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04/12/23 2
Agenda – 1st Session Components of a telecom network Classification of switches Time & space switching H/w overview of a DSS S/w overview of a DSS Events in Basic Voice Call Types of Line access Types of trunk interfaces Signaling protocols on voice trunks
04/12/23 3
Agenda – 2nd Session Intelligent Network (IN) at a glance Multiple Access Technologies GSM Network Overview Next Generation Networks – Birds eye View Transmission Standards in use Customer demands at a Glance Future Trends in Telecom
04/12/23 4
Components of a Telecom Network
Customer premises equipment (CPE) Customer loop Switch or Node Links/Trunks interconnecting switches Signaling Systems Transmission Backbone Network Management Centre (NMC)
04/12/23 5
Customer premises equipment
Telephone, Telex, ISDN terminal, & Fax Computer, Modems, LAN VSAT PBX Satellite receiver Mobile hand set and Pagers Video-conferencing terminals
04/12/23 6
Customer loop
Wireless In Local Loop (WILL) Fiber to the Kerb / Home / Neighborhood ISDN access Wide band on copper ( DSL )
There is a problem with any copper wire transmission system -- Cross-talk.This is caused by the electrical signal in one wire being induced onto an adjacent wire, a
problem that is especially prevalent in central offices, where large bundles of wires enter the building. The solution was relatively simple. Experiments showed that balancing out the undesired induced currents by "turning over" or transposing the relative positions of the
disturbing and disturbed circuits could solve the inductance problem. Physically, this can be accomplished very easily on wire pairs (two wires) by giving them a twist every few inches. The careful manufacture of twisted-pair wires effectively eliminated this problem. Twisted pair wires are the 22- or 24-gauge subscriber line wires in your house that connect your
telephone or computer modem to the telephone central office.
Pair of copper wire ( twisted pair ?)
04/12/23 7
The Switch Why is a switch required ?
1
2 3
4
5
The increase in the cost cabling will be directly
proportional to the increase in size of the network.
Number of links required for connecting “n” subscribers is
given as n!/(2*(n-2)!)
The increase in the number of devices at CPE will be directly proportional to the
increase in the size of the network.
The cost of maintaining such a setup will spiral up as the size of the
network increases.
04/12/23 8
What is the Solution ?
to/fromotherlocations
LocalExchange(switch)
A switched Network
04/12/23 9
The Structure of a typical Telephone Network
EO
EO
EO
Access tandem TAX TAX
Access tandem
EO
EO
EO
AT
AT AT
AT
04/12/23 10
Packet switches take a user's data stream, break it down into smaller segments, called packets.
They add network control information, and then transmit the packets through the network in bursts.
The size of the packet can vary based on nature/needs of the application. Unlike circuit switches, packet switches don't use dedicated paths. All packet-switched traffic comes in bursts with a variable bit rate (VBR) In a packet switch, incoming traffic is passed through the switch on a first-come, first-
served basis, and packet traffic is routed according to the address in the packet header. Since a customer's data can arrive at the switch at any time, packet switching is called
asynchronous switching.
Circuit switch provides a physical, dedicated path -- called a time slot -- for a call through the switching matrix.
No other callers can use that switch path until the call is ended. The call has an end-to-end dedicated circuit for the duration of the call, hence the switch is
called a circuit switch. Circuit switching is used for voice switching and to support data services that have a
constant bit rate (CBR). Circuit switching is called synchronous because the user's information is transmitted in a
specific time slot, and only in that time slot. This concept of a dedicated path guarantees high-quality, almost error-free transmission
for the call. Since the average voice conversation is about three to four minutes long, network switch
resources used to set up the path can be reused over and over during the course of the day.
