02 BSSSIG Signalling Protocols Ppt v1

CTXX 2900 /1.0 en 1 Tarun Sharma 15.04.1999 Copyright Nokia Telecommunications – Restyled by Mario Piuri 12-07-2002

Welcome to

BSSSIGBase Station SubBase Station Sub--system system SignallingSignalling CourseCourse

Trainer’s Slides


BSSSIGBSSSIG -- Course ContentsCourse Contents• GSM Network Review• BSS Signalling on A, Abis & Air Interface• Signalling Examples - Sign. Flow in MOC, MTC, LUP & HO• Use of Nethawk• Useful BSC/MSC Commands• Successful Call Cases• Failing Call Cases/Troubleshooting


SignallingSignalling is...is......all kinds of information exchange that enables speech or data connections between two or more subscribers. It can be on betweennetwork and subscribers or between different network elements.

Its main tasks in general are:- call control (establishment, supervision & maintenance, release)- control of servicesMobile specific additional tasks are:- subscriber administration- mobility management

• Signalling information is made of sets of standardized messages.• The GSM network uses pre-existent protocols developed for modern telecommunication networks, i.e. CCS7.• The CCS7 used in PSTN networks was redefined in order to fulfill the signalling requirements of mobile networks.


SignallingSignalling in the BSSin the BSS

DX 200

MSCTC

HLROMC

BSC

DX 200

BTS

BTS

BTS

MS

NSS

CCS7

LAPDLAPDm

BSS

NMS NSS


OSI OSI ReferenceReference ModelModel

application

host A

transmission medium

Communication hardware/software

application

host B

Communication hardware/software

OSI Stack

1 Physical Layer

2 Data Link Layer

3 Network Layer

4 Transport Layer

5 Session Layer

6 Presentation Layer

7 Application Layer

Protocol peer-to-peer

communication

User Part

QoS

Network delivery service (network type dependent)


GSM GSM SignallingSignalling LayersLayers• The Physical Layer (L1)

Air interface - data transmission at 270.833 kbits/sA/Abis interface - data transmission at 2,048 kbits/s (2Mbps) Data to signals convertion according to the physical medium

• The Link Layer (L2)Air interface – GSM-specific LAPDm protocolAbis interface – LAPD protocolA interface – MTP (CCS7) protocolSegmentation, Error detection/correction, Retransmission

• The Network Layer (L3)Air interface – RR / DTAPAbis interface – BTSM A interface – BSSMAP Channel allocation, transport function, mobility and transaction handling

<< In BSS, << In BSS, applicationsapplications are are often referred as often referred as GSM_L3, GSM_L3, but it is notbut it is not OSI_L3 >>OSI_L3 >>


SignallingSignalling Protocols in GSMProtocols in GSM

CMCMB

SSAP

BSSAP

DTAP

CMCM

SCCPSCCP

MTPMTP

SMS

SS

CC

MMMM

BSSMAPBSSMAP

A Interface (G.703)A Interface (G.703)

BSSMAPBSSMAP

SCCPSCCP

MTPMTP

RRRR

BTSMBTSM

LAPDLAPD

RR’RR’

BTSMBTSM

LAPDLAPD LAPDmLAPDm

Abis Interface (G.703)Abis Interface (G.703) Air InterfaceAir Interface

SMS

SS

CC

MMMM

RRRR

MSC BSC BTS MS

LAPDmLAPDm

GSML3

GSML3

04.08 *

04.80

04.11

04.08

04.08 04.0808.08

08.58

08.56 04.06

08.54 04.04

08.06

08.04

08. 04* ETSI specifications


Module ContentsModule Contents• Introduction to BSS Signalling• CCS7

- MTP- SCCP

• LapD-LapDm

• BTSM• RR• BSSAP

- BSSMAP- DTAP


CCS7CCS7


Where is CCS7 on A interface?Where is CCS7 on A interface?T S 1 2 3 4 5 6 7 8

0 S Y N C H1 T C H2 T C H3 T C H4 T C H5 T C H6 T C H7 T C H8 T C H9 T C H

1 0 T C H1 1 T C H1 2 T C H1 3 T C H1 4 T C H1 5 T C H1 6 C C S 71 7 T C H1 8 T C H1 9 T C H2 0 T C H2 1 T C H2 2 T C H2 3 T C H2 4 T C H2 5 T C H2 6 T C H2 7 T C H2 8 T C H2 9 T C H3 0 T C H3 1 T C H

•Traffic channels' baud rate is 64 kbit/s

•TCH are located in TS's 1-15 17-31

•TS 16 can be used for CCS7 signalling


…….and on Ater interface?.and on Ater interface?

CCS7CCS7CCS7

•The traffic channels and signalling channels coming from three (four) different PCMs from the MSC are reallocated in the transcoder

•Traffic channels (16 Kbits/s) form each PCM (30) go to 8 consecutive time slots

•Signalling channels (64 Kbits/s) are allocated in the last time slots of the frame

•One LAPD channel is allocated in TS 1, sub TS 1-2 for communication between TC and BSC


CCommon ommon CChannel hannel SignallingSignalling nn°°77 –– CCS7CCS7

1 Physical layer

2 Data link layer

3 Network layer

4 Transport layer

5 Session layer

6 Presentation layer

7 Application layer

MTP (levels 1-3)

User Part (level 4)

OSI Reference ModelCCITT Common

Channel SignallingNo 7


MTPMTP


CCS7CCS7--MTPMTP• MTP is the message transfer part. It is responsible for transferring of

signalling messages from one element to another within the samesignalling network. It consists of three sub layers.

