Dasar TelekomunikasiPensinyalan

Definition

• The IEEE defines signaling as the exchange of information specifically concerned with the establishment and control of connections and the transfer of user-to-user and management information in a telecommunication network

• Conventional signaling has evolved with the telephone network

• With telephony, signaling is broken down in three functional areas:• Supervisory

• Address

• Call progress: audible-visual

• Another signaling breakdown is• Subscriber signaling

• Interswitch (interregister) signaling

Supervisory Signaling

• Supervisory signaling provides information on line or circuit condition

• It informs a switch whether a circuit (internal to the switch) or a trunk (external to the switch) is busy or idle, when a called party is off-hook or on-hook, and when a calling party is on-hook or off-hook

Address Signaling

• Address signaling directs and routes a telephone call to the called subscriber• It originates as dialed digits or activated push-buttons from a calling

subscriber• The local switch accepts these digits and, by using the information

contained in the digits, directs the call to the called subscriber• If more than one switch is involved in the call setup, signaling is

required between switches (both address and supervisory)

• Address signaling between switches is called interregistersignaling

Call Progress: Audible-Visual

• This type of signaling we categorize in the forward direction and in the backward direction

• In the forward direction there is alerting• This provides some sort of audible-visual means of

informing the called subscriber that there is a telephone call waiting

• This is often done by ringing a telephone’s bell

• A buzzer, chime, or light may also be used for alerting.

• In the backward direction, among these are audible tones or voice announcements that will inform the calling subscriber the following:• Ringback

• This tells the calling subscriber that the distant telephone is ringing.• Busyback

• This tells the calling subscriber that the called line is busy• ATB-All Trunks Busy

• There is congestion on the routing. Sometimes a recorded voice announcement is used here.

• Loud Warble on Telephone Instrument—Timeout• This occurs when a telephone instrument has been left off-hook

unintentionally

Signalling

Subscriber - exchange Exchange - exchange

Channel associated Common channel

Klasifikasi Signaling

Areas of Signaling

• There are mainly three areas of signaling during a telephone call :• between subscribers and exchanges.

• within exchanges.

• between exchanges.

Exchange A Exchange B

between Subscriber and

exchangewithin exchange

between exchanges

Subscriber – Exchange Signaling

• Dari pelanggan ke sentral

– Informasi kondisi off-hook

– Informasi nomor B (nomor tujuan)

– Informasi jumlah uang yang dimasukkan (khusus untukpayphone)

– Informasi kondisi on-hook ketika panggilan usai

• Dari sentral ke pelanggan A (nomor pemanggil)

– Informasi bahwa sentral siap menerima nomor B

– Informasi mengenai status B (busy atau tidak)

– Informasi kongesti atau interception

– Sinyal charging (khusus untuk payphone)

• Dari sentral ke pelanggan B

– Sinyal ringing untuk menarik perhatian pelanggan B

• Pelanggan A mengangkat telepon, hal ini dapat berarti

– A ingin menghubungi seseorang

– Pesawat A berbunyi lalu menjawab

• Sentral dapat mendeteksi keadaantelepon apakah merupakanpanggilan atau jawaban

• Sentral menanggapi panggilandengan mengirimkan dial tone

• A mengirimkan digit nomor B (B number)

• Sentral menganalisa digit lalumencek apakah B ada dan tidakbusy. Ringing tone dikirimkan ke A sedangkan sinyal ringing ke B

• B mengangkat handset, sentralmendeteksinya sebagai jawaban

• Ketika A dan B menyimpan handset, sentral mendeteksi sebagai sinyalclear lalu koneksi diputuskan

Bsentral

Off-hook

Dialling tone

conversation

A

N

O

M

O

R

Ringing tone Ringing signal

~425Hz ~90V, 20-25 Hz

answer

Clear forward

Clear back

Off-Hook Signaling (Analog)• Loop Start (almost all telephones)

• Seizure is detected when current flows through local loop, due to off-hook

• Ground Start (antar PBX (Private Branch Exchange) atau antara PBX dengan Sentral Lokal)

• Seizure (upaya pendudukan kanal komunikasi) is detected when one wire is grounded

• Seizure can be initiated in both directions

• Untuk mengindikasikan status on/off-hook ke sentral lokal

Ground Start

Source: Cisco Interactive Mentor

Switch Switch

Loop Start Ground Start

Exchange – exchange Signaling

• Channel Associated Signalling (CAS)

• Common Channel Signalling (CCS)

Common Channel Signaling

Signaling dilakukan menggunakan kanal yang

juga digunakan untuk mentransfer informasi

Common Channel Signalling

• Informasi speech dan informasi signalling

mengalir melalui jalur yang sama

• Beberapa macam CAS

– Signalling dilakukan secara bersama pada

kanal untuk speech (DC signalling, inband)

– Signalling dilakukan pada kanal yang sama

dengan speech tetapi menggunakan

frekuensi yang berbeda (out-band)• Contoh: Signalling dilakukan melalui timeslot 16 (PCM signalling)

Seizure acknowledgment

Pelanggan A Pelanggan B

sentral sentral

seizure

B number

answer

conversation

Clear forward

Clear backB- hangs up

A- hangs up

Forward and Reverse direction

• Forward signal mengalir dari sentral telepon tempat A berada menuju sentral telepon tempat B berada

• Backward signal mengalir pada arah yang berlawanan dengan forward signal

Channel Associated Signaling

Signaling menggunakan kanal yang terpisah

dari kanal untuk mentransfer informasi Terdapat

jaringan signaling tersendiri

Signaling System Number 7 (SS #7)

Signaling System NO. 7

• Signaling System No. 7 (SS No. 7) was developed to meet the stringent signaling requirements of the all-digital network based on the 64-kbps channel

• It is a data network entirely dedicated to interswitch signaling• defined by Telecommunication Standardization Sector

(ITU-T).

