Telecom ss7 basic.pdf

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CCS Associated

CCS Quasi associated

CCS Non associated.

TELECOM BASICS

E1a) 256 bytes per frameb) 8 bits Each TS in E1 Framec) 0.125uS time taken by one framed) Total 8000 frames in One Second

Voice Theorma) Voice Frequency ~ 300 to 3300 Hz , bandwidth = 4000 Hzb) Nyquist theorm = Min 8000 sampling rate reqd ( 4000*2 )c) One Sample = 8 bits ( Reprsntation of 256 Voice Levels , 2 pow 8 =256)

Erlanga) Unit of Traffic descibes total traffic volume in one hour b) Erlang = Busy time for ckts / Avl Time for measurment , Ex : 20/60 = 3Er 15ckt - 8.1 Er 31ckt - 21.5 Er 3 E1 - 77 Er 10 E1 - 286 Er 20 - 59230ckt - 20.3 Er 02 E1 - 48 Er 5 E1 - 136 15 E1 - 439 Er 30 - 901

E1 Physical Interfacea) 0th TS used for synchronization ( 0011011)b) Modes of Operation

1. Unframed - No TS at all2. Framed - All 32 TS used for data3.Multiframe - 0 TS for sync, rest 31 for data

c) Bit '1' - 3V , Bit '0' - 0~0.3 V

CAS ( Channel Associated Signalling )a) Uses INBAND Signalling ( Voice frequencies )b) Signaliing Associated in that E1 only - TS = 16 Line Sig. And TS=All RegisteredSignalling

CAS Line Signallinga) Uses TS = 16 for indication of ck t. Status only ( I.e.FREE , SIEZ , FREE BY A/B , BUSY etc….)

ABCD Fwd ABCD Bckwd STATUS

10XX 10XX IDLE

00XX 10XX SIEZ

00XX 11XX SIEZ ACK

00XX 01XX ANS

00XX 11XX B PARTY REL

10XX 0/10XX A PARTY REL

Ist Frame : TS-1 & TS-17 (4+4 bits)

IInd Frame : TS-2 & TS-18

....

....15th Frame : TS-15 & TS-31

CAS Registered Signallinga) Uses voice TS for Registered Signalling .b) Types : DECADIC , DTMF , R2 Semi C , R2FullyCc) R2MF - R2 Multi Freq Fully Compled (Ack Reqd)

d) MF - Combination of 2 Freq to represent one info

CAS Registered Signalling

Grp A Bwd Sig. Grp B Bwd Sig.

1 Send Next Dig. 2 Changed No.

2 Restart 3 Called Line Busy

3 Change over grp B 4 Congestion

4 CLI 5 Unallocated No.

5 Send Cat of A Party 6 Normal subs free

6 Switch to speech

7 Send last but 2 digits8 Send last but 3 digits

9 Send last but 1 digitGrp 1 Fwd Sig. Grp II Fwd Sig.

1 Digit '1' 1 Ordinary Subs

2 Digit '2' 2 Priority Subs

3 Digit '3' 5 Operator

4 Digit '4' 6 STD Coin Box



CCS STRUCTURE



8 7 1 7 1 6 2 8

Layer#2

FLAG BSN BIB FSN FIB LI SPARE DATA CRC

Layer#

3

SubService Field Service Indicator

Priority - 1,2,3

( Low to High )

Network

Indicator

NAT0/1,

INAT0/1

SIOSIF

CCS 7 Layers

0 FISU1-2 LSSU3-63 MSU

Layer-2 : CRC , Retransmission ( PCR ) , Error Correction and detection Etc

Layer-3 :b. Signalling Route Management - Traffic / Sharing / Overloading Routingc. Signalling Link Management - Control / Monitor / Status of Linkse Signalling Traffic Management - Change over/ Back in case of Faile. Alignment - SIO , SIN , SIE , SIOSf. Message Distribution - Distributing the MSG to ISUP , SCCPg. Message Discrimination - Mine or Other DPC / NW

Service Indicator 0 - SNM ( Signalling NW Management Message )1 - MTN ( Mtc Regular Msg )2 - MTNs ( Mtc Special Message )3 - SCCP ( Carry Non-Voice Traffic Ex: SMS )4 - TUP5 - ISUP ( Voice related traffic )6 - Data User Part ( Call & ckt Related )7 - Data User part ( Facility Regn & Cancellation )