Classification of Switches
Circuit Switches Packet Switches
04/12/23 11
Classification of Sw itches
P o in t to Po int M anu al
S tro w g er(S tep by S tep S w itchin g)
(D istribu ted C on tro l Eq uip m en t)
C ro ssb ar(C o m m on C on tro l E qu ip m en t)
E lectro -M ech anical(m ake use of m ag netic re lays)
T im e S p ace
A n alo g sw itch(sw itch es the an alo g aud io sig na l )
T im e D ivis ion S p ace D ivis ion C o m b ina tion
D igita l sw itch(sw itches d ig itised vo ice sam ples)
E lec tro n ic(U ses IC 's & S olid s ta te dev ices )S to red P ro gram C o n tro l S w itch es
A u tom atic
Circuit Switches
04/12/23 12
Basic TDM switch
LP filter
OUTPUTS
Switch Address MemoryCounter
12
3
4
5
6
7
1
2
3
4
5
6
7
inputs outputs
04/12/23 13
Digital Multiplexing
MULTIPLEXER
MULTIPLEXER
125us
125us
125us125us
FFIILLTTEERR
SSAAMMPPLLEERR
QQUUAANNTTIISSEERR
EENNCCOODDIINNGG
04/12/23 14
Time Switch
Read address
3
17
17
3
SAM
Counter
Write address
Y X
173
X Y
173
3
17
VM - 1 VM - 2
3
17
read writewrite read
04/12/23 15
T-S-T switch
T
T
S
T
T
n 17 2 1 125n
125n
X
X
X
n 5 2 1 n 7 2
Y
n 7 2
Y
n17
2
Y
1 1
YX
n 5 2 1
04/12/23 16
Time Switch Information interchange occurring at
different instances Implemented using memory Sequential writing & Random reading Random writing & Sequential reading Faster memory for bigger size switches Engineering Problems at higher mux rate No blocking
04/12/23 17
Merits of Digital Switching Faster call set up Smaller in size Noise immunity & reduced cross talk Less maintenance More reliable More services to the customer Flexible for enhancement of features Integration of Voice & Data Modular growth to large sizes Redundancy and Load sharing modes
04/12/23 18
Basic DSS Hardware Architecture
Signaling
Trunk Interface (Analog/Digital)
Line Interface (Analog/Digital) Control Processor +
Switch control` Ringer ckts
Line
TrunkVoice (TDM)
Voice (TDM)
Voice
I/OSystem
Tone/Annc.Switch
(TDM)
04/12/23 19
DSS Software Architecture
SYSTEM SOFTWARESYSTEM SOFTWARE
APPLICATION SOFTWAREAPPLICATION SOFTWARE
Call ProcessingCall Processing
Feature processingFeature processing
MaintenanceMaintenance
AdministrativeAdministrative
HARDWAREHARDWARE
SignallingSignalling
System SoftwareSystem Software•Switch Operating SystemsSwitch Operating Systems•Scheduling, process managementScheduling, process management•Memory and resource managementMemory and resource management•Database managementDatabase management•Man-machine InterfaceMan-machine Interface
System SoftwareSystem Software•Switch Operating SystemsSwitch Operating Systems•Scheduling, process managementScheduling, process management•Memory and resource managementMemory and resource management•Database managementDatabase management•Man-machine InterfaceMan-machine Interface
SignalingSignaling•LineLine•TrunkTrunk•ProtocolsProtocols•MessagingMessaging
SignalingSignaling•LineLine•TrunkTrunk•ProtocolsProtocols•MessagingMessaging
Call ProcessingCall Processing•Event HandlersEvent Handlers•Digit Collection and AnalysisDigit Collection and Analysis•TranslationTranslation•RoutingRouting•TerminationTermination•SupervisionSupervision•Billing RecordsBilling Records
Call ProcessingCall Processing•Event HandlersEvent Handlers•Digit Collection and AnalysisDigit Collection and Analysis•TranslationTranslation•RoutingRouting•TerminationTermination•SupervisionSupervision•Billing RecordsBilling Records
Feature ProcessingFeature Processing•Call ServicesCall Services
•Call ForwardCall Forward•Call WaitCall Wait•DoNot DisturbDoNot Disturb•Conf CallConf Call•3WC3WC
•Feature ActivationFeature Activation•Feature ChargingFeature Charging
Feature ProcessingFeature Processing•Call ServicesCall Services
•Call ForwardCall Forward•Call WaitCall Wait•DoNot DisturbDoNot Disturb•Conf CallConf Call•3WC3WC
•Feature ActivationFeature Activation•Feature ChargingFeature Charging
Administrative SoftwareAdministrative Software•Subscriber Configuration and User Subscriber Configuration and User PrivilegesPrivileges•ProvisioningProvisioning•Configuration of HardwareConfiguration of Hardware
Administrative SoftwareAdministrative Software•Subscriber Configuration and User Subscriber Configuration and User PrivilegesPrivileges•ProvisioningProvisioning•Configuration of HardwareConfiguration of Hardware
Maintenance SoftwareMaintenance Software•Auditing of resourcesAuditing of resources•Fault Detection and CorrectionFault Detection and Correction
Maintenance SoftwareMaintenance Software•Auditing of resourcesAuditing of resources•Fault Detection and CorrectionFault Detection and Correction
04/12/23 20
Basic Call Process Detecting the incoming call, Receiving the digits, Translating the digits, Selecting a terminating agent, Speech Path, Signaling => terminating agent Detecting an answer Detecting disconnect
04/12/23 21
Line Interface Subscriber loop
• Wired and Wireless (Copper , Cellular, WILL)• Analog and Digital
• Analog• Digital conversion at the switch
• Analog loop functions - BORSCHT
• Digital• Digital conversion at the CPE. E.g. ISDN terminal
• Basic Rate Interface ( BRI )
• 2B + D = 144 KBPS
• Primary Rate Interface ( PRI used for EPABX’s )
• E1 is 30B + D = 2.048 MBPS
• T1 is 23B + D = 1.544 MBPS
04/12/23 22
POTS Access
POTS
••
••
Line cardsLine cards
subscriberloop
subscriberloop
Max : 150 milesMax : 150 miles
RSCRSC
RLURLU
RCC
RCC
T1 / DS1T1 / DS1
Line unitLine unit
RSCRSC
Matrix
Matrix
Central Control
Central Control
04/12/23 23
Business Access
Joe'sSmall
Business
Departmentof Injustice
Kathy'shome
Business
Betty'sBigger
Business
subscriber line
subscriber lines
lines or trunks
IBN (Centrex) lines
KTS
PBX
Centrex Call Processing
POTS Call Processing
Digital Class 5 Local Office
04/12/23 24
ISDN - What Is It?