SignallingData Link

Network Management

MessageHandling

Signalling Link

LAYER 1

LAYER 2

LAYER 3


CCS7 CCS7 -- MTPMTPThe three levels of the MTP are:• Level 1 - Signalling Data Link Level

... to access the physical medium (Signalling Link)• Level 2 - Signalling Link Level

... to provide reliable transfer of signalling messages (Signalling Link Set)Creates signalling units:MSU - Message Signalling UnitLSSU - Line Status Signalling UnitFISU - Fill-In Signal Unit


MTP Layer 2 Frame FormatsMTP Layer 2 Frame Formats

F CK SIF SIO LI F I B

FSN B I B

BSN F

LI F I B

FSN B I B

BSN F

LI F I B

FSN B I B

BSN F

F CK

F CK

SF

First bit transmitted


8 16 8n, n>2 8 2 6 1 7 1 7 8

8 16 8 or 16 2 6 1 7 1 7 8

8 16 2 6 1 7 1 7 8

CK Check Bits SF Status Field F Flag SIF Signalling Information Field LI Length Indicator SIO Service Information Octet FSN Forward Sequence Number BIB Backward Indicator Bits BSN Backward Sequence Number FIB Forward Indicator Bits

(a) Basic format of a message signal unit ( MSU) , Length Indicator (LI) >2

(b) Format of a link status signal unit ( LSSU) , Length Indicator (LI) =1or 2

(c) Format of a fill-in signal unit ( FISU) Length Indicator (LI) =0

MSU

LSSU

FISU


MTP Layer 2 Frame (MSU)MTP Layer 2 Frame (MSU)

CK Check BitsF FlagLI Length IndicatorFSN Forward Sequence Number BSN Backward Sequence Number

SIF Signalling Information FieldSIO Service Information OctetBIB Backward Indicator BitsFIB Forward Indicator Bits

F CK SIF SIO LI

F

I

B

FSN

B

I

B

BSN F

First bit

transmitted

8 16 8n, n>2 8 2 6 1 7 1 7 8


Bit StuffingBit Stuffing

• “0111 1110” is the flag to start and end the Signalling Message• Can not be repeated inside the message• The solution is Bit Stuffing.• One the message is created, MTP layer 2 looks for 5 consecutive

“1”• If they are found, one extra “0” is inserted• This extra “0” is removed at the Reception end, before error

check.


MTP Message Sequencing ExerciseMTP Message Sequencing Exercise

FIB

FSNBIB

BSN

FIB

FSNBIB

BSN

FIB

FSNBIB

BSN

Exchange A Exchange B

ERROR

Retransmission

FIB

FSNBIB

BSNPositive Ack.

Negative Ack.

1 101 1 120

100 0 121 1

0 101 1 121

101 0 122 1

BIB(B)=FIB(A)BIB(B)=last BIB(B)ERROR

FIB(A)= last FIB(A)RETRANSMISSION

FIB

FSNBIB

BSN

100 1 120 1

?

BIB(B)=FIB(A)FIB(B)=BIB(A)ERROR RESOLVED


MTP Message Sequencing ExerciseMTP Message Sequencing Exercise

FIB

FSNBIB

BSN

FIB

FSNBIB

BSN

FIB

FSNBIB

BSN

Exchange A Exchange BLast Seq. # sent : 50Last Seq. # recd. : 100Last FIB/BIB : 1

ERROR

Retransmission

FIB

FSNBIB

BSNPositive Ack.

Negative Ack.

1

2

3

4

Write down the values of BSN, BIB, FSN & FIB at each stage.


MTP Layer 2 Frame (LSSU)MTP Layer 2 Frame (LSSU)

F CK SF LIFIB

FSNBIB

BSN F

First bittransmitted

8 16 8 or 16 2 6 1 7 1 7 8

BCA

BCA000 out of alignment001 normal alignment010 emergency alignment011 out of service101 busy

SPARE

• INITIALIZATION (AFTER SWITCH ON)• ALIGNMENT (AFTER A LINK FAILURE)• FLOW CONTROL (LEVEL 2)

LSSU & FISU ARE NOT RETRANSMITTED


CCS7CCS7 -- MTP ContinuedMTP Continued• Level 3 - Signalling Network Level (Signalling Route Set)

This level has 2 functions:– Message handling - routing of outgoing

messages, distribution of incoming messages (matches OSI layer 3)

– Network management - sending SignallingNetwork Test (SNT) and Signalling Network Management (SNM) messages (functions go beyond OSI layer 3).

L3 uses Signalling Point Code (SPC) to address messages to individual network elements.

L3 uses Service Information Octet (SIO) to address messages to higher level applications.


MTP MTP LLayerayer 33

SLS OPC DPC

OPC Originating Point CodeDPC Destination Point CodeSLS Signalling Link Selection

User informationsubfield Label

DCBASubservice

field

DCBAService

indicator(SI)

Signalling Information Field ( SIF)

Service informationoctet(SIO)

First bittransmitted

4 bits 14 bits 14 bits 4bits 4

Routing label

>> Service indicator: SCCP, TUP, ISUP, DUP, SNM, SNT

>> Subservice field: NA0, NA1, INA0, INA1

>> Routing Label: a STP can modify the SLS field, not OPC and DPC.


