
MS BSS
Alerting
This is only the CC procedures!
Call Proceding
Connnect Acknowledge
admision
Setup
make call
Connect pick up
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5GSM Network and Services 2G1723 Johan Montelius
CC procedures – mobile terminated call
MS BSS
This is only the CC procedures!
Setupcheck
ring
Connect Acknowledge
pick up
Call Confirm
Alerting
Connect
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6GSM Network and Services 2G1723 Johan Montelius
CC procedures – terminate call
MS BSS
Release Comlete
This is only the CC procedures!
Disconnect
hang up
Releaseend call
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7GSM Network and Services 2G1723 Johan Montelius
SMS signalingSMSC
submission
delivery
delivery report
sub. report
status report
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8GSM Network and Services 2G1723 Johan Montelius
Signaling protocols – SMS
CM:SMS
MSC
CM:SMS
SM-RPMAP MAP
SM-RP
SM-TP SM-TP
SMSCMS
SMS submission/delivery/report
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9GSM Network and Services 2G1723 Johan Montelius
SMS - signaling
• SM-TP – short message transport protocol
– The high level communication between the MS and the SMSC.
• SM-RP – short message relay protocol
– Holds a state between submission and submission report (or delivery and delivery report) so that the MM/RR resources can be released between messages.
• SM-CP – short message control protocol (CM:SMS)
– ARQ over the air interface
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10GSM Network and Services 2G1723 Johan Montelius
SMS services
• Mobile Terminating and Mobile Originating SMS is treated as two different services.
• Mobile has the address of a SMS service center (in the home PLMN) to which all messages are sent.
• The SMSC can be reached from external nodes (Short Message Entities) through a number of protocols.
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11GSM Network and Services 2G1723 Johan Montelius
SMS-SUBMIT
RP DHI SRR RDVPF MTI
message reference
7 6 5 4 3 2 1 0
destination address (2 – 12 octets)
protocol identifier
coding scheme
validity period (0, 1 or 7 octets)
user data length
user data ( 0 – 140 octets)
• Message Type Indicator
• Reject Duplicate
• Validity Period Format– no, relative (1), absolute
(7) or extended (7)
• Status Report Request
• User Data Header Ind.
• Reply Path Request
• Message reference– to idenify duplicates etc
• Protocol identifier
• Coding scheme
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12GSM Network and Services 2G1723 Johan Montelius
Coding scheme
• Character coding– GSM 7-bit (3GPP 23.038)
– Universal Character Set (ISO 10646)
– Text compression
• Coding group– automatic deletion, message waiting
• Message class– immediate display
– store: mobile, SIM, terminal eq (PDA, computer ...)
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13GSM Network and Services 2G1723 Johan Montelius
Protocol Identifier
• regular: SME to SMSC
• page: acknowledge but do not notify user
• mobile: handled by the terminal
• SIM: handled by the card
• telematic services: fax, telex, email
• many more ......
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14GSM Network and Services 2G1723 Johan Montelius
SMS-DELIVERY
RP DHI SRI MM MTI
coding scheme
7 6 5 4 3 2 1 0
time stamp (7 octets)
user data length
user data ( 0 – 140 octets)
• Message Type Indicator
• More messages
• Status Report Ind.
• Oiginator address
• Protocol identifier
• Coding scheme
• Time stamp
protocol identifier
originator address (2 -12)
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15GSM Network and Services 2G1723 Johan Montelius
Signaling protocols – MS/BSC/MSC
MTP2
MTP1
MTP3
SCCP
DTAP
MTP2
MTP1
MTP3
SCCP
DTAP
MM
CM
SS7
BSC MSC
RR
A
MS
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16GSM Network and Services 2G1723 Johan Montelius
DTAP - Direct Transfer Application part
• Transports MM and CM messages transparently through the BSC to the mobile station.
• DTAP sessions uses connection oriented SCCP
– each session has a unique SCCP connection to the mobile
• New SCCP connections are established
– Location updates
– Handover to another BSC
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17GSM Network and Services 2G1723 Johan Montelius
Signaling protocols – BSC/MSC
MTP2
MTP1
MTP3
SCCP
BSSMAP
MTP2
MTP1
MTP3
SCCP
BSSMAP
SS7
BSC MSC
A
RR
MM
CM
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18GSM Network and Services 2G1723 Johan Montelius
BSSMAP – BSS Mobile Application Part
• For the Mobility Management layer (and CM) to control the RR layer.
• Global procedures
– using connectionless SCCP
– paging, channel control, over flow,...
• Dedicated procedures
– using connection-oriented SCCP
– channel assignment, ciphering, handover control, ...
