GSM Protocol Stack
Shrish Mammattva Bajpai
What is Protocol Stack ?
A protocol stack (sometimes communications stack)
is a particular software implementation of a
computer networking protocol suite. The terms are
often used interchangeably. Strictly speaking, the
suite is the definition of the protocols, and the
stack is the software implementation of them.
In Windows the TCP/IP stack is implemented by the
Winsock DLL.
What is Protocol Stack ?
The term stack also refers to the actual
software that processes the protocols. So,
for example, programmers sometimes talk
about loading a stack, which means to load
the software required to use a specific set of
protocols.
Um Interface
A Interface
MS End Protocol Stack
• Physical Layer
• Data Link Layer
• Layer 3
Radio Recourse Management
Mobility Management
Connection Management
BTS End Protocol Stack
• Physical Layer
• Data Link Layer
• Layer 3
Radio Recourse
Base Transreceiving Station
Management
BSC End Protocol Stack
• Physical Layer
• Data Link Layer
• Layer 3
Radio Recourse
Base Tranreceiving Station Management
Signaling Connection Control Part
Direct Transfer Application Part
Base Station Subsystem Management
Application Part
MSC End Protocol Stack
Message Transfer Part
Signaling Connection Control Part
Direct Transfer Application Part
Base Station Subsystem Management
Application Part
Connection Management
Mobility Management
Mobile Application Part
Transaction Capabilities Application Part.
Link Layers
Um Interface
• Physical Layer
Implement Logic channels,coding and frames.
Access Capabilities.
Error Detection.
Encryption.
Um Interface Physical Layer Mode
• Mode of operations
Idle Mode.
Dedicated Mode.
Um Interface Physical Layer Mode
Um Interface Physical Layer Frame
Um Interface Physical Layer Frame
• 21 Blocks.
• Power level.
• Timing advance.
Use by ACCH, CCCH, BCCH & DCCH.
Um Interface Data Link Layer Task
Um Interface Data Link Layer
Operation Mode 1
• Unacknowledged Operation
Data Transmitted in UI frame.
No Ack
No Flow control Mechanism.
No L2 error correction technique.
Use for all channels except RACH.
.
Um Interface Data Link Layer
Operation Mode 2
• Acknowledged Operation Mode
Data Transmitted in I frame.
+ Ve Ack
Flow control Mechanism.
Error correction technique.
Use for DCCH Channel
Um Interface Data Link Layer
Um Interface Data Link Layer
Connection End Point Identifiers of L2
connections are labeled with Data Ling Layer
Identifiers
1.Service Access End Point Identifiers
2.Connection End Point Identifiers
SAPI =0 for Signaling.
SAPI = 3 for SMS.
Um Interface Data Link Layer
Procedure 1
• Distribution Procedure
SAP is associated with only one signaling channel
Distribution of L2 frame receive by one channel to
the respective data link procedure.
Not used for RACH
Um Interface Data Link Layer
Procedure 2
• Random Access Procedure
Only for RACH
Unidirectional Procedure
Deals with random control procedure
Retransmission of Random Access Brust
Um Interface Data Link Layer
Frame Formats 1
Points
No flag at start and at last.
Octets are depend upon type of channel.
The end of information field is given by length
indicator.
Frame format contains address field and variable
length.
Connection of SAPI = 0 is initiated by MS.
Address Field is one for control channels
Um Interface Data Link Layer
Frame Formats 2
Um Interface Data Link Layer
Frame Formats
• Type A.
Used in dedicated channels
Bi-directional Use.
No Information Contain.
Ack Mode Operation.
Um Interface Data Link Layer
Frame Formats 2
Um Interface Data Link Layer
Frame Formats
• Type B.
Used in dedicated channels
Bi-directional Use.
Information Contain.
Ack Mode Operation.
Um Interface Data Link Layer
Frame Formats
Um Interface Data Link Layer
Frame Formats
• Type Bbis
Used in common control channels
Uni-directional Use.
Information Contain.
Un Ack Mode Operation.
SAPI =0 is used.
Um Interface Data Link Layer
Frame Formats
Um Interface Data Link Layer
Frame Formats
• Type Abis
Used in common control channels
Uni-directional Use.
No Information Contain.
Un Ack Mode Operation.
SAPI =0 is used.
Um Interface Layer 3
• Layer 3
RR Management.
CM Management.
MM Management.
Um Interface Layer 3 Frame Format 1
• Common for RR, MM and CM.
Um Interface Layer 3 Frame Format 2
• Transaction ID- Enable to perform several
parallel signaling transaction.
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•
•
•
Protocol Discriminator – Operation type.
Message Type – Different type of process.
Information ID – Information elements.
Length Indicator – Length of the Information ID.
Um Interface Layer 3 Radio Recourse
Management. Functions
Um Interface Layer 3 Radio Recourse
Management. Processes
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•
•
•
Connection Set Up And Release.
Handoff.
Channel Change
Ciphering.
Um Interface Layer 3 Radio Recourse
Management. Connection Set Up And
Release Processes
Um Interface Layer 3 Radio Recourse
Management. Connection Set Up And
Release Processes
Um Interface Layer 3 Radio Recourse
Management. Connection Set Up And
Release Processes
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•
•
•
•
Um Interface Layer 3 Radio Recourse
Management. Connection Set Up And
Release Processes
RR Connection between MS & Nwk..