MESSAGEDISCRIM.

MESSAGEDISTRIB.

MESSAGEROUTING

layer 4 layer 2layer 3

MTPL3 MTPL3 -- SSignallingignalling messagemessage handlinghandlingTHE SIGNALLING MESSAGE HANDLING FUNCTIONS ARE DIVIDED INTO :

• MESSAGE ROUTING• MESSAGE DISCRIMINATION• MESSAGE DISTRIBUTION

MSU inDPC=own SPC

DPC<>own SPC

SIO ?

MSU out

SIF

SIF


MTP Message ExampleMTP Message ExampleConn:1 Card:1 TS:25 Subch:0 2016 19:35:50.59 MSU - BSN: 126 (7Eh) BIB: 1 FSN: 7 (07h) FIB: 1 - Signalling Network Test & Maintenance regular - network indicator : national network - data, length : 14, (0Eh) SLTM - SIGNALLING LINK TEST MESSAGE - DPC : 432 (01B0h) OPC : 12600 (3138h) - SLC : 0 (00h) - test pattern length : 8 (8h) 14 15 16 17 18 19 1A 1B Conn :1 Card:1 TS:25 Subch:0 2017 19:35:50.603 MSU - BSN: 7 (07h) BIB: 1 FSN: 127 (7Fh) FIB: 1 - Signalling Network Test & Maintenance regular - network indicator : national network - data, length : 14, (0Eh) SLTA - SIGNALLING LINK TEST ACKNOWLEDGE - DPC : 12600 (3138h) OPC : 432 (01B0h) - SLC : 0 (00h) - test pattern length : 8 (8h) 14 15 16 17 18 19 1A 1B

Conn :1 Card:1 TS:25 Subch:0 2038 19:36:07.732 MSU - BSN: 7 (07h) BIB: 1 FSN: 0 (00h) FIB: 1 - SCCP - network indicator : national network - data, length : 50, (32h)Conn:1 Card:1 TS:25 Subch:0 2039 19:36:07.741 MSU - BSN: 0 (00h) BIB: 1 FSN: 8 (08h) FIB: 1 - SCCP - network indicator : national network - data, length : 13, (0Dh)

SLTM - SIGNALLING LINK TEST MESSAGE - DPC : 432 (01B0h) OPC : 12600 (3138h) - SLC : 0 (00h) - test pattern length : 8 (8h) 14 15 16 17 18 19 1A 1B

Service Indicator :- indicates what type of service provided by the higher layer messages- eg. Sign NW testing, SCCP, TUP..

MTPL2

MTPL3


SCCPSCCP


Protocol Stack inProtocol Stack in GSMGSM

MTP

TUP NUPISUP

SCCP

BSSAPMAP

TCAP


SSignalling ignalling CConnection onnection CControl ontrol PPart art -- SCCPSCCPSCCP provides additional functions to MTP in order to transfer

both call-related and non-call-related (not possible with originalMTP) signalling messages by using connection-oriented and connectionless network services:

• Additional routing functions (OSI layer 3), i.e. SSN, Global Title.

• Logical signalling connection (OSI layer 4). MTP is able to perform only connectionless services. SCCP can provide both Connectionless and Connection-oriented network services.

• Management function (beyond OSI functionality), controlling the availability of sub-systems and broadcasting this information to other nodes in the network.


SCCP SCCP -- servicesservices

• In the connectionless service, all routing information required to route the data to its destination must be contained in each data packet. No logical connection is established between the end nodes.

• Connection-oriented network service is a way to rationalize the exchange of signalling information between two network service users by establishing a logical signalling connection between them. This logical connection is achieved by giving a local reference number to the signalling messages belonging together.


SCCPSCCP network network servicesservices (GSM 08.06)(GSM 08.06)Connection oriented messages include:

• Connection Request (CR)• Connection Confirm (CC)• Data Form (DT1)• Released (RLSD)• Release Complete (RLC)

Connectionless messages include:• Unit Data (UDT)• SCCP Management Messages (by UDT messages)


SLR (A) No. , DLR (B) No.

SLR (B) No. , DLR (A) No.

DLR (B) No.

SLR (B) No. , DLR (A) No.

DLR (A) No.

SLR (A) No.

SCCP CONS SCCP CONS SignallingSignalling

EXCHANGEA

EXCHANGEB

CR

CC

DT1

DT1

RLSD

RLC

SLR No. : Source Local Reference No. DLR No. : Destination Local Reference No.


Calling Address, Called Address



Calling Address,Called Address

SCCP CLNS SCCP CLNS SignallingSignalling

EXCHANGEA

EXCHANGEB

UDT

UDT

UDT

UDT

Addresses can be SPCs or Global Titles


SCCP SCCP -- structure of messagestructure of message (1)(1)