Is Someone Dreaming NonsenseI Studied Data NetworksI Still Don't kNowIntegrated Services Digital Network
04/12/23 25
ISDN Access - What is ISDN?
"Digital end-to-end connectivity through a limited set of network interfaces providing a wide range of service features evolving from the telephone IDN to meet market needs into the 21st century.” - From ITU definition of "ISDN".
ISDN Access InterfacesTerminals
PBXs
LANs
ISDN
Voice Networks
Data Networks
BroadbandNetworks
ISDN Network Interface
04/12/23 26
ISDN Access Types
04/12/23 27
NT - 1
Terminal Adapter
TE1TE1
NT2NT2
TE2TE2
SS TT UU
ISDN ExchangeISDN Exchange
ISDN Modem NT - 2RR SS
Customer Premises Customer Premises
SSRR
ISDN Subscriber – System ConfigurationISDN Subscriber – System Configuration
VVLTLT ETET
04/12/23 28
ISDN User – Network Interface ProtocolsISDN User – Network Interface Protocols
Layer 3Layer 3
Layer 2Layer 2
Layer 1Layer 1
Layer 3Layer 3
Layer 2Layer 2
Layer 1Layer 1
Q.931 Layer 3 protocolQ.931 Layer 3 protocol
Q.921 Layer 2 protocolQ.921 Layer 2 protocol
Layer 1 protocol (Physical)Layer 1 protocol (Physical)
04/12/23 29
Layer – I ( Physical Layer for BRI)
U interface Frame – 240 bits in length – 1.5 ms duration U Interface – 2 wire, 160 kbps connection
Frame overhead – 16 kbps 2 voice channels – 128 kbps 1 Data channel - 16 kbps
Echo cancellation for noise reduction Data encoding schemes (2B1Q in North America, 4B3T in Europe) Synchronization bits - +3 +3 -3 -3 -3 +3 -3 +3 -3 Super-frame consists of 8 - 240-bit frames for a total of 1920 bits (240
octets). The sync field of the first frame in the super-frame is inverted (i.e. -3 -
3 +3 +3 +3 -3 +3 -3 +3).
Sync Bits Sync Bits ( 16 ) ( 16 )
12 * ( B1 + B2 + D channel ) 12 * ( B1 + B2 + D channel ) ( 216 ) ( 216 )
Maintenance Bits Maintenance Bits ( 8 )( 8 )
04/12/23 30
Layer – II ( Data Link Layer) Link Access Protocol – D Channel (LAPD)
FlagFlag(8) (8)
AddressAddress( 8/16 )( 8/16 )
Control Control (16)(16)
Information Information ( Layer –3)( Layer –3)
CRCCRC(16)(16)
Flag Flag (8)(8)
SAPI ( 6 ) SAPI ( 6 )
11 22 33 44 55 66 77 88
Address Field Address Field
C/RC/R EA0EA0
TEI ( 7 )TEI ( 7 ) EA1EA1
SAPI Description0 Call Control Procedures
1 Packet mode using Q.931 call porcedures16 Packet mode communication procedures
32- 47 Reserved for national use63 Management procedures
others Reserved for future use
TEI Description0 - 63 Fixed / static TEI assignments
64 - 126Dynamic TEI assignments ( by the switch at runtime )
127 Broadcast to all devices
04/12/23 31
Layer – II - Initialization
Receive Ready (RR) frames
Unnumbered Information (UI) frame with a SAPI of 63 and TEI of 127
TEI (in the range 64-126)
Set Asynchronous Balanced Mode (SABME) frame with a SAPI of 0 and TEI
TE
Unnumbered Acknowledgement (UA), SAPI=0, TEI=assigned
ISDN Network
04/12/23 32
Layer – III
Message Type Message Type
11 22 33 44 55 66 77 88
Information Field Information Field
Length of CRV Length of CRV
Protocol Discriminator Protocol Discriminator
00 00 00 00
Call Reference Value (1 or 2 octets)Call Reference Value (1 or 2 octets)
00
Mandatory & OptionalMandatory & Optional Information Elements (variable)Information Elements (variable)
04/12/23 33
Layer – III - InitializationCaller
ISDN SwitchCalled
Setup Message
Call Proceeding Message Setup Message
Alerting Message
Alerting Message Connect Message
Connect Message
Connect ACK Message Connect ACK Message
B Channel CommunicationB Channel Communication
Disconn Message Disconn Message
Rel Message Rel Message
Relcom Message Relcom Message
04/12/23 34
Layer – III ( Messages exchanged during the conversation phase)
SUSP Requests suspension of call. SUSP ACK Indicates suspension acknowledge. SUSP REJ Indicates suspend rejected. RES Request that suspended call has
resumed. RES REJ Indicates suspended call cannot be
resumed. USER INFO Use to user signal.