DPC OPC

CIC

(only

ISUP)

ISUPMessage

Type

Optional

FIX

IAM

Optional VariableMandatory Variable

SLS ( 4

Bits ,

Max 16

Selection

Mandatory FIX

A Party Category , Forward Call

Indicator B Party No , User service Info

USER PART

CLI , Carrier , NW , HOPs

ISUP Message Type : IAM ( Initial Address Message )INR ( Information Request )

ACM ( Address Complete ) ANM ( Answer Message )REL ( Release Message )RLC ( Release Complete )BLO ( Blocking )UBL ( Uublocking )BLA ( Blocking Acknowledment )CPG ( Call Progress )

Layer-3 TimersT1 Delay to avoid message mis-sequencing on changeover .5 to 1.2 sec.T2 Wait for changeover Ack .7 to 2. 0 secT3 Delay to avoid message mis-sequencing on changeback .5 to 1.2 sec.T4 Wait for changeback Ack (1st attempt) 5 to 1.2 sec.T5 Wait for changeback Ack (2nd attempt) 5 to 1.2 sec.



SCCPMessage

Type

Optional

FIX

UDT

XUDT

UDTs

XUDTs

Used to transport user data

and SCCP management

messages in the connection-

less mode. It can Segment /

DeSegment data as per itssize

Used to indicate to the

originating SCCP user that a

UDT message cannot be

delivered to the specified

destination. The data field of

the UDT message and the

reason for the return are

Used for Mandatory FIX

1. Called Party

2. Calling Party

3. User Data

Mandatory Variable

1. Called Party

2. Calling Party

3. User Data

1. Return Cause

2. Hop Counter

1. Called Party

2. Calling Party

3. User Data

1. Segmentation data

Optional Variable

1. Called Party

2. Calling Party

3. User Data

1. Return Cause

2. Hop Counter 1. Segmentation data

Protocol Class : Class -0 : Basic Connectionless ( Non Critical,TCAP )Class -1 : Sequenced Connectionless (Critical, TCAP )Class -2 : Basic Connection Oriented (BSSAP )

Class -3 : Flow Control Connection Oriented(BSSAP )Class -4 : Flow Control + Err Recovery

Calling / Called party :1. Address Indicator :

a. Routing Indicator : GT based or ( DPC + SSN )b. GTT Indicator : No GT or GT - 1 or 2 or 3 or 4c. SSN Indicator : Present / Not Presentd. Point Code Indicator : Present / Not Present

2. Address : a. Point Codeb. SSN

c. GT - 1 :i. Nature of Address Ind : Subscriber Number / National Sig. No. / International No.ii. Odd / Even Indicator ( Spr) iii. Address Information ( 919839212499 )

d. GT - 2 :i. Translation Type ii. Address Information ( 919839212499 )

e. GT - 3 :i. Translation Type ii. Encoing Scheme - Unknown / BCD Odd / BCD Eveniv. Address Information iii Numbering Plan - ISDN / Telephony / Data / Telex / Land Mobile / Mobile

e. GT - 4 :i. Translation Type ii. Encoing Scheme - Unknown / BCD Odd / BCD Eveniii. Numbering Plan iv. Nature of Address Indicator v. Address Information ( Contains Address for Example : 919839212499 )

User Data :1. Length Indicator 2. User Data Ex: TCAP etc

Connection Oriented

- Only used in BSSAP where heavy data transfer is required for ex. Between MSC/VLR to BSC to BTS





SCCP - Routing Protocol

SSN1 SCCP Management3 ISDN user part4 OMAP (Operation, Maintenance and Administration Part)5 MAP (Mobile Application Part)6 HLR (Home Location Register)7 VLR (Visitor Location Register)8 MSC (Mobile Switching center)9 EIR (Equipment Identifier register)10 AUC (Authentication Centre)11 ISDN Supplementary Services (SSAP)13 Broadband ISDN edge-to-edge applications254 Base Station System Application Part (BSSAP)

SCMG Functions- Signaling point status management : Failure, recovery, and congestion information of signaling

points, provided by MTP

- Subsystem status management : Subsystem failure and recovery information, and SCCP(SSN 1)

congestion received in SCCP management messages.