OPC DPC


Label 1000=NA0 0011=SCCP

F CK SIF SIO LIFIB

FSNBIB

BSN FMTP message

SCCPmessage

SLS

4bits 14 bits 14 bits

8n bits

Messagetype8 bits

09=UDT

pointersto data

user data

pointertopara-meters(called)

pointertopara-meters(calling)

pointertodata

calledpartypara-meters

callingpartypara-meters

user data


MTP & SCCP Message ExampleMTP & SCCP Message Example

MTPL2

SCCP

Conn:1 Card:1 TS:25 Subch:0 1944 19:34:50.832 MSU - BSN: 124 (7Ch) BIB: 1 FSN: 117 (75h) FIB: 1 - SCCP - network indicator : national network - data, length : 50, (32h) CR - CONNECTION REQUEST Routing Label - DPC : 12600 (3138h) OPC : 432 (01B0h) - SLC : 12 (0Ch) Source Local Reference - 0C8056h Protocol Class - protocol class : 2h, connection oriented Called Party Address - length 2 (02h) - no global title present - routing based on SSN and MTP routing label - subsystem is BSSAP Calling Party Address - length 4 (04h) - no global title present - routing based on SSN and MTP routing label - point code : 432 (01B0h) - subsystem is BSSAP SCCP User Data - length 27 (1Bh) End of Optional Parameters

Service Indicator : ‘SCCP’

SCCP Message : ‘CONNECTION REQUEST’


LAPDLAPD


LinkLink Access Access ProtocolProtocol on Don D--channelchannel --LLapapD (GSM 08.56)D (GSM 08.56)

• LAPD is the layer 2 protocol used on the Abis interface.• The are two different types of LAPD signalling links:OMUSIG:

BSC BTS• download SW, HW database;• download configuration files;• remote session to the Transmission Unit.

BTS BSC• alarms;• upload HW database.

TRXSIG:BSC BTS

• telecom signalling (CM, MM, RR);• network parameters;• Power control

BTS BSC• telecom signalling (CM, MM, RR);• measurements.


AbisAbis InterfaceInterface (Recommended)(Recommended)TS 1 2 3 4 5 6 7 801 TCH0 TCH1 TCH2 TCH32 TCH4 TCH5 TCH6 TCH73 TCH0 TCH1 TCH2 TCH34 TCH4 TCH5 TCH6 TCH75 TCH0 TCH1 TCH2 TCH36 TCH4 TCH5 TCH6 TCH77 TCH0 TCH1 TCH2 TCH38 TCH4 TCH5 TCH6 TCH79 TCH0 TCH1 TCH2 TCH310 TCH4 TCH5 TCH6 TCH711 TCH0 TCH1 TCH2 TCH312 TCH4 TCH5 TCH6 TCH713 TCH0 TCH1 TCH2 TCH314 TCH4 TCH5 TCH6 TCH715 TCH0 TCH1 TCH2 TCH316 TCH4 TCH5 TCH6 TCH717 TCH0 TCH1 TCH2 TCH318 TCH4 TCH5 TCH6 TCH719 TCH0 TCH1 TCH2 TCH320 TCH4 TCH5 TCH6 TCH721 TCH0 TCH1 TCH2 TCH322 TCH4 TCH5 TCH6 TCH723 TCH0 TCH1 TCH2 TCH324 TCH4 TCH5 TCH6 TCH725 TRXSIG1 OMU1 TRXSIG2 OMU226 TRXSIG3 OMU3 TRXSIG4 OMU427 TRXSIG5 OMU5 TRXSIG6 OMU628 TRXSIG7 OMU7 TRXSIG8 OMU829 TRXSIG9 OMU9 TRXSIG10 OMU1030 TRXSIG11 OMU11 TRXSIG12 OMU1231 XX XX XX XX

TCHs FOR TRX 1

TCHs FOR TRX 2

TCHs FOR TRX 12

SIGNALLING (LAPD)

.

.

.


LAPD LAPD -- Information(I) FrameInformation(I) Frame

F ADDRESS CONTROL INFO FCS F

SAPI 0 TEI

8 16 bits 16 bits 16 bits 8

C/R 1

N (S) N (R)0 P/F

6 bits 1 bit 1 bit 7 bits 1 bit

1 bit 1 bit7 bits 7 bits

EA EA

SAPI : Service Access Point Identifier C/R : Command/Response EA : Ext. AddressTEI : Terminal Endpoint Identifier P/F : Poll/Final bit FCS:Frame CheksumN(S) : Send Sequence # N(R) : Sequence # of next expected frame

Upto 260 octetsFirst bit transmitted


Types of LTypes of LapapD/LD/LapapDm FramesDm Frames ((11) ) • INFORMATION FRAMES (I-Frames)

… transfer Layer 3 Information messages.

Sequencing is used on these frames - N(S), N(R)

• SUPERVISORY FRAMES (S-Frames)... perform data link supervisory control functions like acknowledging I-frames or requesting retransmission of I-frames.

>> RR (Receive Ready): positive acknowledgement to an I-frame.

>> RNR (Receive Not Ready): used as an Indication to the transmitting side to stop sending more messages because the buffer is full. A timer starts at its receiving.

>> REJ (Reject): negative acknowledgement.

Only N(R) is used for sequencing.


Types of LTypes of LapapD/LD/LapapDm Frames (Dm Frames (22) ) • UNNUMBERED FRAMES (U-Frames)

... provide setting up of acknowledged & unacknowledged mode of Information transfer:

>> SABM (Set Asynchronous Balance Mode): sent to begin acknowledged mode of Information transfer.

>> UI (Unnumbered Information): used for unacknowledged mode Information transfer.

>> DISC (Disconnect): used for termination of acknowledged mode of Information transfer.

>> UA (Unnumbered Acknowledge): used as a response to acknowledge SABM & DISC frames.

Sequencing (N(S), N(R)) is not used in U-Frames.