LAPDm Connection between MS &
Nwk..
Initiated by MS or Nwk. .
RR connection Establish then higher
link comes in picture.
SAPI =0 is used.
Um Interface Layer 3 Radio Recourse
Management. Channel Change Processes
Um Interface Layer 3 Radio Recourse
Management. Channel Change Processes
• Requested By CM, MM or by RR.
• Initiated By Nwk..
• MS get assignment command to shut
down the connection.
Um Interface Layer 3 Radio Recourse
Management. Handoff Process
Um Interface Layer 3 Radio Recourse
Management. Handoff Process
Um Interface Layer 3 Radio Recourse
Management. Handoff Process
• Cell Information BCCH
• Handoff Command ACCH
• Handoff Access DCCH
Um Interface Layer 3 Radio Recourse
Management. Activation of Ciphering
Process
Um Interface Layer 3 Radio Recourse
Management. Activation of Ciphering
Process
• Done By BSS.
• MS get the message and done the task.
Um Interface Layer 3 Mobility
Management Functions
Um Interface Layer 3 Mobility
Management Process
• Common Mobility Management Process.
TMSI Assignment.
Identification Process.
Authentication Process.
IMSI Detach.
• Specific Mobility Management Process
IMSI Attach
Location Updation.
MM Connection Management Process
Um Interface Layer 3 Mobility
Management Process. TMSI Assignment 1
Um Interface Layer 3 Mobility
Management Process. TMSI Assignment 2
• Unique identifier for each MS
• Change with every location updation.
• Send through BCCH with LAI identifier.
Um Interface Layer 3 Mobility
Management Process. Identification
Process. 1
Um Interface Layer 3 Mobility
Management Process. Identification
Process. 2
• At any time when network wants.
• IMSI + IMEI sends to Network.
Um Interface Layer 3 Mobility
Management Process. Authentication
Process. 1
Um Interface Layer 3 Mobility
Management Process. Authentication
Process. 2
• Started by Network, when MS send the
request to establish RR connection.
• RAND and Kc.
• When fails then IMSI and TMSI will send.
• Two time only.
• Fail then cancel all the connections.
• Emergency Calls can made only.
Um Interface Layer 3 Mobility
Management Process. IMSI Detach. 1
Um Interface Layer 3 Mobility
Management Process. IMSI Detach. 2
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•
•
•
Switch off the cell.
Cancel the paging load from network.
Send the message to MS on BCCH and SCCH.
This process will start after the any specific
operation.
Um Interface Layer 3 Mobility
Management Process. Location Upadation
• Channel Used BCCH.
• Identifier TMSI & LAI.
• Register HLR & VLR.
Um Interface Layer 3 Mobility
Management Process. IMSI Attach.
• Switch on the cell.
• New TMSI and LAI.
Um Interface Layer 3 Connection
Management
• Three Entities
1.Call Control.
2.Supplementary Services.
3. Short Message Services.
Um Interface Layer 3 Connection
Management
A Interface Protocol Stack
Message Transfer Part
Signaling Connection Control Part
Direct Transfer Application Part
Base Station Subsystem Management
Application Part
Connection Management
Mobility Management
Mobile Application Part
Transaction Capabilities Application Part.
A Interface Message Transfer Part
• Comprise lower 3 layer of OSI model.
• Routing.
• Transportation of the signaling message.
A Interface Mobile Application Part
A Interface Signaling Connection Control
Part
• Provides Connection less and connection
oriented Services.
• Messages through BSC.
• Two Reasons for setting the SCCP
Connection.
1.Location Update.
2.Call Connection Setup.
A Interface Transaction Capabilities
Application Part
• Connectionless Service given By SCCP.
• Exchange of MAP messages(Between
different MSC, HLR, VLR and GMSC)
done through this part.
A Interface Base Station System
Application Part
• Two Parts
Base Station System Management Application Part.
Direct Transfer Application Part.
A Interface Direct Transfer Application
Part.
• The messages through CM & MM are passed
on transparently through BSS using DTAP
Protocol.
• Only Connection Oriented Services.
• One signaling connection for each active MS
with one or more transaction.
• New connection establish each time when
the new transaction start between MS and
MSC.
A Interface BSSMAP
• Responsible for all admin and control of the
radio recourses.
• Handoff and channel ass. is control by
BSSMAP.
• Two type of procedure.
1.Global BSSMAP procedure.
2.Dedicated BSSMAP procedure.
A Interface BSSMAP
Dedicated BSSMAP procedure
• Channel Assignment.
• Channel Release.
• Cyphering Control.
A Interface BSSMAP
Dedicated BSSMAP procedure
A Interface BSSMAP
Global BSSMAP procedure
• Paging
• Flow Control
• Closing and Opening of the channel.
A Interface BSSMAP
Global BSSMAP procedure
Abis Interface BTSM
• Task
Random Access of the channel.
Paging process of MS.
Ciphering process of MS.
Power Control of MS.
Abis Interface BTSM Frame
Abis Interface BTSM Frame
• Message Discriminator
1 for passes through BTS.
2-5 serve by BTS.