• defines the procedures and protocol by which network elements in the PSTN exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup,routing and control.

The SS7 network and protocol are used for:• basic call setup, management, and tear down

• wireless services such as personal communications services (PCS), wireless roaming, and mobile subscriber authentication

• local number portability (LNP)

• toll-free (800/888) and toll (900) wireline services

• enhanced call features such as call forwarding, calling party name/number display, andthree-way calling

• efficient and secure worldwide telecommunications

• SS No. 7 is described as an international standardized general-purpose common-channel signaling system that:• Is optimized for operation with digital networks where

switches used stored-program control (SPC)• Can meet present and future requirements of

information transfer for interprocessor transactions with digital communications networks for call control, remote control, network database access and management, and maintenance signaling

• Provides a reliable means of information transfer in correct sequence without loss or duplication

SS7 Signaling Points Diagram

Signaling Architecture ComponentsComponent Function

SSP's are telephone switches (end offices or tandems) equipped

Signal Switching Points with SS7-capable software and terminating signaling links. They

(SSP's) generally originate, terminate, or switch calls.

STP's are the packet switches of the SS7 network. The receive

Signal Transfer Points (STP's) and route incoming signaling messages towards the proper

destination. They also perform specialized routing functions.

SCP's are databases that provide information necessary for

Signal Control Points (SCP's) advanced call-processing capabilities

Basic SS7 Signalling Architecture

SS7 Signaling Links

SS7 Link Types

• “A” Link: An access link connects a SSP or SCP to an STP.

• “B” Link: A bridge link connects an STP to another STP.

• “C” Link: A cross link connects two “mated pair” STP. This is done to improve reliability

• “D” Link: A diagonal links similarly to a B link

• “E” Link: An extended link connects an SSP to an extra STP in the event that the A link cannot reach one.

• “F” Link: A fully associated link connects SSP’s

CCS7 Network Components

• The CCS7 Network consists of the following Components :• SP – Signaling Point : The SP is the source or originating entity of

the signaling message.

• STP – Signaling Transit Point : These entities transfer the signaling message to another SP or STP without processing the signaling message.

• SRP – Signaling Relay Point : These are STPs with ability to process the signaling message.

• SEP – Signaling End Point : The SEP is defined to be the terminating point of the signaling message

SS7 Network Architecture

• A typical SS7 network is a mixture of various SPs STPs SRPs and SEPs, As shown below :

SP (SPC=100) SRP (SPC=400)

STP

(SPC=300)

STP (SPC=200)

SEP (SPC=500)

CCS7 Terminologies

• SPC : SPC is defined as signaling point code which uniquely identifies each element within the SS7 network.

• Signaling Links : The signaling links transmit signaling messages between the communicating entities.

• Signaling Link Set : A signaling link set is a collection of signaling links between two signaling entities.

• Signaling Route : A signaling route is defined to be the path through which signaling messages are exchanged between two entities. There can be multiple signaling routes between two SPCs, wherein there will be one primary route and several alternate routes.

SS7 Routing Modes

• Associated Mode :

In the associated mode, the signaling link is routed together with the circuit group belonging to the link. In other words, the signaling link is directly connected to signaling points which are also the terminal points of the circuit group. This mode of signaling is recommended when the capacity of the traffic relation between the signaling points A and B is heavily utilized.

Associated Mode of Signaling

SS7 Routing Modes

• Quasi associated mode :

In the quasi-associated mode of signaling, the signaling link and the circuit group run along different routes, the circuit group connecting the signaling point. A is directly connected with the signaling point B. For this mode the signaling, the circuit group is carried out via one or more defined signaling transfer points. This signaling mode is favorable for traffic relations with low capacity utilization, as the various signaling links can be used for several destinations.

SS7 Network Structure

SPC=100

SPC=200

SPC=300

SPC=100

SPC=400

SPC=500

SPC=600

SPC=400

SPC=900 SPC=800

SPC=700

SPC=800

SPC=100

SPC=100

SPC=300

SPC=200

INAT 0

NAT 0

NAT 1

NAT 1 NAT 1

SS7 Protocol Structure

• SS7 protocol stack can be broadly divided into two main categories :

• A ) MTP – Message Transfer Part : The message transfer part has three levels , namely MTP Layer 1, Layer 2 and Layer 3. The message transfer part (MTP) represents a user-neutral means of transport for messages between the users.

• B ) User Parts (UP) : Each user part (UP) encompasses the functions, protocols and coding for the signaling via SS7 for a specific user type (e.g. data service, ISDN). In this way, the user parts control the set-up and release of circuit connections, the processing of facilities as well as administration and maintenance functions for the circuits.

SS7 Protocol Structure

MTP Layer 3 (Network Management)

MTP Layer 1 (Signaling Data Link)

MTP Layer 2 (Signaling Link)

SCCP

B

S

S

A

P

I

S

U

PTCAP

TCAP Users

SS7 Users

M

U

P

Other User Parts

Contoh signaling CCS#7

IAM: Paket pertama yang membawa informasi nomor B

Sisa nomor berikutnya dibawa oleh SAM

ACM: Paket yang berisi

konfirmasi dari sentral B

bahwa seluruh digit sudah

diterima; selain itu paket ini

berisi pula informasi apakah

panggilan dapat di-charge

atau tidak juga apakah

pelanggan tujuan sibuk atau

tidak

Ketika pelanggan B off-

hook, sentral B

mengirimkan

sinyal ACN untuk

mengaktifkan charging