LapDLapD FrameFrameFLAG FLAGSAPI C

REATEIE

A CONTROL INFO (opt.) FCS

8 6 1 1 1 8168 or 16* n

PF

PF

0

0 1

N(S) N(R)

N(R)not used

I-frame

S-frame

1 1U-frame

C/R shows if the message is either a command or a response to a command SAPI is the logical address of a group of elementsTEI is used to access an element belonging to a group addressed by SAPIN(R), N(S) (7+7) are the Sequence Numbers: N(S) is the number of theN(S) is the number of the framframe e being sentbeing sent;;

N(R) is the number of the next N(R) is the number of the next expected frameexpected frame..P/F Poll/Final bit

FCS Error detection field.

S

PFM M M = SABM, DISC, UA, UI

* always 8 bits for LapDm

7

S = RR, RNR, REJ



Modes of LModes of LapapD/LD/LapapDm transmission in GSMDm transmission in GSM• ACKNOWLEDGED MODE

Sent frames are acknowledged (using N(R) field of a RR frame or I-frame) according to the defined “ ack window” (1...127)

Default window size (LapD): 2 for TRXSIG; 1 for BCFSIGDefault window size (LapDm) : 1

If the expected acknowledgement is lacking, “polling” is used to force it.

• UNACKNOWLEDGED MODENo acknowledgement required for sent frames.


EExamplesxamples ofof generic generic LLapDapD operationsoperationsA B A AB B

SABM

UA

UA

DISC

INFO,N(S)=0,N(R)=0

INFO,N(S)=0,N(R)=1

INFO,N(S)=1,N(R)=1

RR,N(R)=2

INFO,N(S)=3,N(R)=0

RNR,N(R)=4

RR,N(R)=0,P

RNR,N(R)=4,F

RR,N(R)=0,P

RR,N(R)=4,F

INFO,N(S)=4,N(R)=0

INFO,N(S)=3,N(R)=0

INFO,N(S)=4,N(R)=0

INFO,N(S)=5,N(R)=0

RR,N(R)=4

INFO,N(S)=4,N(R)=0

INFO,N(S)=5,N(R)=0

N.B. There may be differences with GSM specific implementation.


LAPDm LAPDm (GSM 04.06)(GSM 04.06)• LAPDm is a modified version of LAPD for use over the air

interface.• Frame delineation and the Frame Check Sequence are not

necessary.• The amount of data contained in a single frame is limited to 23

bytes (octets) in BCCH/SDCCH/AGCH/PCH and 21bytes in SACCH.

• A segmentation and reassembly facility is introduced for longer messages.


LLapapDm FDm Framerame

Address : SAPI 0 for MM, CC, RR; 3 for SMS

information

Control : supervisory

unnumbered

ADDRESS CONTROL L3 INFO

8 bits 8 bits 20(18) octets

LENGTH

8 bits

Fill Bits(00101011)

SDCCH, FACCH(SACCH)

LAYER 3 INFORMATION

8 bits 22 octets

LENGTH Fill Bits (00101011)

BCCH, AGCHPCH

EA

CR SAPI 0 0

0 N(S)

1 0

1 1

P/F N(R)

P/F

P/FS S N(R)

MM M M 0


SSignalling Channels ignalling Channels CCodingoding inin thethe AAirir IInterfacenterface(BCCH,(BCCH, PCH,PCH, AGCH,AGCH, SACCH,SACCH, SDCCH,SDCCH, FACCH)FACCH)

L3 INFO + L2 INFO = 23 OCTECTS = 184 BIT(APPL.) (LAPDm)

224 BIT

BLOCK CODING (FIRE)using g(D) = D40 + D26 + D23 + D17 + D3 + 1

4 TAIL BIT ‘0’

228 BIT

CONVOLUTIONAL CODINGR=1/2 (THE SAME USED FOR SPEECH), with generators: g0(D) = D4 + D3 + 1 ; g1(D) = D4 + D3 + D + 1.

456

114 BIT

114 BIT

114 BIT

114 BIT

4 NORMAL BURSTS(no 2nd level interleaving

procedure is used)


Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Channel codingChannel coding

Interleaving

Burst Formatting

CipheringModulation

SpeechDigitising andSource Coding

Channel Coding

Block coding

Convolutionalcoding

22.8kbits/s456 bits


Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Interleaving Interleaving -- 11stst levellevelb1b9

b17

b2b10

b18

b3b11

b19

b4b12

b20

b5b13

b21

b6b14

b22

b7b15

b23

b8b16

b24

b441 b442 b443 b444 b445 b446 b447 b448

b449 b450 b451 b452 b453 b454 b455 b456

8 sub-blocks (SB#1 .. SB#8) of 57 bits

SB#1 SB#2 SB#3 SB#4 SB#5 SB#6 SB#7 SB#8


Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Burst FormattingBurst FormattingThe information sent in the Air interface is formatted

and packed. Its physical content is called "BURST"

Speech Digitising andSource Coding

Channel Coding

Interleaving

Burst Formatting CipheringModulation

Stealing Flags

3 357 571 126 8.25

TB Encrypted bits Encrypted bitsTraining Seq. TB GP

33.8 kbit/s = 156.25 bits per 4.615 ms


Logical ChannelsLogical ChannelsLOGICAL

CHANNELS

COMMONCHANNELS

DEDICATEDCHANNELS

BROADCASTCHANNELS

FCCH SCH BCCH

COMMONCONTROL

CHANNELS

PCH RACH AGCH

SDCCH SACCH FACCH

DEDICATEDCONTROL

CHANNELS

TCH/FR TCH/HR

TRAFFICCHANNELS

TCH/EFR

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface


Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

r

f s bb b b c fc fc sc c c c cc c c fc fsc c c c cc c c f fc c c c cc c c fs fc c c c cc c cs

r rr r r r rr rr r r r r rr r r rr r r r r r rr r r r r r r r rr r r rr r r r rr r rr