- Subsystem status test : SSP , SSA , SST , SOR , SOG



Hop Counter ( 15 to 1 ) : Counter is decremented upon GTTSegmentation : Max 16 Segments , each carries 246 bytes

GTT CASES1. SPC + SSN2. SPC + SSN + GT3. SSN + GT4. SPC + GT5. GT only

GT is performed on given SPC + SSN on the basis of GT info , to find outthe final A/B Party Address



GTT> Method of hiding the SS7 point code and sub-system number from the originator of a message

a) GT Consists of – Translation type (TT) – Numbering plan (NP) – Nature of address (NA) – Global title digits (GTDIG)

b) GT Benefits – Central administration of routing information makes it easier to restructure the network – It is possible to set up alternative routing schemes and load sharing – More compact and dyanmic routing tables – The function is required for the introduction of certain new services (such as call completion to busy subscriber, CCBS and 800 free phone)

a) The result of a global title translation can be: – the point code for a signaling destination – a subsystem service group ( this is used in the intelligent network to guarantee a fail-safe service control point (SCP). Two SCPs can be combined to form a subsystem service group that is accessed frothe relevant service switching point (SSP) via globa l title translation. )

– a translator service group ( this consists of up to four signaling points, each of which can perform the necessary translation ) – a further translation in the same network node





TRANSACTION DIALOG TAG COMPONENT TAG

TCAP :

1. Transaction Part : ( Deals with SCCP Message ) a. TCAP Message Type : BEGIN / UNI / END / CONTINUE / ABORTb. Length Indicatior of Transaction Tag ( Max 2048 , SCCP takes Care of Segmenting / Breaking )c. Transaction Info ( Not Valid for UNI )

i. Origination Transaction Id ( Mandatory for BEGIN , CONTINUE )- Length Indicator & Value

i. Destination Transaction Id ( Mandatory for END , ABORT , CONTINUE )- Length Indicator & Value

i. P_Abort Cause ( Mandatory for TC_P_Abort Request )- Reason for Abort

2. Dialog Part :a. Dialog Indicator Tagb. Length Indicatior of Dialog Tagc. Dialog Information - Depend on USER For Ex : MAP , INAP

3. Message Component Part : ( Deals with USERs such as MAP , INAP ...) a. Component Indicator Tagb. Length Indicatior of Component Tagc.Component Type : ( Invoke / Return Result Last / Return Result Not Last / Return Error / Reject )d. Component lengthe. Component User Information by MAP , INAP , CAMEL , OMAP , SSAP Etc..........

Functions of TCAP are to control:· The transaction between both endpoints in the network· The communication to the users of TCAP.



Message type Function

Abort

Used to terminate the structured dialogue in a normal way

Used to terminate the structured dialogue in an off normal way.

Indicates that one of the Invoke, Return Result, or Return Error components received from the remote user/CSL could not be und

or was not expected.

Used to transport data in an unstructured dialogue

First message, to start a structured dialogue, sent once

Used to sustain the structured dialogue, more continue messages can be sent

Initiates/invokes a desired operation at the remote peer application entity.nvoke

Return result not last

Return result last

Return error

Begin

Continue

Used to carry a segment of the result of a successfully completed operation. It is used when a success reply is physically too lar

into a single message.

Represents the final success reply to an operation invocation. If the success reply was segmented, this component would repre

final segment of the reply

Indicates an operation invoked previously has failed due to some processing error. Error codes are supplied by TCAP users, and

passed transparently by TCAP.

Unidirectional

End

Reject



SMSC1. SMS are stored in SMSC before they can be sent to MS ( 140 bytes each SMS )2. MAP USED is

> Forward Short Message Submit> Send Routing Info for SM> Forward Short Message Deliver

3. MO Forward SM : A party MS to SMSC ( Forward Short Message Submit )4. MT Forward SM : SMSC to B Party MS ( Forward Short Message Deliver )

HLR

GMS MSC/VLR

TCAP Begin/Invoke - SRI for SMTCAP End / Retrun Res - SRI Ack

SM_DELIVERBTS

TCAP Begin/Invoke - Forward SM

TCAP End / Retrun Res - Forward SM Ack





SCP

SCP

STP

STP

STP

STP

A-

A-Access

A-

E-Extended

C-Cross D- B-Bridge Other STP NWService Control Pt C-Cross

VLR V

BTS

GMSCHLR

AUC-SIM

M

SMSC EIR

EC

G

B

H

F

D D

A

HLR

GM MSC/VLR

TCAP Begin/Invoke - Provide MSRNTCAP End / Retrun Res - MSRN Ack

TCAP Begin/Invoke - SRITCAP End / Retrun Res - SRI

IAM -

IAM - MSISDN

BTS

IMSI

IMEI

Mobile Terminating Call ( MTC )