04/12/23 35
Layer – III ( Messages exchanged during the Call Clearing phase)
DISC Call disconnection request. REL Indicates channel disconnection
completed. REL COM Indicates channel & call reference release
completed. REST Requests initialization completed. REST ACK Indicates initialization completed.
04/12/23 36
Layer – III ( Miscellaneous messages )
FAC Requests & ACK supplementary service initialization.
INFO Information on additional call control. NOTIFY Indicates info. Related to the call. STATUS ENQ Inquires about station status. STATUS Indicates user/network status. CON CON Congestion control of user to user
signaling.
04/12/23 37
Digital Subscriber Lines
DSL ADSL HDSL RADSL VADSL VDSL Universal ADSL
Digital subscriber line, which operates at a maximum of 144 Kb/s for ISDN subscriber, lines. ISDN is used for
voice and data communications.
Asymmetric digital subscriber line, which operates at 32Kb/s to 8.19 Mb/s downstream to the customer and 16 to 640 Kb/s
upstream to the network over existing twisted-pair copper wire. ADSL is envisioned for use for Internet access, video on
demand (VOD), simplex video, remote LAN access, and interactive multimedia.
High-bit rate digital subscriber line delivers data symmetrically at rates up to at 1.544 Mb/s full-duplex for
equivalent T1/E1 service, or at 2.48 Mb/s duplex (requires two pairs of wire) for subscriber lines. It delivers at 2.49 Mb/s
duplex (requires three pairs of wire) for feeder plant, WAN services, LAN access, or server access.
Rate adaptive ADSL is a version of ADSL where the ADSL modems test the line at start up and adapts the data rate to
within 32 Kb/s of the maximum throughput the line is capable of supporting.
Very high-bit-rate asymmetric digital subscriber line, which operates at a subset of speeds of VDSL when it supports symmetric
operation.
It describes a form of ADSL that does not require a splitter at the customer location to separate voice signals from
digital signals in the data stream. This approach leads to a "plug-and-play" ADSL where the user can simply connect
the line to a PC and be in service. Universal ADSL will operate at lower bit rates than "existing" ADSL systems,
but it is up to 25 times faster than today's 56Kb/s modems and just as easy to install.
Very high-bit rate digital subscriber line is under development for twisted-pair access
service at 12.9Mb/s to 52.8Mb/s downstream and 1.5 to 2.3Mb/s upstream.
However, the maximum reach will be reduced from 4,500 to 1,000 feet and it will need fiber-optics cable. Applications are the
same as ADSL, plus high-definition TV.
04/12/23 38
Trunk Interfaces• Analog trunks
• Two Wire • 4 Wire
• Digital Trunks• Code conversion (HDB3 to Binary)• Frame alignment• Signaling Information injection/extraction• Transmission system interface• E1(30 channel)/T1 (24 channel)
04/12/23 39
Signalling Classification
D C L o w F re q u e n cy
In -B a nd O u t-B a nd
V o ice F re q u e n cy P C M(C A S )
In -C h a n n e l
A sso cia te d M o de Q u a s i-A sso c ia ted M o de
C o m m o n C h a n n e l
O u t o f C h a n n e l
S ig n a llin g
04/12/23 40
Subscriber signaling
• Analog• Pulse signaling
• DTMF signaling
• Digital• ISDN (Digital subscriber signaling system 1)
04/12/23 41
Pulse Signaling
Pulse signaling uses the concept of loop make & break
E.g. Suppose you want to dial 31
MakeMakeperiodperiod
BreakBreakperiodperiod
Inter-digit timerInter-digit timer
04/12/23 42
DTMF Signaling
A dial pad key is represented by a combination of two frequencies
1 2 3
4 5 6
7 8 9
* 0 #
1209 1336 1477
697
770
852
941
Hz
04/12/23 43
Trunk signaling
Request for Trunk (seizure)Request for Trunk (seizure)
Acknowledgement of the seizure (Seize Ack )Acknowledgement of the seizure (Seize Ack )
AnswerAnswer
ConversationConversation
End of the call (release)End of the call (release)
Acknowledgement of the releaseAcknowledgement of the release
Dial digitsDial digits
04/12/23 44
Regional Signaling systems (R1 for N.A. R2 for Europe and rest of the world). Also referred to as Channel Associated signaling systems
CCITT recommended signaling systems (SS1 to SS7). SS6 & 7 also referred to as common channel signaling systems.