Downlink

Uplink

CHANNELS: f = FCCH b = BCCH r = RACH i = idles = SCH c = CCCH (PCH - AGCH)

51 TDMA frames = 235 ms

i

1 51

CHANNEL CONFIGURATIONSCHANNEL CONFIGURATIONSBCCH/CCCHBCCH/CCCH MultiframeMultiframe

i

1. 8. 9.6. 7.4. 5.2. 3.

r


Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

CHANNEL CONFIGURATIONSCHANNEL CONFIGURATIONSSDCCH/8SDCCH/8 MultiframeMultiframe

t t tt t t t ft tt t t t t t tt t t tt ft t t t t tt t t t fs s s s ss s s s fs s s s ss

s s ss s s s fs ss s t tt t t ts ft t t t t tt t t t ft t t t tt t t tt ft t t t st s st

Downlink

Uplink

CHANNELS: t = SDCCH/8 s = SACCH/8 i = idle

s

t


s

5. 6. 7. 8.1. 2. 3. 4.

1 51

iii

iii

1. 2. 3. 4.5. 6. 7. 8.

5. 6. 7. 8.1. 2. 3. 4.1. 2. 3. 4.5. 6. 7. 8.


Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

CHANNEL CONFIGURATIONSCHANNEL CONFIGURATIONSCombined CCCH/SDCCH/4Combined CCCH/SDCCH/4 MultiframeMultiframe

f s bb b b c fc fc sc c c c cc c c fc fs t t t t tt t t f ft t t t tt t t fs fh hh h hh h hs

t t tt r r h fh hh h h hr r rr r r rh fr r r r r rr r r r fr r r r tr t t tr ft t t r tr t tt

Downlink

Uplink

CHANNELS: f = FCCH b = BCCH h = SACCH/4 s = SCHc = CCCH r = RACH t = SDCCH/4 i = idle


t

1 51

1. 2. 3. 4.

i

1. 2.1. 2. 3.3. 4.

1. 2. 3.4. 1. 2.3. 4.


Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

CHANNEL CONFIGURATIONSCHANNEL CONFIGURATIONSFull Rate Traffic Channel (TCH/FR)Full Rate Traffic Channel (TCH/FR) MultiframeMultiframe

t t tt t t t ft tt t t tt t t tt ft t t tt

Downlink and Uplink

CHANNELS: t = TCH s = SACCH i=idle

ts


0 25

i


Normal BurstNormal BurstStealing Flags

3 357 571 126 8.25

TB Encrypted bits Encrypted bitsTraining Seq. TB GP

Used to carry information on traffic and control channels:

TCH, BCCH, CCCH, SDCCH, SACCH and FACCH

156.25 bits per slot duration 577 µs

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface


Frequency Correction BurstFrequency Correction Burst

3 3142 8.25

TB TB GPFixed bits


FCCH is used for synchronization of the Mobile Station

It is equivalent to an unmodulated carrier = pure sine wave, the bits being all fixed at "0"s

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface


Synchronization BurstSynchronization Burst

3 339 64 8.2539


TB TB GPSynchronization seq.Information bits

Information bits

It is used for time synchronization of the Mobile Station

it contains a long synchronization sequence, since the training sequence of the cell is not kown yet.

It contains information about the TDMA frame number, FN

It contains Base Station Identity Code, BSIC

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface


Access BurstAccess Burst

8 341 68.2536


TB TB Guard PeriodFIXED Synchro. seq.

The Access Burst has a long guard period to cater for burst transmission from a mobile that does not know the timing advance at the first access or after a handover

Encrypted bits

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface

Air Interface


SegmentationSegmentation of of LapDm messagesLapDm messages

LapDm message over 23 octects

1 T

1 T

1 T

0 TFF

0,1 = “more” bits

T = tail bits

F = fill bits


GSM Application PartsGSM Application Parts• BTSM - used for BTS Management and transporting

high layer messages across the Abis interface.• RR - responsible for management and allocation of

Radio Resources• BSSAP - BSS Applications are divided into 2 parts:

• BSSMAP - BSS Management used for resource allocation assignments, circuit handling, paging, handovers, etc. Also used to transport higher layer messages across the A interface.

• DTAP - the Direct Transfer Application Part is used to carry the transparent messages from Connection Management (CM) and Mobility Management (MM)applications.


More on DTAPMore on DTAP• MM - Mobility Management is responsible for registration,

identification and authorization of users.

• CM - Connection Management is the highest GSM signallinglayer and provides a direct interface between the network and the user, via:

• CC - Call Control for establishing, maintaining & clearing calls.

• SS - Supplementary Services provide call forwarding, call barring, conference calls etc.

• SMS - Short Message Service allows the subscribers to send and receive text messages of up to 160 characters


BTSMBTSM Message StructureMessage Structure

F ADDRESS CONTROL FCS F

MD MT CH. NO. LINK ID. ADDITIONAL INFO.