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19GSM Network and Services 2G1723 Johan Montelius
BSSMAP dedicated procedures
MS BSS MSCAssignment Assignment Req
Assignment ComplAssignment Compl
MS BSS MSCCipher Mode Cipher Mode Cmd
Cipher Mode ComplCipher Mode Compl
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20GSM Network and Services 2G1723 Johan Montelius
BSSMAP handover proceduresMS BSS-1 MSC
Req Ack
Handover Complete
Handover required
handover
BSS-2
Handover request
Handover CmdHandover Cmd
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21GSM Network and Services 2G1723 Johan Montelius
Interfaces
HLR
VLR
BTS
BSCMSC
A
A-bisUm
B
C
EIR
F
D
G
VLR
E
MSC
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22GSM Network and Services 2G1723 Johan Montelius
Signaling protocols – MSC/HLR/VLR/...
MTP2
MTP1
MTP3
SCCP
• TCAP - transaction capabilities application part, defined in the SS7 stack
• MAP – mobile application part, this is the application layer protocol used by MSC/VLR/HLR communication.
TCAP
MAP
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23GSM Network and Services 2G1723 Johan Montelius
MAP – mobile application part
• The network side of Mobility Management
• Defines the interface between the MSC and the VLR/HLR/AUC databases.
• Also defines the interface between multiple MSCs and multiple PLMN.
• Resposible for mobility inside a PLMN and roaming between different PLMN.
• Also used by to implement for example SMS services in side a PLMN.
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24GSM Network and Services 2G1723 Johan Montelius
Location Update procedure
MS BSS/MSC VLR HLR AUC
Loc Upd.IMSI/LAI
Auth. Info.RAND/SRES/Kc
Loc Upd.IMSI/LAI
Auth. req.IMSI
Auth. req.IMSI
Auth. info.RAND/SRES/Kc
AuthenticateRAND
AuthenticateRAND
Auth. resp.SRES
Auth. resp.SRES
Loc. upd.IMSI/MSRN
Start Ciph.Kc
Ciph. Mode
TMSI real. ack
New TMSITMSI
TMSI real. cmd
Loc. Upd. ack
Ciph. Mode
TMSI ack
Kc
Sub. dataIMSI
Sub. data ack
Loc. Upd. acc.IMSI
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25GSM Network and Services 2G1723 Johan Montelius
Location update
• If MS does not have a TMSI it will identify itself with IMSI.
• VLR might have to do a new authentication but this can be avoided if TMSI and Kc is know.
• HLR might have to ask AUC for new set of triplets.
• A new TMSI is generated by the VLR that is the address to the MSC of the location area and when asked identifies the TMSI in the VLR.
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26GSM Network and Services 2G1723 Johan Montelius
Location update - optional procedures
• VLR initiates ciphering in order to send the new TMSI in encrypted form.
• If the location are is under the same MSC the HLR need not be informed. If it is under a new MSC under the sam VLR a new MSRN is generated and sent to the HLR.
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27GSM Network and Services 2G1723 Johan Montelius
Location update - inter VLR update
• If the location are update arrives to a new VLR the VLR has to ask the old VLR for encryption triplest identified by the TMSI.
• Once the mobile is autheticated the HLR is updated.
• The HLR asks the old VLR to cancle its register for the mobile.
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28GSM Network and Services 2G1723 Johan Montelius
Connection establishment
MS BSS/MSC
page respTMSI
IAMMSISDN
MSRN
VLR HLR GMSC
MSISDN
IAMMSRN
MSRN
TMSI/LApageTMSI
Call Control
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29GSM Network and Services 2G1723 Johan Montelius
Connection establishment
• If the HLR does not have the MSRN then it has the address of the VLR. It will then ask the VLR for a MSRN given the IMSI that is tied to the MSISDN.
• If the calling network is MAP capable, and is allowed to, it can ask the HLR directly for the MSRN.
• If the subscriber is roaming in another PLMN then the local VLR will talk to the HLR of the home PLMN.
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30GSM Network and Services 2G1723 Johan Montelius
Handover
• Intracell handover: local decision of the RR in the BSC to switch to a timeslot or frequency with better radio conditions or a traffic channel with other (FR/HR/EFR) coding.
• Intercell handover:
– decision made by the BSC
• internal handover, MSC not involved
• external handover, MSC involved
– decision made by the MSC to improve load balancing in the network
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31GSM Network and Services 2G1723 Johan Montelius
Intra-MSC Handover
• A inter-MSC handover is an external handover (the MSC is involved) that does a handover from one BSC to another but the two BSC are controlled by the same MSC.
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32GSM Network and Services 2G1723 Johan Montelius
Intra-MSC handover
MS BSS1
Handover Compl.
Handover required
MSCBSS2
Handover request
Clear Cmd.
Handover Ack
Handover Cmd.
Handover
Handover Compl.
Clear Compl.
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33GSM Network and Services 2G1723 Johan Montelius
Inter-MSC Handover
• The anchor MSC is the MSC that handled the first call procedure. It will always be in charge of the call.
• If mobile moves to another MSC the call will go to the anchor MSC and then to the second MSC.
• If the mobile moves to a third MSC the second MSC will be no longer be part of the call.