Signaling systems
04/12/23 45
T1 - Overview
24 channels each with a 64kbps capacity. 8000 frames per second (125 us per frame) Each frame consists of 193 bits One bit per frame for frame alignment 12 frames make a super frame. LSB in 6th and 12th frame is used for signaling (
bit stealing or robbed bit signaling) Total bandwidth 1.544kbps
04/12/23 46
T1 - Frame Structure
Frame Frame
alignment bitalignment bit
TS NTS NTS 0TS 0 TS 23TS 23
Signaling bit Signaling bit
(Frame 6 and 12)(Frame 6 and 12)
TS 23TS 23TS NTS NTS 0TS 0
TS 0TS 0 TS NTS N TS 23TS 23
TS 0TS 0 TS NTS N TS 23TS 23
Frame 1Frame 1
Frame 12Frame 12
Frame 6Frame 6
Frame XFrame X
04/12/23 47
E1 - Overview
32 channels each with 64kbps capacity 8000 frames per second (125 us per frame) 256 bits per frame 30 channels are used for transmitting voice TS0 of each frame is used for frame alignment TS16 of each frame is used for line signaling 16 frames make a Multi frame Total bandwidth 2.048 Mbps
04/12/23 48
E1 - Frame Structure
Frame Frame
alignment bytealignment byte
TS 0TS 0 TS 16TS 16
TS 31TS 31
TS 31TS 31
TS 16TS 16TS 0TS 0
TS 0TS 0 TS 31TS 31
Signaling byteSignaling byte
(Frames 1-15)(Frames 1-15)
synch bytesynch byte
Frame 0 TS16Frame 0 TS16
TS 16TS 16
ABCDABCD
TS1TS1
ABCDABCD
TS17TS17
ABCDABCD
TS15TS15
ABCDABCD
TS31TS31
Frame 1Frame 1
Frame 0Frame 0
Frame 15Frame 15
04/12/23 49
Line signaling v/s Register signaling
Line Signaling – Used for line (trunk) supervision
– Represents the events that occur on a trunk I.e SZD, SZA, ANS, CLF, RLG
Register Signaling– Used for address signaling I.e. called party number
etc.
– Normally done using MF tones but pulse signaling is also possible
04/12/23 50
R1 Line Signals
Analog system– A continuous tone of 2600 Hz represents
onhook– Offhook is represented by absence of
supervision tone Digital system (T1)
– Only the bit in the 6th frame is actually used for signaling
– Offhook is 1, Onhook is 0
04/12/23 51
R1 line signals
Forward signals– Seize (Onhook -> Offhook)– Clear forward (Offhook -> Onhook)
Backward signals– Wink (Offhook pulse)– Answer (Onhook -> offhook)– clear backward (offhook -> onhook)
04/12/23 52
R1 register signals
Six frequencies are used (700, 900, 1100, 1300, 1500, 1700) Hz
A combination of two frequencies represent a digit
R1 register signals are sent only in forward direction
04/12/23 53
A typical R1 call
Send connectSend connect
Delayed dialDelayed dial
Audible ringingAudible ringing
ConversationConversation
Send hang upSend hang up
Send hang upSend hang up
Dial digitsDial digits
Proceed to sendProceed to send
AnswerAnswer
04/12/23 54
R2 Signaling system
Used in Europe and most parts of the world Analog system uses SF tone of 3825 Hz
(out of band) for line signaling. Digital System (E1) uses a dedicated time
slot for signaling (No bit stealing here!). Only AB bits are used
04/12/23 55
R2 line signals Line signal protocols vary from country to country Typical Forward line signals (Digital system)
– Seize (1,0 --> 0,0)
– Clear forward (0,0 --> 1,0)
Backward line signals– Seize Ack (1,0 --> 1,1)
– Answer (1,1 --> 0,1)
– Clear back (0,1 -->1,1)
– Release Guard (x,1 -->1,0)
04/12/23 56
R2 register signaling
Multi Frequency Compelled signaling is used for register signaling
Frequencies used in forward direction– 1380, 1500, 1620, 1740, 1860, 1980 Hz
Frequencies used in backward direction– 1140, 1020, 900, 780, 660 and 540 Hz
04/12/23 57
R2 signaling groups
R2 register signals are divided in following group– Forward Signal Group I
Used for transmitting calling and called party digits
– Forward Signal Group II Used for transferring calling and called party
categories
04/12/23 58
Backward signaling is done to acknowledge forward signals– Backward signal Group A
Used to acknowledge Group I signals
– Backward signal Group B Used to acknowledge Group II signals
R2 signaling groups (contd ..)