MD MT CH. NO. ADDITIONAL INFO.

MD MT CH. NO. ADDITIONAL INFO.

MD MT ADDITIONAL INFO.

RLLM

CCM

DCM

TRXMMD: Message Discriminator MT: Message TypeAdditional Info. : Information Elements of BTSM or/and L3 Info.

8 16 bits 16 bits 16 bits 8

BTSM MESSAGES

Radio Link Layer Mgmt.

Common Channel Mgmt.

Dedicated Channel Mgmt.

TRX Mgmt.

up to 260 octets

8 bits 8 bits 8 bits 8 bits

LapD INFO


BTSM Message BTSM Message HeaderHeader

8 7 6 5 4 3 2 1MESSAGE GROUP T

Ext MESSAGE TYPE

Message Discriminator + Message Type

Message Discriminator

Message type

T = Transparent bit “0” non- transparent message“1” transparent message

Message type = (channel activation, etc…) in 08.58

Message group0000001 Radio Link Layer Mangement0000100 Dedicated Channel Management 0000110 Common Channel Management 0001000 TRX management

Ext = extension bit (reserved for future use)


BTSM Messages (GSM 08.58)BTSM Messages (GSM 08.58)RADIO LINK LAYER (RLLM) DEDICATED CHANNEL (DCM) TRX MANAGEMENT MESSAGESMANAGEMENT MESSAGES MANAGEMENT MESSAGES (TRXM)

Data Request Channel Activation RF Resource IndicationData Indication Channel Activation Ack SACCH FillingError Indication Channel Activation Nack OverloadEstablish Request Connection Fail Error ReportEstablish Confirmation Deactivate SACCHEstablish Indication Encryption CommandRelease Request Handover DetectRelease Confirm Measurement ResultRelease Indication Mode Modify RequestUnit Data Request Mode Modify AckUnit Data Indication Mode Modify Nack

Physical Context RequestCOMMON CHANNEL (CCM) Physical Context ConfirmationMANAGEMENT MESSAGES RF Channel Release

MS Power ControlBCCH Information BS Power ControlCCCH Load Indication Preprocess ConfigureChannel Required Preprocessed Measurement ResultDelete Indication RF Channel release Ack Paging CommandImmediate assignment CommandSMS Broadcast Request


GSM GSM L3 Message StructureL3 Message Structure

8 7 6 5 4 3 2 1

MESSAGE TYPEN(SD)SProtocol DiscriminatorTI ValueTf CC e MM

8 7 6 5 4 3 2 1

MESSAGE TYPEN(SD)SProtocol DiscriminatorSkip Indicator RR

Skip Indicator = always equal 0000

Protocol discriminator0011 CC 0101 MM (GSM Ph2, no GPRS)0110 RR1000 MM (for GPRS)1010 Session Management (GPRS)

Message type = (setup, immediate assignment,…) in 04.08

Tf = “0” if the sender of message is the side that has initiated the transaction;

TI Value: Transaction Identifier; value indicating the transaction which the message is part of.

S = spare

N(SD) = sequence number


RRadioadio RResourceesource MManagementanagement (RR)(RR)• The role of radio resource management is to establish and release

stable physical connections between MS and MSC - for instance - for the duration of a call, and to maintain them despite of user movements.

• Its functions are: • initialization (RACH or PGCH);• definition of required service;• measurements;• handover handling;• timing advance and power control management; • handling of logical channels on physical channels (i.e. inserting in

these channels the system information).• The functions of the RR layer are mainly performed by the BSC and MS.

It implements the layer 5 of OSI model (session layer).


Radio Resource Messages (GSML3) 04.08Radio Resource Messages (GSML3) 04.08RR MESSAGES RR’ MESSAGES

Partial Release Assignment Command Channel requestChannel Release Assignment Failure Ciphering Mode commandPartial Release Complete Ciphering Mode Complete Handover accessChannel Mode Modify Ciphering Mode Command Immediate assignmentRR Status Immediate assignment extended Immediate assignment extended Frequency Redefinition Immediate assignment reject Immediate assignment rejectMeasurement Report Measurement reportClassmark Change Paging request type 1Channel Mode Modify Ack Paging request type 2System information type 1 Paging request type 3System information type 2 Physical informationSystem information type 2bis Synchronisation channel infoSystem information type 3 System information type 1System information type 4 System information type 2System information type 5 System information type 2bisSystem information type 5bis System information type 3System information type 6 System information type 4System information type 7 System information type 5System information type 8 System information type 5bisPaging Response System information type 6Handover Failure System information type 7Assignment Complete System information type 8Handover CommandHandover Complete


BSS Application Layer (BSSAP)BSS Application Layer (BSSAP)• It is divided in two parts:

• BSSMAP (BSS Management Application Part): it implements the procedures for radio resource managementbetween BSC and MSC. It represents the RR layer in MSC;

• DTAP (Direct Transfer Protocol): it carries messages concerning MM and CM procedures. These messages will pass transparently in the BSS that will change only the layer 2 of these messages.

• The message exchange between MSC and BSC contains a protocol discriminator in order to distinguish between BSSMAP and DTAP messages.