GSM

C7 Network



SSP (Service Switching Pt )



GPRS ( General Packet Radio Services )a) Key Features

Speed immediacyNew applicationsBetter applicationsService access

b) Key Network Features of GPRSPacket switchingSpectrum efficiencyInternet awareSupports tdma and gsm

c) Limitations of GPRSLimited cell capacity for all usersSpeeds much lower in realitySupport of gprs mobile terminate by terminals is not ensuredSuboptimal modulationTransit delaysNo store and forward

d) SGSN - Serving GPRS Support Nodehandles session management, mobility management, billing and traffic measurementsbit level encryption of data which is to be sent over the air interface.Put GPRS data received from the BSC in IP format for sending to the GGSN and vice-versa.Provide GPRS routing to BSC’s

d) GGSN - GPRS Gateway Support NodeThe GGSN is the gateway in and out of the GPRS system.It routes packets from an external network ( "the Internet" ) to the SGSN which is currently serving the MS,and routes packets from the SGSNs to which it is connected to the external network. Th is concept is called tunnelling.

d) Similar TechniquesEnhanced Data rates for GSM Evolution (EDGE)Universal Mobile Telephone System (UMTS)





FLAG

BSN

BIB

FIB

FSN

LI

SIO

SIF

SPARE USER DATA

CRC SLS

A PARTY - GT(N) /

SSN / SUB NO

USER DATA

DIALOG ID

COMPONENT TYPE = INVOKE

COMPONENT USER DATA , MT Forward

SM , MSIN DIGIT

DPC

OPC

TRANSACTION ID , BEGIN

UDT MESSAGE

PROTOCOL CLASS

= 0 / 1

B PARTY - GT(N) /

SSN / SUB NO



MTP - 2 LAYER 3 SCCP TCAP

GSM Overview

IMSI : International Mobile Subs Identity [ SIM , MCC(3) + MNC(2) + MSISDN(<10) ]TMSI : Temporary Mobile Subs Identity [ VLR , MCC(3) + MNC(2) + MSISDN(<10) ]MSISDN : Mobile Stn Integrated Services Digital NW [ CC(1-3) + NDC(1-3) +MDN(10) ]

VLR VLR

BTS

GMHLR

AUC-

MSC

SMSC

EIR

EC

G

B

H

F

D D

A

IMSI

IMEIGSM Overview

IMSI Vs TMSIOne can't take hacking benefits with TMSI as it is dyanmically allocated by VLR, moreover TMSI is 4 octet shorter than IMSI .

MAP D ( HLR-VLR )Provide MSRN / MSRN Ack Update Location / Cancel Location / AckInsert / Delete Subs Data / AckSend Param / AckResetDeregister Mobile DataNote MS Present

MAP C ( HLR-MSC )Send Routing info SRI /

AckSend Routing info for SM / AckSet Message waitingdata

Alert Service CentreRegisster charging info

MAP E ( GMSC - MSC )Process access sigmnalling CCS 7Forward access Signalling CCS 7Send End Signal CCS 7Perform Handovers / Subsequent HOPerform Internal HandoversTrace subs activity

MAP I ( Subservices - MSC )Get Pwd / Register Pwd

Activate / Deactivate / Erase / Register SSInterrogate / Invoke SSForward SS Notification

MAP F ( EIR - MSC )Check IMEI

MAP H ( SMSC - MSC )Forward Short Message

MAP G ( VLR - VLR )Send Param

Intelligent Network ( IN )Requirement / Advantages

Rapid deployment of Vendor / SSP Free Services which are centrally administered

SSPCCF - Call Control Functions ( Takes Care of all call related processing in Switch )SSF - Service Switching functions ( Provides IN Triggering and IN Accessibility )SRF - Specialized resource function ( Provides interactioon bw Call processing SW

in SSP)

SCPSCF - Service Control Functions ( Executes IN service logic and interfaces witrh

SSP via SSF )SDF - Service data function ( Maintains all customer and nw data )SMP - Service Management Point ( Administration and Operation of IN )



















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Telecom ss7 basic.pdf