04/12/23 59
A typical R2 call
SeizeSeize
Seize AckSeize Ack
AnswerAnswer
ConversationConversation
Clear forwardClear forward
Release GaurdRelease Gaurd
Register signalingRegister signaling
04/12/23 60
Inter-register signaling SeizeSeize
Seize AckSeize Ack
AnswerAnswer
Forward group I signal (called party digit)Forward group I signal (called party digit)
Forward Group II signal (regular)Forward Group II signal (regular)
Forward Group III signal (end of digits)Forward Group III signal (end of digits)
Forward Group III signal (calling party digit)Forward Group III signal (calling party digit)
Forward group II signal (regular)Forward group II signal (regular)
Backward group A-1 signal (next digit)Backward group A-1 signal (next digit)
Backward Group A-6 signal (req_dn_cat)Backward Group A-6 signal (req_dn_cat)
Backward Group C-1 signal (next ANI digit)Backward Group C-1 signal (next ANI digit)
Backward group C-1 signal (next ANI digit)Backward group C-1 signal (next ANI digit)
Backward group A-3 signal (req_bill_cat)Backward group A-3 signal (req_bill_cat)
Backward Group B signal (connect_call_chg)Backward Group B signal (connect_call_chg)
Forward group I signal (called party digit)Forward group I signal (called party digit)
04/12/23 61
Overall Architecture of CCS7
Message Transfer Part ( MTP )Message Transfer Part ( MTP )
ISUPISUP TUP TUP
SCCPSCCP
TCAPTCAPDUP DUP
1 - 3 1 - 3
1-3 1-3
4-74-74 - 6 4 - 6
77 UserUserPartsParts
OSI Layer OSI Layer MappingMapping
OSI Layer OSI Layer MappingMapping
04/12/23 62
CCS7 Network Components
Signal Transfer Point (STP) Signal Transfer Point (STP) is node in the Network that is node in the Network that routes messages between routes messages between nodes. It does not originate nodes. It does not originate any CCS7 messages other any CCS7 messages other then NM messagesthen NM messages
Signal Transfer Point (STP) Signal Transfer Point (STP) is node in the Network that is node in the Network that routes messages between routes messages between nodes. It does not originate nodes. It does not originate any CCS7 messages other any CCS7 messages other then NM messagesthen NM messages
Service Control Service Control Point(SCP)provides Point(SCP)provides network access to network access to transaction services transaction services ( Database queries )( Database queries )
Service Control Service Control Point(SCP)provides Point(SCP)provides network access to network access to transaction services transaction services ( Database queries )( Database queries )
Service Switching Point Service Switching Point (SSP) is a node in the (SSP) is a node in the network that originates & network that originates & terminates CCS7 messages terminates CCS7 messages ( both connection oriented ( both connection oriented and connectionless )and connectionless )
Service Switching Point Service Switching Point (SSP) is a node in the (SSP) is a node in the network that originates & network that originates & terminates CCS7 messages terminates CCS7 messages ( both connection oriented ( both connection oriented and connectionless )and connectionless )
SSP ASSP ASSP ASSP A
SCPSCP
SSP BSSP BSSP BSSP B
STP - IISTP - IISTP - IISTP - II
STP - ISTP - ISTP - ISTP - I
VoiceVoiceVoiceVoice
Signaling Point(SP) is Signaling Point(SP) is a node in the network a node in the network
that provides CCS7 that provides CCS7 trunk signaling onlytrunk signaling only
Signaling Point(SP) is Signaling Point(SP) is a node in the network a node in the network
that provides CCS7 that provides CCS7 trunk signaling onlytrunk signaling only
Quasi AssociatedQuasi Associated
Associated ModeAssociated ModeAssociated ModeAssociated ModeSPSPSPSP Trunks
04/12/23 63
CCS7 Signaling Link-Sets
STP
STP
STP
STP
SCP
SSP
SP
SSP
a
a
a a
ef
b
b
b bc c
a
a
f
Access links connect SP,
SSP & SCP to STPs
Bridge links connect mated
STP pairs to other mated STP pairs
Cross links connect two STP nodes creating a
mated pair
Fully Associated links connect SP, SSP & SCP nodes using
associated signaling
Extended links connect an SP, SSP
& SCP to an STP of a different region.
Diagonal links connect STP quads in different regions ( for instance primary to secondary
STP )
04/12/23 64
Basic CCS7 ISUP CallSwitch X - Originator Switch Y - Terminator
IAM
SAM
ACM
ANM
REL
RLC
TalkingTalking
LineLine LineLine
04/12/23 65
IN Components
IP
Service Creation Environment SMS
STP
SCP
SS7 Network
Upload Service
Query
Response
Exchange
It is not a physical network It is not a physical network but a set of software features packagesbut a set of software features packages
It enhances switch call processing capabilities to use centralized operating company-provided service logic
programs placed at SCP
It enhances switch call processing capabilities to use centralized operating company-provided service logic
programs placed at SCP
Queries & responses between DMS & SCP use CCS7 protocol.
04/12/23 66
IN Services examples 1-800 numbers (1-600 service in Bangalore) MCCS (Mechanized Calling Card Services) Billed Number Screening Centralized translations & routing
04/12/23 67
Time of Day Call Routing
What is the time now?What is the time now?What is the time now?What is the time now?
9:00 a.m. to 5:00 p.m.9:00 a.m. to 5:00 p.m.