BSSMAP Messages (GSM 08.08)BSSMAP Messages (GSM 08.08)Assignment Request SAPI n rejectAssignment Complete ResetAssignment Failure Reset ACKHandover Request OverloadHandover Required Trace InvocationHandover Request ACK Reset CircuitHandover Command Reset Circuit ACKHandover Complete BlockHandover Failure Block ACKHandover Performed UnblockHandover Candidate Enquiry Unblock ACKHandover Candidate Response Resource RequestHandover Required Reject Resource IndicationHandover Detect PagingClear Command Cipher Mode CommandClear Complete Classmark UpdateClear Request Cipher Mode CompleteSAPI n Clear Command Queuing IndicationSAPI n Clear Complete Complete L3 Information


MMobilityobility MManagementanagement (MM)(MM)• The two ends of this layer are located in MSC and MS.

It deals with user mobility (i.e. location, paging,...), user authentication and privacy of information exchange on air interface (ciphering).

• It’s possible to identify 3 classes of functions:• MM connected-related procedures: to establish,

maintaining and releasing a MM connection between MS and MSC;

• MM specific procedures: Location Updating, Periodic Location Updating, Implicit Detach and IMSI attach;

• MM common procedures: these procedure can be started when a connection between MS and network has already established. These are: authentication, TMSI reallocations, identification procedures, IMSI detach.


DTAP Messages (1) DTAP Messages (1) -- GSML3 MM (04.08)GSML3 MM (04.08)

MOBILITY MANAGEMENT MESSAGES (MM)

IMSI Detach Indication Identity responseLocation Update Accept TMSI Reallocation CommandLocation Update Reject TMSI Reallocation CompleteLocation Update Request CM Service AcceptAuthentication Reject CM Service RejectAuthentication Request CM Service RequestAuthentication Response CM Re-Establish RequestIdentity request MM Status


CConnectiononnection MManagementanagement (CM)(CM)

• It is the highest layer in the GSM implementation of the OSI model. Its functions consist in setting up calls between users at their request, maintaining and releasing these calls.

• It uses MM connections.• It is divided in three category:

• Call control (CC) : routing, analysis of users parameters;• Short message Service (SMS);• Supplementary Service.


DTAP Messages (2) DTAP Messages (2) -- GSML3 CM (04.08)GSML3 CM (04.08)

CALL CONTROL MESSAGES (CC)Alerting DisconnectCall Proceeding Release CompleteProgress ReleaseSetup Stop DTMFConnect Stop DTMF ACKCall Confirmed Status EnquiryEmergency Setup Start DTMFConnect ACK Start DTMF ACKUser Information Start DTMF RejectModify Reject Congestion ControlModify StatusModify Complete Notify


DTAP Messages (3) DTAP Messages (3) -- GSML3 CM (04.80)GSML3 CM (04.80)SUPPLEMENTARY SERVICES MESSAGES (SS)

RegisterSS GetDigitsEraseSS GetStringActivateSS UnstructuredNotifySSDeactivateSS ForwardChargeAdviseInterrogateSS NotifySSRegisterPassword ForwardCUG infoGetPassword BuildMTPYProcessUnsructuredSSData HoldMTPYForwardCheckSSIndication RetrieveMTPYProcessSSRequest SplitMTPY


DTAP Messages (4) DTAP Messages (4) -- GSML3 CM (04.11)GSML3 CM (04.11)

SHORT MESSAGES SERVICE MESSAGES (SMS)SMR (relay) SMC (control)RP_Data CP_DataRP_SMMA CP_AckRP_Ack. CP_ErrorRP_Error


MSC BSC BTS MS

CONN. REQ. (SCCP)

COMPLETEL3 INFO (BSSMAP)

ESTABLISH IND.(BTSM)

L3 SERVICE REQ.(MM)

SABM (LAPDm)

CONNECT. CONF.(SCCP)

L3 SERVICE REQ.(MM)

L3 SERVICE REQ.(MM)

UA (LAPDm)

L3 SERVICE REQ.= CM SERVICE REQUEST (MOC)PAGING RESPONSELOC. UPD. REQ.IMSI DETACH IND.

BSSMAP &DTAP in thesame message!

Typical proceduresTypical procedures –– initial messageinitial message


MSC BSC BTS MS

DT1(SCCP)

DTAP

BTSM - DATA REQ.

DTAPDTAP

LAPDmLAPD – I frameMTP

DT1(SCCP)

DTAP

BTSM - DATA IND.

DTAPDTAP

LAPDmLAPD – I frame

MTP

Typical proceduresTypical procedures –– MSC/MS MSC/MS communicationcommunication

Note: no BSSMAP encapsulating

message is used


MSC BSC BTS MS

DT1(SCCP)

BSSMAP

BTSM

RRRR

LAPDmLAPDMTP

DT1(SCCP)

BSSMAP

BTSM

RRRR

LAPDmLAPD

MTP

Typical proceduresTypical procedures –– MSC/BSS/MS MSC/BSS/MS communicationcommunication

i.e. Cipher_Mode command (BSSMAP & RR): MSC BSC MSAssignment_Complete (RR & BSSMAP): MS BSC MSC


COMMUNICATION PROTOCOLS COMMUNICATION PROTOCOLS BETWEEN PEER ENTITIES: HIGH LAYERSBETWEEN PEER ENTITIES: HIGH LAYERS

MSC BSC BTS MS MSC - BSSMAP - DTAPBSC BSSMAP - BTSM RRBTS - BTSM - RR'MS DTAP RR RR' -

02 BSSSIG Signalling Protocols Ppt v1

Documents

Transcript of 02 BSSSIG Signalling Protocols Ppt v1