OfficeOfficeResidenceResidence
AA
04/12/23 68
The nearest distribution The nearest distribution point to this caller is the point to this caller is the West-side locationWest-side location
Advertised DNAdvertised DNPizza HutPizza Hut999-9999999-9999
West-sideWest-sideLocationLocation
EastsideEastsideLocationLocation
Pizza HutPizza Hut Pizza HutPizza Hut
Neighborhood Dealer Routing
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IN Advantages
Service Independence Multi-vendor Support Decrease in the time-to-market for new
services Telephone operating company control of
service “building blocks” Seamless multi-vendor environment
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Frequency Frequency Division Division Multiple Multiple AccessAccess
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Time Time Division Division Multiple Multiple AccessAccess
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Frequency & Frequency & Time Time Division Division Multiple Multiple AccessAccess
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Code Code Division Division Multiple Multiple AccessAccess
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Combination of TDMA and FDMA 890 – 915 MHz for Uplink 935 – 960 MHz for Downlink 124 Radio carriers, inter carrier spacing of 200 KHz 8 channels per carrier Air interface at 13 kb/sec Uses RPE - linear predictive speech encoding - information
from previous samples to predict the current sample
GSM Network ArchitectureGSM Network Architecture
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GSM Network ElementsGSM Network Elements
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GSM Network AreasGSM Network Areas
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GSM Signaling ProtocolsGSM Signaling Protocols
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RADIO RESOURCE MANAGEMENT (RR)
ESTABLISHES CONNECTION BETWEEN MS & MSC FOR THE DURATION OF CALL AND MAINTAIN THEM TAKING INTO ACCOUNT USER MOVEMENTS.
MUST COPE WITH LIMITED RADIO RESOURCES AND SHARE IT DYNAMICALLY BETWEEN ALL NEEDS
RESPONSIBILTY OF THE HANDOVER PROCESS LIES ENTIRELY WITHIN THE RR LAYER FUNCTION
FUNCTIONS OF RR LAYER ARE MAINLY PERFORMED BETWEEN MS & BSC
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MOBILITY MANAGEMENT (MM)
RESPONSIBLE FOR THE MOBILITY MANAGEMENT & SECURITY MANAGEMENT.
AUTHENTICATION, IMSI DETACH/ATTACH LOCATION REGISTRATION
MACHINES CONCERNED WITH MOBILITY MANAGEMENT ARE MAINLY THE
MS (MORE PRECISELY THE SIM INSIDE THE MS) HLR (MORE PARTICULARLY THE AuC INSIDE THE
HLR) , MSC/VLR
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COMMUNICATION MANAGEMENT (CM)
RESPONSIBLE FOR CALL SETUP, CALL RELEASE AND MAINTAINING CALL FOR GSM USERS
MSC/VLR, GMSC, HLR, IWF ARE RESPONSIBLE FOR THE BASIC CALL MANAGEMENT FUNCTIONS
ANOTHER IMPORTANT ASPECT OF CM FUNCTION IS ROUTING THROUGH DIFFERENT GSM ENTITIES.
CM LAYER ALSO MANAGES THE SUPPLEMENTARY SERVICES.
CM LAYER IS RESPONSIBLE FOR POINT-TO-POINT SHORT MESSAGE SERVICES IN CONTACT THROUGH SHORT MESSAGE SERVICE CENTRE
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PSTNPSTN
GMSCGMSC
GSM/PLMNGSM/PLMN
• PSTN SUBSCRIBER DIALS MOBILE NUMBERPSTN SUBSCRIBER DIALS MOBILE NUMBER• LINK IS SET UP FROM LOCAL EXCHANGE TO THE GMSCLINK IS SET UP FROM LOCAL EXCHANGE TO THE GMSC
MOBILE TERMINATED CALLMOBILE TERMINATED CALL
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PSTNPSTN
GMSCGMSC
GSM/PLMNGSM/PLMN
HLRHLRVLRVLR
MSCMSC
• HLR HLR TRANSLATES THE DIALLED MOBILE NUMBERTRANSLATES THE DIALLED MOBILE NUMBER
INTO A GSM/PLMN IDENTITY (INTO A GSM/PLMN IDENTITY (IMSI)IMSI)
• MSISDNMSISDN TO TO IMSIIMSI
• HLRHLR POINTS OUT THE SERVICE AREA OF THE CALLED NUMBER AND POINTS OUT THE SERVICE AREA OF THE CALLED NUMBER AND SENDS THE SENDS THE IMSIIMSI TO THE TO THE VLRVLR WITH A REQUEST FOR WITH A REQUEST FOR MSRNMSRN
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PSTNPSTN
GMSCGMSCGSM/PLMNGSM/PLMN
HLRHLRVLRVLR
MSCMSC
• VLRVLR WILL TEMPORARILY ALLOCATE A ROAMING NUMBER WILL TEMPORARILY ALLOCATE A ROAMING NUMBER (MSRN)(MSRN) TO THE CALLED SUBSCRIBER AND SENDS IT BACK TO THE TO THE CALLED SUBSCRIBER AND SENDS IT BACK TO THE HLRHLR..• HLRHLR WILL SEND IT THE GATEWAY MSC WILL SEND IT THE GATEWAY MSC (GMSC)(GMSC)
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PSTNPSTN
GMSCGMSC
GSM/PLMNGSM/PLMN
HLRHLR
VLRVLR
MSCMSC
• LINK IS SET UP FROM LINK IS SET UP FROM GMSCGMSC TO TO MSC/VLRMSC/VLR
• GMSCGMSC IN POSSESSION OF THE CORRECT IN POSSESSION OF THE CORRECT MSRNMSRN WILL BEWILL BE
SET UP THE INCOMING CALL TO THE SET UP THE INCOMING CALL TO THE MSC/VLRMSC/VLR WHERE WHERE CALLED SUBSCRIBER IS CURRENTLY LOCATEDCALLED SUBSCRIBER IS CURRENTLY LOCATED
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PSTNPSTN
GMSCGMSC
GSM/PLMNGSM/PLMN
HLRHLR
VLRVLR
MSCMSC
BTSBTS
BSCBSC
• PAGING MESSAGE IS SENT TO THE BSSPAGING MESSAGE IS SENT TO THE BSS
• VLRVLR POINTS TO THE LOCATION AREA IDENTITY POINTS TO THE LOCATION AREA IDENTITY (LAI)(LAI) FOR THE CALLED FOR THE CALLED
SUBSCRIBER SUBSCRIBER (IMSI --- LAI)(IMSI --- LAI)• MSC/VLRMSC/VLR SENDS THE PAGING MESSAGE TO ALL THE BASE STATIONS SENDS THE PAGING MESSAGE TO ALL THE BASE STATIONS
(BTS)(BTS) WITHIN THE LOCATION AREA WITHIN THE LOCATION AREA
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PSTNPSTN
GMSCGMSC
GSM/PLMNGSM/PLMN
HLRHLR
VLRVLR
MSCMSC
BTSBTS
BSCBSC
• BTSBTS ON RECEIVING THE PAGING MESSAGE WILL SEND IT OVER THE ON RECEIVING THE PAGING MESSAGE WILL SEND IT OVER THE RADIO PATH ON THE PAGING CHANNEL RADIO PATH ON THE PAGING CHANNEL • MSMS WILL RECEIVE PAGING MESSAGE ON ONE OF THE CELLS BELONGING WILL RECEIVE PAGING MESSAGE ON ONE OF THE CELLS BELONGING
TO THE LOCATION AREA, RECOGNISES THE TO THE LOCATION AREA, RECOGNISES THE IMSIIMSI AND THEN SENDS A AND THEN SENDS A RESPONSE TO THE PAGING MESSAGE```RESPONSE TO THE PAGING MESSAGE```
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PSTNPSTN
GMSCGMSC
GSM/PLMNGSM/PLMN
HLRHLR
VLRVLR
MSCMSC
BTSBTS
BSCBSC
• LINK IS SET-UP FROM THE LINK IS SET-UP FROM THE MSC/VLRMSC/VLR TO THE TO THE MSMS • CONNECTION IS ESTABLISHED BETWEEN THE CONNECTION IS ESTABLISHED BETWEEN THE PSTNPSTN & & MOBILE MOBILE SUBSCRIBERSUBSCRIBER
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Need for convergence of Voice and Data Networks
Attractive because of low cost , flat rate pricing of public internet
Optimization of bandwidth utilized in data network when compared to fixed bandwidth in telecom network
Growth in technology faster in data networks than in telecom networks
Demand for new types of integrated voice/data applications
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CALL SERVERCALL SERVER
T1/E1/ J1/T3ISDN, R1/R2, CAS
SS7
Signal &Signal &TrunkTrunkAccessAccessGatewayGatewayFast EthernetFast Ethernet
SS7
ATMIP
T1/E1/ J1/T3ISDN, R1/R2, CAS
SS7SS7
Fast EthernetFast Ethernet
EO EOPBXPBX
NetworkNetworkManagementManagement
SystemSystem
Signal & Signal & TrunkTrunkAccessAccessGatewayGateway
Convergence of Telecom and Data Networks
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20001850
10
1012
106
Mono-mode fibre 1,7,16 Gbs/s
3600ch M/W
60ch coax
First telephone
Ist telephone ch
multi mode fibre 140 Mbs/s
10800ch over coaxial
voice ch ~ 600bps
voice ch ~1200
voice ch~4800bps
PCM voice ch~56bps
Strowger
Crossbar
Electronic switches Satcom
High capacity Radios
Bits/s The Telecom story
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Customer Demands
More and more facilities and features. Image communication, video services to
home Digital film on demand for normal quality
1-2Mbps and HDTV (15-20Mbps)will be reality in 2005. Any movie can be selected
Personalized assistance in business, shopping, & home activities
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Customer demands (contd)
Video conferencing popular among business users- Videophone, video education
Multimedia services: basic components of broadband service: voice, image, video and data
Demand for mobility, any where any time personal communication ...
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The Crystal view -Technology Trends Information highways and use of CCS no7
signaling Intelligent Networks and AIN B- ISDN (Integrated services digital network) PCs and phone merge- computer telephony Merger of transmission and switching Interactive video on demand SDH hierarchy in transmission technology
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Technology Trends (contd.) Communication satellites at lower orbits ATM as prime multimedia standard Same infrastructure for telecom and
Entertainment Wide band on copper Passive optical networks
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Technology Trends (contd.)
Wireless in the local loop Cellular mobile radios Fixed radio access Personal communication services Satellite networks like TDM/TDMA
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These and many more futuristic These and many more futuristic technological challenges make it technological challenges make it
exciting to work in the area of exciting to work in the area of Telecom in general and Telecom Telecom in general and Telecom
software in particular.software in particular.
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Thank you for your attention!
